Bug 1144096 part 24 - [css-grid] Move the child frame merging code at the start of ReflowOverflowContainerChildren into a new method: DrainExcessOverflowContainersList. Make both take a param so that we can override how the OC child lists are merged together (normally just an Append; MergeSortedFrameLists for Grid). r=dholbert

layout/generic/nsContainerFrame.cpp

@@ -1230,46 +1230,12 @@ nsContainerFrame::ReflowOverflowContainerChildren(nsPresContext*           aPres
                                                   const nsHTMLReflowState& aReflowState,
                                                   nsOverflowAreas&         aOverflowRects,
                                                   uint32_t                 aFlags,
-                                                  nsReflowStatus&          aStatus)
+                                                  nsReflowStatus&          aStatus,
+                                                  ChildFrameMerger         aMergeFunc)
 {
   NS_PRECONDITION(aPresContext, "null pointer");
 
-  nsFrameList* overflowContainers =
-               GetPropTableFrames(OverflowContainersProperty());
-
-  NS_ASSERTION(!(overflowContainers && GetPrevInFlow()
-                 && static_cast<nsContainerFrame*>(GetPrevInFlow())
-                      ->GetPropTableFrames(ExcessOverflowContainersProperty())),
-               "conflicting overflow containers lists");
-
-  if (!overflowContainers) {
-    // Drain excess from previnflow
-    nsContainerFrame* prev = (nsContainerFrame*) GetPrevInFlow();
-    if (prev) {
-      nsFrameList* excessFrames =
-        prev->RemovePropTableFrames(ExcessOverflowContainersProperty());
-      if (excessFrames) {
-        excessFrames->ApplySetParent(this);
-        nsContainerFrame::ReparentFrameViewList(*excessFrames, prev, this);
-        overflowContainers = excessFrames;
-        SetPropTableFrames(overflowContainers, OverflowContainersProperty());
-      }
-    }
-  }
-
-  // Our own excess overflow containers from a previous reflow can still be
-  // present if our next-in-flow hasn't been reflown yet.
-  nsFrameList* selfExcessOCFrames =
-    RemovePropTableFrames(ExcessOverflowContainersProperty());
-  if (selfExcessOCFrames) {
-    if (overflowContainers) {
-      overflowContainers->AppendFrames(nullptr, *selfExcessOCFrames);
-      selfExcessOCFrames->Delete(aPresContext->PresShell());
-    } else {
-      overflowContainers = selfExcessOCFrames;
-      SetPropTableFrames(overflowContainers, OverflowContainersProperty());
-    }
-  }
+  nsFrameList* overflowContainers = DrainExcessOverflowContainersList(aMergeFunc);
   if (!overflowContainers) {
     return; // nothing to reflow
   }
@@ -1687,6 +1653,49 @@ nsContainerFrame::DrainSelfOverflowList()
   return false;
 }
 
+nsFrameList*
+nsContainerFrame::DrainExcessOverflowContainersList(ChildFrameMerger aMergeFunc)
+{
+  nsFrameList* overflowContainers =
+    GetPropTableFrames(OverflowContainersProperty());
+
+  NS_ASSERTION(!(overflowContainers && GetPrevInFlow()
+                 && static_cast<nsContainerFrame*>(GetPrevInFlow())
+                      ->GetPropTableFrames(ExcessOverflowContainersProperty())),
+               "conflicting overflow containers lists");
+
+  if (!overflowContainers) {
+    // Drain excess from previnflow
+    nsContainerFrame* prev = (nsContainerFrame*) GetPrevInFlow();
+    if (prev) {
+      nsFrameList* excessFrames =
+        prev->RemovePropTableFrames(ExcessOverflowContainersProperty());
+      if (excessFrames) {
+        excessFrames->ApplySetParent(this);
+        nsContainerFrame::ReparentFrameViewList(*excessFrames, prev, this);
+        overflowContainers = excessFrames;
+        SetPropTableFrames(overflowContainers, OverflowContainersProperty());
+      }
+    }
+  }
+
+  // Our own excess overflow containers from a previous reflow can still be
+  // present if our next-in-flow hasn't been reflown yet.
+  nsFrameList* selfExcessOCFrames =
+    RemovePropTableFrames(ExcessOverflowContainersProperty());
+  if (selfExcessOCFrames) {
+    if (overflowContainers) {
+      aMergeFunc(*overflowContainers, *selfExcessOCFrames, this);
+      selfExcessOCFrames->Delete(PresContext()->PresShell());
+    } else {
+      overflowContainers = selfExcessOCFrames;
+      SetPropTableFrames(overflowContainers, OverflowContainersProperty());
+    }
+  }
+
+  return overflowContainers;
+}
+
 nsIFrame*
 nsContainerFrame::GetNextInFlowChild(ContinuationTraversingState& aState,
                                      bool* aIsInOverflow)

