do not assert for slow alpha blending if mirroring is used (tdf#136223)

The blend calls obviously will be skipped if mirroring is involved.
Given how long it took for somebody to notice, this is probably a rare
case, so just alter the assert, until this functionality is actually
needed to be fast.

Change-Id: If1f558cd4a7aac2bb52b677b5901585d878c6543
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/103414
Tested-by: Jenkins
Reviewed-by: Luboš Luňák <l.lunak@collabora.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/vcl/source/outdev/bitmap.cxx b/vcl/source/outdev/bitmap.cxx
index fc6095812b6c..a9f264fa2854 100644
--- a/vcl/source/outdev/bitmap.cxx
+++ b/vcl/source/outdev/bitmap.cxx
@@ -686,10 +686,14 @@ void OutputDevice::DrawDeviceAlphaBitmap( const Bitmap& rBmp, const AlphaMask& r
     }
 
     // we need to make sure OpenGL never reaches this slow code path
+    // tdf#136223: The slow code path will be obviously also reached if mirroring
+    // is used, which makes the block above be skipped, as the blend bitmap calls
+    // do not handle that case. Given that this seems to be rather rare, just
+    // disable the assert, until faster mirroring is actually needed.
 
-    assert(!SkiaHelper::isVCLSkiaEnabled());
+    assert(!SkiaHelper::isVCLSkiaEnabled() || !bTryDirectPaint);
 #if HAVE_FEATURE_OPENGL
-    assert(!OpenGLHelper::isVCLOpenGLEnabled());
+    assert(!OpenGLHelper::isVCLOpenGLEnabled() || !bTryDirectPaint);
 #endif
     tools::Rectangle aBmpRect(Point(), rBmp.GetSizePixel());
     if (!aBmpRect.Intersection(tools::Rectangle(rSrcPtPixel, rSrcSizePixel)).IsEmpty())