Bug 174688. Don't apply top border-padding to block frames that aren't first in flow. Also, when a block is incomplete, ensure the frame extends to fill the entire available height. r+sr=dbaron,a=asa

layout/generic/nsBlockFrame.cpp

@@ -1349,32 +1349,43 @@ nsBlockFrame::ComputeFinalSize(const nsHTMLReflowState& aReflowState,
   // Compute final height
   if (NS_UNCONSTRAINEDSIZE != aReflowState.mComputedHeight) {
     if (NS_FRAME_IS_COMPLETE(aState.mReflowStatus)) {
-      // Calculate the total unconstrained height including borders and padding. A continuation 
-      // will have the same value as the first-in-flow, since the reflow state logic is based on
-      // style and doesn't alter mComputedHeight based on prev-in-flows.
-      aMetrics.height = borderPadding.top + aReflowState.mComputedHeight + borderPadding.bottom;
+      // Figure out how much of the computed height should be
+      // applied to this frame.
+      nscoord computedHeightLeftOver = aReflowState.mComputedHeight;
       if (mPrevInFlow) {
-        // Reduce the height by the height of prev-in-flows. The last-in-flow will automatically
-        // pick up the bottom border/padding, since it was part of the original aMetrics.height.
+        // Reduce the height by the computed height of prev-in-flows.
         for (nsIFrame* prev = mPrevInFlow; prev; prev = prev->GetPrevInFlow()) {
-          aMetrics.height -= prev->GetRect().height;
-          // XXX: All block level next-in-flows have borderPadding.top applied to them (bug 174688). 
-          // The following should be removed when this gets fixed. bug 174688 prevents us from honoring 
-          // a style height (exactly) and this hack at least compensates by increasing the height by the
-          // excessive borderPadding.top.
-          aMetrics.height += borderPadding.top;
+          nscoord contentHeight = prev->GetRect().height;
+          if (prev == mPrevInFlow) {
+            // subtract off the style top borderpadding to get the
+            // content height
+            contentHeight -= aReflowState.mComputedBorderPadding.top;
+          }
+          computedHeightLeftOver -= contentHeight;
         }
-        aMetrics.height = PR_MAX(0, aMetrics.height);
+        // We may have stretched the frame beyond its computed height. Oh well.
+        computedHeightLeftOver = PR_MAX(0, computedHeightLeftOver);
       }
-      if (aMetrics.height > aReflowState.availableHeight) {
-        // Take up the available height; continuations will take up the rest.
+
+      aMetrics.height = borderPadding.top + computedHeightLeftOver + borderPadding.bottom;
+      if (computedHeightLeftOver > 0 &&
+          aMetrics.height > aReflowState.availableHeight) {
+        // We don't fit and we consumed some of the computed height,
+        // so we should consume all the available height and then
+        // break.  If our bottom border/padding straddles the break
+        // point, then this will increase our height and push the
+        // border/padding to the next page/column.
         aMetrics.height = aReflowState.availableHeight;
-        aState.mReflowStatus = NS_FRAME_NOT_COMPLETE;
+        aState.mReflowStatus |= NS_FRAME_NOT_COMPLETE;
       }
     }
     else {
       // Use the current height; continuations will take up the rest.
-      aMetrics.height = aState.mY + nonCarriedOutVerticalMargin;
+      // Do extend the height to at least consume the available
+      // height, otherwise our left/right borders (for example) won't
+      // extend all the way to the break.
+      aMetrics.height = PR_MAX(aReflowState.availableHeight,
+                               aState.mY + nonCarriedOutVerticalMargin);
     }
 
     // Don't carry out a bottom margin when our height is fixed.

layout/generic/nsBlockReflowState.cpp

@@ -70,6 +70,8 @@ nsBlockReflowState::nsBlockReflowState(const nsHTMLReflowState& aReflowState,
     mFlags(0),
     mFloatBreakType(NS_STYLE_CLEAR_NONE)
 {
+  SetFlag(BRS_ISFIRSTINFLOW, aFrame->GetPrevInFlow() == nsnull);
+
   const nsMargin& borderPadding = BorderPadding();
 
   if (aReflowState.availableHeight != NS_UNCONSTRAINEDSIZE) {

layout/generic/nsBlockReflowState.h

@@ -47,6 +47,19 @@
 
 class nsBlockFrame;
 
+  // block reflow state flags
+#define BRS_UNCONSTRAINEDWIDTH    0x00000001
+#define BRS_UNCONSTRAINEDHEIGHT   0x00000002
+#define BRS_SHRINKWRAPWIDTH       0x00000004
+#define BRS_NEEDRESIZEREFLOW      0x00000008
+#define BRS_ISTOPMARGINROOT       0x00000020  // Is this frame a root for top/bottom margin collapsing?
+#define BRS_ISBOTTOMMARGINROOT    0x00000040
+#define BRS_APPLYTOPMARGIN        0x00000080  // See ShouldApplyTopMargin
+#define BRS_COMPUTEMAXELEMENTWIDTH 0x00000100
+#define BRS_COMPUTEMAXWIDTH       0x00000200
+#define BRS_ISFIRSTINFLOW         0x00000400
+#define BRS_LASTFLAG              BRS_ISFIRSTINFLOW
+
 class nsBlockReflowState {
 public:
   nsBlockReflowState(const nsHTMLReflowState& aReflowState,
@@ -91,13 +104,23 @@ public:
   nscoord ClearFloats(nscoord aY, PRUint8 aBreakType);
 
   PRBool IsAdjacentWithTop() const {
-    return mY == mReflowState.mComputedBorderPadding.top;
+    return mY ==
+      ((mFlags & BRS_ISFIRSTINFLOW) ? mReflowState.mComputedBorderPadding.top : 0);
   }
 
-  const nsMargin& BorderPadding() const {
-    return mReflowState.mComputedBorderPadding;
+  /**
+   * Adjusts the border/padding to return 0 for the top if
+   * we are no the first in flow.
+   */
+  nsMargin BorderPadding() const {
+    nsMargin result = mReflowState.mComputedBorderPadding;
+    if (!(mFlags & BRS_ISFIRSTINFLOW)) {
+      result.top = 0;
+    }
+    return result;
   }
 
+  // XXX maybe we should do the same adjustment for continuations here
   const nsMargin& Margin() const {
     return mReflowState.mComputedMargin;
   }
@@ -230,18 +253,6 @@ public:
 
   PRInt32 mLineNumber;
 
-  // block reflow state flags
-#define BRS_UNCONSTRAINEDWIDTH    0x00000001
-#define BRS_UNCONSTRAINEDHEIGHT   0x00000002
-#define BRS_SHRINKWRAPWIDTH       0x00000004
-#define BRS_NEEDRESIZEREFLOW      0x00000008
-#define BRS_ISTOPMARGINROOT       0x00000020  // Is this frame a root for top/bottom margin collapsing?
-#define BRS_ISBOTTOMMARGINROOT    0x00000040
-#define BRS_APPLYTOPMARGIN        0x00000080  // See ShouldApplyTopMargin
-#define BRS_COMPUTEMAXELEMENTWIDTH 0x00000100
-#define BRS_COMPUTEMAXWIDTH       0x00000200
-#define BRS_LASTFLAG              BRS_COMPUTEMAXWIDTH
-
   PRInt16 mFlags;
  
   PRUint8 mFloatBreakType;