diff --git a/common/gr_text.cpp b/common/gr_text.cpp
index fce5f51bb8..0ccea23c7d 100644
--- a/common/gr_text.cpp
+++ b/common/gr_text.cpp
@@ -8,8 +8,8 @@
  *
  * Copyright (C) 2018 Jean-Pierre Charras, jp.charras at wanadoo.fr
  * Copyright (C) 2012 SoftPLC Corporation, Dick Hollenbeck <dick@softplc.com>
- * Copyright (C) 2012 Wayne Stambaugh <stambaughw@verizon.net>
- * Copyright (C) 1992-2018 KiCad Developers, see AUTHORS.txt for contributors.
+ * Copyright (C) 2012 Wayne Stambaugh <stambaughw@gmail.com>
+ * Copyright (C) 1992-2021 KiCad Developers, see AUTHORS.txt for contributors.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -41,9 +41,8 @@
 
 
 /**
- * Function GetPensizeForBold
- * @return the "best" value for a pen size to draw/plot a bold text
- * @param aTextSize = the char size (height or width)
+ * @param aTextSize is the char size (height or width).
+ * @return the "best" value for a pen size to draw/plot a bold text.
  */
 int GetPenSizeForBold( int aTextSize )
 {
@@ -58,13 +57,13 @@ int GetPenSizeForNormal( int aTextSize )
 
 
 /**
- * Function  Clamp_Text_PenSize
  * Don't allow text to become cluttered up in its own fatness.  Bold fonts are generally around
  * aSize/5 in width, so we limit them to aSize/4, and normal text to aSize/6.
- * @param aPenSize = the pen size to clamp
- * @param aSize the char size (height or width)
- * @param aBold = true if text accept bold pen size
- * @return the max pen size allowed
+ *
+ * @param aPenSize is the pen size to clamp.
+ * @param aSize is the character size (height or width).
+ * @param aBold use true if text accept bold pen size.
+ * @return the max pen size allowed.
  */
 int Clamp_Text_PenSize( int aPenSize, int aSize, bool aBold )
 {
@@ -105,27 +104,27 @@ int GraphicTextWidth( const wxString& aText, const wxSize& aSize, bool aItalic,
 
 
 /**
- * Function GRText
- * Draw a graphic text (like footprint texts)
- *  @param aDC = the current Device Context. NULL if draw within a 3D GL Canvas
- *  @param aPos = text position (according to h_justify, v_justify)
- *  @param aColor (COLOR4D) = text color
- *  @param aText = text to draw
- *  @param aOrient = angle in 0.1 degree
- *  @param aSize = text size (size.x or size.y can be < 0 for mirrored texts)
- *  @param aH_justify = horizontal justification (Left, center, right)
- *  @param aV_justify = vertical justification (bottom, center, top)
- *  @param aWidth = line width (pen width) (use default width if aWidth = 0)
+ * Draw a graphic text (like footprint texts).
+ *
+ *  @param aDC is the current Device Context. NULL if draw within a 3D GL Canvas.
+ *  @param aPos is the text position (according to h_justify, v_justify).
+ *  @param aColor is the text color.
+ *  @param aText is the text to draw.
+ *  @param aOrient is the angle in 0.1 degree.
+ *  @param aSize is the text size (size.x or size.y can be < 0 for mirrored texts).
+ *  @param aH_justify is the horizontal justification (Left, center, right).
+ *  @param aV_justify is the vertical justification (bottom, center, top).
+ *  @param aWidth is the line width (pen width) (use default width if aWidth = 0).
  *      if width < 0 : draw segments in sketch mode, width = abs(width)
- *      Use a value min(aSize.x, aSize.y) / 5 for a bold text
- *  @param aItalic = true to simulate an italic font
- *  @param aBold = true to use a bold font. Useful only with default width value (aWidth = 0)
+ *      Use a value min(aSize.x, aSize.y) / 5 for a bold text.
+ *  @param aItalic is the true to simulate an italic font.
+ *  @param aBold use true to use a bold font. Useful only with default width value (aWidth = 0).
  *  @param aCallback( int x0, int y0, int xf, int yf, void* aData ) is a function called
  *                  (if non null) to draw each segment. used to draw 3D texts or for plotting.
  *                  NULL for normal drawings
- *  @param aCallbackData = is the auxiliary parameter aData for the callback function.
- *                         can be nullptr if no auxiliary parameter is needed
- *  @param aPlotter = a pointer to a PLOTTER instance, when this function is used to plot
+ *  @param aCallbackData is the auxiliary parameter aData for the callback function.
+ *                       can be nullptr if no auxiliary parameter is needed
+ *  @param aPlotter is a PLOTTER instance, when this function is used to plot
  *                  the text. NULL to draw this text.
  */
 void GRText( wxDC* aDC, const wxPoint& aPos, COLOR4D aColor, const wxString& aText,
@@ -168,12 +167,11 @@ void GRText( wxDC* aDC, const wxPoint& aPos, COLOR4D aColor, const wxString& aTe
     basic_gal.m_DC = aDC;
     basic_gal.m_Color = aColor;
     basic_gal.SetClipBox( nullptr );
-
     basic_gal.StrokeText( aText, VECTOR2D( aPos ), aOrient * M_PI/1800 );
 }
 
 
-void GRHaloText( wxDC * aDC, const wxPoint &aPos, COLOR4D aBgColor, COLOR4D aColor1,
+void GRHaloText( wxDC* aDC, const wxPoint &aPos, COLOR4D aBgColor, COLOR4D aColor1,
                  COLOR4D aColor2, const wxString &aText, double aOrient, const wxSize &aSize,
                  enum EDA_TEXT_HJUSTIFY_T aH_justify, enum EDA_TEXT_VJUSTIFY_T aV_justify,
                  int aWidth, bool aItalic, bool aBold,
@@ -200,24 +198,24 @@ void GRHaloText( wxDC * aDC, const wxPoint &aPos, COLOR4D aBgColor, COLOR4D aCol
 
 
 /**
- * Function PLOTTER::Text
- * same as GRText, but plot graphic text instead of draw it
- *  @param aPos = text position (according to aH_justify, aV_justify)
- *  @param aColor (COLOR4D) = text color
- *  @param aText = text to draw
- *  @param aOrient = angle in 0.1 degree
- *  @param aSize = text size (size.x or size.y can be < 0 for mirrored texts)
- *  @param aH_justify = horizontal justification (Left, center, right)
- *  @param aV_justify = vertical justification (bottom, center, top)
- *  @param aPenWidth = line width (if = 0, use plot default line width)
- *  @param aItalic = true to simulate an italic font
- *  @param aBold = true to use a bold font Useful only with default width value (aWidth = 0)
- *  @param aMultilineAllowed = true to plot text as multiline, otherwise single line
- *  @param aData = a parameter used by some plotters in SetCurrentLineWidth(),
- * not directly used here.
+ * Same as GRText, but plot graphic text instead of draw it.
+ *
+ * @param aPos is the text position (according to aH_justify, aV_justify).
+ * @param aColor is the text color.
+ * @param aText is the text to draw.
+ * @param aOrient is the angle in 0.1 degree.
+ * @param aSize is the text size (size.x or size.y can be < 0 for mirrored texts).
+ * @param aH_justify is the horizontal justification (Left, center, right).
+ * @param aV_justify is the vertical justification (bottom, center, top).
+ * @param aPenWidth is the line width (if = 0, use plot default line width).
+ * @param aItalic is the true to simulate an italic font.
+ * @param aBold use true to use a bold font Useful only with default width value (aWidth = 0).
+ * @param aMultilineAllowed use true to plot text as multiline, otherwise single line.
+ * @param aData is a parameter used by some plotters in SetCurrentLineWidth(),
+ *              not directly used here.
  */
 void PLOTTER::Text( const wxPoint&              aPos,
-                    const COLOR4D               aColor,
+                    const COLOR4D&              aColor,
                     const wxString&             aText,
                     double                      aOrient,
                     const wxSize&               aSize,
diff --git a/common/plotters/DXF_plotter.cpp b/common/plotters/DXF_plotter.cpp
index a0c5a76b3a..d918ab988c 100644
--- a/common/plotters/DXF_plotter.cpp
+++ b/common/plotters/DXF_plotter.cpp
@@ -5,7 +5,7 @@
 /*
  * This program source code file is part of KiCad, a free EDA CAD application.
  *
- * Copyright (C) 2017 KiCad Developers, see AUTHORS.txt for contributors.
+ * Copyright (C) 2017-2021 KiCad Developers, see AUTHORS.txt for contributors.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -115,7 +115,7 @@ static const char* getDXFLineType( PLOT_DASH_TYPE aType )
 
 // A helper function to create a color name acceptable in DXF files
 // DXF files do not use a RGB definition
-static wxString getDXFColorName( COLOR4D aColor )
+static wxString getDXFColorName( const COLOR4D& aColor )
 {
     EDA_COLOR_T color = COLOR4D::FindNearestLegacyColor( int( aColor.r * 255 ),
                                                          int( aColor.g * 255 ),
@@ -144,11 +144,6 @@ void DXF_PLOTTER::SetUnits( DXF_UNITS aUnit )
 }
 
 
-/**
- * Set the scale/position for the DXF plot
- * The DXF engine doesn't support line widths and mirroring. The output
- * coordinate system is in the first quadrant (in mm)
- */
 void DXF_PLOTTER::SetViewport( const wxPoint& aOffset, double aIusPerDecimil,
                                double aScale, bool aMirror )
 {
@@ -172,9 +167,7 @@ void DXF_PLOTTER::SetViewport( const wxPoint& aOffset, double aIusPerDecimil,
     m_currentColor = COLOR4D::BLACK;
 }
 
-/**
- * Opens the DXF plot with a skeleton header
- */
+
 bool DXF_PLOTTER::StartPlot()
 {
     wxASSERT( m_outputFile );
@@ -404,10 +397,7 @@ bool DXF_PLOTTER::EndPlot()
 }
 
 
-/**
- * The DXF exporter handles 'colors' as layers...
- */
-void DXF_PLOTTER::SetColor( COLOR4D color )
+void DXF_PLOTTER::SetColor( const COLOR4D& color )
 {
     if( ( m_colorMode )
        || ( color == COLOR4D::BLACK )
@@ -421,9 +411,7 @@ void DXF_PLOTTER::SetColor( COLOR4D color )
     }
 }
 
-/**
- * DXF rectangle: fill not supported
- */
+
 void DXF_PLOTTER::Rect( const wxPoint& p1, const wxPoint& p2, FILL_TYPE fill, int width )
 {
     wxASSERT( m_outputFile );
@@ -435,17 +423,12 @@ void DXF_PLOTTER::Rect( const wxPoint& p1, const wxPoint& p2, FILL_TYPE fill, in
 }
 
 
-/**
- * DXF circle: full functionality; it even does 'fills' drawing a
- * circle with a dual-arc polyline wide as the radius.
- *
- * I could use this trick to do other filled primitives
- */
 void DXF_PLOTTER::Circle( const wxPoint& centre, int diameter, FILL_TYPE fill, int width )
 {
     wxASSERT( m_outputFile );
     double radius = userToDeviceSize( diameter / 2 );
     DPOINT centre_dev = userToDeviceCoordinates( centre );
+
     if( radius > 0 )
     {
         wxString cname = getDXFColorName( m_currentColor );
@@ -460,29 +443,23 @@ void DXF_PLOTTER::Circle( const wxPoint& centre, int diameter, FILL_TYPE fill, i
         if( fill == FILL_TYPE::FILLED_SHAPE )
         {
             double r = radius*0.5;
-            fprintf( m_outputFile, "0\nPOLYLINE\n");
-            fprintf( m_outputFile, "8\n%s\n66\n1\n70\n1\n", TO_UTF8( cname ));
+            fprintf( m_outputFile, "0\nPOLYLINE\n" );
+            fprintf( m_outputFile, "8\n%s\n66\n1\n70\n1\n", TO_UTF8( cname ) );
             fprintf( m_outputFile, "40\n%g\n41\n%g\n", radius, radius);
-            fprintf( m_outputFile, "0\nVERTEX\n8\n%s\n", TO_UTF8( cname ));
+            fprintf( m_outputFile, "0\nVERTEX\n8\n%s\n", TO_UTF8( cname ) );
             fprintf( m_outputFile, "10\n%g\n 20\n%g\n42\n1.0\n",
-                    centre_dev.x-r, centre_dev.y );
-            fprintf( m_outputFile, "0\nVERTEX\n8\n%s\n", TO_UTF8( cname ));
+                     centre_dev.x-r, centre_dev.y );
+            fprintf( m_outputFile, "0\nVERTEX\n8\n%s\n", TO_UTF8( cname ) );
             fprintf( m_outputFile, "10\n%g\n 20\n%g\n42\n1.0\n",
-                    centre_dev.x+r, centre_dev.y );
+                     centre_dev.x+r, centre_dev.y );
             fprintf( m_outputFile, "0\nSEQEND\n");
         }
     }
 }
 
 
-/**
- * DXF polygon: doesn't fill it but at least it close the filled ones
- * DXF does not know thick outline.
- * It does not know thick segments, therefore filled polygons with thick outline
- * are converted to inflated polygon by aWidth/2
- */
 void DXF_PLOTTER::PlotPoly( const std::vector<wxPoint>& aCornerList,
-                            FILL_TYPE aFill, int aWidth, void * aData )
+                            FILL_TYPE aFill, int aWidth, void* aData )
 {
     if( aCornerList.size() <= 1 )
         return;
@@ -509,7 +486,6 @@ void DXF_PLOTTER::PlotPoly( const std::vector<wxPoint>& aCornerList,
         return;
     }
 
-
     // if the polygon outline has thickness, and is not filled
     // (i.e. is a polyline) plot outlines with thick segments
     if( aWidth > 0 && aFill == FILL_TYPE::NO_FILL )
@@ -517,8 +493,7 @@ void DXF_PLOTTER::PlotPoly( const std::vector<wxPoint>& aCornerList,
         MoveTo( aCornerList[0] );
 
         for( unsigned ii = 1; ii < aCornerList.size(); ii++ )
-            ThickSegment( aCornerList[ii-1], aCornerList[ii],
-                          aWidth, FILLED, NULL );
+            ThickSegment( aCornerList[ii-1], aCornerList[ii], aWidth, FILLED, NULL );
 
         return;
     }
@@ -591,6 +566,7 @@ void DXF_PLOTTER::PenTo( const wxPoint& pos, char plume )
     {
         return;
     }
+
     DPOINT pos_dev = userToDeviceCoordinates( pos );
     DPOINT pen_lastpos_dev = userToDeviceCoordinates( m_penLastpos );
 
@@ -605,6 +581,7 @@ void DXF_PLOTTER::PenTo( const wxPoint& pos, char plume )
                  TO_UTF8( cname ), lname,
                  pen_lastpos_dev.x, pen_lastpos_dev.y, pos_dev.x, pos_dev.y );
     }
+
     m_penLastpos = pos;
 }
 
@@ -628,6 +605,7 @@ void DXF_PLOTTER::ThickSegment( const wxPoint& aStart, const wxPoint& aEnd, int
         const SHAPE_LINE_CHAIN& path = outlineBuffer.COutline( 0 );
 
         cornerList.reserve( path.PointCount() );
+
         for( int jj = 0; jj < path.PointCount(); jj++ )
             cornerList.emplace_back( path.CPoint( jj ).x, path.CPoint( jj ).y );
 
@@ -644,6 +622,7 @@ void DXF_PLOTTER::ThickSegment( const wxPoint& aStart, const wxPoint& aEnd, int
     }
 }
 
+
 /* Plot an arc in DXF format
  * Filling is not supported
  */
@@ -675,9 +654,7 @@ void DXF_PLOTTER::Arc( const wxPoint& centre, double StAngle, double EndAngle, i
              StAngle / 10.0, EndAngle / 10.0 );
 }
 
-/**
- * DXF oval pad: always done in sketch mode
- */
+
 void DXF_PLOTTER::FlashPadOval( const wxPoint& pos, const wxSize& aSize, double orient,
                                 OUTLINE_MODE trace_mode, void* aData )
 {
@@ -696,21 +673,14 @@ void DXF_PLOTTER::FlashPadOval( const wxPoint& pos, const wxSize& aSize, double
 }
 
 
-/**
- * DXF round pad: always done in sketch mode; it could be filled but it isn't
- * pretty if other kinds of pad aren't...
- */
 void DXF_PLOTTER::FlashPadCircle( const wxPoint& pos, int diametre,
-                                    OUTLINE_MODE trace_mode, void* aData )
+                                  OUTLINE_MODE trace_mode, void* aData )
 {
     wxASSERT( m_outputFile );
     Circle( pos, diametre, FILL_TYPE::NO_FILL );
 }
 
 
-/**
- * DXF rectangular pad: always done in sketch mode
- */
 void DXF_PLOTTER::FlashPadRect( const wxPoint& pos, const wxSize& padsize,
                                 double orient, OUTLINE_MODE trace_mode, void* aData )
 {
@@ -723,6 +693,7 @@ void DXF_PLOTTER::FlashPadRect( const wxPoint& pos, const wxSize& padsize,
 
     if( size.x < 0 )
         size.x = 0;
+
     if( size.y < 0 )
         size.y = 0;
 
@@ -739,6 +710,7 @@ void DXF_PLOTTER::FlashPadRect( const wxPoint& pos, const wxSize& padsize,
         FinishTo( wxPoint( fx, fy ) );
         return;
     }
+
     if( size.y == 0 )
     {
         ox = pos.x - size.x;
@@ -775,13 +747,14 @@ void DXF_PLOTTER::FlashPadRect( const wxPoint& pos, const wxSize& padsize,
     FinishTo( wxPoint( ox, oy ) );
 }
 
