tdf#40863 only use polygons with area for WinClipRegions

Due to a former fix CustomShapes have extra polygons with a single
point in the top-left and bottom-right corner of their BoundRect,
a workaround to allow getting their correct BoundRect in slideshow.
Unfortunately this makes the win command CreatePolyPolygonRgn fail
to create the needed ClipRegions so that the geometry is processed
without clipping. Changed to only use polygons as input that have an
area.

Change-Id: I0eeda5776402777ed00de92f42a55f206575f58b
Reviewed-on: https://gerrit.libreoffice.org/24059
Reviewed-by: Noel Grandin <noelgrandin@gmail.com>
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Armin Le Grand <Armin.Le.Grand@cib.de>

1 files changed, 32 insertions, 12 deletions

diff --git a/vcl/win/gdi/gdiimpl.cxx b/vcl/win/gdi/gdiimpl.cxx
index b3a39f162847..0317ca06319a 100644
--- a/vcl/win/gdi/gdiimpl.cxx
+++ b/vcl/win/gdi/gdiimpl.cxx
@@ -1151,6 +1151,7 @@ bool WinSalGraphicsImpl::setClipRegion( const vcl::Region& i_rClip )
             aPolyPoints.reserve( 1024 );
             std::vector< INT > aPolyCounts( nCount, 0 );
             basegfx::B2DHomMatrix aExpand;
+            sal_uInt32 nTargetCount(0);
             static bool bExpandByOneInXandY(true);
 
             if(bExpandByOneInXandY)
@@ -1167,26 +1168,45 @@ bool WinSalGraphicsImpl::setClipRegion( const vcl::Region& i_rClip )
                         aPolyPolygon.getB2DPolygon(a),
                         1));
                 const sal_uInt32 nPoints(aPoly.count());
-                aPolyCounts[a] = nPoints;
 
-                for( sal_uInt32 b = 0; b < nPoints; b++ )
+                // tdf#40863 For CustomShapes there is a hack (see
+                // f64ef72743e55389e446e0d4bc6febd475011023) that adds polygons
+                // with a single point in top-left and bottom-right corner
+                // of the BoundRect to be able to determine the correct BoundRect
+                // in the slideshow. Unfortunately, CreatePolyPolygonRgn below
+                // fails with polygons containing a single pixel, so clipping is
+                // lost. For now, use only polygons with more than two points - the
+                // ones that may have an area.
+                // Note: polygons with one point which are curves may have an area,
+                // but the polygon is already subdivided here, so no need to test
+                // this.
+                if(nPoints > 2)
                 {
-                    basegfx::B2DPoint aPt(aPoly.getB2DPoint(b));
+                    aPolyCounts[nTargetCount] = nPoints;
+                    nTargetCount++;
 
-                    if(bExpandByOneInXandY)
+                    for( sal_uInt32 b = 0; b < nPoints; b++ )
                     {
-                        aPt = aExpand * aPt;
-                    }
+                        basegfx::B2DPoint aPt(aPoly.getB2DPoint(b));
+
+                        if(bExpandByOneInXandY)
+                        {
+                            aPt = aExpand * aPt;
+                        }
 
-                    POINT aPOINT;
-                    // #i122149# do correct rounding
-                    aPOINT.x = basegfx::fround(aPt.getX());
-                    aPOINT.y = basegfx::fround(aPt.getY());
-                    aPolyPoints.push_back( aPOINT );
+                        POINT aPOINT;
+                        // #i122149# do correct rounding
+                        aPOINT.x = basegfx::fround(aPt.getX());
+                        aPOINT.y = basegfx::fround(aPt.getY());
+                        aPolyPoints.push_back( aPOINT );
+                    }
                 }
             }
 
-            mrParent.mhRegion = CreatePolyPolygonRgn( &aPolyPoints[0], &aPolyCounts[0], nCount, ALTERNATE );
+            if(nTargetCount)
+            {
+                mrParent.mhRegion = CreatePolyPolygonRgn( &aPolyPoints[0], &aPolyCounts[0], nTargetCount, ALTERNATE );
+            }
         }
     }
     else