vcl/qa/cppunit/bitmaprender/BitmapRenderTest.cxx | 10 ++++++++++
vcl/source/gdi/virdev.cxx | 10 +++++++++-
2 files changed, 19 insertions(+), 1 deletion(-)
New commits:
commit 72d523f4010647041f7ed95bf3329529e0a48af8
Author: Noel Grandin <noel.gran...@collabora.co.uk>
AuthorDate: Sun Aug 3 13:05:32 2025 +0200
Commit: Noel Grandin <noelgran...@gmail.com>
CommitDate: Sun Aug 3 21:58:26 2025 +0200
SetOutputSizePixel(bAlphaMaskTransparent=true) should make..
the background transparent.
I initially tried debugging this on both Windwos and macOS.
Both quickly descended into nightmare.
On macOS we have CGLayer interposing itself with a bunch
of extra weirdness.
On Windows we have WinSalVirtualDevice sometimes rendering
to a GDI bitmap and then inexplicably switching to using
a skia surface.
I will leave all that alone for now and just use a bigger
hammer.
Change-Id: I0a485b526af29e841e7267430800bd8ca394d871
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/188869
Reviewed-by: Noel Grandin <noel.gran...@collabora.co.uk>
Tested-by: Jenkins
diff --git a/vcl/qa/cppunit/bitmaprender/BitmapRenderTest.cxx
b/vcl/qa/cppunit/bitmaprender/BitmapRenderTest.cxx
index 5a39f97c8d10..b62ba4239de4 100644
--- a/vcl/qa/cppunit/bitmaprender/BitmapRenderTest.cxx
+++ b/vcl/qa/cppunit/bitmaprender/BitmapRenderTest.cxx
@@ -45,6 +45,7 @@ public:
void testDrawAlphaBitmapEx();
void testAlphaVirtualDevice();
void testTdf116888();
+ void testAlphaErase();
CPPUNIT_TEST_SUITE(BitmapRenderTest);
CPPUNIT_TEST(testTdf104141);
@@ -52,6 +53,7 @@ public:
CPPUNIT_TEST(testDrawAlphaBitmapEx);
CPPUNIT_TEST(testAlphaVirtualDevice);
CPPUNIT_TEST(testTdf116888);
+ CPPUNIT_TEST(testAlphaErase);
CPPUNIT_TEST_SUITE_END();
};
@@ -280,6 +282,14 @@ void BitmapRenderTest::testTdf116888()
pAccess->GetColor(pAccess->Height() - 1,
pAccess->Width() - 1));
}
+void BitmapRenderTest::testAlphaErase()
+{
+ // verify that SetOutputSizePixel correctly produces a transparent
background
+ ScopedVclPtrInstance<VirtualDevice> xDev(DeviceFormat::WITH_ALPHA);
+ xDev->SetOutputSizePixel(Size(10, 10), /*bErase*/ true,
/*bAlphaMaskTransparent*/ true);
+ CPPUNIT_ASSERT_EQUAL(Color(ColorAlpha, 0x00, 0x00, 0x00, 0x00),
xDev->GetPixel(Point(0, 0)));
+}
+
CPPUNIT_TEST_SUITE_REGISTRATION(BitmapRenderTest);
CPPUNIT_PLUGIN_IMPLEMENT();
diff --git a/vcl/source/gdi/virdev.cxx b/vcl/source/gdi/virdev.cxx
index 07729bba42f0..c8245a4c4934 100644
--- a/vcl/source/gdi/virdev.cxx
+++ b/vcl/source/gdi/virdev.cxx
@@ -286,7 +286,15 @@ bool VirtualDevice::InnerImplSetOutputSizePixel( const
Size& rNewSize, bool bEra
{
mnOutWidth = rNewSize.Width();
mnOutHeight = rNewSize.Height();
- Erase();
+ // So, in theory, the bAlphaMaskTransparent param to the SetSize()
call just above should
+ // be initialising the data to transparent. But this only works on
Linux. On Windows and macOS we
+ // have two different kinds of problems in the VirtualDevice
subclasses,
+ // which means that it ends up being completely ineffective.
+ // So just take the heavy handed approach here and force the data
to transparent.
+ if (bAlphaMaskTransparent)
+ DrawWallpaper(tools::Rectangle(0, 0, mnOutWidth, mnOutHeight),
Wallpaper(COL_TRANSPARENT));
+ else
+ Erase();
}
}
else