+
 void DXF_PLOTTER::FlashPadRoundRect( const wxPoint& aPadPos, const wxSize& aSize,
                                      int aCornerRadius, double aOrient,
                                      OUTLINE_MODE aTraceMode, void* aData )
 {
     SHAPE_POLY_SET outline;
-    TransformRoundChamferedRectToPolygon( outline, aPadPos, aSize, aOrient,
-                                 aCornerRadius, 0.0, 0, GetPlotterArcHighDef(), ERROR_INSIDE );
+    TransformRoundChamferedRectToPolygon( outline, aPadPos, aSize, aOrient, aCornerRadius,
+                                          0.0, 0, GetPlotterArcHighDef(), ERROR_INSIDE );
 
     // TransformRoundRectToPolygon creates only one convex polygon
     SHAPE_LINE_CHAIN& poly = outline.Outline( 0 );
@@ -812,9 +785,6 @@ void DXF_PLOTTER::FlashPadCustom( const wxPoint& aPadPos, const wxSize& aSize,
 }
 
 
-/**
- * DXF trapezoidal pad: only sketch mode is supported
- */
 void DXF_PLOTTER::FlashPadTrapez( const wxPoint& aPadPos, const wxPoint *aCorners,
                                   double aPadOrient, OUTLINE_MODE aTrace_Mode, void* aData )
 {
@@ -837,9 +807,8 @@ void DXF_PLOTTER::FlashPadTrapez( const wxPoint& aPadPos, const wxPoint *aCorner
 }
 
 
-void DXF_PLOTTER::FlashRegularPolygon( const wxPoint& aShapePos,
-                            int aRadius, int aCornerCount,
-                            double aOrient, OUTLINE_MODE aTraceMode, void* aData )
+void DXF_PLOTTER::FlashRegularPolygon( const wxPoint& aShapePos, int aRadius, int aCornerCount,
+                                       double aOrient, OUTLINE_MODE aTraceMode, void* aData )
 {
     // Do nothing
     wxASSERT( 0 );
@@ -847,10 +816,12 @@ void DXF_PLOTTER::FlashRegularPolygon( const wxPoint& aShapePos,
 
 
 /**
- * Checks if a given string contains non-ASCII characters.
- * FIXME: the performance of this code is really poor, but in this case it can be
- * acceptable because the plot operation is not called very often.
- * @param string String to check
+ * Check if a given string contains non-ASCII characters.
+ *
+ * @fixme The performance of this code is really poor, but in this case it can be
+ *        acceptable because the plot operation is not called very often.
+ *
+ * @param string String to check.
  * @return true if it contains some non-ASCII character, false if all characters are
  *         inside ASCII range (<=255).
  */
@@ -865,8 +836,9 @@ bool containsNonAsciiChars( const wxString& string )
     return false;
 }
 
+
 void DXF_PLOTTER::Text( const wxPoint&              aPos,
-                        COLOR4D                     aColor,
+                        const COLOR4D&              aColor,
                         const wxString&             aText,
                         double                      aOrient,
                         const wxSize&               aSize,
@@ -901,6 +873,7 @@ void DXF_PLOTTER::Text( const wxPoint&              aPos,
         wxString cname = getDXFColorName( m_currentColor );
         DPOINT size_dev = userToDeviceSize( aSize );
         int h_code = 0, v_code = 0;
+
         switch( aH_justify )
         {
         case GR_TEXT_HJUSTIFY_LEFT:
@@ -913,6 +886,7 @@ void DXF_PLOTTER::Text( const wxPoint&              aPos,
             h_code = 2;
             break;
         }
+
         switch( aV_justify )
         {
         case GR_TEXT_VJUSTIFY_TOP:
@@ -1042,6 +1016,7 @@ void DXF_PLOTTER::Text( const wxPoint&              aPos,
                 putc( ch, m_outputFile );
             }
         }
+
         putc( '\n', m_outputFile );
     }
 }
diff --git a/common/plotters/GERBER_plotter.cpp b/common/plotters/GERBER_plotter.cpp
index 7ba2f88ae3..85ae7c0027 100644
--- a/common/plotters/GERBER_plotter.cpp
+++ b/common/plotters/GERBER_plotter.cpp
@@ -66,7 +66,8 @@
 #define GBR_MACRO_FOR_CUSTOM_PAD_MAX_CORNER_COUNT 4990
 #define AM_FREEPOLY_BASENAME "FreePoly"
 
-// A helper function to compare 2 polygons: polygons are similar if they havve the same
+
+// A helper function to compare 2 polygons: polygons are similar if they have the same
 // number of vertices and each vertex coordinate are similar, i.e. if the difference
 // between coordinates is small ( <= margin to accept rounding issues coming from polygon
 // geometric transforms like rotation
@@ -121,7 +122,7 @@ GERBER_PLOTTER::GERBER_PLOTTER()
 
 
 void GERBER_PLOTTER::SetViewport( const wxPoint& aOffset, double aIusPerDecimil,
-                  double aScale, bool aMirror )
+                                  double aScale, bool aMirror )
 {
     wxASSERT( aMirror == false );
     m_plotMirror = false;
@@ -130,6 +131,7 @@ void GERBER_PLOTTER::SetViewport( const wxPoint& aOffset, double aIusPerDecimil,
     m_plotScale = 1;                      // Plot scale is *always* 1.0
 
     m_IUsPerDecimil = aIusPerDecimil;
+
     // gives now a default value to iuPerDeviceUnit (because the units of the caller is now known)
     // which could be modified later by calling SetGerberCoordinatesFormat()
     m_iuPerDeviceUnit = pow( 10.0, m_gerberUnitFmt ) / ( m_IUsPerDecimil * 10000.0 );
@@ -240,7 +242,8 @@ bool GERBER_PLOTTER::StartPlot()
     m_hasApertureRoundRect = false;     // true is at least one round rect aperture is in use
     m_hasApertureRotOval = false;       // true is at least one oval rotated aperture is in use
     m_hasApertureRotRect = false;       // true is at least one rect. rotated aperture is in use
-    m_hasApertureOutline4P = false;     // true is at least one rotated rect/trapezoid aperture is in use
+    m_hasApertureOutline4P = false;     // true is at least one rotated rect/trapezoid aperture
+                                        // is in use
     m_hasApertureChamferedRect = false; // true is at least one chamfered rect is in use
     m_am_freepoly_list.ClearList();
 
@@ -248,7 +251,8 @@ bool GERBER_PLOTTER::StartPlot()
 
     finalFile = m_outputFile;     // the actual gerber file will be created later
 
-    // Create a temp file in system temp to avoid potential network share buffer issues for the final read and save
+    // Create a temp file in system temp to avoid potential network share buffer issues for
+    // the final read and save.
     m_workFilename = wxFileName::CreateTempFileName( "" );
     workFile   = wxFopen( m_workFilename, wxT( "wt" ));
     m_outputFile = workFile;
@@ -278,6 +282,7 @@ bool GERBER_PLOTTER::StartPlot()
              m_gerberUnitInch ? "inch" : "mm" );
 
     wxString Title = m_creator + wxT( " " ) + GetBuildVersion();
+
     // In gerber files, ASCII7 chars only are allowed.
     // So use a ISO date format (using a space as separator between date and time),
     // not a localized date format
@@ -366,7 +371,7 @@ bool GERBER_PLOTTER::EndPlot()
 
                 if( m_am_freepoly_list.AmCount() )
                 {
-                    // apertude sizes are in inch or mm, regardless the
+                    // aperture sizes are in inch or mm, regardless the
                     // coordinates format
                     double fscale = 0.0001 * m_plotScale / m_IUsPerDecimil; // inches
 
@@ -443,12 +448,12 @@ int GERBER_PLOTTER::GetOrCreateAperture( const wxSize& aSize, int aRadius, doubl
 
 
 int GERBER_PLOTTER::GetOrCreateAperture( const std::vector<wxPoint>& aCorners, double aRotDegree,
-                         APERTURE::APERTURE_TYPE aType, int aApertureAttribute )
+                                         APERTURE::APERTURE_TYPE aType, int aApertureAttribute )
 {
     int last_D_code = 9;
 
     // For APERTURE::AM_FREE_POLYGON aperture macros, we need to create the macro
-    // on the fly, because due to the fact the vertice count is not a constant we
+    // on the fly, because due to the fact the vertex count is not a constant we
     // cannot create a static definition.
     if( APERTURE::AM_FREE_POLYGON == aType )
     {
@@ -496,8 +501,7 @@ int GERBER_PLOTTER::GetOrCreateAperture( const std::vector<wxPoint>& aCorners, d
 
 
 void GERBER_PLOTTER::selectAperture( const wxSize& aSize, int aRadius, double aRotDegree,
-                                     APERTURE::APERTURE_TYPE aType,
-                                     int aApertureAttribute )
+                                     APERTURE::APERTURE_TYPE aType, int aApertureAttribute )
 {
     bool change = ( m_currentApertureIdx < 0 ) ||
                   ( m_apertures[m_currentApertureIdx].m_Type != aType ) ||
@@ -519,7 +523,7 @@ void GERBER_PLOTTER::selectAperture( const wxSize& aSize, int aRadius, double aR
 
 
 void GERBER_PLOTTER::selectAperture( const std::vector<wxPoint>& aCorners, double aRotDegree,
-                         APERTURE::APERTURE_TYPE aType, int aApertureAttribute )
+                                     APERTURE::APERTURE_TYPE aType, int aApertureAttribute )
 {
     bool change = ( m_currentApertureIdx < 0 ) ||
                   ( m_apertures[m_currentApertureIdx].m_Type != aType ) ||
@@ -552,14 +556,14 @@ void GERBER_PLOTTER::selectAperture( const std::vector<wxPoint>& aCorners, doubl
 
 
 void GERBER_PLOTTER::selectAperture( int aDiameter, double aPolygonRotation,
-                     APERTURE::APERTURE_TYPE aType, int aApertureAttribute )
+                                     APERTURE::APERTURE_TYPE aType, int aApertureAttribute )
 {
     // Pick an existing aperture or create a new one, matching the
     // aDiameter, aPolygonRotation, type and attributes for type =
     // AT_REGULAR_POLY3 to AT_REGULAR_POLY12
 
     wxASSERT( aType>= APERTURE::APERTURE_TYPE::AT_REGULAR_POLY3 &&
-                      aType <= APERTURE::APERTURE_TYPE::AT_REGULAR_POLY12 );
+              aType <= APERTURE::APERTURE_TYPE::AT_REGULAR_POLY12 );
 
     wxSize size( aDiameter, (int)( aPolygonRotation * 1000.0 ) );
     selectAperture( wxSize( 0, 0), aDiameter/2, aPolygonRotation, aType, aApertureAttribute );
@@ -579,7 +583,7 @@ void GERBER_PLOTTER::writeApertureList()
     // Init
     for( APERTURE& tool : m_apertures )
     {
-        // apertude sizes are in inch or mm, regardless the
+        // aperture sizes are in inch or mm, regardless the
         // coordinates format
         double fscale = 0.0001 * m_plotScale / m_IUsPerDecimil; // inches
 
@@ -602,7 +606,7 @@ void GERBER_PLOTTER::writeApertureList()
            exponential syntax is *not* allowed and the decimal point should
            also be always inserted. So the %g format is ruled out, but %f is fine
            (the # modifier forces the decimal point). Sadly the %f formatter
-           can't remove trailing zeros but thats not a problem, since nothing
+           can't remove trailing zeros but that's not a problem, since nothing
            forbid it (the file is only slightly longer) */
 
         switch( tool.m_Type )
@@ -641,7 +645,7 @@ void GERBER_PLOTTER::writeApertureList()
             break;
 
         case APERTURE::AM_ROUND_RECT:       // Aperture macro for round rect pads
-            {
+        {
             // The aperture macro needs coordinates of the centers of the 4 corners
             std::vector<VECTOR2I> corners;
             wxSize half_size( tool.m_Size.x/2-tool.m_Radius, tool.m_Size.y/2-tool.m_Radius );
@@ -668,7 +672,7 @@ void GERBER_PLOTTER::writeApertureList()
             }
 
             sprintf( cbuf, "0*%%\n" );
-            }
+        }
             break;
 
         case APERTURE::AM_ROT_RECT:         // Aperture macro for rotated rect pads
@@ -716,9 +720,9 @@ void GERBER_PLOTTER::writeApertureList()
 
         case APERTURE::AM_ROTATED_OVAL:         // Aperture macro for rotated oval pads
                                                 // (not rotated is a primitive)
-            // m_Size.x = full lenght; m_Size.y = width, and the macro aperure expects
+            // m_Size.x = full length; m_Size.y = width, and the macro aperture expects
             // the position of ends
-            {
+        {
                 // the seg_len is the distance between the 2 circle centers
                 int seg_len = tool.m_Size.x - tool.m_Size.y;
                 // Center of the circle on the segment start point:
@@ -733,21 +737,21 @@ void GERBER_PLOTTER::writeApertureList()
                          tool.m_Size.y * fscale,                // width
                          start.x * fscale, -start.y * fscale,   // X,Y corner start pos
                          end.x * fscale, -end.y * fscale );     // X,Y cornerend  pos
-            }
+        }
             break;
 
-            case APERTURE::AM_FREE_POLYGON:
-            {
-                // Find the aperture macro name in the list of aperture macro
-                // created on the fly for this polygon:
-                int idx = m_am_freepoly_list.FindAm( tool.m_Corners );
+        case APERTURE::AM_FREE_POLYGON:
+        {
+            // Find the aperture macro name in the list of aperture macro
+            // created on the fly for this polygon:
+            int idx = m_am_freepoly_list.FindAm( tool.m_Corners );
 
-                // Write DCODE id ( "%ADDxx" is already in buffer) and rotation
-                // the full line is something like :%ADD12FreePoly1,45.000000*%
-                sprintf( cbuf, "%s%d,%#f*%%\n", AM_FREEPOLY_BASENAME, idx, tool.m_Rotation );
-            }
+            // Write DCODE id ( "%ADDxx" is already in buffer) and rotation
+            // the full line is something like :%ADD12FreePoly1,45.000000*%
+            sprintf( cbuf, "%s%d,%#f*%%\n", AM_FREEPOLY_BASENAME, idx, tool.m_Rotation );
             break;
         }
+        }
 
         buffer += cbuf;
         fputs( buffer.c_str(), m_outputFile );
@@ -826,6 +830,7 @@ void GERBER_PLOTTER::Arc( const wxPoint& aCenter, double aStAngle, double aEndAn
     plotArc( aCenter, aStAngle, aEndAngle, aRadius, false );
 }
 
+
 void GERBER_PLOTTER::Arc( const SHAPE_ARC& aArc )
 {
     SetCurrentLineWidth( aArc.GetWidth() );
@@ -860,12 +865,12 @@ void GERBER_PLOTTER::plotArc( const SHAPE_ARC& aArc, bool aPlotInRegion )
              KiROUND( devEnd.x ), KiROUND( devEnd.y ),
              KiROUND( devCenter.x ), KiROUND( devCenter.y ) );
 
-    fprintf( m_outputFile, "G01*\n" ); // Back to linear interpol (perhaps useless here).
+    fprintf( m_outputFile, "G01*\n" ); // Back to linear interpolate (perhaps useless here).
 }
 
 
 void GERBER_PLOTTER::plotArc( const wxPoint& aCenter, double aStAngle, double aEndAngle,
-                  int aRadius, bool aPlotInRegion )
+                              int aRadius, bool aPlotInRegion )
 {
     wxPoint start, end;
     start.x = aCenter.x + KiROUND( cosdecideg( aRadius, aStAngle ) );
@@ -892,12 +897,11 @@ void GERBER_PLOTTER::plotArc( const wxPoint& aCenter, double aStAngle, double aE
              KiROUND( devEnd.x ), KiROUND( devEnd.y ),
              KiROUND( devCenter.x ), KiROUND( devCenter.y ) );
 
-    fprintf( m_outputFile, "G01*\n" ); // Back to linear interpol (perhaps useless here).
+    fprintf( m_outputFile, "G01*\n" ); // Back to linear interpolate (perhaps useless here).
 }
 
 
-void GERBER_PLOTTER::PlotGerberRegion( const SHAPE_LINE_CHAIN& aPoly,
-                                 void* aData )
+void GERBER_PLOTTER::PlotGerberRegion( const SHAPE_LINE_CHAIN& aPoly, void* aData )
 {
     if( aPoly.PointCount() <= 2 )
         return;
@@ -934,8 +938,7 @@ void GERBER_PLOTTER::PlotGerberRegion( const SHAPE_LINE_CHAIN& aPoly,
 }
 
 
-void GERBER_PLOTTER::PlotGerberRegion( const std::vector< wxPoint >& aCornerList,
-                                 void* aData )
+void GERBER_PLOTTER::PlotGerberRegion( const std::vector< wxPoint >& aCornerList, void* aData )
 {
     if( aCornerList.size() <= 2 )
         return;
@@ -971,8 +974,9 @@ void GERBER_PLOTTER::PlotGerberRegion( const std::vector< wxPoint >& aCornerList
     }
 }
 
-void GERBER_PLOTTER::PlotPoly( const SHAPE_LINE_CHAIN& aPoly,
-                               FILL_TYPE aFill, int aWidth, void* aData )
+
+void GERBER_PLOTTER::PlotPoly( const SHAPE_LINE_CHAIN& aPoly, FILL_TYPE aFill, int aWidth,
+                               void* aData )
 {
     if( aPoly.CPoints().size() <= 1 )
         return;
@@ -1100,7 +1104,7 @@ void GERBER_PLOTTER::PlotPoly( const std::vector< wxPoint >& aCornerList,
 
 
 void GERBER_PLOTTER::ThickSegment( const wxPoint& start, const wxPoint& end, int width,
-                            OUTLINE_MODE tracemode, void* aData )
+                                   OUTLINE_MODE tracemode, void* aData )
 {
     if( tracemode == FILLED )
     {
@@ -1130,15 +1134,17 @@ void GERBER_PLOTTER::ThickArc( const wxPoint& centre, double StAngle, double End
         formatNetAttribute( &gbr_metadata->m_NetlistMetadata );
 
     if( tracemode == FILLED )
+    {
         Arc( centre, StAngle, EndAngle, radius, FILL_TYPE::NO_FILL, DO_NOT_SET_LINE_WIDTH );
+    }
     else
     {
         SetCurrentLineWidth( USE_DEFAULT_LINE_WIDTH );
         Arc( centre, StAngle, EndAngle,
              radius - ( width - m_currentPenWidth ) / 2, FILL_TYPE::NO_FILL,
              DO_NOT_SET_LINE_WIDTH );
-        Arc( centre, StAngle, EndAngle, radius + ( width - m_currentPenWidth ) / 2, FILL_TYPE::NO_FILL,
-             DO_NOT_SET_LINE_WIDTH );
+        Arc( centre, StAngle, EndAngle, radius + ( width - m_currentPenWidth ) / 2,
+             FILL_TYPE::NO_FILL, DO_NOT_SET_LINE_WIDTH );
     }
 }
 
