Bug 743402, Part 1: Add a GetConsumedHeight() function to nsSplittableFrame in order to retrieve the portion of the computed height that was consumed by previous-in-flows. [r=roc]

layout/generic/nsBlockReflowState.cpp

@@ -35,7 +35,8 @@ nsBlockReflowState::nsBlockReflowState(const nsHTMLReflowState& aReflowState,
                                        nsBlockFrame* aFrame,
                                        bool aTopMarginRoot,
                                        bool aBottomMarginRoot,
-                                       bool aBlockNeedsFloatManager)
+                                       bool aBlockNeedsFloatManager,
+                                       nscoord aConsumedHeight)
   : mBlock(aFrame),
     mPresContext(aPresContext),
     mReflowState(aReflowState),
@@ -44,7 +45,8 @@ nsBlockReflowState::nsBlockReflowState(const nsHTMLReflowState& aReflowState,
     mPrevBottomMargin(),
     mLineNumber(0),
     mFlags(0),
-    mFloatBreakType(NS_STYLE_CLEAR_NONE)
+    mFloatBreakType(NS_STYLE_CLEAR_NONE),
+    mConsumedHeight(aConsumedHeight)
 {
   SetFlag(BRS_ISFIRSTINFLOW, aFrame->GetPrevInFlow() == nullptr);
   SetFlag(BRS_ISOVERFLOWCONTAINER,
@@ -113,6 +115,16 @@ nsBlockReflowState::nsBlockReflowState(const nsHTMLReflowState& aReflowState,
   mMinLineHeight = aReflowState.CalcLineHeight();
 }
 
+nscoord
+nsBlockReflowState::GetConsumedHeight()
+{
+  if (mConsumedHeight == NS_INTRINSICSIZE) {
+    mConsumedHeight = mBlock->GetConsumedHeight();
+  }
+
+  return mConsumedHeight;
+}
+
 void
 nsBlockReflowState::ComputeReplacedBlockOffsetsForFloats(nsIFrame* aFrame,
                                                          const nsRect& aFloatAvailableSpace,

layout/generic/nsBlockReflowState.h

@@ -40,7 +40,8 @@ public:
                      nsPresContext* aPresContext,
                      nsBlockFrame* aFrame,
                      bool aTopMarginRoot, bool aBottomMarginRoot,
-                     bool aBlockNeedsFloatManager);
+                     bool aBlockNeedsFloatManager,
+                     nscoord aConsumedHeight = NS_INTRINSICSIZE);
 
   /**
    * Get the available reflow space (the area not occupied by floats)
@@ -110,6 +111,11 @@ public:
     return result;
   }
 
+  /**
+   * Retrieve the height "consumed" by any previous-in-flows.
+   */
+  nscoord GetConsumedHeight();
+
   // Reconstruct the previous bottom margin that goes above |aLine|.
   void ReconstructMarginAbove(nsLineList::iterator aLine);
 
@@ -257,6 +263,9 @@ public:
  
   uint8_t mFloatBreakType;
 
+  // The amount of computed height "consumed" by previous-in-flows.
+  nscoord mConsumedHeight;
+
   void SetFlag(uint32_t aFlag, bool aValue)
   {
     NS_ASSERTION(aFlag<=BRS_LASTFLAG, "bad flag");

layout/generic/nsHTMLReflowState.h

@@ -480,15 +480,28 @@ public:
     }
     return std::max(aWidth, mComputedMinWidth);
   }
+
   /**
    * Apply the mComputed(Min/Max)Height constraints to the content
    * size computed so far.
+   *
+   * @param aHeight The height that we've computed an to which we want to apply
+   *        min/max constraints.
+   * @param aConsumed The amount of the computed height that was consumed by
+   *        our prev-in-flows.
    */
-  nscoord ApplyMinMaxHeight(nscoord aHeight) const {
+  nscoord ApplyMinMaxHeight(nscoord aHeight, nscoord aConsumed = 0) const {
+    aHeight += aConsumed;
+
     if (NS_UNCONSTRAINEDSIZE != mComputedMaxHeight) {
       aHeight = std::min(aHeight, mComputedMaxHeight);
     }
-    return std::max(aHeight, mComputedMinHeight);
+
+    if (NS_UNCONSTRAINEDSIZE != mComputedMinHeight) {
+      aHeight = std::max(aHeight, mComputedMinHeight);
+    }
+
+    return aHeight - aConsumed;
   }
 
   bool ShouldReflowAllKids() const {

layout/generic/nsSplittableFrame.cpp

@@ -203,6 +203,19 @@ nsSplittableFrame::RemoveFromFlow(nsIFrame* aFrame)
   aFrame->SetNextInFlow(nullptr);
 }
 
+nscoord
+nsSplittableFrame::GetConsumedHeight() const
+{
+  nscoord height = 0;
+
+  // Reduce the height by the computed height of prev-in-flows.
+  for (nsIFrame* prev = GetPrevInFlow(); prev; prev = prev->GetPrevInFlow()) {
+    height += prev->GetRect().height;
+  }
+
+  return height;
+}
+
 #ifdef DEBUG
 void
 nsSplittableFrame::DumpBaseRegressionData(nsPresContext* aPresContext, FILE* out, int32_t aIndent)

layout/generic/nsSplittableFrame.h

@@ -76,6 +76,15 @@ public:
 protected:
   nsSplittableFrame(nsStyleContext* aContext) : nsFrame(aContext) {}
 
+  /**
+   * Determine the height consumed by our previous-in-flows.
+   *
+   * @note (bz) This makes laying out a splittable frame with N in-flows
+   *       O(N^2)! So, use this function with caution and minimize the number
+   *       of calls to this method.
+   */
+  nscoord GetConsumedHeight() const;
+
 #ifdef DEBUG
   virtual void DumpBaseRegressionData(nsPresContext* aPresContext, FILE* out, int32_t aIndent) MOZ_OVERRIDE;
 #endif