optimize Bitmap::Erase() for Skia by delaying the erase (tdf#134363)

Tdf#134363 causes OutputDevice::DrawTransformBitmapExDirect()
to create a huge 1bpp bitmap as mask, and Skia code then tries
to convert all the bits to a format Skia would understand. Which
is wasteful, as SkShader with the color given will do the same
task much more efficiently.

Change-Id: If0bba16f56fed9c3720be801b25a1e703054ed8d
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/97488
Tested-by: Jenkins
Reviewed-by: Luboš Luňák <l.lunak@collabora.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/vcl/source/bitmap/bitmappaint.cxx b/vcl/source/bitmap/bitmappaint.cxx
index 22ddf2ea5e6b..046b0e3ba3b5 100644
--- a/vcl/source/bitmap/bitmappaint.cxx
+++ b/vcl/source/bitmap/bitmappaint.cxx
@@ -36,6 +36,19 @@ bool Bitmap::Erase(const Color& rFillColor)
     if (IsEmpty())
         return true;
 
+    if (mxSalBmp)
+    {
+        // implementation specific replace
+        std::shared_ptr<SalBitmap> xImpBmp(ImplGetSVData()->mpDefInst->CreateSalBitmap());
+        if (xImpBmp->Create(*mxSalBmp) && xImpBmp->Erase(rFillColor))
+        {
+            ImplSetSalBitmap(xImpBmp);
+            maPrefMapMode = MapMode(MapUnit::MapPixel);
+            maPrefSize = xImpBmp->GetSize();
+            return true;
+        }
+    }
+
     BitmapScopedWriteAccess pWriteAcc(*this);
     bool bRet = false;