Reimplement fix for tdf#156629 and tdf#156630

Reimplement fix in commit 926c5246b6694d469a6caed5d7ea4c3a68648468
in an attempt to reduce the fix's performance hit. Instead of
invoking EnsureBitmapData() and converting the SkImage to a
memory buffer, any pending scaling on alpha masks is handled by
creating a new, scaled SkImage.

Note that in commit 926c5246b6694d469a6caed5d7ea4c3a68648468,
EnsureBitmapData() was invoked which converted the SkImage to a
memory buffer. That in turn would make Invert() a noop which
fixed the related bug where an image has been opened and, before
it has been printed or run in a slideshow, the alpha mask would
unexpectedly be inverted. So keep this immutable behavior without
calling EnsureBitmapData() by adding a new mutability flag.

Change-Id: I99dc272b40c53664ea49333402a6a637b1548a5f
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/155850
Tested-by: Jenkins
Reviewed-by: Patrick Luby <plubius@neooffice.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/vcl/inc/skia/salbmp.hxx b/vcl/inc/skia/salbmp.hxx
index 3c8b1a964806..c42aa30f4654 100644
--- a/vcl/inc/skia/salbmp.hxx
+++ b/vcl/inc/skia/salbmp.hxx
@@ -211,6 +211,7 @@ private:
     boost::shared_ptr<sal_uInt8[]> mBuffer;
     int mScanlineSize; // size of one row in mBuffer (based on mPixelsSize)
     sk_sp<SkImage> mImage; // possibly GPU-backed
+    bool mImageImmutable = false;
     sk_sp<SkImage> mAlphaImage; // cached contents as alpha image, possibly GPU-backed
     // Actual scaling triggered by scale() is done on-demand. This is the size of the pixel
     // data in mBuffer, if it differs from mSize, then there is a scaling operation pending.