FIX: add parameter to GAL::DrawCurve to control the curve to polyline

conversion.
Cairo supports curves, but not Opengl, that needs a conversion to polyline.
This control allows optimization in conversion

common/bezier_curves.cpp

@@ -59,7 +59,7 @@ void BEZIER_POLY::GetPoly( std::vector<VECTOR2D>& aOutput, double aMinSegLen )
     aOutput.clear();
     aOutput.push_back( m_ctrlPts[0] );
 
-    // If the Bezier curve is degenerated (straight line), skip that:
+    // If the Bezier curve is degenerated (straight line), skip intermediate points:
     bool degenerated = m_ctrlPts[0] == m_ctrlPts[1] && m_ctrlPts[2] == m_ctrlPts[3];
 
     if( !degenerated )

common/gal/cairo/cairo_gal.cpp

@@ -424,8 +424,11 @@ void CAIRO_GAL_BASE::DrawPolygon( const SHAPE_LINE_CHAIN& aPolygon )
 
 
 void CAIRO_GAL_BASE::DrawCurve( const VECTOR2D& aStartPoint, const VECTOR2D& aControlPointA,
-                           const VECTOR2D& aControlPointB, const VECTOR2D& aEndPoint )
+                                const VECTOR2D& aControlPointB, const VECTOR2D& aEndPoint,
+                                double aFilterValue )
 {
+    // Note: aFilterValue is not used because the cubic Bezier curve is
+    // supported by Cairo.
     syncLineWidth();
 
     const auto sp = roundp( xform( aStartPoint ) );

common/gal/opengl/opengl_gal.cpp

@@ -1035,7 +1035,8 @@ void OPENGL_GAL::DrawPolygon( const SHAPE_LINE_CHAIN& aPolygon )
 
 
 void OPENGL_GAL::DrawCurve( const VECTOR2D& aStartPoint, const VECTOR2D& aControlPointA,
-                            const VECTOR2D& aControlPointB, const VECTOR2D& aEndPoint )
+                            const VECTOR2D& aControlPointB, const VECTOR2D& aEndPoint,
+                            double aFilterValue )
 {
     std::vector<VECTOR2D> output;
     std::vector<VECTOR2D> pointCtrl;
@@ -1046,7 +1047,7 @@ void OPENGL_GAL::DrawCurve( const VECTOR2D& aStartPoint, const VECTOR2D& aContro
     pointCtrl.push_back( aEndPoint );
 
     BEZIER_POLY converter( pointCtrl );
-    converter.GetPoly( output, GetLineWidth() );
+    converter.GetPoly( output, aFilterValue );
 
     DrawPolyline( &output[0], output.size() );
 }

include/gal/cairo/cairo_gal.h

@@ -101,7 +101,8 @@ public:
 
     /// @copydoc GAL::DrawCurve()
     virtual void DrawCurve( const VECTOR2D& startPoint, const VECTOR2D& controlPointA,
-                            const VECTOR2D& controlPointB, const VECTOR2D& endPoint ) override;
+                            const VECTOR2D& controlPointB, const VECTOR2D& endPoint,
+                            double aFilterValue = 0.0 ) override;
 
     /// @copydoc GAL::DrawBitmap()
     virtual void DrawBitmap( const BITMAP_BASE& aBitmap ) override;

include/gal/graphics_abstraction_layer.h

@@ -179,9 +179,13 @@ public:
      * @param controlPointA is the first control point.
      * @param controlPointB is the second control point.
      * @param endPoint      is the end point of the spline.
+     * @param aFilterValue  is used by Bezier to segments approximation, if
+     * the Bezier curve is not supported and needs a curve to polyline conversion.
+     * aFilterValue = 0 means no filtering.
      */
     virtual void DrawCurve( const VECTOR2D& startPoint,    const VECTOR2D& controlPointA,
-                            const VECTOR2D& controlPointB, const VECTOR2D& endPoint ) {};
+                            const VECTOR2D& controlPointB, const VECTOR2D& endPoint,
+                            double aFilterValue = 0.0 ) {};
 
     /**
      * @brief Draw a bitmap image.

include/gal/opengl/opengl_gal.h

@@ -139,7 +139,8 @@ public:
 
     /// @copydoc GAL::DrawCurve()
     virtual void DrawCurve( const VECTOR2D& startPoint, const VECTOR2D& controlPointA,
-                            const VECTOR2D& controlPointB, const VECTOR2D& endPoint ) override;
+                            const VECTOR2D& controlPointB, const VECTOR2D& endPoint,
+                            double aFilterValue = 0.0 ) override;
 
     /// @copydoc GAL::DrawBitmap()
     virtual void DrawBitmap( const BITMAP_BASE& aBitmap ) override;

pcbnew/pcb_painter.cpp

@@ -1016,10 +1016,12 @@ void PCB_PAINTER::draw( const DRAWSEGMENT* aSegment, int aLayer )
         m_gal->SetIsFill( false );
         m_gal->SetIsStroke( true );
         m_gal->SetLineWidth( thickness );
+        // Use thickness as filter value to convert the curve to polyline
+        // when the curve is not supported
         m_gal->DrawCurve( VECTOR2D( aSegment->GetStart() ),
                           VECTOR2D( aSegment->GetBezControl1() ),
                           VECTOR2D( aSegment->GetBezControl2() ),
-                          VECTOR2D( aSegment->GetEnd() ) );
+                          VECTOR2D( aSegment->GetEnd() ), thickness );
         break;
 
     case S_LAST: