tdf#153306 prevent subpixel shifting of X coordinate
HACK: for some unknown reason, if the X coordinate of the
path's bounds is more than 1024, SkBlendMode::kExclusion will
shift by about a half a pixel to the right with Skia/Metal on
a Retina display. Weirdly, if the same polygon is repeatedly
drawn, the total shift is cumulative so if the drawn polygon
is more than a few pixels wide, the blinking cursor in Writer
will exhibit this bug but only for one thin vertical slice at
a time. Apparently, shifting drawing a very tiny amount to
the left seems to be enough to quell this runaway cumulative
X coordinate shift.
Change-Id: Ic1ac8a390df51c4aa1cc3183590dce72059af6b6
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/166766
Reviewed-by: Patrick Luby <guibomacdev@gmail.com>
Tested-by: Jenkins
diff --git a/vcl/skia/gdiimpl.cxx b/vcl/skia/gdiimpl.cxx
index f90fbac..4c34d9a 100644
--- a/vcl/skia/gdiimpl.cxx
+++ b/vcl/skia/gdiimpl.cxx
@@ -1508,6 +1508,26 @@ void SkiaSalGraphicsImpl::invert(basegfx::B2DPolygon const& rPoly, SalInvert eFl
aPaint.setShader(aBitmap.makeShader(SkTileMode::kRepeat, SkTileMode::kRepeat,
SkSamplingOptions()));
}
#ifdef SK_METAL
// tdf#153306 prevent subpixel shifting of X coordinate
// HACK: for some unknown reason, if the X coordinate of the
// path's bounds is more than 1024, SkBlendMode::kExclusion will
// shift by about a half a pixel to the right with Skia/Metal on
// a Retina display. Weirdly, if the same polygon is repeatedly
// drawn, the total shift is cumulative so if the drawn polygon
// is more than a few pixels wide, the blinking cursor in Writer
// will exhibit this bug but only for one thin vertical slice at
// a time. Apparently, shifting drawing a very tiny amount to
// the left seems to be enough to quell this runaway cumulative
// X coordinate shift.
if (isGPU())
{
SkMatrix aMatrix;
aMatrix.set(SkMatrix::kMTransX, -0.001);
getDrawCanvas()->concat(aMatrix);
}
#endif
}
getDrawCanvas()->drawPath(aPath, aPaint);
}