@@ -1153,14 +1159,16 @@ void GERBER_PLOTTER::ThickRect( const wxPoint& p1, const wxPoint& p2, int width,
         formatNetAttribute( &gbr_metadata->m_NetlistMetadata );
 
     if( tracemode == FILLED )
+    {
         Rect( p1, p2, FILL_TYPE::NO_FILL, DO_NOT_SET_LINE_WIDTH );
+    }
     else
     {
         SetCurrentLineWidth( USE_DEFAULT_LINE_WIDTH );
         wxPoint offsetp1( p1.x - (width - m_currentPenWidth) / 2,
                           p1.y - (width - m_currentPenWidth) / 2 );
         wxPoint offsetp2( p2.x + (width - m_currentPenWidth) / 2,
-              p2.y + (width - m_currentPenWidth) / 2 );
+                          p2.y + (width - m_currentPenWidth) / 2 );
         Rect( offsetp1, offsetp2, FILL_TYPE::NO_FILL, -1 );
         offsetp1.x += (width - m_currentPenWidth);
         offsetp1.y += (width - m_currentPenWidth);
@@ -1172,7 +1180,7 @@ void GERBER_PLOTTER::ThickRect( const wxPoint& p1, const wxPoint& p2, int width,
 
 
 void GERBER_PLOTTER::ThickCircle( const wxPoint& pos, int diametre, int width,
-                              OUTLINE_MODE tracemode, void* aData )
+                                  OUTLINE_MODE tracemode, void* aData )
 {
     GBR_METADATA *gbr_metadata = static_cast<GBR_METADATA*>( aData );
     SetCurrentLineWidth( width, gbr_metadata );
@@ -1181,7 +1189,9 @@ void GERBER_PLOTTER::ThickCircle( const wxPoint& pos, int diametre, int width,
         formatNetAttribute( &gbr_metadata->m_NetlistMetadata );
 
     if( tracemode == FILLED )
+    {
         Circle( pos, diametre, FILL_TYPE::NO_FILL, DO_NOT_SET_LINE_WIDTH );
+    }
     else
     {
         SetCurrentLineWidth( USE_DEFAULT_LINE_WIDTH, gbr_metadata );
@@ -1205,7 +1215,7 @@ void GERBER_PLOTTER::FilledCircle( const wxPoint& pos, int diametre,
 
     if( tracemode == FILLED )
     {
-        // Draw a circle of diameter = diametre/2 with a line thickness = radius,
+        // Draw a circle of diameter = diameter/2 with a line thickness = radius,
         // To create a filled circle
         SetCurrentLineWidth( diametre/2, gbr_metadata );
         Circle( pos, diametre/2, FILL_TYPE::NO_FILL, DO_NOT_SET_LINE_WIDTH );
@@ -1305,7 +1315,7 @@ void GERBER_PLOTTER::FlashPadOval( const wxPoint& pos, const wxSize& aSize, doub
             // Draw the oval as round rect pad with a radius = 50% min size)
             // In gerber file, it will be drawn as a region with arcs, and can be
             // detected as pads (similar to a flashed pad)
-            FlashPadRoundRect( pos, aSize, std::min( aSize.x, aSize.y ) /2,
+            FlashPadRoundRect( pos, aSize, std::min( aSize.x, aSize.y ) / 2,
                                orient, FILLED, aData );
         }
         else    // Non filled shape: plot outlines:
@@ -1419,8 +1429,8 @@ void GERBER_PLOTTER::FlashPadRoundRect( const wxPoint& aPadPos, const wxSize& aS
     if( aTraceMode != FILLED )
     {
         SHAPE_POLY_SET outline;
-        TransformRoundChamferedRectToPolygon( outline, aPadPos, aSize, aOrient,
-                                     aCornerRadius, 0.0, 0, GetPlotterArcHighDef(), ERROR_INSIDE );
+        TransformRoundChamferedRectToPolygon( outline, aPadPos, aSize, aOrient, aCornerRadius,
+                                              0.0, 0, GetPlotterArcHighDef(), ERROR_INSIDE );
 
         SetCurrentLineWidth( USE_DEFAULT_LINE_WIDTH, &gbr_metadata );
         outline.Inflate( -GetCurrentLineWidth()/2, 16 );
@@ -1458,6 +1468,7 @@ void GERBER_PLOTTER::FlashPadRoundRect( const wxPoint& aPadPos, const wxSize& aS
             emitDcode( pos_dev, 3 );
             return;
         }
+
         // A Pad RoundRect is plotted as a Gerber region.
         // Initialize region metadata:
         bool clearTA_AperFunction = false;     // true if a TA.AperFunction is used
@@ -1605,12 +1616,13 @@ void GERBER_PLOTTER::plotRoundRectAsRegion( const wxPoint& aRectCenter, const wx
         if( aCornerRadius )     // Guard: ensure we do not create arcs with radius = 0
         {
             // LineTo( rr_edge.m_end ); // made in plotArc()
-            plotArc( rr_edge.m_center,
-                     rr_edge.m_arc_angle_start, rr_edge.m_arc_angle_start+arc_angle,
-                     aCornerRadius, true );
+            plotArc( rr_edge.m_center, rr_edge.m_arc_angle_start,
+                     rr_edge.m_arc_angle_start+arc_angle, aCornerRadius, true );
         }
         else
+        {
             LineTo( rr_edge.m_end );
+        }
     }
 
     fputs( "G37*\n", m_outputFile );      // Close region
@@ -1651,7 +1663,9 @@ void GERBER_PLOTTER::FlashPadCustom( const wxPoint& aPadPos, const wxSize& aSize
         cornerList.push_back( cornerList[0] );
 
         if( aTraceMode == SKETCH )
+        {
             PlotPoly( cornerList, FILL_TYPE::NO_FILL, GetCurrentLineWidth(), &gbr_metadata );
+        }
         else
         {
 #ifdef GBR_USE_MACROS_FOR_CUSTOM_PAD
@@ -1684,9 +1698,9 @@ void GERBER_PLOTTER::FlashPadCustom( const wxPoint& aPadPos, const wxSize& aSize
 
 
 void GERBER_PLOTTER::FlashPadChamferRoundRect( const wxPoint& aShapePos, const wxSize& aPadSize,
-                                   int aCornerRadius, double aChamferRatio,
-                                   int aChamferPositions,
-                                   double aPadOrient, OUTLINE_MODE aPlotMode, void* aData )
+                                               int aCornerRadius, double aChamferRatio,
+                                               int aChamferPositions, double aPadOrient,
+                                               OUTLINE_MODE aPlotMode, void* aData )
 
 {
     GBR_METADATA gbr_metadata;
@@ -1726,7 +1740,9 @@ void GERBER_PLOTTER::FlashPadChamferRoundRect( const wxPoint& aShapePos, const w
         {
 #ifdef GBR_USE_MACROS_FOR_CHAMFERED_ROUND_RECT
             if( m_gerberDisableApertMacros )
+            {
                 PlotGerberRegion( cornerList, &gbr_metadata );
+            }
             else
             {
                // An AM will be created. the shape must be in position 0,0 and orientation 0
@@ -1859,10 +1875,9 @@ void GERBER_PLOTTER::FlashPadTrapez( const wxPoint& aPadPos,  const wxPoint* aCo
 }
 
 
-void GERBER_PLOTTER::FlashRegularPolygon( const wxPoint& aShapePos,
-                                          int aDiameter, int aCornerCount,
-                                          double aOrient, OUTLINE_MODE aTraceMode,
-                                          void* aData )
+void GERBER_PLOTTER::FlashRegularPolygon( const wxPoint& aShapePos, int aDiameter,
+                                          int aCornerCount, double aOrient,
+                                          OUTLINE_MODE aTraceMode, void* aData )
 {
     GBR_METADATA* gbr_metadata = static_cast<GBR_METADATA*>( aData );
 
@@ -1909,7 +1924,7 @@ void GERBER_PLOTTER::FlashRegularPolygon( const wxPoint& aShapePos,
 }
 
 
-void GERBER_PLOTTER::Text( const wxPoint& aPos, const COLOR4D aColor,
+void GERBER_PLOTTER::Text( const wxPoint& aPos, const COLOR4D& aColor,
                            const wxString& aText, double aOrient, const wxSize& aSize,
                            enum EDA_TEXT_HJUSTIFY_T aH_justify,
                            enum EDA_TEXT_VJUSTIFY_T aV_justify, int aWidth, bool aItalic,
@@ -1961,8 +1976,7 @@ void APER_MACRO_FREEPOLY::Format( FILE * aOutput, double aIu2GbrMacroUnit )
         fprintf( aOutput, "%#f,%#f,",
                  m_Corners[jj].x * aIu2GbrMacroUnit, -m_Corners[jj].y * aIu2GbrMacroUnit );
 
-        if( curr_line_count_max >= 0
-                && ++curr_line_corner_count >= curr_line_count_max )
+        if( curr_line_count_max >= 0 && ++curr_line_corner_count >= curr_line_count_max )
         {
             fprintf( aOutput, "\n" );
             curr_line_corner_count = 0;
diff --git a/common/plotters/HPGL_plotter.cpp b/common/plotters/HPGL_plotter.cpp
index ce1ed447b9..6858d8ea5f 100644
--- a/common/plotters/HPGL_plotter.cpp
+++ b/common/plotters/HPGL_plotter.cpp
@@ -2,7 +2,7 @@
  * This program source code file is part of KiCad, a free EDA CAD application.
  *
  * Copyright (C) 2017 Jean-Pierre Charras, jp.charras at wanadoo.fr
- * Copyright (C) 2020 KiCad Developers, see AUTHORS.txt for contributors.
+ * Copyright (C) 2020-2021 KiCad Developers, see AUTHORS.txt for contributors.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -239,6 +239,7 @@ void HPGL_PLOTTER::SetViewport( const wxPoint& aOffset, double aIusPerDecimil,
     m_plotScale       = aScale;
     m_IUsPerDecimil   = aIusPerDecimil;
     m_iuPerDeviceUnit = PLUsPERDECIMIL / aIusPerDecimil;
+
     /* Compute the paper size in IUs */
     m_paperSize   = m_pageInfo.GetSizeMils();
     m_paperSize.x *= 10.0 * aIusPerDecimil;
@@ -253,9 +254,6 @@ void HPGL_PLOTTER::SetTargetChordLength( double chord_len )
 }
 
 
-/**
- * At the start of the HPGL plot pen speed and number are requested
- */
 bool HPGL_PLOTTER::StartPlot()
 {
     wxASSERT( m_outputFile );
@@ -269,9 +267,6 @@ bool HPGL_PLOTTER::StartPlot()
 }
 
 
-/**
- * HPGL end of plot: sort and emit graphics, pen return and release
- */
 bool HPGL_PLOTTER::EndPlot()
 {
     wxASSERT( m_outputFile );
@@ -368,13 +363,14 @@ bool HPGL_PLOTTER::EndPlot()
             {
                 loc = item.loc_end;
             }
+
             fputs( "\n", m_outputFile );
         }
     }
 
     fputs( "PU;PA;SP0;\n", m_outputFile );
     fclose( m_outputFile );
-    m_outputFile = NULL;
+    m_outputFile = nullptr;
     return true;
 }
 
@@ -384,6 +380,7 @@ void HPGL_PLOTTER::SetPenDiameter( double diameter )
     penDiameter = diameter;
 }
 
+
 void HPGL_PLOTTER::Rect( const wxPoint& p1, const wxPoint& p2, FILL_TYPE fill, int width )
 {
     wxASSERT( m_outputFile );
@@ -406,9 +403,7 @@ void HPGL_PLOTTER::Rect( const wxPoint& p1, const wxPoint& p2, FILL_TYPE fill, i
 }
 
 
-// HPGL circle
-void HPGL_PLOTTER::Circle( const wxPoint& centre, int diameter, FILL_TYPE fill,
-                           int width )
+void HPGL_PLOTTER::Circle( const wxPoint& centre, int diameter, FILL_TYPE fill, int width )
 {
     wxASSERT( m_outputFile );
     double radius = userToDeviceSize( diameter / 2 );
@@ -454,12 +449,8 @@ void HPGL_PLOTTER::Circle( const wxPoint& centre, int diameter, FILL_TYPE fill,
 }
 
 
-/**
- * HPGL polygon:
- */
-
-void HPGL_PLOTTER::PlotPoly( const std::vector<wxPoint>& aCornerList,
-                             FILL_TYPE aFill, int aWidth, void * aData )
+void HPGL_PLOTTER::PlotPoly( const std::vector<wxPoint>& aCornerList, FILL_TYPE aFill,
+                             int aWidth, void* aData )
 {
     if( aCornerList.size() <= 1 )
         return;
@@ -551,9 +542,6 @@ void HPGL_PLOTTER::PenTo( const wxPoint& pos, char plume )
 }
 
 
-/**
- * HPGL supports dashed lines
- */
 void HPGL_PLOTTER::SetDash( PLOT_DASH_TYPE dashed )
 {
     dashType = dashed;
@@ -579,14 +567,6 @@ void HPGL_PLOTTER::ThickSegment( const wxPoint& start, const wxPoint& end,
 }
 
 
-/* Plot an arc:
- * Center = center coord
- * Stangl, endAngle = angle of beginning and end
- * Radius = radius of the arc
- * Command
- * PU PY x, y; PD start_arc_X AA, start_arc_Y, angle, NbSegm; PU;
- * Or PU PY x, y; PD start_arc_X AA, start_arc_Y, angle, PU;
- */
 void HPGL_PLOTTER::Arc( const wxPoint& centre, double StAngle, double EndAngle, int radius,
                         FILL_TYPE fill, int width )
 {
@@ -637,8 +617,6 @@ void HPGL_PLOTTER::Arc( const wxPoint& centre, double StAngle, double EndAngle,
 }
 
 
-/* Plot oval pad.
- */
 void HPGL_PLOTTER::FlashPadOval( const wxPoint& pos, const wxSize& aSize, double orient,
                                  OUTLINE_MODE trace_mode, void* aData )
 {
@@ -646,9 +624,7 @@ void HPGL_PLOTTER::FlashPadOval( const wxPoint& pos, const wxSize& aSize, double
     int     deltaxy, cx, cy;
     wxSize  size( aSize );
 
-    /* The pad will be drawn as an oblong shape with size.y > size.x
-     * (Oval vertical orientation 0)
-     */
+    // The pad will be drawn as an oblong shape with size.y > size.x (Oval vertical orientation 0).
     if( size.x > size.y )
     {
         std::swap( size.x, size.y );
@@ -675,8 +651,6 @@ void HPGL_PLOTTER::FlashPadOval( const wxPoint& pos, const wxSize& aSize, double
 }
 
 
-/* Plot round pad or via.
- */
 void HPGL_PLOTTER::FlashPadCircle( const wxPoint& pos, int diametre,
                                    OUTLINE_MODE trace_mode, void* aData )
 {
@@ -759,8 +733,8 @@ void HPGL_PLOTTER::FlashPadRect( const wxPoint& pos, const wxSize& padsize,
 
 
 void HPGL_PLOTTER::FlashPadRoundRect( const wxPoint& aPadPos, const wxSize& aSize,
-                                        int aCornerRadius, double aOrient,
-                                        OUTLINE_MODE aTraceMode, void* aData )
+                                      int aCornerRadius, double aOrient,
+                                      OUTLINE_MODE aTraceMode, void* aData )
 {
     SHAPE_POLY_SET outline;
 
@@ -841,9 +815,8 @@ void HPGL_PLOTTER::FlashPadTrapez( const wxPoint& aPadPos, const wxPoint* aCorne
 }
 
 
-void HPGL_PLOTTER::FlashRegularPolygon( const wxPoint& aShapePos,
-                            int aRadius, int aCornerCount,
-                            double aOrient, OUTLINE_MODE aTraceMode, void* aData )
+void HPGL_PLOTTER::FlashRegularPolygon( const wxPoint& aShapePos, int aRadius, int aCornerCount,
+                                        double aOrient, OUTLINE_MODE aTraceMode, void* aData )
 {
     // Do nothing
     wxASSERT( 0 );
@@ -884,6 +857,7 @@ bool HPGL_PLOTTER::startOrAppendItem( DPOINT location, wxString const& content )
     }
 }
 
+
 void HPGL_PLOTTER::sortItems( std::list<HPGL_ITEM>& items )
 {
     if( items.size() < 2 )
@@ -932,6 +906,7 @@ void HPGL_PLOTTER::sortItems( std::list<HPGL_ITEM>& items )
             }
 
             double const dist = dpoint_dist( last_item.loc_end, search_it->loc_start );
+
             if( dist < best_dist )
             {
                 best_it   = search_it;
@@ -948,6 +923,7 @@ void HPGL_PLOTTER::sortItems( std::list<HPGL_ITEM>& items )
     items.splice( items.begin(), target );
 }
 
