Consolidate background fill layer opaqueness into one method

third_party/WebKit/Source/core/style/FillLayer.cpp

Index: third_party/WebKit/Source/core/style/FillLayer.cpp
diff --git a/third_party/WebKit/Source/core/style/FillLayer.cpp b/third_party/WebKit/Source/core/style/FillLayer.cpp
index fd248537ea206ce98593c9aa8954f2487f991b5f..5941fb654956f7e53d470660b16a2425160eed7a 100644
--- a/third_party/WebKit/Source/core/style/FillLayer.cpp
+++ b/third_party/WebKit/Source/core/style/FillLayer.cpp
@@ -21,6 +21,7 @@
 
 #include "core/style/FillLayer.h"
 
+#include "core/layout/LayoutObject.h"
 #include "core/style/DataEquivalency.h"
 
 namespace blink {
@@ -370,27 +371,40 @@ bool FillLayer::imagesAreLoaded() const
     return true;
 }
 
-bool FillLayer::hasOpaqueImage(const LayoutObject* layoutObject) const
+bool FillLayer::imageIsOpaqueAndTilesLayer(const LayoutObject& layoutObject) const

[Stephen Chennney, 2016/03/16 20:54:16]

Put almost all the conditions surround images here.

 {
-    if (!m_image)
-        return false;
+    // Returns true if we have an image and tiling that will cover the content below it when
+    // m_composite == CompositeSourceOver && m_blendMode == WebBlendModeNormal.
+    // Otherwise false.
+    // TODO(schenney) We could relax the repeat mode requirement if we also knew the rect we
+    // had to fill, and the portion of the image we need to use, and know that the latter
+    // covers the former
+    return m_image
+        && m_image->canRender()

[Stephen Chennney, 2016/03/16 20:54:16]

Forgot to remove these. Will follow up.

+        && m_image->knownToBeOpaque(layoutObject)
+        && !m_image->imageSize(layoutObject, layoutObject.style()->effectiveZoom(), LayoutSize()).isEmpty()
+        && (m_repeatX == RepeatFill || m_repeatX == RoundFill)
+        && (m_repeatY == RepeatFill || m_repeatY == RoundFill);
 
-    // TODO(trchen): Should check blend mode before composite mode.
-    if (m_composite == CompositeClear || m_composite == CompositeCopy)
-        return true;
+}
 
-    if (m_blendMode != WebBlendModeNormal)
+bool FillLayer::imageOccludesNextLayers(const LayoutObject& layoutObject) const

[Stephen Chennney, 2016/03/16 20:54:16]

Due to the compositing modes behavior, it's not really possible to get a nice
breakdown of single conditions.

+{
+    // We can't cover without an image, regardless of other parameters
+    if (!m_image || !m_image->canRender())
         return false;
 
-    if (m_composite == CompositeSourceOver)
-        return m_image->knownToBeOpaque(*layoutObject);
-
-    return false;
-}
+    if (imageIsOpaqueAndTilesLayer(layoutObject)) {
+        // Check that the compositing and blend modes maintain the opaqueness
+        return (m_composite == CompositeClear
+            || m_composite == CompositeCopy
+            || m_composite == CompositeSourceOver)
+            && m_blendMode == WebBlendModeNormal;
+    }
 
-bool FillLayer::hasRepeatXY() const
-{
-    return m_repeatX == RepeatFill && m_repeatY == RepeatFill;
+    // The image is not opaque, but these composite modes overwrite the background
+    // regardless of the foreground.
+    return (m_composite == CompositeClear || m_composite == CompositeCopy);

[Stephen Chennney, 2016/03/16 20:54:16]

This is really the else clause, but we do not put the else clause before an
immediate method return.

 }
 
 static inline bool layerImagesIdentical(const FillLayer& layer1, const FillLayer& layer2)