Bug 1018464 - Add nsDisplayItem::IsInvisibleInRect API to expose holes in display items. r=roc

--HG--
extra : rebase_source : 9f362283113c0ce925ca81c3613ac8c6d19dfebe

layout/base/nsDisplayList.cpp

@@ -1709,6 +1709,15 @@ nsDisplayItem::ZIndex() const
   return 0;
 }
 
+bool
+nsDisplayItem::ComputeVisibility(nsDisplayListBuilder* aBuilder,
+                                 nsRegion* aVisibleRegion,
+                                 const nsRect& aAllowVisibleRegionExpansion)
+{
+  return !mVisibleRect.IsEmpty() &&
+    !IsInvisibleInRect(aVisibleRegion->GetBounds());
+}
+
 bool
 nsDisplayItem::RecomputeVisibility(nsDisplayListBuilder* aBuilder,
                                    nsRegion* aVisibleRegion) {
@@ -2646,26 +2655,20 @@ nsDisplayOutline::Paint(nsDisplayListBuilder* aBuilder,
 }
 
 bool
-nsDisplayOutline::ComputeVisibility(nsDisplayListBuilder* aBuilder,
-                                    nsRegion* aVisibleRegion,
-                                    const nsRect& aAllowVisibleRegionExpansion) {
-  if (!nsDisplayItem::ComputeVisibility(aBuilder, aVisibleRegion,
-                                        aAllowVisibleRegionExpansion)) {
-    return false;
-  }
-
+nsDisplayOutline::IsInvisibleInRect(const nsRect& aRect)
+{
   const nsStyleOutline* outline = mFrame->StyleOutline();
   nsRect borderBox(ToReferenceFrame(), mFrame->GetSize());
-  if (borderBox.Contains(aVisibleRegion->GetBounds()) &&
+  if (borderBox.Contains(aRect) &&
       !nsLayoutUtils::HasNonZeroCorner(outline->mOutlineRadius)) {
     if (outline->mOutlineOffset >= 0) {
-      // the visible region is entirely inside the border-rect, and the outline
-      // isn't rendered inside the border-rect, so the outline is not visible
-      return false;
+      // aRect is entirely inside the border-rect, and the outline isn't
+      // rendered inside the border-rect, so the outline is not visible.
+      return true;
     }
   }
 
-  return true;
+  return false;
 }
 
 void
@@ -2725,30 +2728,24 @@ nsDisplayCaret::Paint(nsDisplayListBuilder* aBuilder,
 }
 
 bool
-nsDisplayBorder::ComputeVisibility(nsDisplayListBuilder* aBuilder,
-                                   nsRegion* aVisibleRegion,
-                                   const nsRect& aAllowVisibleRegionExpansion) {
-  if (!nsDisplayItem::ComputeVisibility(aBuilder, aVisibleRegion,
-                                        aAllowVisibleRegionExpansion)) {
-    return false;
-  }
-
+nsDisplayBorder::IsInvisibleInRect(const nsRect& aRect)
+{
   nsRect paddingRect = mFrame->GetPaddingRect() - mFrame->GetPosition() +
     ToReferenceFrame();
   const nsStyleBorder *styleBorder;
-  if (paddingRect.Contains(aVisibleRegion->GetBounds()) &&
+  if (paddingRect.Contains(aRect) &&
       !(styleBorder = mFrame->StyleBorder())->IsBorderImageLoaded() &&
       !nsLayoutUtils::HasNonZeroCorner(styleBorder->mBorderRadius)) {
-    // the visible region is entirely inside the content rect, and no part
+    // aRect is entirely inside the content rect, and no part
     // of the border is rendered inside the content rect, so we are not
     // visible
     // Skip this if there's a border-image (which draws a background
     // too) or if there is a border-radius (which makes the border draw
     // further in).
-    return false;
+    return true;
   }
 
-  return true;
+  return false;
 }
   
 nsDisplayItemGeometry* 
@@ -2879,6 +2876,24 @@ nsDisplayBoxShadowOuter::GetBoundsInternal() {
          ToReferenceFrame();
 }
 
