Add graphics layers for pinch virtual viewport.

Source/core/rendering/RenderLayerCompositor.cpp

Index: Source/core/rendering/RenderLayerCompositor.cpp
diff --git a/Source/core/rendering/RenderLayerCompositor.cpp b/Source/core/rendering/RenderLayerCompositor.cpp
index 4b2c4d051671c05c0ec5db745f3f36cc37cec263..aee304ccb13bb08e0eca3374b47af4482eaea1ac 100644
--- a/Source/core/rendering/RenderLayerCompositor.cpp
+++ b/Source/core/rendering/RenderLayerCompositor.cpp
@@ -1119,7 +1119,12 @@ void RenderLayerCompositor::frameViewDidChangeSize()
 {
     if (m_clipLayer) {
         FrameView* frameView = m_renderView->frameView();
-        m_clipLayer->setSize(frameView->unscaledVisibleContentSize());
+        FloatSize visibleContentSize = frameView->unscaledVisibleContentSize();

[trchen, 2013/05/29 21:32:56]

FloatSize unscaledVisibleContentSize = ...

[wjmaclean, 2013/05/30 14:19:09]

Done.

+        m_clipLayer->setSize(visibleContentSize);
+        if (m_pinchVirtualViewportClipLayer) {

[trchen, 2013/05/29 21:32:56]

FloatSize visibleContentSize = unscaledVisibleContentSize;
visibleContentSize.scale(frameView->visibleContentScaleFactor());

[wjmaclean, 2013/05/30 14:19:09]

Done.

+            visibleContentSize.scale(frameView->visibleContentScaleFactor());
+            m_pinchVirtualViewportClipLayer->setSize(visibleContentSize);
+        }
 
         frameViewDidScroll();
         updateOverflowControlsLayers();
@@ -2393,11 +2398,29 @@ void RenderLayerCompositor::ensureRootLayer()
 #endif
         if (ScrollingCoordinator* scrollingCoordinator = this->scrollingCoordinator())
             scrollingCoordinator->setLayerIsContainerForFixedPositionLayers(m_scrollLayer.get(), true);
-
         // Hook them up
         m_overflowControlsHostLayer->addChild(m_clipLayer.get());
         m_clipLayer->addChild(m_scrollLayer.get());
-        m_scrollLayer->addChild(m_rootContentLayer.get());
+        if (isMainFrame() && m_renderView->document()->settings()->pinchVirtualViewportEnabled()) {

[enne (OOO), 2013/05/29 19:57:10]

Can you add a outline diagram in a comment here of what this hierarchy is
supposed to look like in terms of member variables and parent/child
relationships for both virtual viewport enabled and disabled?

[wjmaclean, 2013/05/29 21:00:30]

Will do.

+            m_pinchVirtualViewportClipLayer = GraphicsLayer::create(graphicsLayerFactory(), this);
+#ifndef NDEBUG
+            m_pinchVirtualViewportClipLayer->setName("pinch virtual viewport clip");
+#endif
+            m_pinchVirtualViewportClipLayer->setMasksToBounds(true);
+
+            m_pinchVirtualViewportScrollLayer = GraphicsLayer::create(graphicsLayerFactory(), this);
+#ifndef NDEBUG
+            m_pinchVirtualViewportScrollLayer->setName("pinch virtual viewport scroll");
+#endif
+
+            if (ScrollingCoordinator* scrollingCoordinator = this->scrollingCoordinator())
+                scrollingCoordinator->setLayerIsContainerForFixedPositionLayers(m_pinchVirtualViewportScrollLayer.get(), true);
+
+            m_scrollLayer->addChild(m_pinchVirtualViewportClipLayer.get());
+            m_pinchVirtualViewportClipLayer->addChild(m_pinchVirtualViewportScrollLayer.get());
+            m_pinchVirtualViewportScrollLayer->addChild(m_rootContentLayer.get());

[trchen, 2013/05/29 21:32:56]

This doesn't look right. According to enne's design doc, the inner(pinch zoom)
viewport is supposed in a higher hierarchy than the outer(main frame) viewport.

And I'm still not convinced why this must belong to RLC. I weakly feel pinch
zoom should be a WebWidget concept, but I can be convinced otherwise. Either
way, at least we should make a separate helper class for it.

[wjmaclean, 2013/05/30 14:19:09]

The layer named m_pinchVirtualViewportScrollLayer here is the outer viewport, so
I think this matches the doc.

+        } else

[enne (OOO), 2013/05/29 19:57:10]

Can you add braces for this else to be in line with
https://codereview.chromium.org/15747011/ when it lands?

[wjmaclean, 2013/05/29 21:00:30]

Will do.

+            m_scrollLayer->addChild(m_rootContentLayer.get());
 
         frameViewDidChangeSize();
         frameViewDidScroll();
@@ -2451,6 +2474,8 @@ void RenderLayerCompositor::destroyRootLayer()
         m_overflowControlsHostLayer = nullptr;
         m_clipLayer = nullptr;
         m_scrollLayer = nullptr;
+        m_pinchVirtualViewportClipLayer = nullptr;
+        m_pinchVirtualViewportScrollLayer = nullptr;
     }
     ASSERT(!m_scrollLayer);
     m_rootContentLayer = nullptr;
@@ -2734,6 +2759,8 @@ void RenderLayerCompositor::reportMemoryUsage(MemoryObjectInfo* memoryObjectInfo
     info.addMember(m_rootContentLayer, "rootContentLayer");
     info.addMember(m_clipLayer, "clipLayer");
     info.addMember(m_scrollLayer, "scrollLayer");
+    info.addMember(m_pinchVirtualViewportClipLayer, "pinch virtual viewport clip layer");

[enne (OOO), 2013/05/29 19:57:10]

For consistency, maybe this should be pinchVirtualClipLayer and
pinchVirtualViewportScrollLayer?

[wjmaclean, 2013/05/29 21:00:30]

I'll rename everything to be inner/out as in the document, as per aelias'
suggestion.

+    info.addMember(m_pinchVirtualViewportScrollLayer, "pinch virtual viewport scroll layer");
     info.addMember(m_viewportConstrainedLayers, "viewportConstrainedLayers");
     info.addMember(m_overflowControlsHostLayer, "overflowControlsHostLayer");
     info.addMember(m_layerForHorizontalScrollbar, "layerForHorizontalScrollbar");