Bug 439004. Check whether there's logically empty content already placed on the line instead of just checking whether the line has advanced horizontally. r+sr=dbaron.

layout/generic/nsBRFrame.cpp

@@ -127,11 +127,9 @@ BRFrame::Reflow(nsPresContext* aPresContext,
   if (ll) {
     // Note that the compatibility mode check excludes AlmostStandards
     // mode, since this is the inline box model.  See bug 161691.
-    if ( ll->CanPlaceFloatNow() ||
+    if ( ll->LineIsEmpty() ||
          aPresContext->CompatibilityMode() == eCompatibility_FullStandards ) {
-      // If we can place a float on the line now it means that the
+      // The line is logically empty; any whitespace is trimmed away.
-      // line is effectively empty (there may be zero sized compressed
-      // white-space frames on the line, but they are to be ignored).
       //
       // If this frame is going to terminate the line we know
       // that nothing else will go on the line. Therefore, in this

layout/generic/nsBlockReflowState.cpp

@@ -578,7 +578,7 @@ nsBlockReflowState::AddFloat(nsLineLayout&       aLineLayout,
   // don't let this one go on the current line, since that would violate
   // float ordering.
   if (mBelowCurrentLineFloats.IsEmpty() &&
-      (aLineLayout.CanPlaceFloatNow() ||
+      (aLineLayout.LineIsEmpty() ||
        mBlock->ComputeFloatWidth(*this, aPlaceholder) <= aAvailableWidth)) {
     // Because we are in the middle of reflowing a placeholder frame
     // within a line (and possibly nested in an inline frame or two

layout/generic/nsLineLayout.cpp

@@ -206,7 +206,7 @@ nsLineLayout::BeginLineReflow(nscoord aX, nscoord aY,
   mPlacedFloats = 0;
   SetFlag(LL_IMPACTEDBYFLOATS, aImpactedByFloats);
   mTotalPlacedFrames = 0;
-  SetFlag(LL_CANPLACEFLOAT, PR_TRUE);
+  SetFlag(LL_LINEISEMPTY, PR_TRUE);
   SetFlag(LL_LINEENDSINBR, PR_FALSE);
   mSpanDepth = 0;
   mMaxTopBoxHeight = mMaxBottomBoxHeight = 0;
@@ -628,15 +628,11 @@ nsLineLayout::NewPerFrameData(PerFrameData** aResult)
   return NS_OK;
 }
 
-PRBool
-nsLineLayout::CanPlaceFloatNow() const
-{
-  return GetFlag(LL_CANPLACEFLOAT);
-}
-
 PRBool
 nsLineLayout::LineIsBreakable() const
 {
+  // XXX mTotalPlacedFrames should go away and we should just use
+  // LL_LINEISEMPTY here instead
   if ((0 != mTotalPlacedFrames) || GetFlag(LL_IMPACTEDBYFLOATS)) {
     return PR_TRUE;
   }
@@ -816,7 +812,7 @@ nsLineLayout::ReflowFrame(nsIFrame* aFrame,
   // Capture this state *before* we reflow the frame in case it clears
   // the state out. We need to know how to treat the current frame
   // when breaking.
-  PRBool notSafeToBreak = CanPlaceFloatNow() && !GetFlag(LL_IMPACTEDBYFLOATS);
+  PRBool notSafeToBreak = LineIsEmpty() && !GetFlag(LL_IMPACTEDBYFLOATS);
   
   // Apply start margins (as appropriate) to the frame computing the
   // new starting x,y coordinates for the frame.
@@ -1014,6 +1010,7 @@ nsLineLayout::ReflowFrame(nsIFrame* aFrame,
                       aReflowStatus, &optionalBreakAfterFits)) {
       if (!isEmpty) {
         psd->mHasNonemptyContent = PR_TRUE;
+        SetFlag(LL_LINEISEMPTY, PR_FALSE);
       }
 
       // Place the frame, updating aBounds with the final size and
@@ -1029,7 +1026,7 @@ nsLineLayout::ReflowFrame(nsIFrame* aFrame,
       }
       
       if (!continuingTextRun) {
-        if (!psd->mNoWrap && (!CanPlaceFloatNow() || placedFloat)) {
+        if (!psd->mNoWrap && (!LineIsEmpty() || placedFloat)) {
           // record soft break opportunity after this content that can't be
           // part of a text run. This is not a text frame so we know
           // that offset PR_INT32_MAX means "after the content".
@@ -1315,11 +1312,6 @@ nsLineLayout::PlaceFrame(PerFrameData* pfd, nsHTMLReflowMetrics& aMetrics)
   if (!emptyFrame) {
     mTotalPlacedFrames++;
   }
-  if (psd->mX != psd->mLeftEdge || pfd->mBounds.x != psd->mLeftEdge) {
-    // As soon as a frame placed on the line advances an X coordinate
-    // of any span we can no longer place a float on the line.
-    SetFlag(LL_CANPLACEFLOAT, PR_FALSE);
-  }
 }
 
 nsresult

layout/generic/nsLineLayout.h

@@ -155,10 +155,9 @@ public:
 protected:
 #define LL_FIRSTLETTERSTYLEOK          0x00000008
 #define LL_ISTOPOFPAGE                 0x00000010
-#define LL_UPDATEDBAND                 0x00000020
 #define LL_IMPACTEDBYFLOATS            0x00000040
 #define LL_LASTFLOATWASLETTERFRAME     0x00000080
-#define LL_CANPLACEFLOAT               0x00000100
+#define LL_LINEISEMPTY                 0x00000100
 #define LL_LINEENDSINBR                0x00000200
 #define LL_NEEDBACKUP                  0x00000400
 #define LL_INFIRSTLINE                 0x00000800
@@ -194,7 +193,14 @@ public:
     mTextJustificationNumLetters = aNumLetters;
   }
 
-  PRBool CanPlaceFloatNow() const;
+  /**
+   * @return true if so far during reflow no non-empty content has been
+   * placed in the line
+   */
+  PRBool LineIsEmpty() const
+  {
+    return GetFlag(LL_LINEISEMPTY);
+  }
 
   PRBool LineIsBreakable() const;
 

layout/generic/nsTextFrameThebes.cpp

@@ -5453,7 +5453,7 @@ nsTextFrame::Reflow(nsPresContext*           aPresContext,
 
   const nsStyleText* textStyle = GetStyleText();
 
-  PRBool atStartOfLine = lineLayout.CanPlaceFloatNow();
+  PRBool atStartOfLine = lineLayout.LineIsEmpty();
   if (atStartOfLine) {
     AddStateBits(TEXT_START_OF_LINE);
   }

layout/reftests/bugs/439004-1-ref.html

@@ -0,0 +1,6 @@
+<!DOCTYPE HTML>
+<html>
+<body>
+&nbsp;Hello
+</body>
+</html>

layout/reftests/bugs/439004-1.html

@@ -0,0 +1,6 @@
+<!DOCTYPE HTML>
+<html>
+<body>
+<img src="mozilla-banner.gif" style="width:0"> Hello
+</body>
+</html>

layout/reftests/bugs/reftest.list

@@ -844,3 +844,4 @@ random == 429849-1.html 429849-1-ref.html # bug 432288
 == 430813-2.html 430813-2-ref.html
 == 430813-3.html 430813-3-ref.html
 == 433640-1.html 433640-1-ref.html
+== 439004-1.html 439004-1-ref.html