+
 const char* HPGL_PLOTTER::lineTypeCommand( PLOT_DASH_TYPE linetype )
 {
     switch( linetype )
@@ -967,6 +943,7 @@ const char* HPGL_PLOTTER::lineTypeCommand( PLOT_DASH_TYPE linetype )
     }
 }
 
+
 static double dpoint_dist( DPOINT a, DPOINT b )
 {
     DPOINT diff = a - b;
diff --git a/common/plotters/PDF_plotter.cpp b/common/plotters/PDF_plotter.cpp
index f36167ccbb..4ee3913b90 100644
--- a/common/plotters/PDF_plotter.cpp
+++ b/common/plotters/PDF_plotter.cpp
@@ -7,7 +7,7 @@
  * This program source code file is part of KiCad, a free EDA CAD application.
  *
  * Copyright (C) 1992-2012 Lorenzo Marcantonio, l.marcantonio@logossrl.com
- * Copyright (C) 1992-2020 KiCad Developers, see AUTHORS.txt for contributors.
+ * Copyright (C) 1992-2021 KiCad Developers, see AUTHORS.txt for contributors.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -123,7 +123,7 @@ bool PDF_PLOTTER::OpenFile( const wxString& aFullFilename )
 
 
 void PDF_PLOTTER::SetViewport( const wxPoint& aOffset, double aIusPerDecimil,
-                              double aScale, bool aMirror )
+                               double aScale, bool aMirror )
 {
     m_plotMirror    = aMirror;
     m_plotOffset    = aOffset;
@@ -162,8 +162,7 @@ void PDF_PLOTTER::SetCurrentLineWidth( int aWidth, void* aData )
 void PDF_PLOTTER::emitSetRGBColor( double r, double g, double b )
 {
     wxASSERT( workFile );
-    fprintf( workFile, "%g %g %g rg %g %g %g RG\n",
-             r, g, b, r, g, b );
+    fprintf( workFile, "%g %g %g rg %g %g %g RG\n", r, g, b, r, g, b );
 }
 
 
@@ -257,7 +256,7 @@ void PDF_PLOTTER::Circle( const wxPoint& pos, int diametre, FILL_TYPE aFill, int
 
 
 void PDF_PLOTTER::Arc( const wxPoint& centre, double StAngle, double EndAngle, int radius,
-                      FILL_TYPE fill, int width )
+                       FILL_TYPE fill, int width )
 {
     wxASSERT( workFile );
 
@@ -282,6 +281,7 @@ void PDF_PLOTTER::Arc( const wxPoint& centre, double StAngle, double EndAngle, i
     start.y = centre.y + KiROUND( sindecideg( radius, -StAngle ) );
     DPOINT pos_dev = userToDeviceCoordinates( start );
     fprintf( workFile, "%g %g m ", pos_dev.x, pos_dev.y );
+
     for( int ii = StAngle + delta; ii < EndAngle; ii += delta )
     {
         end.x = centre.x + KiROUND( cosdecideg( radius, -ii ) );
@@ -310,7 +310,7 @@ void PDF_PLOTTER::Arc( const wxPoint& centre, double StAngle, double EndAngle, i
 
 
 void PDF_PLOTTER::PlotPoly( const std::vector< wxPoint >& aCornerList,
-                           FILL_TYPE aFill, int aWidth, void * aData )
+                            FILL_TYPE aFill, int aWidth, void* aData )
 {
     wxASSERT( workFile );
 
@@ -363,19 +363,16 @@ void PDF_PLOTTER::PenTo( const wxPoint& pos, char plume )
 }
 
 
-void PDF_PLOTTER::PlotImage( const wxImage & aImage, const wxPoint& aPos,
-                            double aScaleFactor )
+void PDF_PLOTTER::PlotImage( const wxImage & aImage, const wxPoint& aPos, double aScaleFactor )
 {
     wxASSERT( workFile );
     wxSize pix_size( aImage.GetWidth(), aImage.GetHeight() );
 
     // Requested size (in IUs)
-    DPOINT drawsize( aScaleFactor * pix_size.x,
-                     aScaleFactor * pix_size.y );
+    DPOINT drawsize( aScaleFactor * pix_size.x, aScaleFactor * pix_size.y );
 
     // calculate the bitmap start position
-    wxPoint start( aPos.x - drawsize.x / 2,
-                   aPos.y + drawsize.y / 2);
+    wxPoint start( aPos.x - drawsize.x / 2, aPos.y + drawsize.y / 2);
 
     DPOINT dev_start = userToDeviceCoordinates( start );
 
@@ -390,9 +387,9 @@ void PDF_PLOTTER::PlotImage( const wxImage & aImage, const wxPoint& aPos,
        4) profit
      */
     fprintf( workFile, "q %g 0 0 %g %g %g cm\n", // Step 1
-            userToDeviceSize( drawsize.x ),
-            userToDeviceSize( drawsize.y ),
-            dev_start.x, dev_start.y );
+             userToDeviceSize( drawsize.x ),
+             userToDeviceSize( drawsize.y ),
+             dev_start.x, dev_start.y );
 
     /* An inline image is a cross between a dictionary and a stream.
        A real ugly construct (compared with the elegance of the PDF
@@ -756,8 +753,7 @@ bool PDF_PLOTTER::EndPlot()
     int infoDictHandle = startPdfObject();
     char date_buf[250];
     time_t ltime = time( NULL );
-    strftime( date_buf, 250, "D:%Y%m%d%H%M%S",
-              localtime( &ltime ) );
+    strftime( date_buf, 250, "D:%Y%m%d%H%M%S", localtime( &ltime ) );
 
     if( m_title.IsEmpty() )
     {
@@ -822,7 +818,7 @@ bool PDF_PLOTTER::EndPlot()
 
 
 void PDF_PLOTTER::Text( const wxPoint&              aPos,
-                        const COLOR4D               aColor,
+                        const COLOR4D&              aColor,
                         const wxString&             aText,
                         double                      aOrient,
                         const wxSize&               aSize,
diff --git a/common/plotters/PS_plotter.cpp b/common/plotters/PS_plotter.cpp
index 32c777abf7..0c898b1cb0 100644
--- a/common/plotters/PS_plotter.cpp
+++ b/common/plotters/PS_plotter.cpp
@@ -2,7 +2,7 @@
  * This program source code file is part of KiCad, a free EDA CAD application.
  *
  * Copyright (C) 2017 Jean-Pierre Charras, jp.charras at wanadoo.fr
- * Copyright (C) 2020 KiCad Developers, see AUTHORS.txt for contributors.
+ * Copyright (C) 2020-2021 KiCad Developers, see AUTHORS.txt for contributors.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -46,6 +46,7 @@ extern const double hvbo_widths[256];
 
 const double PSLIKE_PLOTTER::postscriptTextAscent = 0.718;
 
+
 // return a id used to select a ps macro (see StartPlot() ) from a FILL_TYPE
 // fill mode, for arc, rect, circle and poly draw primitives
 static int getFillId( FILL_TYPE aFill )
@@ -60,9 +61,7 @@ static int getFillId( FILL_TYPE aFill )
 }
 
 
-// Common routines for PostScript-like plotting engines
-
-void PSLIKE_PLOTTER::SetColor( COLOR4D color )
+void PSLIKE_PLOTTER::SetColor( const COLOR4D& color )
 {
     if( m_colorMode )
     {
@@ -112,7 +111,7 @@ void PSLIKE_PLOTTER::FlashPadOval( const wxPoint& aPadPos, const wxSize& aSize,
 
     if( aTraceMode == FILLED )
         ThickSegment( wxPoint( aPadPos.x + x0, aPadPos.y + y0 ),
-                      wxPoint( aPadPos.x + x1, aPadPos.y + y1 ), size.x, aTraceMode, NULL );
+                      wxPoint( aPadPos.x + x1, aPadPos.y + y1 ), size.x, aTraceMode, nullptr );
     else
         sketchOval( aPadPos, size, aPadOrient, -1 );
 }
@@ -122,7 +121,9 @@ void PSLIKE_PLOTTER::FlashPadCircle( const wxPoint& aPadPos, int aDiameter,
                                      OUTLINE_MODE aTraceMode, void* aData )
 {
     if( aTraceMode == FILLED )
+    {
         Circle( aPadPos, aDiameter, FILL_TYPE::FILLED_SHAPE, 0 );
+    }
     else    // Plot a ring:
     {
         SetCurrentLineWidth( USE_DEFAULT_LINE_WIDTH );
@@ -195,7 +196,9 @@ void PSLIKE_PLOTTER::FlashPadRoundRect( const wxPoint& aPadPos, const wxSize& aS
     wxSize size( aSize );
 
     if( aTraceMode == FILLED )
+    {
         SetCurrentLineWidth( 0 );
+    }
     else
     {
         SetCurrentLineWidth( USE_DEFAULT_LINE_WIDTH );
@@ -231,7 +234,9 @@ void PSLIKE_PLOTTER::FlashPadCustom( const wxPoint& aPadPos, const wxSize& aSize
     wxSize size( aSize );
 
     if( aTraceMode == FILLED )
+    {
         SetCurrentLineWidth( 0 );
+    }
     else
     {
         SetCurrentLineWidth( USE_DEFAULT_LINE_WIDTH );
@@ -304,9 +309,8 @@ void PSLIKE_PLOTTER::FlashPadTrapez( const wxPoint& aPadPos, const wxPoint *aCor
 }
 
 
-void PSLIKE_PLOTTER::FlashRegularPolygon( const wxPoint& aShapePos,
-                            int aRadius, int aCornerCount,
-                            double aOrient, OUTLINE_MODE aTraceMode, void* aData )
+void PSLIKE_PLOTTER::FlashRegularPolygon( const wxPoint& aShapePos, int aRadius, int aCornerCount,
+                                          double aOrient, OUTLINE_MODE aTraceMode, void* aData )
 {
     // Do nothing
     wxASSERT( 0 );
@@ -352,12 +356,6 @@ std::string PSLIKE_PLOTTER::encodeStringForPlotter( const wxString& aUnicode )
 }
 
 
-/**
- * Sister function for the GraphicTextWidth in drawtxt.cpp
- * Does the same processing (i.e. calculates a text string width) but
- * using postscript metrics for the Helvetica font (optionally used for
- * PS and PDF plotting
- */
 int PSLIKE_PLOTTER::returnPostscriptTextWidth( const wxString& aText, int aXSize,
                                                bool aItalic, bool aBold )
 {
@@ -381,12 +379,6 @@ int PSLIKE_PLOTTER::returnPostscriptTextWidth( const wxString& aText, int aXSize
 }
 
 
-/**
- * Computes the x coordinates for the overlining in a string of text.
- * Fills the passed vector with couples of (start, stop) values to be
- * used in the text coordinate system (use computeTextParameters to
- * obtain the parameters to establish such a system)
- */
 void PSLIKE_PLOTTER::postscriptOverlinePositions( const wxString& aText, int aXSize,
                                                   bool aItalic, bool aBold,
                                                   std::vector<int> *pos_pairs )
@@ -417,8 +409,9 @@ void PSLIKE_PLOTTER::postscriptOverlinePositions( const wxString& aText, int aXS
         pos_pairs->push_back( KiROUND( aXSize * tally / postscriptTextAscent ) );
 }
 
+
 void PS_PLOTTER::SetViewport( const wxPoint& aOffset, double aIusPerDecimil,
-                  double aScale, bool aMirror )
+                              double aScale, bool aMirror )
 {
     wxASSERT( !m_outputFile );
     m_plotMirror = aMirror;
@@ -433,12 +426,6 @@ void PS_PLOTTER::SetViewport( const wxPoint& aOffset, double aIusPerDecimil,
 }
 
 
-/** This is the core for postscript/PDF text alignment
- * It computes the transformation matrix to generate a user space
- * system aligned with the text. Even the PS uses the concat
- * operator to simplify PDF generation (concat is everything PDF
- * has to modify the CTM. Lots of parameters, both in and out.
- */
 void PSLIKE_PLOTTER::computeTextParameters( const wxPoint&           aPos,
                                             const wxString&          aText,
                                             int                      aOrient,
@@ -530,8 +517,6 @@ void PSLIKE_PLOTTER::computeTextParameters( const wxPoint&           aPos,
 }
 
 
-/* Set the current line width (in IUs) for the next plot
- */
 void PS_PLOTTER::SetCurrentLineWidth( int aWidth, void* aData )
 {
     wxASSERT( m_outputFile );
@@ -561,9 +546,6 @@ void PS_PLOTTER::emitSetRGBColor( double r, double g, double b )
 }
 
 
-/**
- * PostScript supports dashed lines
- */
 void PS_PLOTTER::SetDash( PLOT_DASH_TYPE dashed )
 {
     switch( dashed )
@@ -668,11 +650,7 @@ void PS_PLOTTER::PlotPoly( const std::vector< wxPoint >& aCornerList,
 }
 
 
-/**
- * PostScript-likes at the moment are the only plot engines supporting bitmaps...
- */
-void PS_PLOTTER::PlotImage( const wxImage & aImage, const wxPoint& aPos,
-                            double aScaleFactor )
+void PS_PLOTTER::PlotImage( const wxImage& aImage, const wxPoint& aPos, double aScaleFactor )
 {
     wxSize pix_size;                // size of the bitmap in pixels
     pix_size.x = aImage.GetWidth();
@@ -712,6 +690,7 @@ void PS_PLOTTER::PlotImage( const wxImage & aImage, const wxPoint& aPos,
         fputs( "false 3 colorimage\n", m_outputFile );
     else
         fputs( "image\n", m_outputFile );
+
     // Single data source, 3 colors, Output RGB data (hexadecimal)
     // (or the same downscaled to gray)
     int jj = 0;
@@ -810,19 +789,6 @@ void PS_PLOTTER::PenTo( const wxPoint& pos, char plume )
 }
 
 
-/**
- * The code within this function (and the CloseFilePS function)
- * creates postscript files whose contents comply with Adobe's
- * Document Structuring Convention, as documented by assorted
- * details described within the following URLs:
- *
- * http://en.wikipedia.org/wiki/Document_Structuring_Conventions
- * http://partners.adobe.com/public/developer/en/ps/5001.DSC_Spec.pdf
- *
- *
- * BBox is the boundary box (position and size of the "client rectangle"
- * for drawings (page - margins) in mils (0.001 inch)
- */
 bool PS_PLOTTER::StartPlot()
 {
     wxASSERT( m_outputFile );
@@ -878,10 +844,10 @@ bool PS_PLOTTER::StartPlot()
     "/KicadFont-Oblique /Helvetica-Oblique reencodefont definefont pop\n",
     "/KicadFont-BoldOblique /Helvetica-BoldOblique reencodefont definefont pop\n",
     "%%EndProlog\n",
-    NULL
+    nullptr
     };
 
-    time_t time1970 = time( NULL );
+    time_t time1970 = time( nullptr );
 
     fputs( "%!PS-Adobe-3.0\n", m_outputFile );    // Print header
 
@@ -947,7 +913,7 @@ bool PS_PLOTTER::StartPlot()
 
     // Now specify various other details.
 
-    for( int ii = 0; PSMacro[ii] != NULL; ii++ )
+    for( int ii = 0; PSMacro[ii] != nullptr; ii++ )
     {
         fputs( PSMacro[ii], m_outputFile );
     }
@@ -987,7 +953,7 @@ bool PS_PLOTTER::EndPlot()
            "grestore\n"
            "%%EOF\n", m_outputFile );
     fclose( m_outputFile );
-    m_outputFile = NULL;
+    m_outputFile = nullptr;
 
     return true;
 }
@@ -995,7 +961,7 @@ bool PS_PLOTTER::EndPlot()
 
 
 void PS_PLOTTER::Text( const wxPoint&       aPos,
-                const COLOR4D               aColor,
+                const COLOR4D&              aColor,
                 const wxString&             aText,
                 double                      aOrient,
                 const wxSize&               aSize,
@@ -1061,6 +1027,7 @@ const double hv_widths[256] = {
     0.611, 0.556, 0.556, 0.556, 0.556, 0.500, 0.556, 0.500
 };
 
+
 /**
  * Character widths for Helvetica-Bold
  */
@@ -1099,6 +1066,7 @@ const double hvb_widths[256] = {
     0.611, 0.611, 0.611, 0.611, 0.611, 0.556, 0.611, 0.556
 };
 
+
 /**
  * Character widths for Helvetica-Oblique
  */
@@ -1137,6 +1105,7 @@ const double hvo_widths[256] = {
     0.611, 0.556, 0.556, 0.556, 0.556, 0.500, 0.556, 0.500
 };
 
+
 /**
  * Character widths for Helvetica-BoldOblique
  */
diff --git a/common/plotters/SVG_plotter.cpp b/common/plotters/SVG_plotter.cpp
index 90679e78c1..4bad880679 100644
--- a/common/plotters/SVG_plotter.cpp
+++ b/common/plotters/SVG_plotter.cpp
@@ -7,7 +7,7 @@
  * This program source code file is part of KiCad, a free EDA CAD application.
  *
  * Copyright (C) 2020 Jean-Pierre Charras, jp.charras at wanadoo.fr
- * Copyright (C) 1992-2020 KiCad Developers, see AUTHORS.txt for contributors.
+ * Copyright (C) 1992-2021 KiCad Developers, see AUTHORS.txt for contributors.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -106,8 +106,7 @@
 
 
 /**
- * Function XmlEsc
- * translates '<' to "&lt;", '>' to "&gt;" and so on, according to the spec:
+ * Translates '<' to "&lt;", '>' to "&gt;" and so on, according to the spec:
  * http://www.w3.org/TR/2000/WD-xml-c14n-20000119.html#charescaping
  * May be moved to a library if needed generally, but not expecting that.
  */
@@ -171,7 +170,7 @@ SVG_PLOTTER::SVG_PLOTTER()
     m_brush_rgb_color = 0;       // current color value (black)
     m_dashed          = PLOT_DASH_TYPE::SOLID;
     m_useInch         = true; // decimils is the default
-    m_precision       = 4;    // because there where used before it was changable
+    m_precision       = 4;    // because there where used before it was changeable
 }
 
