AV in TPolygonRenderer32VPR2X.AddLineSegment

[andersmelander]

TPolygonRenderer32VPR2X fails to render the following ellipse:
Ellipse(691, 10, 3, 161)
on a bitmap with the dimensions 694, 333

Call stack:

GR32_VPR2.AddSegment(45089147,-60543,45089185,-125752)
GR32_VPR2.TPolygonRenderer32VPR2X.AddLineSegment(45088768,589822,45089148,-62259)
GR32_VPR2.TPolygonRenderer32VPR2X.PolyPolygonFS((((694, 10), (693,994079589844, 20,1092739105225), (693,976318359375, 30,1786499023438), (693,946838378906, 40,1683921813965), (693,90576171875, 50,0390739440918), (693,853149414062, 59,7517356872559), (693,789306640625, 69,2680587768555), (693,714477539062, 78,5504684448242), (693,62890625, 87,5623474121094), (693,532958984375, 96,2681274414062), (693,427062988281, 104,633430480957), (693,3115234375, 112,625274658203), (693,186889648438, 120,212097167969), (693,053649902344, 127,363967895508), (692,912292480469, 134,052642822266), (692,763366699219, 140,251754760742), (692,607482910156, 145,936813354492), (692,445251464844, 151,085388183594), (692,27734375, 155,677169799805), (692,104370117188, 159,694030761719), (691,927062988281, 163,1201171875), (691,74609375, 165,94189453125), (691,562133789062, 168,148254394531), (691,3759765625, 169,73046875), (691,188354492188, 170,68229675293), (691, 171), (690,811645507812, 170,68229675293), (690,6240234375, 169,73046875), (690,437866210938, 168,148254394531), (690,25390625, 165,94189453125), (690,072937011719, 163,120101928711), (689,895629882812, 159,69401550293), (689,72265625, 155,677154541016), (689,554748535156, 151,085372924805), (689,392517089844, 145,936782836914), (689,236633300781, 140,251724243164), (689,087707519531, 134,052627563477), (688,946350097656, 127,36393737793), (688,813110351562, 120,212066650391), (688,6884765625, 112,625244140625), (688,572937011719, 104,633407592773), (688,467041015625, 96,2680969238281), (688,37109375, 87,5623245239258), (688,285522460938, 78,5504455566406), (688,210693359375, 69,2680358886719), (688,146850585938, 59,7517127990723), (688,09423828125, 50,0390472412109), (688,053161621094, 40,1683654785156), (688,023681640625, 30,1786270141602), (688,005920410156, 20,1092491149902), (688, 9,99997711181641), (688,005920410156, -0,109296590089798), (688,023681640625, -10,1786727905273), (688,053161621094, -20,1684131622314), (688,09423828125, -30,0390911102295), (688,1468505859...
GR32_Polygons.TCustomPolygonRenderer.PolyPolygonFS((((694, 10), (693,994079589844, 20,1092739105225), (693,976318359375, 30,1786499023438), (693,946838378906, 40,1683921813965), (693,90576171875, 50,0390739440918), (693,853149414062, 59,7517356872559), (693,789306640625, 69,2680587768555), (693,714477539062, 78,5504684448242), (693,62890625, 87,5623474121094), (693,532958984375, 96,2681274414062), (693,427062988281, 104,633430480957), (693,3115234375, 112,625274658203), (693,186889648438, 120,212097167969), (693,053649902344, 127,363967895508), (692,912292480469, 134,052642822266), (692,763366699219, 140,251754760742), (692,607482910156, 145,936813354492), (692,445251464844, 151,085388183594), (692,27734375, 155,677169799805), (692,104370117188, 159,694030761719), (691,927062988281, 163,1201171875), (691,74609375, 165,94189453125), (691,562133789062, 168,148254394531), (691,3759765625, 169,73046875), (691,188354492188, 170,68229675293), (691, 171), (690,811645507812, 170,68229675293), (690,6240234375, 169,73046875), (690,437866210938, 168,148254394531), (690,25390625, 165,94189453125), (690,072937011719, 163,120101928711), (689,895629882812, 159,69401550293), (689,72265625, 155,677154541016), (689,554748535156, 151,085372924805), (689,392517089844, 145,936782836914), (689,236633300781, 140,251724243164), (689,087707519531, 134,052627563477), (688,946350097656, 127,36393737793), (688,813110351562, 120,212066650391), (688,6884765625, 112,625244140625), (688,572937011719, 104,633407592773), (688,467041015625, 96,2680969238281), (688,37109375, 87,5623245239258), (688,285522460938, 78,5504455566406), (688,210693359375, 69,2680358886719), (688,146850585938, 59,7517127990723), (688,09423828125, 50,0390472412109), (688,053161621094, 40,1683654785156), (688,023681640625, 30,1786270141602), (688,005920410156, 20,1092491149902), (688, 9,99997711181641), (688,005920410156, -0,109296590089798), (688,023681640625, -10,1786727905273), (688,053161621094, -20,1684131622314), (688,09423828125, -30,0390911102295), (688,1468505...
