Custom pads: fix incorrect shape of masks when the shape is a polygon with holes and the mask margin is < 0.

This is mainly the solder paste layer that shows this issue.
This is due to the fact SHAPE_POLY_SET::Inflate does not work fine with polygons with linked holes.
SHAPE_POLY_SET::InflateWithLinkedHoles it added to fix this issue.

Fixes: lp:1828287
https://bugs.launchpad.net/kicad/+bug/1828287

common/convert_basic_shapes_to_polygon.cpp

@@ -32,11 +32,42 @@
 #include <common.h>
 #include <convert_basic_shapes_to_polygon.h>
 
+/**
+ * Function TransformCircleToPolygon
+ * convert a circle to a polygon, using multiple straight lines
+ * @param aBuffer = a SHAPE_LINE_CHAIN to store the polygon corners
+ * @param aCenter = the center of the circle
+ * @param aRadius = the radius of the circle
+ * @param aCircleToSegmentsCount = the number of segments to approximate a circle
+ * Note: the polygon is inside the circle, so if you want to have the polygon
+ * outside the circle, you should give aRadius calculated with a correction factor
+ */
+void TransformCircleToPolygon( SHAPE_LINE_CHAIN& aBuffer,
+                               wxPoint aCenter, int aRadius,
+                               int aCircleToSegmentsCount )
+{
+    wxPoint corner_position;
+    double delta    = 3600.0 / aCircleToSegmentsCount;    // rot angle in 0.1 degree
+    double halfstep = delta/2;    // the starting value for rot angles
+
+    for( int ii = 0; ii < aCircleToSegmentsCount; ii++ )
+    {
+        corner_position.x   = aRadius;
+        corner_position.y   = 0;
+        double angle = (ii * delta) + halfstep;
+        RotatePoint( &corner_position, angle );
+        corner_position += aCenter;
+        aBuffer.Append( corner_position.x, corner_position.y );
+    }
+
+    aBuffer.SetClosed( true );
+}
+
 
 /**
  * Function TransformCircleToPolygon
  * convert a circle to a polygon, using multiple straight lines
- * @param aCornerBuffer = a buffer to store the polygon
+ * @param aCornerBuffer = a SHAPE_POLY_SET to store the polygon
  * @param aCenter = the center of the circle
  * @param aRadius = the radius of the circle
  * @param aCircleToSegmentsCount = the number of segments to approximate a circle
@@ -454,40 +485,14 @@ void TransformRingToPolygon( SHAPE_POLY_SET& aCornerBuffer,
         return;
     }
 
-    aCornerBuffer.NewOutline();
+    SHAPE_POLY_SET buffer;
 
-    // Draw the inner circle of the ring
+    TransformCircleToPolygon( buffer, aCentre, outer_radius, aCircleToSegmentsCount );
-    int     delta = 3600 / aCircleToSegmentsCount;   // rotate angle in 0.1 degree
 
-    for( int ii = 0; ii < 3600; ii += delta )
+    // Build the hole:
-    {
+    buffer.NewHole();
-        curr_point.x    = inner_radius;
+    TransformCircleToPolygon( buffer.Hole( 0, 0 ), aCentre, inner_radius, aCircleToSegmentsCount );
-        curr_point.y    = 0;
-        RotatePoint( &curr_point, ii );
-        curr_point      += aCentre;
-        aCornerBuffer.Append( curr_point.x, curr_point.y );
-    }
 
-    // Draw the last point of inner circle
+    buffer.Fracture( SHAPE_POLY_SET::PM_FAST );
-    aCornerBuffer.Append( aCentre.x + inner_radius, aCentre.y );
+    aCornerBuffer.Append( buffer );
-
-    // Draw the outer circle of the ring
-    // the first point creates also a segment from the inner to the outer polygon
-    for( int ii = 0; ii < 3600; ii += delta )
-    {
-        curr_point.x    = outer_radius;
-        curr_point.y    = 0;
-        RotatePoint( &curr_point, -ii );
-        curr_point      += aCentre;
-        aCornerBuffer.Append( curr_point.x, curr_point.y );
-    }
-
-    // Draw the last point of outer circle
-    aCornerBuffer.Append( aCentre.x + outer_radius, aCentre.y );
-
-    // And connect the outer polygon to the inner polygon,.
-    // because a segment from inner to the outer polygon was already created,
-    // the final polygon is the inner and the outer outlines connected by
-    // 2 overlapping segments
-    aCornerBuffer.Append( aCentre.x + inner_radius, aCentre.y );
 }

common/geometry/shape_poly_set.cpp

@@ -544,6 +544,14 @@ void SHAPE_POLY_SET::BooleanIntersection( const SHAPE_POLY_SET& a,
 }
 
 
+void SHAPE_POLY_SET::InflateWithLinkedHoles( int aFactor, int aCircleSegmentsCount, POLYGON_MODE aFastMode )
+{
+    Simplify( aFastMode );
+    Inflate( aFactor, aCircleSegmentsCount );
+    Fracture( aFastMode );
+}
+
+
 void SHAPE_POLY_SET::Inflate( int aFactor, int aCircleSegmentsCount )
 {
     // A static table to avoid repetitive calculations of the coefficient

include/geometry/shape_poly_set.h

@@ -830,11 +830,23 @@ class SHAPE_POLY_SET : public SHAPE
         void BooleanIntersection( const SHAPE_POLY_SET& a, const SHAPE_POLY_SET& b,
                                   POLYGON_MODE aFastMode );
 
-        ///> Performs outline inflation/deflation, using round corners.
+        /** Performs outline inflation/deflation, using round corners.
+         * Polygons cna have holes, but not linked holes with main outlines,
+         * if aFactor < 0.
+         * When aFactor is < 0 a bad shape can result from these extra-segments used to
+         * link holes to main outlines
+         * Use InflateWithLinkedHoles for these polygons, especially if aFactor < 0
+         */
         void Inflate( int aFactor, int aCircleSegmentsCount );
 
