Bug 607417 - Part 3: Visibility tricks for fixed items r=roc

--HG--
extra : rebase_source : 7545070d6af5ef10dd4d1504f0d456ece4fd8edb

layout/base/nsDisplayList.cpp

@@ -64,6 +64,7 @@
 #include "nsIInterfaceRequestorUtils.h"
 #include "BasicLayers.h"
 #include "nsBoxFrame.h"
+#include "nsViewportFrame.h"
 
 using namespace mozilla;
 using namespace mozilla::layers;
@@ -86,7 +87,10 @@ nsDisplayListBuilder::nsDisplayListBuilder(nsIFrame* aReferenceFrame,
       mInTransform(PR_FALSE),
       mSyncDecodeImages(PR_FALSE),
       mIsPaintingToWindow(PR_FALSE),
-      mSnappingEnabled(PR_TRUE) {
+      mSnappingEnabled(PR_TRUE),
+      mHasDisplayPort(PR_FALSE),
+      mHasFixedItems(PR_FALSE)
+{
   MOZ_COUNT_CTOR(nsDisplayListBuilder);
   PL_InitArenaPool(&mPool, "displayListArena", 1024,
                    NS_MAX(NS_ALIGNMENT_OF(void*),NS_ALIGNMENT_OF(double))-1);
@@ -101,6 +105,13 @@ nsDisplayListBuilder::nsDisplayListBuilder(nsIFrame* aReferenceFrame,
     }
   }
 
+  if(mReferenceFrame->GetType() == nsGkAtoms::viewportFrame) {
+    ViewportFrame* viewportFrame = static_cast<ViewportFrame*>(mReferenceFrame);
+    if (!viewportFrame->GetChildList(nsGkAtoms::fixedList).IsEmpty()) {
+      mHasFixedItems = PR_TRUE;
+    }
+  }
+
   LayerBuilder()->Init(this);
 
   PR_STATIC_ASSERT(nsDisplayItem::TYPE_MAX < (1 << nsDisplayItem::TYPE_BITS));
@@ -121,10 +132,38 @@ static void MarkFrameForDisplay(nsIFrame* aFrame, nsIFrame* aStopAtFrame) {
   }
 }
 
-static void MarkOutOfFlowFrameForDisplay(nsIFrame* aDirtyFrame, nsIFrame* aFrame,
-                                         const nsRect& aDirtyRect) {
+static PRBool IsFixedFrame(nsIFrame* aFrame)
+{
+  return aFrame && aFrame->GetParent() && !aFrame->GetParent()->GetParent();
+}
+
+static PRBool IsFixedItem(nsDisplayItem *aItem, nsDisplayListBuilder* aBuilder)
+{
+  nsIFrame* activeScrolledRoot =
+    nsLayoutUtils::GetActiveScrolledRootFor(aItem, aBuilder);
+  return activeScrolledRoot &&
+         !nsLayoutUtils::ScrolledByViewportScrolling(activeScrolledRoot,
+                                                     aBuilder);
+}
+
+static PRBool ForceVisiblityForFixedItem(nsDisplayListBuilder* aBuilder,
+                                         nsDisplayItem* aItem)
+{
+  return aBuilder->GetHasDisplayPort() && aBuilder->GetHasFixedItems() &&
+         IsFixedItem(aItem, aBuilder);
+}
+
+void nsDisplayListBuilder::MarkOutOfFlowFrameForDisplay(nsIFrame* aDirtyFrame,
+                                                        nsIFrame* aFrame,
+                                                        const nsRect& aDirtyRect)
+{
   nsRect dirty = aDirtyRect - aFrame->GetOffsetTo(aDirtyFrame);
   nsRect overflowRect = aFrame->GetVisualOverflowRect();
+
+  if (mHasDisplayPort && IsFixedFrame(aFrame)) {
+    dirty = overflowRect;
+  }
+
   if (!dirty.IntersectRect(dirty, overflowRect))
     return;
   aFrame->Properties().Set(nsDisplayListBuilder::OutOfFlowDirtyRectProperty(),
@@ -430,6 +469,10 @@ nsDisplayList::ComputeVisibilityForSublist(nsDisplayListBuilder* aBuilder,
     itemVisible.And(*aVisibleRegion, bounds);
     item->mVisibleRect = itemVisible.GetBounds();
 
