Bug 985303. Part 3: Save a block's 'bottom edge of content' in a frame property if it doesn't match the block's content height, and use it in UpdateOverflow to compute the correct overflow. r=dbaron

--HG--
extra : rebase_source : 11fe6925ee266a2e1feec5a4d5c0e5ed152516f5

layout/generic/nsBlockFrame.cpp

@@ -241,6 +241,7 @@ NS_DECLARE_FRAME_PROPERTY_FRAMELIST(OverflowOutOfFlowsProperty)
 NS_DECLARE_FRAME_PROPERTY_FRAMELIST(PushedFloatProperty)
 NS_DECLARE_FRAME_PROPERTY_FRAMELIST(OutsideBulletProperty)
 NS_DECLARE_FRAME_PROPERTY(InsideBulletProperty, nullptr)
+NS_DECLARE_FRAME_PROPERTY(BottomEdgeOfChildrenProperty, nullptr)
 
 //----------------------------------------------------------------------
 
@@ -1452,6 +1453,14 @@ nsBlockFrame::ComputeFinalSize(const nsHTMLReflowState& aReflowState,
   aMetrics.Height() = std::max(0, aMetrics.Height());
   *aBottomEdgeOfChildren = bottomEdgeOfChildren;
 
+  FrameProperties properties = Properties();
+  if (bottomEdgeOfChildren != aMetrics.Height() - borderPadding.bottom) {
+    properties.Set(BottomEdgeOfChildrenProperty(),
+                   NS_INT32_TO_PTR(bottomEdgeOfChildren));
+  } else {
+    properties.Delete(BottomEdgeOfChildrenProperty());
+  }
+
 #ifdef DEBUG_blocks
   if (CRAZY_SIZE(aMetrics.Width()) || CRAZY_SIZE(aMetrics.Height())) {
     ListTag(stdout);
@@ -1460,6 +1469,22 @@ nsBlockFrame::ComputeFinalSize(const nsHTMLReflowState& aReflowState,
 #endif
 }
 
+static void
+ConsiderBottomEdgeOfChildren(nscoord aBottomEdgeOfChildren,
+                             nsOverflowAreas& aOverflowAreas)
+{
+  // Factor in the bottom edge of the children.  Child frames will be added
+  // to the overflow area as we iterate through the lines, but their margins
+  // won't, so we need to account for bottom margins here.
+  // REVIEW: For now, we do this for both visual and scrollable area,
+  // although when we make scrollable overflow area not be a subset of
+  // visual, we can change this.
+  NS_FOR_FRAME_OVERFLOW_TYPES(otype) {
+    nsRect& o = aOverflowAreas.Overflow(otype);
+    o.height = std::max(o.YMost(), aBottomEdgeOfChildren) - o.y;
+  }
+}
+
 void
 nsBlockFrame::ComputeOverflowAreas(const nsRect&         aBounds,
                                    const nsStyleDisplay* aDisplay,
@@ -1487,17 +1512,9 @@ nsBlockFrame::ComputeOverflowAreas(const nsRect&         aBounds,
       areas.UnionAllWith(outsideBullet->GetRect());
     }
 
-    // Factor in the bottom edge of the children.  Child frames will be added
-    // to the overflow area as we iterate through the lines, but their margins
-    // won't, so we need to account for bottom margins here.
-    // REVIEW: For now, we do this for both visual and scrollable area,
-    // although when we make scrollable overflow area not be a subset of
-    // visual, we can change this.
-    NS_FOR_FRAME_OVERFLOW_TYPES(otype) {
-      nsRect& o = areas.Overflow(otype);
-      o.height = std::max(o.YMost(), aBottomEdgeOfChildren) - o.y;
-    }
+    ConsiderBottomEdgeOfChildren(aBottomEdgeOfChildren, areas);
   }
+
 #ifdef NOISY_COMBINED_AREA
   ListTag(stdout);
   printf(": ca=%d,%d,%d,%d\n", area.x, area.y, area.width, area.height);
@@ -1509,6 +1526,9 @@ nsBlockFrame::ComputeOverflowAreas(const nsRect&         aBounds,
 bool
 nsBlockFrame::UpdateOverflow()
 {
+  nsRect rect(nsPoint(0, 0), GetSize());
+  nsOverflowAreas overflowAreas(rect, rect);
+
   // We need to update the overflow areas of lines manually, as they
   // get cached and re-used otherwise. Lines aren't exposed as normal
   // frame children, so calling UnionChildOverflow alone will end up
@@ -1516,7 +1536,8 @@ nsBlockFrame::UpdateOverflow()
   for (line_iterator line = begin_lines(), line_end = end_lines();
        line != line_end;
        ++line) {
-    nsOverflowAreas lineAreas;
+    nsRect bounds = line->mBounds;
+    nsOverflowAreas lineAreas(bounds, bounds);
 
