kicad-developers team mailing list archive

[Jon Evans <jon@xxxxxxxxxxxxx>]

Hi all,

Eldar found a test case that exposed a bug in my arc drawing code, and this
patch I think fixes the underlying problem.  If you have gerbers with arcs,
give it a shot and let me know if you notice anything wrong.

Thanks,
-Jon

From f6ec11db9404884d83ee98718da525d893c661c7 Mon Sep 17 00:00:00 2001
From: Jon Evans <jon@xxxxxxxxxxxxx>
Date: Wed, 25 Oct 2017 23:30:25 -0400
Subject: [PATCH] Fix arc drawing algorithm in GerbView GAL (Fixes lp:1720384)

---
 gerbview/gerbview_painter.cpp | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/gerbview/gerbview_painter.cpp b/gerbview/gerbview_painter.cpp
index 025886df5..bede8b7ee 100644
--- a/gerbview/gerbview_painter.cpp
+++ b/gerbview/gerbview_painter.cpp
@@ -294,12 +294,17 @@ void GERBVIEW_PAINTER::draw( /*const*/ GERBER_DRAW_ITEM* aItem, int aLayer )
     {
         isFilled = m_gerbviewSettings.m_lineFill;
 
+        // These are swapped because wxDC fills arcs counterclockwise and GAL
+        // fills them clockwise.
+        wxPoint arcStart = aItem->m_End;
+        wxPoint arcEnd = aItem->m_Start;
+
         // Gerber arcs are 3-point (start, center, end)
         // GAL needs center, radius, start angle, end angle
-        double   radius = GetLineLength( aItem->m_Start, aItem->m_ArcCentre );
+        double   radius = GetLineLength( arcStart, aItem->m_ArcCentre );
         VECTOR2D center = aItem->GetABPosition( aItem->m_ArcCentre );
-        VECTOR2D startVec = VECTOR2D( aItem->GetABPosition( aItem->m_Start ) ) - center;
-        VECTOR2D endVec = VECTOR2D( aItem->GetABPosition( aItem->m_End ) ) - center;
+        VECTOR2D startVec = VECTOR2D( aItem->GetABPosition( arcStart ) ) - center;
+        VECTOR2D endVec = VECTOR2D( aItem->GetABPosition( arcEnd ) ) - center;
 
         m_gal->SetIsFill( isFilled );
         m_gal->SetIsStroke( !isFilled );
@@ -308,11 +313,14 @@ void GERBVIEW_PAINTER::draw( /*const*/ GERBER_DRAW_ITEM* aItem, int aLayer )
         double startAngle = startVec.Angle();
         double endAngle = endVec.Angle();
 
-        if( endAngle >= M_PI )
-            endAngle *= -1;
+        // GAL fills in direction of increasing angle, so we have to convert
+        // the angle from the -PI to PI domain of atan2() to ensure that
+        // the arc goes in the right direction
+        if( ( startAngle > endAngle ) && ( endAngle < 0 ) )
+            endAngle += (2 * M_PI);
 
         // 360-degree arcs are stored in the file with start equal to end
-        if( aItem->m_Start == aItem->m_End )
+        if( arcStart == arcEnd )
         {
             startAngle = 0;
             endAngle = 2 * M_PI;
@@ -323,9 +331,9 @@ void GERBVIEW_PAINTER::draw( /*const*/ GERBER_DRAW_ITEM* aItem, int aLayer )
         // Arc Debugging
         // m_gal->SetLineWidth( 5 );
         // m_gal->SetStrokeColor( COLOR4D( 0.0, 1.0, 0.0, 1.0 ) );
-        // m_gal->DrawLine( center, aItem->GetABPosition( aItem->m_Start ) );
+        // m_gal->DrawLine( center, aItem->GetABPosition( arcStart ) );
         // m_gal->SetStrokeColor( COLOR4D( 1.0, 0.0, 0.0, 1.0 ) );
-        // m_gal->DrawLine( center, aItem->GetABPosition( aItem->m_End ) );
+        // m_gal->DrawLine( center, aItem->GetABPosition( arcEnd ) );
         break;
     }
 
-- 
2.11.0