layout/generic/nsContainerFrame.h

@@ -350,6 +350,15 @@ public:
 
   friend class nsOverflowContinuationTracker;
 
+  typedef void (*ChildFrameMerger)(nsFrameList& aDest, nsFrameList& aSrc,
+                                   nsContainerFrame* aParent);
+  static inline void DefaultChildFrameMerge(nsFrameList& aDest,
+                                            nsFrameList& aSrc,
+                                            nsContainerFrame* aParent)
+  {
+    aDest.AppendFrames(nullptr, aSrc);
+  }
+
   /**
    * Reflow overflow container children. They are invisible to normal reflow
    * (i.e. don't affect sizing or placement of other children) and inherit
@@ -372,13 +381,16 @@ public:
    * making sure they are stored properly in the overflow container lists.
    * The nsOverflowContinuationTracker helper class should be used for this.
    *
-   * (aFlags just gets passed through to ReflowChild)
+   * @param aFlags is passed through to ReflowChild
+   * @param aMergeFunc is passed to DrainExcessOverflowContainersList
    */
   void ReflowOverflowContainerChildren(nsPresContext*           aPresContext,
                                        const nsHTMLReflowState& aReflowState,
                                        nsOverflowAreas&         aOverflowRects,
                                        uint32_t                 aFlags,
-                                       nsReflowStatus&          aStatus);
+                                       nsReflowStatus&          aStatus,
+                                       ChildFrameMerger aMergeFunc =
+                                         DefaultChildFrameMerge);
 
   /**
    * Move any frames on our overflow list to the end of our principal list.
@@ -386,6 +398,16 @@ public:
    */
   virtual bool DrainSelfOverflowList() override;
 
+  
+  /**
+   * Move all frames on our prev-in-flow's and our own ExcessOverflowContainers
+   * lists to our OverflowContainers list.  If there are frames on multiple
+   * lists they are merged using aMergeFunc.
+   * @return a pointer to our OverflowContainers list, if any
+   */
+  nsFrameList* DrainExcessOverflowContainersList(ChildFrameMerger aMergeFunc =
+                                                   DefaultChildFrameMerge);
+
   /**
    * Removes aChild without destroying it and without requesting reflow.
    * Continuations are not affected. Checks the primary and overflow

layout/generic/nsGridContainerFrame.cpp

@@ -254,6 +254,13 @@ MergeSortedFrameLists(nsFrameList& aDest, nsFrameList& aSrc,
   MOZ_ASSERT(aSrc.IsEmpty());
 }
 
+static void
+MergeSortedFrameListsFor(nsFrameList& aDest, nsFrameList& aSrc,
+                         nsContainerFrame* aParent)
+{
+  MergeSortedFrameLists(aDest, aSrc, aParent->GetContent());
+}
+
 class nsGridContainerFrame::GridItemCSSOrderIterator
 {
 public:
@@ -4725,7 +4732,8 @@ nsGridContainerFrame::ReflowChildren(GridReflowState&     aState,
   nsReflowStatus ocStatus = NS_FRAME_COMPLETE;
   if (GetPrevInFlow()) {
     ReflowOverflowContainerChildren(PresContext(), *aState.mReflowState,
-                                    ocBounds, 0, ocStatus);
+                                    ocBounds, 0, ocStatus,
+                                    MergeSortedFrameListsFor);
   }
 
   WritingMode wm = aState.mReflowState->GetWritingMode();