GR32_Brushes.TCustomBrush.PolyPolygonFS($2101A80,(((694, 10), (693,994079589844, 20,1092739105225), (693,976318359375, 30,1786499023438), (693,946838378906, 40,1683921813965), (693,90576171875, 50,0390739440918), (693,853149414062, 59,7517356872559), (693,789306640625, 69,2680587768555), (693,714477539062, 78,5504684448242), (693,62890625, 87,5623474121094), (693,532958984375, 96,2681274414062), (693,427062988281, 104,633430480957), (693,3115234375, 112,625274658203), (693,186889648438, 120,212097167969), (693,053649902344, 127,363967895508), (692,912292480469, 134,052642822266), (692,763366699219, 140,251754760742), (692,607482910156, 145,936813354492), (692,445251464844, 151,085388183594), (692,27734375, 155,677169799805), (692,104370117188, 159,694030761719), (691,927062988281, 163,1201171875), (691,74609375, 165,94189453125), (691,562133789062, 168,148254394531), (691,3759765625, 169,73046875), (691,188354492188, 170,68229675293), (691, 171), (690,811645507812, 170,68229675293), (690,6240234375, 169,73046875), (690,437866210938, 168,148254394531), (690,25390625, 165,94189453125), (690,072937011719, 163,120101928711), (689,895629882812, 159,69401550293), (689,72265625, 155,677154541016), (689,554748535156, 151,085372924805), (689,392517089844, 145,936782836914), (689,236633300781, 140,251724243164), (689,087707519531, 134,052627563477), (688,946350097656, 127,36393737793), (688,813110351562, 120,212066650391), (688,6884765625, 112,625244140625), (688,572937011719, 104,633407592773), (688,467041015625, 96,2680969238281), (688,37109375, 87,5623245239258), (688,285522460938, 78,5504455566406), (688,210693359375, 69,2680358886719), (688,146850585938, 59,7517127990723), (688,09423828125, 50,0390472412109), (688,053161621094, 40,1683654785156), (688,023681640625, 30,1786270141602), (688,005920410156, 20,1092491149902), (688, 9,99997711181641), (688,005920410156, -0,109296590089798), (688,023681640625, -10,1786727905273), (688,053161621094, -20,1684131622314), (688,09423828125, -30,0390911102295), (688,146850585...
GR32_Paths.TCanvas32.DrawPath($2059A30)
GR32_Paths.TCustomCanvas.DoChanged
GR32_Paths.TCustomPath.EndUpdate
GR32_Paths.TFlattenedPath.Polygon(((694, 10), (693,994079589844, 20,1092739105225), (693,976318359375, 30,1786499023438), (693,946838378906, 40,1683921813965), (693,90576171875, 50,0390739440918), (693,853149414062, 59,7517356872559), (693,789306640625, 69,2680587768555), (693,714477539062, 78,5504684448242), (693,62890625, 87,5623474121094), (693,532958984375, 96,2681274414062), (693,427062988281, 104,633430480957), (693,3115234375, 112,625274658203), (693,186889648438, 120,212097167969), (693,053649902344, 127,363967895508), (692,912292480469, 134,052642822266), (692,763366699219, 140,251754760742), (692,607482910156, 145,936813354492), (692,445251464844, 151,085388183594), (692,27734375, 155,677169799805), (692,104370117188, 159,694030761719), (691,927062988281, 163,1201171875), (691,74609375, 165,94189453125), (691,562133789062, 168,148254394531), (691,3759765625, 169,73046875), (691,188354492188, 170,68229675293), (691, 171), (690,811645507812, 170,68229675293), (690,6240234375, 169,73046875), (690,437866210938, 168,148254394531), (690,25390625, 165,94189453125), (690,072937011719, 163,120101928711), (689,895629882812, 159,69401550293), (689,72265625, 155,677154541016), (689,554748535156, 151,085372924805), (689,392517089844, 145,936782836914), (689,236633300781, 140,251724243164), (689,087707519531, 134,052627563477), (688,946350097656, 127,36393737793), (688,813110351562, 120,212066650391), (688,6884765625, 112,625244140625), (688,572937011719, 104,633407592773), (688,467041015625, 96,2680969238281), (688,37109375, 87,5623245239258), (688,285522460938, 78,5504455566406), (688,210693359375, 69,2680358886719), (688,146850585938, 59,7517127990723), (688,09423828125, 50,0390472412109), (688,053161621094, 40,1683654785156), (688,023681640625, 30,1786270141602), (688,005920410156, 20,1092491149902), (688, 9,99997711181641), (688,005920410156, -0,109296590089798), (688,023681640625, -10,1786727905273), (688,053161621094, -20,1684131622314), (688,09423828125, -30,0390911102295), (688,146850585938, -39,7517547...
GR32_Paths.TCustomPath.Ellipse(691,10,3,161,100)

The parameter values to AddLineSegment are in fixed format, but the floating point values are:

688; 9,99997711181641; 688,005798339844; 0,0500000007450581

At the point of failure the X and Y values in AddLineSegment are 688, -2. Since these values are used as indices into a TIntegerMap the pointer value returned is outside the map and this pointer value is used in AddSegment causing the AV.

The problem can be reproduced with the Benchmark example.

[andersmelander]

Same problem drawing a line: MoveTo(467, 0), LineTo(466, 280)
Same symptoms. Also reproduced with the Benchmark example.

[andersmelander]

Source of problem appears to be an integer overflow in FixedDiv.

[PatmanSan]

FOpacityMap (TFloatMap in VPR2 and TIntegerMap in VPR2X) is created and set to size, but not initialized with data. Both AddLineSegment and DrawBitmap are reading from the uninitialized map, causing rounding and overflow errors further down the line. Adding FOpacityMap.Clear after FOpacityMap.SetSize eliminates the errors, which indicates that the map needs to be initialized with proper data for the renderer to do its magic.

[andersmelander]

TPolygonRenderer32VPR2X was deprecated in 3aa6cb8.