+    if (ForceVisiblityForFixedItem(aBuilder, item)) {
+      item->mVisibleRect = bounds;
+    }
+
     PRBool containsRootContentDocBG = PR_FALSE;
     if (item->ComputeVisibility(aBuilder, aVisibleRegion, aAllowVisibleRegionExpansion,
                                 containsRootContentDocBG)) {
@@ -757,6 +800,10 @@ PRBool nsDisplayItem::RecomputeVisibility(nsDisplayListBuilder* aBuilder,
   itemVisible.And(*aVisibleRegion, bounds);
   mVisibleRect = itemVisible.GetBounds();
 
+  if (ForceVisiblityForFixedItem(aBuilder, this)) {
+    mVisibleRect = bounds;
+  }
+
   // When we recompute visibility within layers we don't need to
   // expand the visible region for content behind plugins (the plugin
   // is not in the layer).
@@ -819,12 +866,21 @@ nsDisplayBackground::nsDisplayBackground(nsDisplayListBuilder* aBuilder,
   const nsStyleDisplay* disp = mFrame->GetStyleDisplay();
   mIsThemed = mFrame->IsThemed(disp, &mThemeTransparency);
 
+  if (mIsThemed) {
     // Perform necessary RegisterThemeGeometry
-  if (mIsThemed &&
-      (disp->mAppearance == NS_THEME_MOZ_MAC_UNIFIED_TOOLBAR ||
-       disp->mAppearance == NS_THEME_TOOLBAR)) {
+    if (disp->mAppearance == NS_THEME_MOZ_MAC_UNIFIED_TOOLBAR ||
+        disp->mAppearance == NS_THEME_TOOLBAR) {
       RegisterThemeGeometry(aBuilder, aFrame);
     }
+  } else {
+    // Set HasFixedItems if we construct a background-attachment:fixed item
+    nsPresContext* presContext = mFrame->PresContext();
+    nsStyleContext* bgSC;
+    PRBool hasBG = nsCSSRendering::FindBackground(presContext, mFrame, &bgSC);
+    if (hasBG && bgSC->GetStyleBackground()->HasFixedBackground()) {
+      aBuilder->SetHasFixedItems();
+    }
+  }
 }
 
 // Helper for RoundedRectIntersectsRect.

layout/base/nsDisplayList.h

@@ -292,6 +292,20 @@ public:
    */
   void SetInTransform(PRBool aInTransform) { mInTransform = aInTransform; }
 
+  /**
+   * Call this if using display port for scrolling.
+   */
+  void SetHasDisplayPort() { mHasDisplayPort = PR_TRUE; }
+  PRBool GetHasDisplayPort() { return mHasDisplayPort; }
+
+  /**
+   * Call this if ReferenceFrame() is a viewport frame with fixed-position
+   * children, or when we construct an item which will return true from
+   * ShouldFixToViewport()
+   */
+  void SetHasFixedItems() { mHasFixedItems = PR_TRUE; }
+  PRBool GetHasFixedItems() { return mHasFixedItems; }
+
   /**
    * Returns true if snapping is enabled for the final drawing context.
    * The default is true.
@@ -456,6 +470,9 @@ public:
   }
 
 private:
+  void MarkOutOfFlowFrameForDisplay(nsIFrame* aDirtyFrame, nsIFrame* aFrame,
+                                    const nsRect& aDirtyRect);
+
   struct PresShellState {
     nsIPresShell* mPresShell;
     nsIFrame*     mCaretFrame;
@@ -492,6 +509,8 @@ private:
   PRPackedBool                   mSyncDecodeImages;
   PRPackedBool                   mIsPaintingToWindow;
   PRPackedBool                   mSnappingEnabled;
+  PRPackedBool                   mHasDisplayPort;
+  PRPackedBool                   mHasFixedItems;
 };
 
 class nsDisplayItem;

layout/base/nsLayoutUtils.cpp

@@ -1451,6 +1451,10 @@ nsLayoutUtils::PaintFrame(nsIRenderingContext* aRenderingContext, nsIFrame* aFra
 
   nsDisplayListBuilder builder(aFrame, nsDisplayListBuilder::PAINTING,
 		                       !(aFlags & PAINT_HIDE_CARET));
+  if (usingDisplayPort) {
+    builder.SetHasDisplayPort();
+  }
+
   nsDisplayList list;
   if (aFlags & PAINT_IN_TRANSFORM) {
     builder.SetInTransform(PR_TRUE);