[PATCH 0/2] MR10724: gdiplus: Elide empty spans.

[Conor McCarthy (＠cmccarthy)]

We assume a span is never empty and therefore can never begin at the
right bound. An empty span there can break the requirement in
combine_regions_to_spans() that current span Y coordinates are never less
than the loop Y coordinate. Empty spans also break the in_left and
in_right calculation.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=59678

The added test will assert without the fix.

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/10724

[PATCH 1/2] gdiplus: Elide empty spans.

[Conor McCarthy]

From: Conor McCarthy <[e-mail]>

We assume a span is never empty and therefore can never begin at the
right bound. An empty span there can break the requirement in
combine_regions_to_spans() that current span Y coordinates are never less
than the loop Y coordinate. Empty spans also break the in_left and
in_right calculation.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=59678
---
 dlls/gdiplus/region.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/dlls/gdiplus/region.c b/dlls/gdiplus/region.c
index e430308685b..0969aa6aacb 100644
--- a/dlls/gdiplus/region.c
+++ b/dlls/gdiplus/region.c
@@ -2261,6 +2261,10 @@ static GpStatus edge_list_to_spans_alternate(struct edge_list *edges, struct spa
 
         assert(edge[0].y == edge[1].y);
 
+        /* edges can be collapsed to the left or right bound, making an empty span */
+        if (edge[0].x == edge[1].x)
+            continue;
+
         span = &spans->spans[spans->length++];
         span->x[0] = edge[0].x;
         span->x[1] = edge[1].x;
-- 
GitLab


https://gitlab.winehq.org/wine/wine/-/merge_requests/10724

[PATCH 2/2] gdiplus/tests: Test a region intersect which produces empty spans.

[Conor McCarthy]

From: Conor McCarthy <[e-mail]>

---
 dlls/gdiplus/tests/region.c | 49 +++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

diff --git a/dlls/gdiplus/tests/region.c b/dlls/gdiplus/tests/region.c
index 00837096092..2f9d447264f 100644
--- a/dlls/gdiplus/tests/region.c
+++ b/dlls/gdiplus/tests/region.c
@@ -2727,6 +2727,54 @@ static void test_rounding(void)
     GdipDeleteMatrix(matrix);
 }
 
+static void test_empty_spans(void)
+{
+    GpStatus status;
+    GpGraphics *graphics;
+    GpBitmap *bitmap;
+    GpPath *path, *path2;
+    const GpPointF inside_path_points[] = { { 20, 20 }, { 80, 20 }, { 80, 80 } };
+    const GpPointF outside_path_points[] = { { 100, 20 }, { 101, 20 }, { 101, 80 } };
+    GpRegion *region;
+    GpBrush *brush;
+
+    status = GdipCreateBitmapFromScan0(100, 100, 400, PixelFormat32bppARGB, NULL, &bitmap);
+    expect(Ok, status);
+
+    status = GdipGetImageGraphicsContext((GpImage*)bitmap, &graphics);
+    expect(Ok, status);
+
+    GdipCreatePath(FillModeAlternate, &path);
+    status = GdipAddPathPolygon(path, inside_path_points, ARRAY_SIZE(inside_path_points));
+    expect(Ok, status);
+
+    GdipCreatePath(FillModeAlternate, &path2);
+    /* add a path inside the device bounds and one outside,
+     * resulting in an empty span at the end of each scanline */
+    status = GdipAddPathPolygon(path2, inside_path_points, ARRAY_SIZE(inside_path_points));
+    expect(Ok, status);
+    status = GdipAddPathPolygon(path2, outside_path_points, ARRAY_SIZE(outside_path_points));
+    expect(Ok, status);
+
+    status = GdipCreateRegionPath(path, ®ion);
+    expect(Ok, status);
+    status = GdipCombineRegionPath(region, path2, CombineModeIntersect);
+    expect(Ok, status);
+
+    status = GdipCreateSolidFill(0xffffffff, (GpSolidFill**)&brush);
+    expect(Ok, status);
+
+    status = GdipFillRegion(graphics, brush, region);
+    expect(Ok, status);
+
+    GdipDeleteBrush(brush);
+    GdipDeleteRegion(region);
+    GdipDeletePath(path2);
+    GdipDeletePath(path);
+    GdipDisposeImage((GpImage*)bitmap);
+    GdipDeleteGraphics(graphics);
+}
+
 START_TEST(region)
 {
     struct GdiplusStartupInput gdiplusStartupInput;
@@ -2763,6 +2811,7 @@ START_TEST(region)
     test_GdipCreateRegionRgnData();
     test_incombinedregion();
     test_rounding();
+    test_empty_spans();
 
     GdiplusShutdown(gdiplusToken);
 }
-- 
GitLab

https://gitlab.winehq.org/wine/wine/-/merge_requests/10724

[Bartosz Kosiorek (＠gang65)]

Nice fix!

Please swap order of commits.

First should be commit with tests and `todo_wine`. As a result it will be visible what kind of failures you are fixing.

The second commit with fix, and removal of `todo_wine`.

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/10724#note_137405

[Conor McCarthy (＠cmccarthy)]

On Thu Apr 23 05:10:39 2026 +0000, Bartosz Kosiorek wrote:
> Nice fix!
> Please swap order of commits.
> First should be commit with tests and `todo_wine`. As a result it will
> be visible what kind of failures you are fixing.
> The second commit with fix, and removal of `todo_wine`.
> We do not want tests to assert ;)

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/10724#note_137406

[Esme Povirk (＠madewokherd)]

Esme Povirk (@madewokherd) commented about dlls/gdiplus/tests/region.c:
> +    GpStatus status;
> +    GpGraphics *graphics;
> +    GpBitmap *bitmap;
> +    GpPath *path, *path2;
> +    const GpPointF inside_path_points[] = { { 20, 20 }, { 80, 20 }, { 80, 80 } };
> +    const GpPointF outside_path_points[] = { { 100, 20 }, { 101, 20 }, { 101, 80 } };
> +    GpRegion *region;
> +    GpBrush *brush;
> +
> +    status = GdipCreateBitmapFromScan0(100, 100, 400, PixelFormat32bppARGB, NULL, &bitmap);
> +    expect(Ok, status);
> +
> +    status = GdipGetImageGraphicsContext((GpImage*)bitmap, &graphics);
> +    expect(Ok, status);
> +
> +    GdipCreatePath(FillModeAlternate, &path);
> Please test status for the GdipCreatePath calls. We don't need to handle the failure, just need to know if it fails.

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/10724#note_137778