 
@@ -190,7 +189,7 @@ void SVG_PLOTTER::SetViewport( const wxPoint& aOffset, double aIusPerDecimil,
     m_paperSize.y *= 10.0 * aIusPerDecimil;
 
     // set iuPerDeviceUnit, in 0.1mils ( 2.54um )
-    // this was used before the format was changable, so we set is as default
+    // this was used before the format was changeable, so we set is as default
     SetSvgCoordinatesFormat( 4, true );
 }
 
@@ -208,7 +207,7 @@ void SVG_PLOTTER::SetSvgCoordinatesFormat( unsigned aResolution, bool aUseInches
 }
 
 
-void SVG_PLOTTER::SetColor( COLOR4D color )
+void SVG_PLOTTER::SetColor( const COLOR4D& color )
 {
     PSLIKE_PLOTTER::SetColor( color );
 
@@ -273,7 +272,8 @@ void SVG_PLOTTER::setSVGPlotStyle( bool aIsGroup, const std::string& aExtraStyle
         fprintf( m_outputFile, "stroke-dasharray:%f,%f;", GetDotMarkLenIU(), GetDashGapLenIU() );
         break;
     case PLOT_DASH_TYPE::DASHDOT:
-        fprintf( m_outputFile, "stroke-dasharray:%f,%f,%f,%f;", GetDashMarkLenIU(), GetDashGapLenIU(),
+        fprintf( m_outputFile, "stroke-dasharray:%f,%f,%f,%f;",
+                 GetDashMarkLenIU(), GetDashGapLenIU(),
                  GetDotMarkLenIU(), GetDashGapLenIU() );
         break;
     case PLOT_DASH_TYPE::DEFAULT:
@@ -299,8 +299,7 @@ void SVG_PLOTTER::setSVGPlotStyle( bool aIsGroup, const std::string& aExtraStyle
     fputs( "\n", m_outputFile );
 }
 
-/* Set the current line width (in IUs) for the next plot
- */
+
 void SVG_PLOTTER::SetCurrentLineWidth( int aWidth, void* aData )
 {
     if( aWidth == DO_NOT_SET_LINE_WIDTH )
@@ -344,9 +343,6 @@ void SVG_PLOTTER::EndBlock( void* aData )
 }
 
 
-/* initialize m_red, m_green, m_blue ( 0 ... 255)
- * from reduced values r, g ,b ( 0.0 to 1.0 )
- */
 void SVG_PLOTTER::emitSetRGBColor( double r, double g, double b )
 {
     int red     = (int) ( 255.0 * r );
@@ -366,9 +362,6 @@ void SVG_PLOTTER::emitSetRGBColor( double r, double g, double b )
 }
 
 
-/**
- * SVG supports dashed lines
- */
 void SVG_PLOTTER::SetDash( PLOT_DASH_TYPE dashed )
 {
     if( m_dashed != dashed )
@@ -398,7 +391,7 @@ void SVG_PLOTTER::Rect( const wxPoint& p1, const wxPoint& p2, FILL_TYPE fill, in
     setFillMode( fill );
     SetCurrentLineWidth( width );
 
-    // Rectangles having a 0 size value for height or width are just not drawn on Inscape,
+    // Rectangles having a 0 size value for height or width are just not drawn on Inkscape,
     // so use a line when happens.
     if( rect_dev.GetSize().x == 0.0 || rect_dev.GetSize().y == 0.0 )    // Draw a line
     {
@@ -444,7 +437,7 @@ void SVG_PLOTTER::Circle( const wxPoint& pos, int diametre, FILL_TYPE fill, int
 void SVG_PLOTTER::Arc( const wxPoint& centre, double StAngle, double EndAngle, int radius,
                        FILL_TYPE fill, int width )
 {
-    /* Draws an arc of a circle, centred on (xc,yc), with starting point
+    /* Draws an arc of a circle, centered on (xc,yc), with starting point
      *  (x1, y1) and ending at (x2, y2). The current pen is used for the outline
      *  and the current brush for filling the shape.
      *
@@ -523,7 +516,7 @@ void SVG_PLOTTER::Arc( const wxPoint& centre, double StAngle, double EndAngle, i
     // end point
     if( fill != FILL_TYPE::NO_FILL )
     {
-        // Filled arcs (in eeschema) consist of the pie wedge and a stroke only on the arc
+        // Filled arcs (in Eeschema) consist of the pie wedge and a stroke only on the arc
         // This needs to be drawn in two steps.
         setFillMode( fill );
         SetCurrentLineWidth( 0 );
@@ -544,8 +537,8 @@ void SVG_PLOTTER::Arc( const wxPoint& centre, double StAngle, double EndAngle, i
 
 
 void SVG_PLOTTER::BezierCurve( const wxPoint& aStart, const wxPoint& aControl1,
-                           const wxPoint& aControl2, const wxPoint& aEnd,
-                           int aTolerance, int aLineThickness )
+                               const wxPoint& aControl2, const wxPoint& aEnd,
+                               int aTolerance, int aLineThickness )
 {
 #if 1
     setFillMode( FILL_TYPE::NO_FILL );
@@ -566,8 +559,8 @@ void SVG_PLOTTER::BezierCurve( const wxPoint& aStart, const wxPoint& aControl1,
 }
 
 
-void SVG_PLOTTER::PlotPoly( const std::vector<wxPoint>& aCornerList,
-                            FILL_TYPE aFill, int aWidth, void * aData )
+void SVG_PLOTTER::PlotPoly( const std::vector<wxPoint>& aCornerList, FILL_TYPE aFill,
+                            int aWidth, void* aData )
 {
     if( aCornerList.size() <= 1 )
         return;
@@ -601,9 +594,11 @@ void SVG_PLOTTER::PlotPoly( const std::vector<wxPoint>& aCornerList,
         fprintf( m_outputFile, "%f,%f\n", pos.x, pos.y );
     }
 
-    // If the cornerlist ends where it begins, then close the poly
+    // If the corner list ends where it begins, then close the poly
     if( aCornerList.front() == aCornerList.back() )
+    {
         fprintf( m_outputFile, "Z\" /> \n" );
+    }
     else
     {
         pos = userToDeviceCoordinates( aCornerList.back() );
@@ -612,23 +607,17 @@ void SVG_PLOTTER::PlotPoly( const std::vector<wxPoint>& aCornerList,
 }
 
 
-/**
- * PostScript-likes at the moment are the only plot engines supporting bitmaps...
- */
-void SVG_PLOTTER::PlotImage( const wxImage& aImage, const wxPoint& aPos,
-                             double aScaleFactor )
+void SVG_PLOTTER::PlotImage( const wxImage& aImage, const wxPoint& aPos, double aScaleFactor )
 {
     wxSize pix_size( aImage.GetWidth(), aImage.GetHeight() );
 
     // Requested size (in IUs)
-    DPOINT drawsize( aScaleFactor * pix_size.x,
-                     aScaleFactor * pix_size.y );
+    DPOINT drawsize( aScaleFactor * pix_size.x, aScaleFactor * pix_size.y );
 
     // calculate the bitmap start position
-    wxPoint start( aPos.x - drawsize.x / 2,
-                   aPos.y - drawsize.y / 2);
+    wxPoint start( aPos.x - drawsize.x / 2, aPos.y - drawsize.y / 2);
 
-    // Rectangles having a 0 size value for height or width are just not drawn on Inscape,
+    // Rectangles having a 0 size value for height or width are just not drawn on Inkscape,
     // so use a line when happens.
     if( drawsize.x == 0.0 || drawsize.y == 0.0 )    // Draw a line
     {
@@ -648,8 +637,7 @@ void SVG_PLOTTER::PlotImage( const wxImage& aImage, const wxPoint& aPos,
 
         fprintf( m_outputFile,
                  "<image x=\"%f\" y=\"%f\" xlink:href=\"data:image/png;base64,",
-                 userToDeviceSize( start.x ), userToDeviceSize( start.y )
-                 );
+                 userToDeviceSize( start.x ), userToDeviceSize( start.y ) );
 
         for( size_t i = 0; i < encoded.size(); i++ )
         {
@@ -684,7 +672,7 @@ void SVG_PLOTTER::PenTo( const wxPoint& pos, char plume )
     {
         DPOINT pos_dev = userToDeviceCoordinates( pos );
 
-        // Ensure we do not use a fill mode when moving tne pen,
+        // Ensure we do not use a fill mode when moving the pen,
         // in SVG mode (i;e. we are plotting only basic lines, not a filled area
         if( m_fillMode != FILL_TYPE::NO_FILL )
         {
@@ -692,14 +680,12 @@ void SVG_PLOTTER::PenTo( const wxPoint& pos, char plume )
             setSVGPlotStyle();
         }
 
-        fprintf( m_outputFile, "<path d=\"M%d %d\n",
-                 (int) pos_dev.x, (int) pos_dev.y );
+        fprintf( m_outputFile, "<path d=\"M%d %d\n", (int) pos_dev.x, (int) pos_dev.y );
     }
     else if( m_penState != plume || pos != m_penLastpos )
     {
         DPOINT pos_dev = userToDeviceCoordinates( pos );
-        fprintf( m_outputFile, "L%d %d\n",
-                 (int) pos_dev.x, (int) pos_dev.y );
+        fprintf( m_outputFile, "L%d %d\n", (int) pos_dev.x, (int) pos_dev.y );
     }
 
     m_penState    = plume;
@@ -707,10 +693,6 @@ void SVG_PLOTTER::PenTo( const wxPoint& pos, char plume )
 }
 
 
-/**
- * The code within this function
- * creates SVG files header
- */
 bool SVG_PLOTTER::StartPlot()
 {
     wxASSERT( m_outputFile );
@@ -726,11 +708,11 @@ bool SVG_PLOTTER::StartPlot()
         "  xmlns=\"http://www.w3.org/2000/svg\"\n",
         "  xmlns:xlink=\"http://www.w3.org/1999/xlink\"\n",
         "  version=\"1.1\"\n",
-        NULL
+        nullptr
     };
 
     // Write header.
-    for( int ii = 0; header[ii] != NULL; ii++ )
+    for( int ii = 0; header[ii] != nullptr; ii++ )
     {
         fputs( header[ii], m_outputFile );
     }
@@ -740,17 +722,18 @@ bool SVG_PLOTTER::StartPlot()
     fprintf( m_outputFile, "  width=\"%fcm\" height=\"%fcm\" viewBox=\"%d %d %d %d\">\n",
              (double) m_paperSize.x / m_IUsPerDecimil * 2.54 / 10000,
              (double) m_paperSize.y / m_IUsPerDecimil * 2.54 / 10000, origin.x, origin.y,
-             (int) ( m_paperSize.x * m_iuPerDeviceUnit ), (int) ( m_paperSize.y * m_iuPerDeviceUnit) );
+             (int) ( m_paperSize.x * m_iuPerDeviceUnit ),
+             (int) ( m_paperSize.y * m_iuPerDeviceUnit) );
 
     // Write title
     char    date_buf[250];
-    time_t  ltime = time( NULL );
-    strftime( date_buf, 250, "%Y/%m/%d %H:%M:%S",
-              localtime( &ltime ) );
+    time_t  ltime = time( nullptr );
+    strftime( date_buf, 250, "%Y/%m/%d %H:%M:%S", localtime( &ltime ) );
 
     fprintf( m_outputFile,
              "<title>SVG Picture created as %s date %s </title>\n",
              TO_UTF8( XmlEsc( wxFileName( m_filename ).GetFullName() ) ), date_buf );
+
     // End of header
     fprintf( m_outputFile, "  <desc>Picture generated by %s </desc>\n",
              TO_UTF8( XmlEsc( m_creator ) ) );
@@ -772,14 +755,14 @@ bool SVG_PLOTTER::EndPlot()
 {
     fputs( "</g> \n</svg>\n", m_outputFile );
     fclose( m_outputFile );
-    m_outputFile = NULL;
+    m_outputFile = nullptr;
 
     return true;
 }
 
 
 void SVG_PLOTTER::Text( const wxPoint&              aPos,
-                        const COLOR4D               aColor,
+                        const COLOR4D&              aColor,
                         const wxString&             aText,
                         double                      aOrient,
                         const wxSize&               aSize,
@@ -829,7 +812,7 @@ void SVG_PLOTTER::Text( const wxPoint&              aPos,
 
     wxSize text_size;
     // aSize.x or aSize.y is < 0 for mirrored texts.
-    // The actual text size value is the absolue value
+    // The actual text size value is the absolute value
     text_size.x = std::abs( GraphicTextWidth( aText, aSize, aItalic, aWidth ) );
     text_size.y = std::abs( aSize.x * 4/3 ); // Hershey font height to em size conversion
     DPOINT anchor_pos_dev = userToDeviceCoordinates( aPos );
diff --git a/common/plotters/plotter_dxf.h b/common/plotters/plotter_dxf.h
index c6051d283a..132cd8dfd2 100644
--- a/common/plotters/plotter_dxf.h
+++ b/common/plotters/plotter_dxf.h
@@ -1,7 +1,7 @@
 /*
  * This program source code file is part of KiCad, a free EDA CAD application.
  *
- * Copyright (C) 2016-2020 KiCad Developers, see AUTHORS.txt for contributors.
+ * Copyright (C) 2016-2021 KiCad Developers, see AUTHORS.txt for contributors.
  *
  * This program is free software: you can redistribute it and/or modify it
  * under the terms of the GNU General Public License as published by the
@@ -61,37 +61,80 @@ public:
             m_textAsLines = ( mode != PLOT_TEXT_MODE::NATIVE );
     }
 
+    /**
+     * Opens the DXF plot with a skeleton header.
+     */
     virtual bool StartPlot() override;
     virtual bool EndPlot() override;
 
     // For now we don't use 'thick' primitives, so no line width
-    virtual void SetCurrentLineWidth( int width, void* aData = NULL ) override
+    virtual void SetCurrentLineWidth( int width, void* aData = nullptr ) override
     {
         m_currentPenWidth = 0;
     }
 
     virtual void SetDash( PLOT_DASH_TYPE dashed ) override;
 
-    virtual void SetColor( COLOR4D color ) override;
+    /**
+     * The DXF exporter handles 'colors' as layers...
+     */
+    virtual void SetColor( const COLOR4D& color ) override;
 
+    /**
+     * Set the scale/position for the DXF plot.
+     *
+     * The DXF engine doesn't support line widths and mirroring. The output
+     * coordinate system is in the first quadrant (in mm).
+     */
     virtual void SetViewport( const wxPoint& aOffset, double aIusPerDecimil,
-                  double aScale, bool aMirror ) override;
+                              double aScale, bool aMirror ) override;
+
+    /**
+     * DXF rectangle: fill not supported.
+     */
     virtual void Rect( const wxPoint& p1, const wxPoint& p2, FILL_TYPE fill,
                        int width = USE_DEFAULT_LINE_WIDTH ) override;
+
+    /**
+     * DXF circle: full functionality; it even does 'fills' drawing a
+     * circle with a dual-arc polyline wide as the radius.
+     *
+     * I could use this trick to do other filled primitives.
+     */
     virtual void Circle( const wxPoint& pos, int diametre, FILL_TYPE fill,
                          int width = USE_DEFAULT_LINE_WIDTH ) override;
-    virtual void PlotPoly( const std::vector< wxPoint >& aCornerList,
-                           FILL_TYPE aFill, int aWidth = USE_DEFAULT_LINE_WIDTH, void * aData = NULL ) override;
+
+    /**
+     * DXF polygon: doesn't fill it but at least it close the filled ones
+     * DXF does not know thick outline.
+     *
+     * It does not know thick segments, therefore filled polygons with thick outline
+     * are converted to inflated polygon by aWidth/2.
+     */
+    virtual void PlotPoly( const std::vector< wxPoint >& aCornerList, FILL_TYPE aFill,
+                           int aWidth = USE_DEFAULT_LINE_WIDTH, void* aData = nullptr ) override;
     virtual void ThickSegment( const wxPoint& start, const wxPoint& end, int width,
                                OUTLINE_MODE tracemode, void* aData ) override;
     virtual void Arc( const wxPoint& centre, double StAngle, double EndAngle,
                       int rayon, FILL_TYPE fill, int width = USE_DEFAULT_LINE_WIDTH ) override;
     virtual void PenTo( const wxPoint& pos, char plume ) override;
 
+    /**
+     * DXF round pad: always done in sketch mode; it could be filled but it isn't
+     * pretty if other kinds of pad aren't...
+     */
     virtual void FlashPadCircle( const wxPoint& pos, int diametre,
                                  OUTLINE_MODE trace_mode, void* aData ) override;
+
+    /**
+     * DXF oval pad: always done in sketch mode.
+     */
     virtual void FlashPadOval( const wxPoint& pos, const wxSize& size, double orient,
                                OUTLINE_MODE trace_mode, void* aData ) override;
+
+    /**
+     * DXF rectangular pad: always done in sketch mode.
+     */
     virtual void FlashPadRect( const wxPoint& pos, const wxSize& size,
                                double orient, OUTLINE_MODE trace_mode, void* aData ) override;
     virtual void FlashPadRoundRect( const wxPoint& aPadPos, const wxSize& aSize,
@@ -100,13 +143,17 @@ public:
     virtual void FlashPadCustom( const wxPoint& aPadPos, const wxSize& aSize, double aOrient,
                                  SHAPE_POLY_SET* aPolygons,
                                  OUTLINE_MODE aTraceMode, void* aData ) override;
+
+    /**
+     * DXF trapezoidal pad: only sketch mode is supported.
+     */
     virtual void FlashPadTrapez( const wxPoint& aPadPos, const wxPoint *aCorners,
                                  double aPadOrient, OUTLINE_MODE aTraceMode, void* aData ) override;
     virtual void FlashRegularPolygon( const wxPoint& aShapePos, int aDiameter, int aCornerCount,
                             double aOrient, OUTLINE_MODE aTraceMode, void* aData ) override;
 
     virtual void Text( const wxPoint&              aPos,
-                       const COLOR4D               aColor,
+                       const COLOR4D&              aColor,
                        const wxString&             aText,
                        double                      aOrient,
                        const wxSize&               aSize,
@@ -116,7 +163,7 @@ public:
                        bool                        aItalic,
                        bool                        aBold,
                        bool                        aMultilineAllowed = false,
-                       void* aData = NULL ) override;
+                       void* aData = nullptr ) override;
 
