Snap paint offset paint property to pixel boundaries

third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.cpp

Index: third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.cpp b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.cpp
index 80a4da496abba79ce6c567a94452e6957754bc79..ba89b11f9657d8d7b2370c6110f1c11894bad63d 100644
--- a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.cpp
@@ -918,4 +918,24 @@ TEST_F(PaintPropertyTreeBuilderTest, ColumnSpannerUnderRelativePositioned)
     EXPECT_EQ(LayoutPoint(55, 44), spanner.objectPaintProperties()->localBorderBoxProperties()->paintOffset);
 }
 
+TEST_F(PaintPropertyTreeBuilderTest, PaintOffsetPixelSnapping)
+{
+    setBodyInnerHTML(
+        "<style>"
+        "  * { margin: 0; }"
+        "  div { position: relative; }"
+        "</style>"
+        "<div id='a' style='width: 70px; height: 70px; left: 0.7px; top: 0.7px;'>"
+        "  <div id='b' style='background: red; width: 40px; height: 40px; transform: translateZ(0);'>"
+        "    <div id='c' style='background: white; width: 40px; height: 40px; left: 0.7px; top: 0.7px;'></div>"
+        "  </div>"
+        "</div>"
+    );
+
+    ObjectPaintProperties* bProperties = document().getElementById("b")->layoutObject()->objectPaintProperties();
+    EXPECT_EQ(TransformationMatrix().translate3d(0, 0, 0), bProperties->transform()->matrix());
+    // The paint offset transform should be snapped from (0.7,0.7) to (1,1).
+    EXPECT_EQ(TransformationMatrix().translate(1, 1), bProperties->transform()->parent()->matrix());

[chrishtr, 2016/06/29 23:46:30]

Is there already a unittest for not snapping if there is no transform yet
fractional paintOffset?

[pdr., 2016/06/30 16:03:12]

Added one in PaintOffsetWithBasicPixelSnapping.

[chrishtr, 2016/06/30 16:57:17]

That test still uses a transform. I was asking for one that has no transform yet
has fractional pixel offsets, to demonstrate
that they simply get added together, including integral parts.

+}
+
 } // namespace blink