add unittest for SkiaSalBitmap copy-on-write data sharing

Change-Id: I2e331785d49c55116bf9cb893be25da1067df8ee
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/104283
Tested-by: Jenkins
Reviewed-by: Luboš Luňák <l.lunak@collabora.com>

3 files changed, 46 insertions, 0 deletions

diff --git a/vcl/inc/skia/salbmp.hxx b/vcl/inc/skia/salbmp.hxx
index 49aabcf69a7f..9edb1d620e3a 100644
--- a/vcl/inc/skia/salbmp.hxx
+++ b/vcl/inc/skia/salbmp.hxx
@@ -94,6 +94,9 @@ public:
     bool unittestHasImage() const { return mImage.get(); }
     bool unittestHasAlphaImage() const { return mAlphaImage.get(); }
     bool unittestHasEraseColor() const { return mEraseColorSet; }
+    const sal_uInt8* unittestGetBuffer() const { return mBuffer.get(); }
+    const SkImage* unittestGetImage() const { return mImage.get(); }
+    const SkImage* unittestGetAlphaImage() const { return mAlphaImage.get(); }
 
 private:
     // Reset the state to pixel data (resets cached images allocated in GetSkImage()/GetAlphaSkImage()).
diff --git a/vcl/qa/cppunit/skia/skia.cxx b/vcl/qa/cppunit/skia/skia.cxx
index c3f1c215b570..00c99823e986 100644
--- a/vcl/qa/cppunit/skia/skia.cxx
+++ b/vcl/qa/cppunit/skia/skia.cxx
@@ -34,12 +34,14 @@ public:
     void testDrawShaders();
     void testInterpretAs8Bit();
     void testAlphaBlendWith();
+    void testBitmapCopyOnWrite();
 
     CPPUNIT_TEST_SUITE(SkiaTest);
     CPPUNIT_TEST(testBitmapErase);
     CPPUNIT_TEST(testDrawShaders);
     CPPUNIT_TEST(testInterpretAs8Bit);
     CPPUNIT_TEST(testAlphaBlendWith);
+    CPPUNIT_TEST(testBitmapCopyOnWrite);
     CPPUNIT_TEST_SUITE_END();
 
 private:
@@ -261,6 +263,46 @@ void SkiaTest::testAlphaBlendWith()
                          AlphaMask::ScopedReadAccess(alpha)->GetPixelIndex(0, 0));
 }
 
+void SkiaTest::testBitmapCopyOnWrite()
+{
+    if (!SkiaHelper::isVCLSkiaEnabled())
+        return;
+    SkiaSalBitmap bitmap;
+    CPPUNIT_ASSERT(bitmap.Create(Size(10, 10), 24, BitmapPalette()));
+    bitmap.GetSkImage();
+    bitmap.GetAlphaSkImage();
+    CPPUNIT_ASSERT(bitmap.unittestHasBuffer());
+    CPPUNIT_ASSERT(bitmap.unittestHasImage());
+    CPPUNIT_ASSERT(bitmap.unittestHasAlphaImage());
+    SkiaSalBitmap bitmap2;
+    CPPUNIT_ASSERT(bitmap2.Create(bitmap));
+    // Data should be shared.
+    CPPUNIT_ASSERT_EQUAL(bitmap.unittestGetBuffer(), bitmap2.unittestGetBuffer());
+    CPPUNIT_ASSERT(bitmap2.unittestHasImage());
+    CPPUNIT_ASSERT(bitmap2.unittestHasAlphaImage());
+    CPPUNIT_ASSERT_EQUAL(bitmap.unittestGetImage(), bitmap2.unittestGetImage());
+    CPPUNIT_ASSERT_EQUAL(bitmap.unittestGetAlphaImage(), bitmap2.unittestGetAlphaImage());
+    // Reading still should keep the data shrared.
+    const SkImage* oldImage = bitmap.unittestGetImage();
+    const SkImage* oldAlphaImage = bitmap.unittestGetAlphaImage();
+    BitmapBuffer* buffer = bitmap.AcquireBuffer(BitmapAccessMode::Read);
+    CPPUNIT_ASSERT_EQUAL(bitmap.unittestGetBuffer(), bitmap2.unittestGetBuffer());
+    bitmap.ReleaseBuffer(buffer, BitmapAccessMode::Read);
+    // Images get possibly updated only after releasing the buffer.
+    CPPUNIT_ASSERT_EQUAL(bitmap.unittestGetImage(), bitmap2.unittestGetImage());
+    CPPUNIT_ASSERT_EQUAL(bitmap.unittestGetAlphaImage(), bitmap2.unittestGetAlphaImage());
+    CPPUNIT_ASSERT_EQUAL(bitmap.unittestGetImage(), oldImage);
+    CPPUNIT_ASSERT_EQUAL(bitmap.unittestGetAlphaImage(), oldAlphaImage);
+    // Writing should unshare.
+    buffer = bitmap.AcquireBuffer(BitmapAccessMode::Write);
+    CPPUNIT_ASSERT(bitmap.unittestGetBuffer() != bitmap2.unittestGetBuffer());
+    bitmap.ReleaseBuffer(buffer, BitmapAccessMode::Write);
+    CPPUNIT_ASSERT(bitmap.unittestGetImage() != bitmap2.unittestGetImage());
+    CPPUNIT_ASSERT(bitmap.unittestGetAlphaImage() != bitmap2.unittestGetAlphaImage());
+    CPPUNIT_ASSERT(bitmap.unittestGetImage() != oldImage);
+    CPPUNIT_ASSERT(bitmap.unittestGetAlphaImage() != oldAlphaImage);
+}
+
 } // namespace
 
 CPPUNIT_TEST_SUITE_REGISTRATION(SkiaTest);
diff --git a/vcl/skia/salbmp.cxx b/vcl/skia/salbmp.cxx
index d1cd76b61d5f..49ca73beac0f 100644
--- a/vcl/skia/salbmp.cxx
+++ b/vcl/skia/salbmp.cxx
@@ -289,6 +289,7 @@ void SkiaSalBitmap::ReleaseBuffer(BitmapBuffer* pBuffer, BitmapAccessMode nMode)
     assert(pBuffer->mnWidth == mSize.Width());
     assert(pBuffer->mnHeight == mSize.Height());
     assert(pBuffer->mnBitCount == mBitCount);
+    assert(pBuffer->mpBits == mBuffer.get());
     verify();
     delete pBuffer;
 }