     int32_t n = line->GetChildCount();
     for (nsIFrame* lineFrame = line->mFirstChild;
@@ -1532,13 +1553,26 @@ nsBlockFrame::UpdateOverflow()
     }
 
     line->SetOverflowAreas(lineAreas);
+    overflowAreas.UnionWith(lineAreas);
   }
 
   // Line cursor invariants depend on the overflow areas of the lines, so
   // we must clear the line cursor since those areas may have changed.
   ClearLineCursor();
 
-  return nsBlockFrameSuper::UpdateOverflow();
+  // Union with child frames, skipping the principal and float lists
+  // since we already handled those using the line boxes.
+  nsLayoutUtils::UnionChildOverflow(this, overflowAreas,
+                                    kPrincipalList | kFloatList);
+
+  bool found;
+  nscoord bottomEdgeOfChildren = NS_PTR_TO_INT32(
+    Properties().Get(BottomEdgeOfChildrenProperty(), &found));
+  if (found) {
+    ConsiderBottomEdgeOfChildren(bottomEdgeOfChildren, overflowAreas);
+  }
+
+  return FinishAndStoreOverflow(overflowAreas, GetSize());
 }
 
 void

layout/reftests/bugs/985303-1-ref.html

@@ -0,0 +1,34 @@
+<!DOCTYPE html>
+<html>
+<head>
+<style>
+#container {
+  position: absolute;
+  width: 200px;
+  height: 200px;
+  overflow: scroll;
+}
+#image {
+  width: 100px;
+  height: 100px;
+  margin: 100px;
+  background: blue;
+  display: inline-block;
+}
+#cursor {
+  position: absolute;
+  left: 10px;
+  top: 0;
+  width: 10px;
+  height: 10px;
+  background: red;
+}
+</style>
+</head>
+<body>
+<div id='container'>
+  <div id='image'></div>
+  <div id='cursor'></div>
+</div>
+</body>
+</html>

layout/reftests/bugs/985303-1a.html

@@ -0,0 +1,38 @@
+<!DOCTYPE html>
+<html>
+<head>
+<style>
+#container {
+  position: absolute;
+  width: 200px;
+  height: 200px;
+  overflow: scroll;
+}
+#image {
+  width: 100px;
+  height: 100px;
+  margin: 100px;
+  background: blue;
+  display: inline-block;
+}
+#cursor {
+  position: absolute;
+  left: 0;
+  top: 0;
+  width: 10px;
+  height: 10px;
+  background: red;
+}
+</style>
+</head>
+<body>
+<div id='container'>
+  <div id='image'></div>
+  <div id='cursor'></div>
+</div>
+</body>
+<script>
+var x = image.getBoundingClientRect();
+cursor.style.left = '10px';
+</script>
+</html>

layout/reftests/bugs/985303-1b.html

@@ -0,0 +1,40 @@
+<!DOCTYPE html>
+<html>
+<head>
+<style>
+#container {
+  position: absolute;
+  width: 200px;
+  height: 200px;
+  overflow: scroll;
+}
+#image {
+  width: 100px;
+  height: 100px;
+  margin: 100px;
+  background: blue;
+  display: inline-block;
+}
+#cursor {
+  position: absolute;
+  left: 0;
+  top: 0;
+  width: 10px;
+  height: 10px;
+  background: red;
+}
+</style>
+</head>
+<body>
+<div id='container'>
+  <div style="position:relative">
+    <div id='image'></div>
+    <div id='cursor'></div>
+  </div>
+</div>
+</body>
+<script>
+var x = image.getBoundingClientRect();
+cursor.style.left = '10px';
+</script>
+</html>

layout/reftests/bugs/reftest.list

@@ -1804,6 +1804,8 @@ skip-if(Android) == 966510-2.html 966510-2-ref.html # same as above
 == 983084-2.html 983084-2-ref.html
 == 983084-3.html 983084-1-ref.html
 == 983691-1.html 983691-ref.html
+== 985303-1a.html 985303-1-ref.html
+== 985303-1b.html 985303-1-ref.html
 == 987680-1.html 987680-1-ref.html
 fuzzy-if(/^Windows\x20NT\x206\.2/.test(http.oscpu),1,24) == 991046-1.html 991046-1-ref.html
 pref(layout.css.overflow-clip-box.enabled,true) == 992447.html 992447-ref.html