+bool
+nsDisplayBoxShadowOuter::IsInvisibleInRect(const nsRect& aRect)
+{
+  nsPoint origin = ToReferenceFrame();
+  nsRect frameRect(origin, mFrame->GetSize());
+  if (!frameRect.Contains(aRect))
+    return false;
+
+  // the visible region is entirely inside the border-rect, and box shadows
+  // never render within the border-rect (unless there's a border radius).
+  nscoord twipsRadii[8];
+  bool hasBorderRadii = mFrame->GetBorderRadii(twipsRadii);
+  if (!hasBorderRadii)
+    return true;
+
+  return RoundedRectContainsRect(frameRect, twipsRadii, aRect);
+}
+
 bool
 nsDisplayBoxShadowOuter::ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                            nsRegion* aVisibleRegion,
@@ -2890,21 +2905,7 @@ nsDisplayBoxShadowOuter::ComputeVisibility(nsDisplayListBuilder* aBuilder,
 
   // Store the actual visible region
   mVisibleRegion.And(*aVisibleRegion, mVisibleRect);
-
-  nsPoint origin = ToReferenceFrame();
-  nsRect visibleBounds = aVisibleRegion->GetBounds();
-  nsRect frameRect(origin, mFrame->GetSize());
-  if (!frameRect.Contains(visibleBounds))
-    return true;
-
-  // the visible region is entirely inside the border-rect, and box shadows
-  // never render within the border-rect (unless there's a border radius).
-  nscoord twipsRadii[8];
-  bool hasBorderRadii = mFrame->GetBorderRadii(twipsRadii);
-  if (!hasBorderRadii)
-    return false;
-
-  return !RoundedRectContainsRect(frameRect, twipsRadii, visibleBounds);
+  return true;
 }
 
 void

layout/base/nsDisplayList.h

@@ -933,6 +933,14 @@ public:
     *aSnap = false;
     return nsRect(ToReferenceFrame(), Frame()->GetSize());
   }
+  /**
+   * Returns true if nothing will be rendered inside aRect, false if uncertain.
+   * aRect is assumed to be contained in this item's bounds.
+   */
+  virtual bool IsInvisibleInRect(const nsRect& aRect)
+  {
+    return false;
+  }
   /**
    * Returns the result of GetBounds intersected with the item's clip.
    * The intersection is approximate since rounded corners are not taking into
@@ -1191,8 +1199,7 @@ public:
    */
   virtual bool ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                    nsRegion* aVisibleRegion,
-                                   const nsRect& aAllowVisibleRegionExpansion)
-  { return !mVisibleRect.IsEmpty(); }
+                                   const nsRect& aAllowVisibleRegionExpansion);
 
   /**
    * Try to merge with the other item (which is below us in the display
@@ -2022,11 +2029,9 @@ public:
   }
 #endif
 
+  virtual bool IsInvisibleInRect(const nsRect& aRect) MOZ_OVERRIDE;
   virtual nsRect GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap) MOZ_OVERRIDE;
   virtual void Paint(nsDisplayListBuilder* aBuilder, nsRenderingContext* aCtx) MOZ_OVERRIDE;
-  virtual bool ComputeVisibility(nsDisplayListBuilder* aBuilder,
-                                   nsRegion* aVisibleRegion,
-                                   const nsRect& aAllowVisibleRegionExpansion) MOZ_OVERRIDE;
   NS_DISPLAY_DECL_NAME("Border", TYPE_BORDER)
   
   virtual nsDisplayItemGeometry* AllocateGeometry(nsDisplayListBuilder* aBuilder) MOZ_OVERRIDE;
@@ -2344,6 +2349,7 @@ public:
 
   virtual void Paint(nsDisplayListBuilder* aBuilder, nsRenderingContext* aCtx) MOZ_OVERRIDE;
   virtual nsRect GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap) MOZ_OVERRIDE;
+  virtual bool IsInvisibleInRect(const nsRect& aRect) MOZ_OVERRIDE;
   virtual bool ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                    nsRegion* aVisibleRegion,
                                    const nsRect& aAllowVisibleRegionExpansion) MOZ_OVERRIDE;
@@ -2430,11 +2436,9 @@ public:
   }
 #endif
 
+  virtual bool IsInvisibleInRect(const nsRect& aRect) MOZ_OVERRIDE;
   virtual nsRect GetBounds(nsDisplayListBuilder* aBuilder, bool* aSnap) MOZ_OVERRIDE;
   virtual void Paint(nsDisplayListBuilder* aBuilder, nsRenderingContext* aCtx) MOZ_OVERRIDE;
-  virtual bool ComputeVisibility(nsDisplayListBuilder* aBuilder,
-                                   nsRegion* aVisibleRegion,
-                                   const nsRect& aAllowVisibleRegionExpansion) MOZ_OVERRIDE;
   NS_DISPLAY_DECL_NAME("Outline", TYPE_OUTLINE)
 };