 
     /**
diff --git a/common/plotters/plotter_gerber.h b/common/plotters/plotter_gerber.h
index 5f219d71d0..8a45f8eb8d 100644
--- a/common/plotters/plotter_gerber.h
+++ b/common/plotters/plotter_gerber.h
@@ -2,7 +2,7 @@
  * This program source code file is part of KiCad, a free EDA CAD application.
  *
  * Copyright (C) 2020 Jean-Pierre Charras, jp.charras at wanadoo.fr
- * Copyright (C) 2016-2020 KiCad Developers, see AUTHORS.txt for contributors.
+ * Copyright (C) 2016-2021 KiCad Developers, see AUTHORS.txt for contributors.
  *
  * This program is free software: you can redistribute it and/or modify it
  * under the terms of the GNU General Public License as published by the
@@ -51,23 +51,22 @@ public:
     }
 
     /**
-     * Function StartPlot
-     * Write GERBER header to file
-     * initialize global variable g_Plot_PlotOutputFile
+     * Write GERBER header to file initialize global variable g_Plot_PlotOutputFile.
      */
     virtual bool StartPlot() override;
     virtual bool EndPlot() override;
-    virtual void SetCurrentLineWidth( int width, void* aData = NULL ) override;
+    virtual void SetCurrentLineWidth( int width, void* aData = nullptr ) override;
 
-    // RS274X has no dashing, nor colours
+    // RS274X has no dashing, nor colors
     virtual void SetDash( PLOT_DASH_TYPE dashed ) override
     {
     }
 
-    virtual void SetColor( COLOR4D color ) override {}
+    virtual void SetColor( const COLOR4D& color ) override {}
+
     // Currently, aScale and aMirror are not used in gerber plotter
     virtual void SetViewport( const wxPoint& aOffset, double aIusPerDecimil,
-                          double aScale, bool aMirror ) override;
+                              double aScale, bool aMirror ) override;
 
     // Basic plot primitives
     virtual void Rect( const wxPoint& p1, const wxPoint& p2, FILL_TYPE fill,
@@ -96,17 +95,16 @@ public:
      * Gerber polygon: they can (and *should*) be filled with the
      * appropriate G36/G37 sequence
      */
-    virtual void PlotPoly( const std::vector< wxPoint >& aCornerList,
-                           FILL_TYPE aFill, int aWidth = USE_DEFAULT_LINE_WIDTH,
-                           void* aData = nullptr ) override;
+    virtual void PlotPoly( const std::vector< wxPoint >& aCornerList, FILL_TYPE aFill,
+                           int aWidth = USE_DEFAULT_LINE_WIDTH, void* aData = nullptr ) override;
 
     virtual void PlotPoly( const SHAPE_LINE_CHAIN& aCornerList, FILL_TYPE aFill,
-                           int aWidth = USE_DEFAULT_LINE_WIDTH, void * aData = NULL ) override;
+                           int aWidth = USE_DEFAULT_LINE_WIDTH, void* aData = nullptr ) override;
 
     virtual void PenTo( const wxPoint& pos, char plume ) override;
 
     virtual void Text( const wxPoint&              aPos,
-                       const COLOR4D               aColor,
+                       const COLOR4D&              aColor,
                        const wxString&             aText,
                        double                      aOrient,
                        const wxSize&               aSize,
@@ -116,7 +114,7 @@ public:
                        bool                        aItalic,
                        bool                        aBold,
                        bool                        aMultilineAllowed = false,
-                       void* aData = NULL ) override;
+                       void* aData = nullptr ) override;
 
     /**
      * Filled circular flashes are stored as apertures
@@ -144,146 +142,154 @@ public:
                             double aOrient, OUTLINE_MODE aTraceMode, void* aData ) override;
 
     /**
-     * flash a chamfered round rect pad.
-     * @param aShapePos = position of the pad shape
-     * @param aPadSize = size of the rectangle
-     * @param aCornerRadius = radius of rounded corners
-     * @param aChamferRatio = chamfer value (ratio < 0.5 between smallest size and chamfer)
-     * @param aChamferPositions = identifier of the corners to chamfer:
+     * Flash a chamfered round rect pad.
+     *
+     * @param aShapePos is the position of the pad shape.
+     * @param aPadSize is the size of the rectangle.
+     * @param aCornerRadius is the radius of rounded corners.
+     * @param aChamferRatio is the chamfer value (ratio < 0.5 between smallest size and chamfer).
+     * @param aChamferPositions is the identifier of the corners to chamfer:
      *  0 = no chamfer
      *  1 = TOP_LEFT
      *  2 = TOP_RIGHT
      *  4 = BOTTOM_LEFT
      *  8 = BOTTOM_RIGHT
-     * @param aPadOrient = rotation in 0.1 degrees of the shape
-     * @param aPlotMode = FILLED or SKETCH
-     * @param aData = a reference to Gerber attributes descr
+     * @param aPadOrient is the rotation in 0.1 degrees of the shape.
+     * @param aPlotMode is the drawing mode, FILLED or SKETCH.
+     * @param aData is the a reference to Gerber attributes descr.
      */
     void FlashPadChamferRoundRect( const wxPoint& aShapePos, const wxSize& aPadSize,
                                    int aCornerRadius, double aChamferRatio,
-                                   int aChamferPositions,
-                                   double aPadOrient, OUTLINE_MODE aPlotMode, void* aData );
+                                   int aChamferPositions, double aPadOrient,
+                                   OUTLINE_MODE aPlotMode, void* aData );
 
     /**
      * Plot a Gerber region: similar to PlotPoly but plot only filled polygon,
      * and add the TA.AperFunction if aData contains this attribute, and clear it
-     * after plotting
+     * after plotting.
      */
-    void PlotGerberRegion( const std::vector< wxPoint >& aCornerList,
-                           void * aData = NULL );
+    void PlotGerberRegion( const std::vector< wxPoint >& aCornerList, void* aData = nullptr );
 
-    void PlotGerberRegion( const SHAPE_LINE_CHAIN& aPoly,
-                           void * aData = NULL );
+    void PlotGerberRegion( const SHAPE_LINE_CHAIN& aPoly, void* aData = nullptr );
 
     /**
-     * Change the plot polarity and begin a new layer
-     * Used to 'scratch off' silk screen away from solder mask
+     * Change the plot polarity and begin a new layer.
+     *
+     * Used to 'scratch off' silk screen away from solder mask.
      */
     virtual void SetLayerPolarity( bool aPositive ) override;
 
     /**
-     * Function SetGerberCoordinatesFormat
-     * selection of Gerber units and resolution (number of digits in mantissa)
-     * @param aResolution = number of digits in mantissa of coordinate
-     *                      use 5 or 6 for mm and 6 or 7 for inches
-     *                      do not use value > 6 (mm) or > 7 (in) to avoid overflow
-     * @param aUseInches = true to use inches, false to use mm (default)
+     * Selection of Gerber units and resolution (number of digits in mantissa).
      *
-     * Should be called only after SetViewport() is called
+     * Should be called only after SetViewport() is called.
+     *
+     * @param aResolution is the number of digits in mantissa of coordinate
+     *                    use 5 or 6 for mm and 6 or 7 for inches
+     *                    do not use value > 6 (mm) or > 7 (in) to avoid overflow.
+     * @param aUseInches use true to use inches, false to use mm (default).
      */
     virtual void SetGerberCoordinatesFormat( int aResolution, bool aUseInches = false ) override;
 
     void UseX2format( bool aEnable ) { m_useX2format = aEnable; }
     void UseX2NetAttributes( bool aEnable ) { m_useNetAttributes = aEnable; }
 
-    /** Disable Aperture Macro (AM) command, only for broken Gerber Readers
-     * Regions will be used instead of AM shapes to draw complex shapes
-     * @param aDisable = true to disable Aperture Macro (AM) command.
+    /**
+     * Disable Aperture Macro (AM) command, only for broken Gerber Readers.
+     *
+     * Regions will be used instead of AM shapes to draw complex shapes.
+     *
+     * @param aDisable use true to disable Aperture Macro (AM) command.
      */
     void DisableApertMacros( bool aDisable ) { m_gerberDisableApertMacros = aDisable; }
 
     /**
-     * calling this function allows one to define the beginning of a group
-     * of drawing items (used in X2 format with netlist attributes)
-     * @param aData can define any parameter
+     * Calling this function allows one to define the beginning of a group
+     * of drawing items (used in X2 format with netlist attributes).
+     *
+     * @param aData can define any parameter.
      */
     virtual void StartBlock( void* aData ) override;
 
     /**
-     * calling this function allows one to define the end of a group of drawing
-     * items the group is started by StartBlock()
-     * (used in X2 format with netlist attributes)
+     * Define the end of a group of drawing items the group is started by StartBlock().
+     *
+     * Used in X2 format with netlist attributes.
+     *
      * @param aData can define any parameter
      */
     virtual void EndBlock( void* aData ) override;
 
-    /** Remove (clear) all attributes from object attributes dictionary (TO. and TA commands)
-     * similar to clearNetAttribute(), this is an unconditional reset of TO. and TA. attributes
+    /**
+     * Remove (clear) all attributes from object attributes dictionary (TO. and TA commands)
+     * similar to clearNetAttribute(), this is an unconditional reset of TO. and TA. attributes.
      */
     void ClearAllAttributes();
 
     /**
-     * @return a index to the aperture in aperture list which meets the size and type of tool
-     * if the aperture does not exist, it is created and entered in aperture list
-     * @param aSize = the size of tool
-     * @param aRadius = the radius used for some shapes tool (oval, roundrect macros)
-     * @param aRotDegree = the rotation of tool (primitives round, oval rect accept only 0.0)
-     * @param aType = the type ( shape ) of tool
-     * @param aApertureAttribute = an aperture attribute of the tool (a tool can have only one attribute)
-     * 0 = no specific attribute
+     * @param aSize is the size of tool.
+     * @param aRadius is the radius used for some shapes tool (oval, roundrect macros).
+     * @param aRotDegree is the rotation of tool (primitives round, oval rect accept only 0.0).
+     * @param aType is the type ( shape ) of tool.
+     * @param aApertureAttribute is an aperture attribute of the tool (a tool can have only one
+     *                           attribute) 0 = no specific attribute.
+     * @return an index to the aperture in aperture list which meets the size and type of tool
+     *         if the aperture does not exist, it is created and entered in aperture list.
      */
     int GetOrCreateAperture( const wxSize& aSize, int aRadius, double aRotDegree,
-                    APERTURE::APERTURE_TYPE aType, int aApertureAttribute );
+                             APERTURE::APERTURE_TYPE aType, int aApertureAttribute );
 
     /**
-     * @return a index to the aperture in aperture list which meets the data and type of tool
-     * if the aperture does not exist, it is created and entered in aperture list
-     * @param aCorners = the corner list
-     * @param aRotDegree = the rotation of tool
-     * @param aType = the type ( shape ) of tool that can manage a list of corners (polygon)
-     * @param aApertureAttribute = an aperture attribute of the tool (a tool can have only one attribute)
-     * 0 = no specific attribute
+     * @param aCorners is the corner list.
+     * @param aRotDegree is the rotation of tool.
+     * @param aType is the type ( shape ) of tool that can manage a list of corners (polygon).
+     * @param aApertureAttribute is an aperture attribute of the tool (a tool can have only one
+     *        attribute) 0 = no specific attribute.
+     * @return an index to the aperture in aperture list which meets the data and type of tool
+     *         if the aperture does not exist, it is created and entered in aperture list.
      */
     int GetOrCreateAperture( const std::vector<wxPoint>& aCorners, double aRotDegree,
-                    APERTURE::APERTURE_TYPE aType, int aApertureAttribute );
+                             APERTURE::APERTURE_TYPE aType, int aApertureAttribute );
 
 protected:
-    /** Plot a round rect (a round rect shape in fact) as a Gerber region
-     * using lines and arcs for corners
-     * @param aRectCenter is the center of the rectangle
-     * @param aSize is the size of the rectangle
-     * @param aCornerRadius is the radius of the corners
-     * @param aOrient is the rotation of the rectangle
-     * Note: only the G36 ... G37 region is created.
+    /**
+     * Plot a round rect (a round rect shape in fact) as a Gerber region using lines and arcs
+     * for corners.
+     *
+     * @note Only the G36 ... G37 region is created.
+     *
+     * @param aRectCenter is the center of the rectangle.
+     * @param aSize is the size of the rectangle.
+     * @param aCornerRadius is the radius of the corners.
+     * @param aOrient is the rotation of the rectangle.
      */
     void plotRoundRectAsRegion( const wxPoint& aRectCenter, const wxSize& aSize,
                                 int aCornerRadius, double aOrient );
     /**
      * Plot a Gerber arc.
-     * if aPlotInRegion = true, the current pen position will not be
-     * initialized to the arc start position, and therefore the arc can be used
-     * to define a region outline item
-     * a line will be created from current ^position to arc start point
-     * if aPlotInRegion = false, the current pen position will be initialized
-     * to the arc start position, to plot an usual arc item
-     * The line thickness is not initialized in plotArc, and must be initialized
-     * before calling it if needed.
+     *
+     * If aPlotInRegion = true, the current pen position will not be initialized to the arc
+     * start position, and therefore the arc can be used to define a region outline item
+     * a line will be created from current position to arc start point.  If aPlotInRegion
+     * = false, the current pen position will be initialized to the arc start position, to
+     * plot an usual arc item.  The line thickness is not initialized in plotArc, and must
+     * be initialized before calling it if needed.
      */
     void plotArc( const wxPoint& aCenter, double aStAngle, double aEndAngle,
-                      int aRadius, bool aPlotInRegion );
+                  int aRadius, bool aPlotInRegion );
     void plotArc( const SHAPE_ARC& aArc, bool aPlotInRegion );
 
     /**
-     * Pick an existing aperture or create a new one, matching the
-     * size, type and attributes.
-     * write the DCode selection on gerber file
+     * Pick an existing aperture or create a new one, matching the size, type and attributes.
+     *
+     * Write the DCode selection on gerber file.
      */
     void selectAperture( const wxSize& aSize, int aRadius, double aRotDegree,
-                         APERTURE::APERTURE_TYPE aType,
-                         int aApertureAttribute );
+                         APERTURE::APERTURE_TYPE aType, int aApertureAttribute );
     /**
-     * Pick an existing aperture or create a new one, matching the
-     * aDiameter, aPolygonRotation, type and attributes.
+     * Pick an existing aperture or create a new one, matching the aDiameter, aPolygonRotation,
+     * type and attributes.
+     *
      * It apply only to apertures with type = AT_REGULAR_POLY3 to AT_REGULAR_POLY12
      * write the DCode selection on gerber file
      */
@@ -291,35 +297,39 @@ protected:
                          APERTURE::APERTURE_TYPE aType, int aApertureAttribute );
 
     /**
-     * Pick an existing aperture or create a new one, matching the
-     * corner list, aRotDegree, type and attributes.
-     * It apply only to apertures managing a polygon that differs from AT_REGULAR_POLY3
-     * to AT_REGULAR_POLY12 (for instance APER_MACRO_TRAPEZOID )
-     * write the DCode selection on gerber file
+     * Pick an existing aperture or create a new one, matching the corner list, aRotDegree,
+     * type and attributes.
+     *
+     * It only applies to apertures managing a polygon that differs from AT_REGULAR_POLY3
+     * to AT_REGULAR_POLY12 (for instance APER_MACRO_TRAPEZOID ) write the DCode selection
+     * on gerber file.
      */
     void selectAperture( int aDiameter, double aRotDegree,
                          APERTURE::APERTURE_TYPE aType, int aApertureAttribute );
 
     /**
-     * Emit a D-Code record, using proper conversions
-     * to format a leading zero omitted gerber coordinate
-     * (for n decimal positions, see header generation in start_plot
+     * Emit a D-Code record, using proper conversions to format a leading zero omitted gerber
+     * coordinate.
+     *
+     * For n decimal positions, see header generation in start_plot.
      */
     void emitDcode( const DPOINT& pt, int dcode );
 
     /**
-     * print a Gerber net attribute object record.
-     * In a gerber file, a net attribute is owned by a graphic object
-     * formatNetAttribute must be called before creating the object
+     * Print a Gerber net attribute object record.
+     *
+     * In a gerber file, a net attribute is owned by a graphic object formatNetAttribute must
+     * be called before creating the object.  The generated string depends on the type of
+     * netlist info.
+     *
      * @param aData contains the data to format.
-     * the generated string depends on the type of netlist info
      */
     void formatNetAttribute( GBR_NETLIST_METADATA* aData );
 
     /**
-     * clear a Gerber net attribute record (clear object attribute dictionary)
+     * Clear a Gerber net attribute record (clear object attribute dictionary)
      * and output the clear object attribute dictionary command to gerber file
-     * has effect only if a net attribute is stored in m_objectAttributesDictionary
+     * has effect only if a net attribute is stored in m_objectAttributesDictionary.
      */
     void clearNetAttribute();
 
diff --git a/common/plotters/plotter_hpgl.h b/common/plotters/plotter_hpgl.h
index 96a2b22c25..5b92348b7c 100644
--- a/common/plotters/plotter_hpgl.h
+++ b/common/plotters/plotter_hpgl.h
@@ -60,19 +60,29 @@ public:
     /// Set whether the user coordinate system is fit to content
     void SetUserCoordsFit( bool user_coords_fit ) { fitUserCoords = user_coords_fit; }
 
