work around copy-to-self SkSurface::draw() being buggy (tdf#132051)

This may become the actual fix or may be removed later depending
on the outcome of
https://groups.google.com/d/msgid/skia-discuss/202004151937.05051.l.lunak%40collabora.com .

Change-Id: I709f3e7bffbe86ddb2f6d75724bf30e4b0f0116e
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/92587
Tested-by: Jenkins
Reviewed-by: Luboš Luňák <l.lunak@collabora.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/vcl/skia/gdiimpl.cxx b/vcl/skia/gdiimpl.cxx
index 1937115e1c23..6926823a5db0 100644
--- a/vcl/skia/gdiimpl.cxx
+++ b/vcl/skia/gdiimpl.cxx
@@ -897,6 +897,16 @@ static void copyArea(SkCanvas* canvas, sk_sp<SkSurface> surface, long nDestX, lo
     // Using SkSurface::draw() should be more efficient than SkSurface::makeImageSnapshot(),
     // because it may detect copying to itself and avoid some needless copies.
     // It cannot do a subrectangle though, so clip.
+    if (canvas == surface->getCanvas())
+    {
+        // TODO: Currently copy-to-self is buggy with SkSurface::draw().
+        SkPaint paint;
+        paint.setBlendMode(SkBlendMode::kSrc); // copy as is, including alpha
+        canvas->drawImageRect(surface->makeImageSnapshot(),
+                              SkIRect::MakeXYWH(nSrcX, nSrcY, nSrcWidth, nSrcHeight),
+                              SkRect::MakeXYWH(nDestX, nDestY, nSrcWidth, nSrcHeight), &paint);
+        return;
+    }
     canvas->save();
     canvas->clipRect(SkRect::MakeXYWH(nDestX, nDestY, nSrcWidth, nSrcHeight));
     SkPaint paint;