Issue #146 - Part 3: Create nsDisplayTableBackgroundImage to avoid

display list collisions when processing the background image of a table.

layout/base/nsDisplayList.cpp

@@ -2751,9 +2751,19 @@ nsDisplayBackgroundImage::AppendBackgroundItemsToTop(nsDisplayListBuilder* aBuil
     }
 
     nsDisplayList thisItemList;
-    nsDisplayBackgroundImage* bgItem =
+    nsDisplayBackgroundImage* bgItem;
-      new (aBuilder) nsDisplayBackgroundImage(aBuilder, aFrame, i, bgOriginRect, bg);
+    if (aSecondaryReferenceFrame) {
-
+      bgItem =
+        new (aBuilder) nsDisplayTableBackgroundImage(aBuilder,
+                                                     aFrame,
+                                                     i,
+                                                     bgOriginRect,
+                                                     bg,
+                                                     aSecondaryReferenceFrame);
+    } else {
+      bgItem =
+        new (aBuilder) nsDisplayBackgroundImage(aBuilder, aFrame, i, bgOriginRect, bg);
+    }
     if (bgItem->ShouldFixToViewport(aBuilder)) {
       if (aSecondaryReferenceFrame) {
         thisItemList.AppendNewToTop(
@@ -2906,7 +2916,7 @@ nsDisplayBackgroundImage::ImageLayerization
 nsDisplayBackgroundImage::ShouldCreateOwnLayer(nsDisplayListBuilder* aBuilder,
                                                LayerManager* aManager)
 {
-  nsIFrame* backgroundStyleFrame = nsCSSRendering::FindBackgroundStyleFrame(mFrame);
+  nsIFrame* backgroundStyleFrame = nsCSSRendering::FindBackgroundStyleFrame(StyleFrame());
   if (ActiveLayerTracker::IsBackgroundPositionAnimated(aBuilder,
                                                        backgroundStyleFrame)) {
     return WHENEVER_POSSIBLE;
@@ -3161,16 +3171,16 @@ nsDisplayBackgroundImage::PaintInternal(nsDisplayListBuilder* aBuilder,
   StyleGeometryBox clip = mBackgroundStyle->mImage.mLayers[mLayer].mClip;
 
   if (clip == StyleGeometryBox::Text) {
-    if (!GenerateAndPushTextMask(mFrame, aCtx, mBackgroundRect, aBuilder)) {
+    if (!GenerateAndPushTextMask(StyleFrame(), aCtx, mBackgroundRect, aBuilder)) {
       return;
     }
   }
 
   nsCSSRendering::PaintBGParams params =
-    nsCSSRendering::PaintBGParams::ForSingleLayer(*mFrame->PresContext(),
+    nsCSSRendering::PaintBGParams::ForSingleLayer(*StyleFrame()->PresContext(),
                                                   *aCtx,
                                                   aBounds, mBackgroundRect,
-                                                  mFrame, flags, mLayer,
+                                                  StyleFrame(), flags, mLayer,
                                                   CompositionOp::OP_OVER);
   params.bgClipRect = aClipRect;
   image::DrawResult result =
@@ -3272,6 +3282,27 @@ nsDisplayBackgroundImage::GetPerFrameKey()
     nsDisplayItem::GetPerFrameKey();
 }
 
+nsDisplayTableBackgroundImage::nsDisplayTableBackgroundImage(nsDisplayListBuilder* aBuilder,
+                                                             nsIFrame* aFrame,
+                                                             uint32_t aLayer,
+                                                             const nsRect& aBackgroundRect,
+                                                             const nsStyleBackground* aBackgroundStyle,
+                                                             nsIFrame* aCellFrame)
+  : nsDisplayBackgroundImage(aBuilder, aFrame, aLayer, aBackgroundRect, aBackgroundStyle)
+  , mStyleFrame(aFrame)
+  , mTableType(GetTableTypeFromFrame(mStyleFrame))
+{
+  mFrame = aCellFrame;
+}
+
+bool
+nsDisplayTableBackgroundImage::IsInvalid(nsRect& aRect)
+{
+  bool result = mStyleFrame ? mStyleFrame->IsInvalid(aRect) : false;
+  aRect += ToReferenceFrame();
+  return result;
+}
+
 nsDisplayThemedBackground::nsDisplayThemedBackground(nsDisplayListBuilder* aBuilder,
                                                      nsIFrame* aFrame,
                                                      const nsRect& aBackgroundRect)

layout/base/nsDisplayList.h

@@ -2814,6 +2814,8 @@ protected:
   void PaintInternal(nsDisplayListBuilder* aBuilder, nsRenderingContext* aCtx,
                      const nsRect& aBounds, nsRect* aClipRect);
 
+  virtual nsIFrame* StyleFrame() { return mFrame; }
+
   // Determine whether we want to be separated into our own layer, independent
   // of whether this item can actually be layerized.
   enum ImageLayerization {
@@ -2859,6 +2861,41 @@ static_assert(
   "TableType cannot fit with TableTypeBits::COUNT");
 TableType GetTableTypeFromFrame(nsIFrame* aFrame);
 
+/**
+ * A display item to paint background image for table. For table parts, such
+ * as row, row group, col, col group, when drawing its background, we'll
+ * create separate background image display item for its containning cell.
+ * Those background image display items will reference to same DisplayItemData
+ * if we keep the mFrame point to cell's ancestor frame. We don't want to this
+ * happened bacause share same DisplatItemData will cause many bugs. So that
+ * we let mFrame point to cell frame and store the table type of the ancestor
+ * frame. And use mFrame and table type as key to generate DisplayItemData to
+ * avoid sharing DisplayItemData.
+ *
+ * Also store ancestor frame as mStyleFrame for all rendering informations.
+ */
+class nsDisplayTableBackgroundImage : public nsDisplayBackgroundImage {
+public:
+  nsDisplayTableBackgroundImage(nsDisplayListBuilder* aBuilder,
+                                nsIFrame* aFrame,
+                                uint32_t aLayer,
+                                const nsRect& aBackgroundRect,
+                                const nsStyleBackground* aBackgroundStyle,
+                                nsIFrame* aCellFrame);
+
+  virtual uint32_t GetPerFrameKey() override {
+    return (static_cast<uint8_t>(mTableType) << nsDisplayItem::TYPE_BITS) |
+           nsDisplayItem::GetPerFrameKey();
+  }
+
+  virtual bool IsInvalid(nsRect& aRect) override;
+protected:
+  virtual nsIFrame* StyleFrame() override { return mStyleFrame; }
+
+  nsIFrame* mStyleFrame;
+  TableType mTableType;
+};
+
 /**
  * A display item to paint the native theme background for a frame.
  */