+    /**
+     * At the start of the HPGL plot pen speed and number are requested.
+     */
     virtual bool StartPlot() override;
+
+    /**
+     * HPGL end of plot: sort and emit graphics, pen return and release.
+     */
     virtual bool EndPlot() override;
 
     /// HPGL doesn't handle line thickness or color
-    virtual void SetCurrentLineWidth( int width, void* aData = NULL ) override
+    virtual void SetCurrentLineWidth( int width, void* aData = nullptr ) override
     {
         // This is the truth
         m_currentPenWidth = userToDeviceSize( penDiameter );
     }
 
+    /**
+     * HPGL supports dashed lines.
+     */
     virtual void SetDash( PLOT_DASH_TYPE dashed ) override;
 
-    virtual void SetColor( COLOR4D color ) override {}
+    virtual void SetColor( const COLOR4D& color ) override {}
 
     virtual void SetPenSpeed( int speed )
     {
@@ -94,10 +104,23 @@ public:
                          int width = USE_DEFAULT_LINE_WIDTH ) override;
     virtual void PlotPoly( const std::vector< wxPoint >& aCornerList,
                            FILL_TYPE aFill, int aWidth = USE_DEFAULT_LINE_WIDTH,
-                           void * aData = NULL ) override;
+                           void* aData = nullptr ) override;
 
     virtual void ThickSegment( const wxPoint& start, const wxPoint& end, int width,
                                OUTLINE_MODE tracemode, void* aData ) override;
+
+    /**
+     * Plot an arc.
+     *
+     * Command
+     * PU PY x, y; PD start_arc_X AA, start_arc_Y, angle, NbSegm; PU;
+     * Or PU PY x, y; PD start_arc_X AA, start_arc_Y, angle, PU;
+     *
+     * center is the center of the arc.
+     * StAngled is the start angle of the arc.
+     * EndAngle is end angle the arc.
+     * Radius is the radius of the arc.
+     */
     virtual void Arc( const wxPoint& centre, double StAngle, double EndAngle,
                       int rayon, FILL_TYPE fill, int width = USE_DEFAULT_LINE_WIDTH ) override;
     virtual void PenTo( const wxPoint& pos, char plume ) override;
@@ -123,9 +146,9 @@ public:
 protected:
     /// Start a new HPGL_ITEM if necessary, keeping the current one if it exists.
     ///
-    /// @param location - location of the item
+    /// @param location is the location of the item.
     ///
-    /// @return whether a new item was made
+    /// @return whether a new item was made.
     bool startItem( DPOINT location );
 
     /// Flush the current HPGL_ITEM and clear out the current item pointer.
@@ -134,8 +157,8 @@ protected:
     /// Start a new HPGL_ITEM with the given string if necessary, or append the
     /// string to the current item.
     ///
-    /// @param location - location of the item, if a new one is made
-    /// @param content - content substring
+    /// @param location is the location of the item, if a new one is made.
+    /// @param content is the content substring.
     ///
     /// @return whether a new item was made
     bool startOrAppendItem( DPOINT location, wxString const& content );
diff --git a/common/plotters/plotters_pslike.h b/common/plotters/plotters_pslike.h
index e96ec75214..a1e79ffa32 100644
--- a/common/plotters/plotters_pslike.h
+++ b/common/plotters/plotters_pslike.h
@@ -1,7 +1,7 @@
 /*
  * This program source code file is part of KiCad, a free EDA CAD application.
  *
- * Copyright (C) 2016-2020 KiCad Developers, see AUTHORS.txt for contributors.
+ * Copyright (C) 2016-2021 KiCad Developers, see AUTHORS.txt for contributors.
  *
  * This program is free software: you can redistribute it and/or modify it
  * under the terms of the GNU General Public License as published by the
@@ -32,9 +32,8 @@
 
 
 /**
- * The PSLIKE_PLOTTER class is an intermediate class to handle common
- * routines for engines working more or less with the postscript imaging
- * model
+ * The PSLIKE_PLOTTER class is an intermediate class to handle common routines for engines
+ * working more or less with the postscript imaging model.
  */
 class PSLIKE_PLOTTER : public PLOTTER
 {
@@ -69,9 +68,8 @@ public:
                                  OUTLINE_MODE aTraceMode, void* aData ) override;
     virtual void FlashPadOval( const wxPoint& aPadPos, const wxSize& aSize, double aPadOrient,
                                OUTLINE_MODE aTraceMode, void* aData ) override;
-    virtual void FlashPadRect( const wxPoint& aPadPos, const wxSize& aSize,
-                               double aPadOrient, OUTLINE_MODE aTraceMode,
-                               void* aData ) override;
+    virtual void FlashPadRect( const wxPoint& aPadPos, const wxSize& aSize, double aPadOrient,
+                               OUTLINE_MODE aTraceMode, void* aData ) override;
     virtual void FlashPadRoundRect( const wxPoint& aPadPos, const wxSize& aSize,
                                     int aCornerRadius, double aOrient,
                                     OUTLINE_MODE aTraceMode, void* aData ) override;
@@ -81,16 +79,25 @@ public:
     virtual void FlashPadTrapez( const wxPoint& aPadPos, const wxPoint *aCorners,
                                  double aPadOrient, OUTLINE_MODE aTraceMode, void* aData ) override;
     virtual void FlashRegularPolygon( const wxPoint& aShapePos, int aDiameter, int aCornerCount,
-                            double aOrient, OUTLINE_MODE aTraceMode, void* aData ) override;
+                                      double aOrient, OUTLINE_MODE aTraceMode,
+                                      void* aData ) override;
 
     /**
      * The SetColor implementation is split with the subclasses:
      * The PSLIKE computes the rgb values, the subclass emits the
      * operator to actually do it
      */
-    virtual void SetColor( COLOR4D color ) override;
+    virtual void SetColor( const COLOR4D& color ) override;
 
 protected:
+    /**
+     * This is the core for postscript/PDF text alignment.
+     *
+     * It computes the transformation matrix to generate a user space
+     * system aligned with the text. Even the PS uses the concat
+     * operator to simplify PDF generation (concat is everything PDF
+     * has to modify the CTM. Lots of parameters, both in and out.
+     */
     void computeTextParameters( const wxPoint&           aPos,
                                 const wxString&          aText,
                                 int                      aOrient,
@@ -109,8 +116,14 @@ protected:
                                 double                   *ctm_e,
                                 double                   *ctm_f,
                                 double                   *heightFactor );
-    void postscriptOverlinePositions( const wxString& aText, int aXSize,
-                                      bool aItalic, bool aBold,
+
+    /**
+     * Computes the x coordinates for the overlining in a string of text.
+     * Fills the passed vector with couples of (start, stop) values to be
+     * used in the text coordinate system (use computeTextParameters to
+     * obtain the parameters to establish such a system)
+     */
+    void postscriptOverlinePositions( const wxString& aText, int aXSize, bool aItalic, bool aBold,
                                       std::vector<int> *pos_pairs );
 
     /// convert a wxString unicode string to a char string compatible with the accepted
@@ -123,8 +136,13 @@ protected:
     /// Height of the postscript font (from the AFM)
     static const double postscriptTextAscent; // = 0.718;
 
-    int returnPostscriptTextWidth( const wxString& aText, int aXSize,
-                                   bool aItalic, bool aBold );
+    /**
+     * Sister function for the GraphicTextWidth in drawtxt.cpp
+     * Does the same processing (i.e. calculates a text string width) but
+     * using postscript metrics for the Helvetica font (optionally used for
+     * PS and PDF plotting
+     */
+    int returnPostscriptTextWidth( const wxString& aText, int aXSize, bool aItalic, bool aBold );
 
     /// Fine user scale adjust ( = 1.0 if no correction)
     double plotScaleAdjX, plotScaleAdjY;
@@ -154,13 +172,34 @@ public:
         return PLOT_FORMAT::POST;
     }
 
+    /**
+     * The code within this function (and the CloseFilePS function)
+     * creates postscript files whose contents comply with Adobe's
+     * Document Structuring Convention, as documented by assorted
+     * details described within the following URLs:
+     *
+     * http://en.wikipedia.org/wiki/Document_Structuring_Conventions
+     * http://partners.adobe.com/public/developer/en/ps/5001.DSC_Spec.pdf
+     *
+     *
+     * BBox is the boundary box (position and size of the "client rectangle"
+     * for drawings (page - margins) in mils (0.001 inch)
+     */
     virtual bool StartPlot() override;
     virtual bool EndPlot() override;
-    virtual void SetCurrentLineWidth( int width, void* aData = NULL ) override;
+
+    /**
+     * Set the current line width (in IUs) for the next plot.
+     */
+    virtual void SetCurrentLineWidth( int width, void* aData = nullptr ) override;
+
+    /**
+     * PostScript supports dashed lines.
+     */
     virtual void SetDash( PLOT_DASH_TYPE dashed ) override;
 
     virtual void SetViewport( const wxPoint& aOffset, double aIusPerDecimil,
-                  double aScale, bool aMirror ) override;
+                              double aScale, bool aMirror ) override;
     virtual void Rect( const wxPoint& p1, const wxPoint& p2, FILL_TYPE fill,
                        int width = USE_DEFAULT_LINE_WIDTH ) override;
     virtual void Circle( const wxPoint& pos, int diametre, FILL_TYPE fill,
@@ -168,16 +207,18 @@ public:
     virtual void Arc( const wxPoint& centre, double StAngle, double EndAngle,
                       int rayon, FILL_TYPE fill, int width = USE_DEFAULT_LINE_WIDTH ) override;
 
-    virtual void PlotPoly( const std::vector< wxPoint >& aCornerList,
-                           FILL_TYPE aFill, int aWidth = USE_DEFAULT_LINE_WIDTH,
-                           void * aData = NULL ) override;
+    virtual void PlotPoly( const std::vector< wxPoint >& aCornerList, FILL_TYPE aFill,
+                           int aWidth = USE_DEFAULT_LINE_WIDTH, void* aData = nullptr ) override;
 
+    /**
+     * PostScript-likes at the moment are the only plot engines supporting bitmaps.
+     */
     virtual void PlotImage( const wxImage& aImage, const wxPoint& aPos,
                             double aScaleFactor ) override;
 
     virtual void PenTo( const wxPoint& pos, char plume ) override;
     virtual void Text( const wxPoint&              aPos,
-                       const COLOR4D               aColor,
+                       const COLOR4D&              aColor,
                        const wxString&             aText,
                        double                      aOrient,
                        const wxSize&               aSize,
@@ -187,7 +228,7 @@ public:
                        bool                        aItalic,
                        bool                        aBold,
                        bool                        aMultilineAllowed = false,
-                       void* aData = NULL ) override;
+                       void* aData = nullptr ) override;
 protected:
     virtual void emitSetRGBColor( double r, double g, double b ) override;
 };
@@ -216,31 +257,30 @@ public:
     }
 
     /**
-     * Open or create the plot file aFullFilename
+     * Open or create the plot file aFullFilename.
      *
      * The base class open the file in text mode, so we should have this
-     * function overlaid for PDF files, which are binary files
+     * function overlaid for PDF files, which are binary files.
      *
-     * @param aFullFilename = the full file name of the file to create
-     * @return true if success, false if the file cannot be created/opened
+     * @param aFullFilename is the full file name of the file to create.
+     * @return true if success, false if the file cannot be created/opened.
      */
     virtual bool OpenFile( const wxString& aFullFilename ) override;
 
     /**
-     * The PDF engine supports multiple pages; the first one is opened
-     * 'for free' the following are to be closed and reopened. Between
-     * each page parameters can be set
+     * The PDF engine supports multiple pages; the first one is opened 'for free' the following
+     * are to be closed and reopened. Between each page parameters can be set.
      */
     virtual bool StartPlot() override;
     virtual bool EndPlot() override;
 
     /**
-     * Starts a new page in the PDF document
+     * Start a new page in the PDF document.
      */
     virtual void StartPage();
 
     /**
-     * Close the current page in the PDF document (and emit its compressed stream)
+     * Close the current page in the PDF document (and emit its compressed stream).
      */
     virtual void ClosePage();
 
@@ -252,7 +292,7 @@ public:
      * Note pen width = 0 is used in plot polygons to plot filled polygons with no outline
      * thickness.  Use in this case pen width = 1 does not actually change the polygon.
      */
-    virtual void SetCurrentLineWidth( int width, void* aData = NULL ) override;
+    virtual void SetCurrentLineWidth( int width, void* aData = nullptr ) override;
 
     /**
      * PDF supports dashed lines
@@ -264,10 +304,10 @@ public:
      * with the outputFile open (but not inside a page stream!)
      */
     virtual void SetViewport( const wxPoint& aOffset, double aIusPerDecimil,
-                  double aScale, bool aMirror ) override;
+                              double aScale, bool aMirror ) override;
 
     /**
-     * Rectangles in PDF. Supported by the native operator
+     * Rectangles in PDF. Supported by the native operator.
      */
     virtual void Rect( const wxPoint& p1, const wxPoint& p2, FILL_TYPE fill,
                        int width = USE_DEFAULT_LINE_WIDTH ) override;
@@ -288,14 +328,13 @@ public:
     /**
      * Polygon plotting for PDF. Everything is supported
      */
-    virtual void PlotPoly( const std::vector< wxPoint >& aCornerList,
-                           FILL_TYPE aFill, int aWidth = USE_DEFAULT_LINE_WIDTH,
-                           void * aData = NULL ) override;
+    virtual void PlotPoly( const std::vector< wxPoint >& aCornerList, FILL_TYPE aFill,
+                           int aWidth = USE_DEFAULT_LINE_WIDTH, void* aData = nullptr ) override;
 
     virtual void PenTo( const wxPoint& pos, char plume ) override;
 
     virtual void Text( const wxPoint&              aPos,
-                       const COLOR4D               aColor,
+                       const COLOR4D&              aColor,
                        const wxString&             aText,
                        double                      aOrient,
                        const wxSize&               aSize,
@@ -305,7 +344,7 @@ public:
                        bool                        aItalic,
                        bool                        aBold,
                        bool                        aMultilineAllowed = false,
-                       void* aData = NULL ) override;
+                       void* aData = nullptr ) override;
     /**
      * PDF images are handles as inline, not XObject streams...
      */
@@ -360,13 +399,13 @@ protected:
      */
     void closePdfStream();
 
-    int pageTreeHandle;		 /// Handle to the root of the page tree object
-    int fontResDictHandle;	 /// Font resource dictionary
+    int pageTreeHandle;      /// Handle to the root of the page tree object
+    int fontResDictHandle;   /// Font resource dictionary
     std::vector<int> pageHandles;/// Handles to the page objects
-    int pageStreamHandle;	 /// Handle of the page content object
+    int pageStreamHandle;    /// Handle of the page content object
     int streamLengthHandle;      /// Handle to the deferred stream length
     wxString workFilename;
-    FILE* workFile;  	         /// Temporary file to construct the stream before zipping
+    FILE* workFile;              /// Temporary file to construct the stream before zipping
     std::vector<long> xrefTable; /// The PDF xref offset table
 };
 
@@ -386,10 +425,22 @@ public:
         return PLOT_FORMAT::SVG;
     }
 
-    virtual void SetColor( COLOR4D color ) override;
+    virtual void SetColor( const COLOR4D& color ) override;
+
+    /**
+     * Create SVG file header.
+     */
     virtual bool StartPlot() override;
     virtual bool EndPlot() override;
-    virtual void SetCurrentLineWidth( int width, void* aData = NULL ) override;
+
+    /**
+     * Set the current line width (in IUs) for the next plot.
+     */
+    virtual void SetCurrentLineWidth( int width, void* aData = nullptr ) override;
+
+    /**
+     * SVG supports dashed lines.
+     */
     virtual void SetDash( PLOT_DASH_TYPE dashed ) override;
 
     virtual void SetViewport( const wxPoint& aOffset, double aIusPerDecimil,
@@ -408,8 +459,11 @@ public:
 
     virtual void PlotPoly( const std::vector< wxPoint >& aCornerList,
                            FILL_TYPE aFill, int aWidth = USE_DEFAULT_LINE_WIDTH,
-                           void * aData = NULL ) override;
+                           void * aData = nullptr ) override;
 
+    /**
+     * PostScript-likes at the moment are the only plot engines supporting bitmaps.
+     */
     virtual void PlotImage( const wxImage& aImage, const wxPoint& aPos,
                             double aScaleFactor ) override;
 
@@ -443,7 +497,7 @@ public:
     virtual void EndBlock( void* aData ) override;
 
     virtual void Text( const wxPoint&              aPos,
-                       const COLOR4D               aColor,
+                       const COLOR4D&              aColor,
                        const wxString&             aText,
                        double                      aOrient,
                        const wxSize&               aSize,
@@ -453,9 +507,28 @@ public:
                        bool                        aItalic,
                        bool                        aBold,
                        bool                        aMultilineAllowed = false,
-                       void* aData = NULL ) override;
+                       void* aData = nullptr ) override;
 
 protected:
+    /**
+     * Initialize m_pen_rgb_color from reduced values r, g ,b
+     * ( reduced values are 0.0 to 1.0 )
+     */
+    virtual void emitSetRGBColor( double r, double g, double b ) override;
+
+    /**
+     * Output the string which define pen and brush color, shape, transparency
+     *
+     * @param aIsGroup If false, do not form a new group for the style.
+     * @param aExtraStyle If given, the string will be added into the style string before closing
+     */
+    void setSVGPlotStyle( bool aIsGroup = true, const std::string& aExtraStyle = {} );
+
+    /**
+     * Prepare parameters for setSVGPlotStyle()
+     */
+    void setFillMode( FILL_TYPE fill );
+
     FILL_TYPE      m_fillMode;          // true if the current contour
                                         // rect, arc, circle, polygon must be filled
     long           m_pen_rgb_color;     // current rgb color value: each color has
@@ -475,23 +548,4 @@ protected:
                                         // Use 3-6 (3 means um precision, 6 nm precision) in PcbNew
                                         // 3-4 in other modules (avoid values >4 to avoid overflow)
                                         // see also comment for m_useInch.
-
-    /**
-     * Initialize m_pen_rgb_color from reduced values r, g ,b
-     * ( reduced values are 0.0 to 1.0 )
-     */
-    virtual void emitSetRGBColor( double r, double g, double b ) override;
-
-    /**
-     * Output the string which define pen and brush color, shape, transparency
-     *
-     * @param aIsGroup If false, do not form a new group for the style.
-     * @param aExtraStyle If given, the string will be added into the style string before closing
-     */
-    void setSVGPlotStyle( bool aIsGroup = true, const std::string& aExtraStyle = {} );
-
-    /**
-     * Prepare parameters for setSVGPlotStyle()
-     */
-    void setFillMode( FILL_TYPE fill );
 };
diff --git a/include/plotter.h b/include/plotter.h
index 7d623fe003..60bf37b08d 100644
--- a/include/plotter.h
+++ b/include/plotter.h
@@ -2,7 +2,7 @@
  * This program source code file is part of KiCad, a free EDA CAD application.
  *
  * Copyright (C) 2016 Jean-Pierre Charras, jp.charras at wanadoo.fr
- * Copyright (C) 2016-2020 KiCad Developers, see AUTHORS.txt for contributors.
+ * Copyright (C) 2016-2021 KiCad Developers, see AUTHORS.txt for contributors.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -147,7 +147,8 @@ public:
 
