Bug 398332. Merge reflow statuses from out-of-flow frames more carefully so that we don't lose information about the primary reflow. r=fantasai,r+sr=dbaron,a=shaver

layout/generic/nsAbsoluteContainingBlock.cpp

@@ -181,7 +181,7 @@ nsAbsoluteContainingBlock::Reflow(nsContainerFrame*        aDelegatingFrame,
         // See bug 154892. Not sure how to do it "right" yet; probably want
         // to keep continuations within an nsAbsoluteContainingBlock eventually.
         tracker.Insert(nextFrame, kidStatus);
-        reflowStatus = NS_FRAME_MERGE_INCOMPLETE(reflowStatus, kidStatus);
+        NS_MergeReflowStatusInto(&reflowStatus, kidStatus);
       }
       else {
         // Delete any continuations
@@ -205,7 +205,7 @@ nsAbsoluteContainingBlock::Reflow(nsContainerFrame*        aDelegatingFrame,
   if (NS_FRAME_IS_NOT_COMPLETE(reflowStatus))
     NS_FRAME_SET_OVERFLOW_INCOMPLETE(reflowStatus);
 
-  aReflowStatus = NS_FRAME_MERGE_INCOMPLETE(reflowStatus, aReflowStatus);
+  NS_MergeReflowStatusInto(&aReflowStatus, reflowStatus);
   return NS_OK;
 }
 

layout/generic/nsBlockFrame.cpp

@@ -3132,8 +3132,7 @@ nsBlockFrame::ReflowBlockFrame(nsBlockReflowState& aState,
 
             // Put it in our overflow list
             aState.mOverflowTracker.Insert(nextFrame, frameReflowStatus);
-            aState.mReflowStatus = NS_FRAME_MERGE_INCOMPLETE(frameReflowStatus,
-                                     aState.mReflowStatus);
+            NS_MergeReflowStatusInto(&aState.mReflowStatus, frameReflowStatus);
 
 #ifdef NOISY_VERTICAL_MARGINS
             ListTag(stdout);

layout/generic/nsContainerFrame.cpp

@@ -1010,7 +1010,7 @@ nsContainerFrame::ReflowOverflowContainerChildren(nsPresContext*           aPres
 
         tracker.Insert(nif, frameStatus);
       }
-      aStatus = NS_FRAME_MERGE_INCOMPLETE(aStatus, frameStatus);
+      NS_MergeReflowStatusInto(&aStatus, frameStatus);
       // At this point it would be nice to assert !frame->GetOverflowRect().IsEmpty(),
       // but we have some unsplittable frames that, when taller than
       // availableHeight will push zero-height content into a next-in-flow.

layout/generic/nsContainerFrame.h

@@ -525,8 +525,7 @@ public:
     NS_PRECONDITION(aChild, "null ptr");
     if (aChild == mSentry) {
       StepForward();
-      aReflowStatus = NS_FRAME_MERGE_INCOMPLETE(aReflowStatus,
-                                                NS_FRAME_OVERFLOW_INCOMPLETE);
+      NS_MergeReflowStatusInto(&aReflowStatus, NS_FRAME_OVERFLOW_INCOMPLETE);
     }
   }
 

layout/generic/nsFrame.cpp

@@ -279,6 +279,17 @@ nsIFrameDebug::RootFrameList(nsPresContext* aPresContext, FILE* out, PRInt32 aIn
 #endif
 // end nsIFrameDebug
 
+void
+NS_MergeReflowStatusInto(nsReflowStatus* aPrimary, nsReflowStatus aSecondary)
+{
+  *aPrimary |= aSecondary &
+    (NS_FRAME_NOT_COMPLETE | NS_FRAME_OVERFLOW_INCOMPLETE |
+     NS_FRAME_TRUNCATED | NS_FRAME_REFLOW_NEXTINFLOW);
+  if (*aPrimary & NS_FRAME_NOT_COMPLETE) {
+    *aPrimary &= ~NS_FRAME_OVERFLOW_INCOMPLETE;
+  }
+}
+
 void
 nsWeakFrame::Init(nsIFrame* aFrame)
 {

layout/generic/nsIFrame.h

@@ -316,7 +316,7 @@ enum nsSpread {
  * frame. See nsContainerFrame.h for more information.
  * This bit is mutually exclusive with NS_FRAME_NOT_COMPLETE.
  * 
- * Please use the SET and MERGE macros below for handling
+ * Please use the SET macro for handling
  * NS_FRAME_NOT_COMPLETE and NS_FRAME_OVERFLOW_INCOMPLETE.
  *
  * NS_FRAME_REFLOW_NEXTINFLOW bit flag means that the next-in-flow is
@@ -358,15 +358,6 @@ typedef PRUint32 nsReflowStatus;
 #define NS_FRAME_SET_OVERFLOW_INCOMPLETE(status) \
   status = status & ~NS_FRAME_NOT_COMPLETE | NS_FRAME_OVERFLOW_INCOMPLETE
 
-// Combines two statuses and returns the most severe bits of the pair
-#define NS_FRAME_MERGE_INCOMPLETE(status1, status2)        \
-  ( (NS_FRAME_REFLOW_NEXTINFLOW & (status1 | status2))     \
-  | ( (NS_FRAME_NOT_COMPLETE & (status1 | status2))        \
-    ? NS_FRAME_NOT_COMPLETE                                \
-    : NS_FRAME_OVERFLOW_INCOMPLETE & (status1 | status2)   \
-    )                                                      \
-  )
-
 // This macro tests to see if an nsReflowStatus is an error value
 // or just a regular return value
 #define NS_IS_REFLOW_ERROR(_status) (PRInt32(_status) < 0)
@@ -429,6 +420,11 @@ typedef PRUint32 nsReflowStatus;
 #define NS_FRAME_SET_TRUNCATION(status, aReflowState, aMetrics) \
   aReflowState.SetTruncated(aMetrics, &status);
 
+// Merge the incompleteness, truncation and NS_FRAME_REFLOW_NEXTINFLOW
+// status from aSecondary into aPrimary.
+void NS_MergeReflowStatusInto(nsReflowStatus* aPrimary,
+                              nsReflowStatus aSecondary);
+
 //----------------------------------------------------------------------
 
 /**