Bug 1227327 - Invalidate table parts and MathML frames when background-position changes on them. r=dbaron

Theoretically we should do the same for nsTreeBodyFrame, but that frame type is
harder to detect and I'm not sure it's worth adding code to support updating
background-position on XUL trees.

MozReview-Commit-ID: 8HPT53MX6bO

--HG--
extra : rebase_source : 1e84e83616832debe8f6da394630a5a2e014e7df

layout/base/RestyleManager.cpp

@@ -886,6 +886,19 @@ RestyleManager::ProcessRestyledFrames(nsStyleChangeList& aChangeList)
         hint |= nsChangeHint_RepaintFrame;
       }
 
+      if (hint & nsChangeHint_UpdateBackgroundPosition) {
+        // For most frame types, DLBI can detect background position changes,
+        // so we only need to schedule a paint.
+        hint |= nsChangeHint_SchedulePaint;
+        if (frame->IsFrameOfType(nsIFrame::eTablePart) ||
+            frame->IsFrameOfType(nsIFrame::eMathML)) {
+          // Table parts and MathML frames don't build display items for their
+          // backgrounds, so DLBI can't detect background-position changes for
+          // these frames. Repaint the whole frame.
+          hint |= nsChangeHint_RepaintFrame;
+        }
+      }
+
       if (hint & (nsChangeHint_RepaintFrame | nsChangeHint_SyncFrameView |
                   nsChangeHint_UpdateOpacityLayer | nsChangeHint_UpdateTransformLayer |
                   nsChangeHint_ChildrenOnlyTransform | nsChangeHint_SchedulePaint)) {

layout/base/nsChangeHint.h

@@ -194,6 +194,15 @@ enum nsChangeHint {
    */
   nsChangeHint_UpdateUsesOpacity = 1 << 25,
 
+  /**
+   * Indicates that the 'background-position' property changed.
+   * Regular frames can invalidate these changes using DLBI, but
+   * for some frame types we need to repaint the whole frame because
+   * the frame does not build individual background image display items
+   * for each background layer.
+   */
+  nsChangeHint_UpdateBackgroundPosition = 1 << 26,
+
   // IMPORTANT NOTE: When adding new hints, consider whether you need to
   // add them to NS_HintsNotHandledForDescendantsIn() below.  Please also
   // add them to RestyleManager::ChangeHintToString.
@@ -303,7 +312,8 @@ inline nsChangeHint operator^=(nsChangeHint& aLeft, nsChangeHint aRight)
           nsChangeHint_ReflowChangesSizeOrPosition | \
           nsChangeHint_ClearAncestorIntrinsics | \
           nsChangeHint_UpdateComputedBSize | \
-          nsChangeHint_UpdateUsesOpacity)
+          nsChangeHint_UpdateUsesOpacity | \
+          nsChangeHint_UpdateBackgroundPosition)
 
 inline nsChangeHint NS_HintsNotHandledForDescendantsIn(nsChangeHint aChangeHint) {
   nsChangeHint result = nsChangeHint(aChangeHint & (
@@ -319,7 +329,8 @@ inline nsChangeHint NS_HintsNotHandledForDescendantsIn(nsChangeHint aChangeHint)
     nsChangeHint_UpdateContainingBlock |
     nsChangeHint_BorderStyleNoneChange |
     nsChangeHint_UpdateComputedBSize |
-    nsChangeHint_UpdateUsesOpacity));
+    nsChangeHint_UpdateUsesOpacity | \
+    nsChangeHint_UpdateBackgroundPosition));
 
   if (!NS_IsHintSubset(nsChangeHint_NeedDirtyReflow, aChangeHint)) {
     if (NS_IsHintSubset(nsChangeHint_NeedReflow, aChangeHint)) {

layout/style/nsStyleStruct.cpp

@@ -2651,7 +2651,7 @@ nsStyleImageLayers::Layer::CalcDifference(const nsStyleImageLayers::Layer& aOthe
   }
 
   if (mPosition != aOther.mPosition) {
-    hint |= nsChangeHint_SchedulePaint;
+    hint |= nsChangeHint_UpdateBackgroundPosition;
   }
 
   return hint;

layout/style/nsStyleStruct.h

@@ -801,7 +801,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleBackground {
   static nsChangeHint MaxDifference() {
      return nsChangeHint_UpdateEffects |
            nsChangeHint_RepaintFrame |
-           nsChangeHint_SchedulePaint |
+           nsChangeHint_UpdateBackgroundPosition |
            nsChangeHint_NeutralChange;
   }
   static nsChangeHint DifferenceAlwaysHandledForDescendants() {