     /**
      * Plot in B/W or color.
-     * @param aColorMode = true to plot in color, false to plot in black and white
+     *
+     * @param aColorMode use true to plot in color, false to plot in black and white.
      */
     virtual void SetColorMode( bool aColorMode ) { m_colorMode = aColorMode; }
     bool GetColorMode() const { return m_colorMode; }
@@ -160,13 +161,14 @@ public:
 
     /**
      * Set the line width for the next drawing.
-     * @param width is specified in IUs
-     * @param aData is an auxiliary parameter, mainly used in gerber plotter
+     *
+     * @param width is specified in IUs.
+     * @param aData is an auxiliary parameter, mainly used in gerber plotter.
      */
-    virtual void SetCurrentLineWidth( int width, void* aData = NULL ) = 0;
+    virtual void SetCurrentLineWidth( int width, void* aData = nullptr ) = 0;
     virtual int GetCurrentLineWidth() const  { return m_currentPenWidth; }
 
-    virtual void SetColor( COLOR4D color ) = 0;
+    virtual void SetColor( const COLOR4D& color ) = 0;
 
     virtual void SetDash( PLOT_DASH_TYPE dashed ) = 0;
 
@@ -175,7 +177,8 @@ public:
     virtual void SetTitle( const wxString& aTitle ) { m_title = aTitle; }
 
     /**
-     * Add a line to the list of free lines to print at the beginning of the file
+     * Add a line to the list of free lines to print at the beginning of the file.
+     *
      * @param aExtraString is the string to print
      */
     void AddLineToHeader( const wxString& aExtraString )
@@ -193,20 +196,22 @@ public:
 
     /**
      * Set the plot offset and scaling for the current plot
-     * @param aOffset is the plot offset
+     *
+     * @param aOffset is the plot offset.
      * @param aIusPerDecimil gives the scaling factor from IUs to device units
      * @param aScale is the user set plot scaling factor (either explicitly
-     * 		or using 'fit to A4')
+     *      or using 'fit to A4').
      * @param aMirror flips the plot in the Y direction (useful for toner
-     * 		transfers or some kind of film)
+     *      transfers or some kind of film).
      */
     virtual void SetViewport( const wxPoint& aOffset, double aIusPerDecimil,
-        double aScale, bool aMirror ) = 0;
+                              double aScale, bool aMirror ) = 0;
 
     /**
-     * Open or create the plot file aFullFilename
-     * @param aFullFilename = the full file name of the file to create
-     * @return true if success, false if the file cannot be created/opened
+     * Open or create the plot file \a aFullFilename.
+     *
+     * @param aFullFilename is the full file name of the file to create.
+     * @return true if success, false if the file cannot be created/opened.
      *
      * Virtual because some plotters use ascii files, some others binary files (PDF)
      * The base class open the file in text mode
@@ -230,7 +235,7 @@ public:
                          int width = USE_DEFAULT_LINE_WIDTH ) = 0;
 
     /**
-     * Generic fallback: arc rendered as a polyline
+     * Generic fallback: arc rendered as a polyline.
      */
     virtual void Arc( const wxPoint& centre, double StAngle, double EndAngle,
                       int rayon, FILL_TYPE fill, int width = USE_DEFAULT_LINE_WIDTH );
@@ -243,15 +248,15 @@ public:
      */
     virtual void BezierCurve( const wxPoint& aStart, const wxPoint& aControl1,
                               const wxPoint& aControl2, const wxPoint& aEnd,
-                              int aTolerance,
-                              int aLineThickness = USE_DEFAULT_LINE_WIDTH );
+                              int aTolerance, int aLineThickness = USE_DEFAULT_LINE_WIDTH );
 
     /**
-     * moveto/lineto primitive, moves the 'pen' to the specified direction
-     * @param pos is the target position
+     * Moveto/lineto primitive, moves the 'pen' to the specified direction.
+     *
+     * @param pos is the target position.
      * @param plume specifies the kind of motion: 'U' only moves the pen,
-     * 		'D' draw a line from the current position and 'Z' finish
-     *		the drawing and returns the 'pen' to rest (flushes the trace)
+     *      'D' draw a line from the current position and 'Z' finish
+     *      the drawing and returns the 'pen' to rest (flushes the trace).
      */
     virtual void PenTo( const wxPoint& pos, char plume ) = 0;
 
@@ -279,39 +284,38 @@ public:
     }
 
     /**
-     * Draw a polygon ( filled or not )
-     * @param aCornerList = corners list (a std::vector< wxPoint >)
-     * @param aFill = type of fill
-     * @param aWidth = line width
-     * @param aData an auxiliary info (mainly for gerber format)
+     * Draw a polygon ( filled or not ).
+     *
+     * @param aCornerList is the corners list (a std::vector< wxPoint >).
+     * @param aFill is the type of fill.
+     * @param aWidth is the line width.
+     * @param aData is an auxiliary info (mainly for gerber format).
      */
     virtual void PlotPoly( const std::vector< wxPoint >& aCornerList, FILL_TYPE aFill,
-               int aWidth = USE_DEFAULT_LINE_WIDTH, void * aData = NULL ) = 0;
+                           int aWidth = USE_DEFAULT_LINE_WIDTH, void* aData = nullptr ) = 0;
 
     /**
-     * Draw a polygon ( filled or not )
-     * @param aCornerList = corners list (a SHAPE_LINE_CHAIN).
-     * must be closed (IsClosed() == true) for a polygon. Otherwise this is a polyline
-     * @param aFill = type of fill
-     * @param aWidth = line width
-     * @param aData an auxiliary info (mainly for gerber format)
+     * Draw a polygon ( filled or not ).
+     * @param aCornerList is the corners list (a SHAPE_LINE_CHAIN).
+     *        must be closed (IsClosed() == true) for a polygon. Otherwise this is a polyline.
+     * @param aFill is the type of fill.
+     * @param aWidth is the line width.
+     * @param aData is an auxiliary info (mainly for gerber format).
      */
     virtual void PlotPoly( const SHAPE_LINE_CHAIN& aCornerList, FILL_TYPE aFill,
-               int aWidth = USE_DEFAULT_LINE_WIDTH, void * aData = NULL );
+                           int aWidth = USE_DEFAULT_LINE_WIDTH, void* aData = nullptr );
 
     /**
      * Only PostScript plotters can plot bitmaps.
      *
      * A rectangle is plotted for plotters that cannot plot a bitmap.
      *
-     * @brief Draw an image bitmap
-     * @param aImage = the bitmap
-     * @param aPos = position of the center of the bitmap
-     * @param aScaleFactor = the scale factor to apply to the bitmap size
-     *                      (this is not the plot scale factor)
+     * @param aImage is the bitmap.
+     * @param aPos is position of the center of the bitmap.
+     * @param aScaleFactor is the scale factor to apply to the bitmap size
+     *                      (this is not the plot scale factor).
      */
-    virtual void PlotImage( const wxImage & aImage, const wxPoint& aPos,
-                            double aScaleFactor );
+    virtual void PlotImage( const wxImage& aImage, const wxPoint& aPos, double aScaleFactor );
 
     // Higher level primitives -- can be drawn as line, sketch or 'filled'
     virtual void ThickSegment( const wxPoint& start, const wxPoint& end, int width,
@@ -329,89 +333,93 @@ public:
     // Flash primitives
 
     /**
-     * @param aPadPos Position of the shape (center of the rectangle
-     * @param aDiameter diameter of round pad
-     * @param aTraceMode FILLED or SKETCH
-     * @param aData an auxiliary info (mainly for gerber format attributes)
+     * @param aPadPos Position of the shape (center of the rectangle.
+     * @param aDiameter is the diameter of round pad.
+     * @param aTraceMode is the drawing mode, FILLED or SKETCH.
+     * @param aData is an auxiliary info (mainly for gerber format attributes).
      */
     virtual void FlashPadCircle( const wxPoint& aPadPos, int aDiameter,
                                  OUTLINE_MODE aTraceMode, void* aData ) = 0;
 
     /**
-     * @param aPadPos Position of the shape (center of the rectangle
-     * @param aSize = size of oblong shape
-     * @param aPadOrient The rotation of the shape
-     * @param aTraceMode FILLED or SKETCH
-     * @param aData an auxiliary info (mainly for gerber format attributes)
+     * @param aPadPos Position of the shape (center of the rectangle.
+     * @param aSize is the size of oblong shape.
+     * @param aPadOrient The rotation of the shape.
+     * @param aTraceMode is the drawing mode, FILLED or SKETCH.
+     * @param aData an auxiliary info (mainly for gerber format attributes).
      */
     virtual void FlashPadOval( const wxPoint& aPadPos, const wxSize& aSize, double aPadOrient,
                                OUTLINE_MODE aTraceMode, void* aData ) = 0;
 
     /**
-     * @param aPadPos Position of the shape (center of the rectangle
-     * @param aSize = size of rounded rect
-     * @param aPadOrient The rotation of the shape
-     * @param aTraceMode FILLED or SKETCH
-     * @param aData an auxiliary info (mainly for gerber format attributes)
+     * @param aPadPos Position of the shape (center of the rectangle).
+     * @param aSize is the size of rounded rect.
+     * @param aPadOrient The rotation of the shape.
+     * @param aTraceMode is the drawing mode, FILLED or SKETCH.
+     * @param aData an auxiliary info (mainly for gerber format attributes).
      */
     virtual void FlashPadRect( const wxPoint& aPadPos, const wxSize& aSize,
                                double aPadOrient, OUTLINE_MODE aTraceMode, void* aData ) = 0;
 
     /**
-     * @param aPadPos Position of the shape (center of the rectangle
-     * @param aSize = size of rounded rect
-     * @param aCornerRadius Radius of the rounded corners
-     * @param aOrient The rotation of the shape
-     * @param aTraceMode FILLED or SKETCH
-     * @param aData an auxiliary info (mainly for gerber format attributes)
+     * @param aPadPos Position of the shape (center of the rectangle.
+     * @param aSize is the size of rounded rect.
+     * @param aCornerRadius Radius of the rounded corners.
+     * @param aOrient The rotation of the shape.
+     * @param aTraceMode is the drawing mode, FILLED or SKETCH.
+     * @param aData an auxiliary info (mainly for gerber format attributes).
      */
     virtual void FlashPadRoundRect( const wxPoint& aPadPos, const wxSize& aSize,
                                     int aCornerRadius, double aOrient,
                                     OUTLINE_MODE aTraceMode, void* aData ) = 0;
 
     /**
-     * @param aPadPos Position of the shape
-     * @param aSize = size of round reference pad
-     * @param aPadOrient = pad rotation, used only with aperture macros (Gerber plotter)
-     * @param aPolygons the shape as polygon set
-     * @param aTraceMode FILLED or SKETCH
-     * @param aData an auxiliary info (mainly for gerber format attributes)
+     * @param aPadPos Position of the shape.
+     * @param aSize is the size of round reference pad.
+     * @param aPadOrient is the pad rotation, used only with aperture macros (Gerber plotter).
+     * @param aPolygons the shape as polygon set.
+     * @param aTraceMode is the drawing mode, FILLED or SKETCH.
+     * @param aData an auxiliary info (mainly for gerber format attributes).
      */
     virtual void FlashPadCustom( const wxPoint& aPadPos, const wxSize& aSize,
                                  double aPadOrient, SHAPE_POLY_SET* aPolygons,
                                  OUTLINE_MODE aTraceMode, void* aData ) = 0;
 
     /**
-     * Flash a trapezoidal pad
-     * @param aPadPos = the position of the shape
-     * @param aCorners = the list of 4 corners positions,
-     * 		relative to the shape position, pad orientation 0
-     * @param aPadOrient = the rotation of the shape
-     * @param aTraceMode = FILLED or SKETCH
-     * @param aData an auxiliary info (mainly for gerber format attributes)
+     * Flash a trapezoidal pad.
+     *
+     * @param aPadPos is the the position of the shape.
+     * @param aCorners is the list of 4 corners positions, relative to the shape position,
+     *                 pad orientation 0.
+     * @param aPadOrient is the rotation of the shape.
+     * @param aTraceMode is the drawing mode, FILLED or SKETCH.
+     * @param aData an auxiliary info (mainly for gerber format attributes).
      */
     virtual void FlashPadTrapez( const wxPoint& aPadPos, const wxPoint *aCorners,
                                  double aPadOrient, OUTLINE_MODE aTraceMode,
                                  void* aData ) = 0;
 
     /**
-     * Flash a regular polygon. Useful only in Gerber files to flash a regular polygon
-     * @param aShapePos is the center of the circle containing the polygon
-     * @param aRadius is the radius of the circle containing the polygon
-     * @param aCornerCount is the number of vertices
-     * @param aOrient is the polygon rotation in degrees
+     * Flash a regular polygon. Useful only in Gerber files to flash a regular polygon.
+     *
+     * @param aShapePos is the center of the circle containing the polygon.
+     * @param aRadius is the radius of the circle containing the polygon.
+     * @param aCornerCount is the number of vertices.
+     * @param aOrient is the polygon rotation in degrees.
      * @param aData is a auxiliary parameter used (if needed) to handle extra info
-     * specific to the plotter
+     *              specific to the plotter.
      */
     virtual void FlashRegularPolygon( const wxPoint& aShapePos, int aDiameter, int aCornerCount,
-                            double aOrient, OUTLINE_MODE aTraceMode, void* aData ) = 0 ;
+                                      double aOrient, OUTLINE_MODE aTraceMode, void* aData ) = 0 ;
 
     /**
-     * Draws text with the plotter. For convenience it accept the color to use
-     * for specific plotters (GERBER) aData is used to pass extra parameters
+     * Draw text with the plotter.
+     *
+     * For convenience it accept the color to use for specific plotters (GERBER) aData is used
+     * to pass extra parameters.
      */
     virtual void Text( const wxPoint&              aPos,
-                       const COLOR4D               aColor,
+                       const COLOR4D&              aColor,
                        const wxString&             aText,
                        double                      aOrient,
                        const wxSize&               aSize,
@@ -421,17 +429,19 @@ public:
                        bool                        aItalic,
                        bool                        aBold,
                        bool                        aMultilineAllowed = false,
-                       void* aData = NULL );
+                       void* aData = nullptr );
 
     /**
-     * Draw a marker (used for the drill map)
+     * Draw a marker (used for the drill map).
      */
     static const unsigned MARKER_COUNT = 58;
 
     /**
      * Draw a pattern shape number aShapeId, to coord position.
-     * Diameter diameter = (coord table) hole
-     * AShapeId = index (used to generate forms characters)
+     *
+     * @param aPosition is the position of the marker.
+     * @param aDiameter is the diameter of the marker.
+     * @param aShapeId is the index (used to generate forms characters).
      */
     void Marker( const wxPoint& position, int diametre, unsigned aShapeId );
 
@@ -439,6 +449,7 @@ public:
      * Set the current Gerber layer polarity to positive or negative
      * by writing \%LPD*\% or \%LPC*\% to the Gerber file, respectively.
      * (obviously starts a new Gerber layer, too)
+     *
      * @param aPositive is the layer polarity and true for positive.
      * It's not useful with most other plotter since they can't 'scratch'
      * the film like photoplotter imagers do
@@ -450,7 +461,7 @@ public:
 
     /**
      * Change the current text mode. See the PlotTextMode
-     * explanation at the beginning of the file
+     * explanation at the beginning of the file.
      */
     virtual void SetTextMode( PLOT_TEXT_MODE mode )
     {
@@ -536,21 +547,19 @@ protected:
     // Coordinate and scaling conversion functions
 
     /**
-     * Modifies coordinates according to the orientation,
-     * scale factor, and offsets trace. Also convert from a wxPoint to DPOINT,
-     * since some output engines needs floating point coordinates.
+     * Modify coordinates according to the orientation, scale factor, and offsets trace. Also
+     * convert from a wxPoint to DPOINT, since some output engines needs floating point
+     * coordinates.
      */
     virtual DPOINT userToDeviceCoordinates( const wxPoint& aCoordinate );
 
     /**
-     * Modifies size according to the plotter scale factors
-     * (wxSize version, returns a DPOINT)
+     * Modify size according to the plotter scale factors (wxSize version, returns a DPOINT).
      */
     virtual DPOINT userToDeviceSize( const wxSize& size );
 
     /**
-     * Modifies size according to the plotter scale factors
-     * (simple double version)
+     * Modify size according to the plotter scale factors (simple double version).
      */
     virtual double userToDeviceSize( double size ) const;