-        ///> Converts a set of polygons with holes to a singe outline with "slits"/"fractures" connecting the outer ring
+        ///> Performs outline inflation/deflation, using round corners.
-        ///> to the inner holes
+        ///> Polygons can have holes, and/or linked holes with main outlines.
+        ///> The resulting polygons are laso polygons with linked holes to main outlines
+        ///> For aFastMode meaning, see function booleanOp
+        void InflateWithLinkedHoles( int aFactor, int aCircleSegmentsCount, POLYGON_MODE aFastMode );
+
+        ///> Converts a set of polygons with holes to a singe outline with "slits"/"fractures"
+        ///> connecting the outer ring to the inner holes
         ///> For aFastMode meaning, see function booleanOp
         void Fracture( POLYGON_MODE aFastMode );
 

pcbnew/board_items_to_polygon_shape_transform.cpp

@@ -791,11 +791,12 @@ void D_PAD::TransformShapeWithClearanceToPolygon( SHAPE_POLY_SET& aCornerBuffer,
     case PAD_SHAPE_CUSTOM:
     {
         int clearance = KiROUND( aClearanceValue * aCorrectionFactor );
-
         SHAPE_POLY_SET outline;     // Will contain the corners in board coordinates
         outline.Append( m_customShapeAsPolygon );
         CustomShapeAsPolygonToBoardPosition( &outline, GetPosition(), GetOrientation() );
+        outline.Simplify( SHAPE_POLY_SET::PM_FAST );
         outline.Inflate( clearance, aCircleToSegmentsCount );
+        outline.Fracture( SHAPE_POLY_SET::PM_FAST );
         aCornerBuffer.Append( outline );
     }
         break;

pcbnew/pad_draw_functions.cpp

@@ -530,24 +530,19 @@ void D_PAD::DrawShape( EDA_RECT* aClipBox, wxDC* aDC, PAD_DRAWINFO& aDrawInfo )
         const int segmentToCircleCount = ARC_APPROX_SEGMENTS_COUNT_HIGH_DEF;
 
         if( aDrawInfo.m_Mask_margin.x )
-        {
+            outline.InflateWithLinkedHoles( aDrawInfo.m_Mask_margin.x,
-            SHAPE_POLY_SET clearance_outline;
+                        segmentToCircleCount, SHAPE_POLY_SET::PM_FAST );
-            clearance_outline.Append( outline );
-            clearance_outline.Inflate( aDrawInfo.m_Mask_margin.x, segmentToCircleCount );
-        }
-        else
-        {
-            // Draw the polygon: only one polygon is expected
-            // However we provide a multi polygon shape drawing
-            // ( for the future or to show a non expected shape )
-            for( int jj = 0; jj < outline.OutlineCount(); ++jj )
-            {
-                poly = &outline.Outline( jj );
 
-                GRClosedPoly( aClipBox, aDC, poly->PointCount(),
+        // Draw the polygon: only one polygon is expected
-                        (wxPoint*)&poly->Point( 0 ), aDrawInfo.m_ShowPadFilled, 0,
+        // However we provide a multi polygon shape drawing
-                        aDrawInfo.m_Color, aDrawInfo.m_Color );
+        // ( can happen with CUSTOM pads and negative margins )
-            }
+        for( int jj = 0; jj < outline.OutlineCount(); ++jj )
+        {
+            poly = &outline.Outline( jj );
+
+            GRClosedPoly( aClipBox, aDC, poly->PointCount(),
+                    (wxPoint*)&poly->Point( 0 ), aDrawInfo.m_ShowPadFilled, 0,
+                    aDrawInfo.m_Color, aDrawInfo.m_Color );
         }
 
         if( aDrawInfo.m_PadClearance )

pcbnew/pcb_painter.cpp

@@ -846,7 +846,10 @@ void PCB_PAINTER::draw( const D_PAD* aPad, int aLayer )
             SHAPE_POLY_SET outline;
             outline.Append( aPad->GetCustomShapeAsPolygon() );
             const int segmentToCircleCount = ARC_APPROX_SEGMENTS_COUNT_HIGH_DEF;
-            outline.Inflate( custom_margin, segmentToCircleCount );
+            // outline polygon can have holes linked to the main outline.
+            // So use InflateWithLinkedHoles(), not Inflate() that can create
+            // bad shapes if custom_margin is < 0
+            outline.InflateWithLinkedHoles( custom_margin, segmentToCircleCount, SHAPE_POLY_SET::PM_FAST );
             m_gal->DrawPolygon( outline );
         }
         else

pcbnew/plot_board_layers.cpp

@@ -451,7 +451,11 @@ void PlotStandardLayer( BOARD *aBoard, PLOTTER* aPlotter,
                 D_PAD dummy( *pad );
                 SHAPE_POLY_SET shape;
                 pad->MergePrimitivesAsPolygon( &shape, 64 );
-                shape.Inflate( margin.x, ARC_APPROX_SEGMENTS_COUNT_HIGH_DEF );
+                // shape polygon can have holes linked to the main outline.
+                // So use InflateWithLinkedHoles(), not Inflate() that can create
+                // bad shapes if margin.x is < 0
+                shape.InflateWithLinkedHoles( margin.x, ARC_APPROX_SEGMENTS_COUNT_HIGH_DEF,
+                                              SHAPE_POLY_SET::PM_FAST );
                 dummy.DeletePrimitivesList();
                 dummy.AddPrimitive( shape, 0 );
                 dummy.MergePrimitivesAsPolygon();