Bug 844178 - Make RecomputePosition adjust the CB size as ViewportFrame::Reflow does. r=tn

layout/base/nsCSSFrameConstructor.cpp

@@ -92,6 +92,7 @@
 #include "nsAnimationManager.h"
 #include "nsTransitionManager.h"
 #include "nsSVGIntegrationUtils.h"
+#include "nsViewportFrame.h"
 #include <algorithm>
 
 #ifdef MOZ_XUL
@@ -12453,7 +12454,7 @@ nsCSSFrameConstructor::RecomputePosition(nsIFrame* aFrame)
 
     // Construct a bogus parent reflow state so that there's a usable
     // containing block reflow state.
-    nsIFrame *parentFrame = aFrame->GetParent();
+    nsIFrame* parentFrame = aFrame->GetParent();
     nsSize parentSize = parentFrame->GetSize();
 
     nsFrameState savedState = parentFrame->GetStateBits();
@@ -12477,7 +12478,10 @@ nsCSSFrameConstructor::RecomputePosition(nsIFrame* aFrame)
     nsSize availSize(parentSize.width, NS_INTRINSICSIZE);
 
     nsSize size = aFrame->GetSize();
-    nsSize cbSize = aFrame->GetContainingBlock()->GetSize();
+    ViewportFrame* viewport = do_QueryFrame(parentFrame);
+    nsSize cbSize = viewport ?
+      viewport->AdjustReflowStateAsContainingBlock(&parentReflowState).Size()
+      : aFrame->GetContainingBlock()->GetSize();
     const nsMargin& parentBorder =
       parentReflowState.mStyleBorder->GetComputedBorder();
     cbSize -= nsSize(parentBorder.LeftRight(), parentBorder.TopBottom());

layout/generic/nsViewportFrame.cpp

@@ -28,6 +28,9 @@ NS_NewViewportFrame(nsIPresShell* aPresShell, nsStyleContext* aContext)
 }
 
 NS_IMPL_FRAMEARENA_HELPERS(ViewportFrame)
+NS_QUERYFRAME_HEAD(ViewportFrame)
+  NS_QUERYFRAME_ENTRY(ViewportFrame)
+NS_QUERYFRAME_TAIL_INHERITING(nsContainerFrame)
 
 void
 ViewportFrame::Init(nsIContent*      aContent,
@@ -132,13 +135,9 @@ ViewportFrame::GetPrefWidth(nsRenderingContext *aRenderingContext)
 nsPoint
 ViewportFrame::AdjustReflowStateForScrollbars(nsHTMLReflowState* aReflowState) const
 {
-  // Calculate how much room is available for fixed frames. That means
-  // determining if the viewport is scrollable and whether the vertical and/or
-  // horizontal scrollbars are visible
-
   // Get our prinicpal child frame and see if we're scrollable
   nsIFrame* kidFrame = mFrames.FirstChild();
-  nsIScrollableFrame *scrollingFrame = do_QueryFrame(kidFrame);
+  nsIScrollableFrame* scrollingFrame = do_QueryFrame(kidFrame);
 
   if (scrollingFrame) {
     nsMargin scrollbars = scrollingFrame->GetActualScrollbarSizes();
@@ -152,6 +151,32 @@ ViewportFrame::AdjustReflowStateForScrollbars(nsHTMLReflowState* aReflowState) c
   return nsPoint(0, 0);
 }
 
+nsRect
+ViewportFrame::AdjustReflowStateAsContainingBlock(nsHTMLReflowState* aReflowState) const
+{
+#ifdef DEBUG
+  nsPoint offset =
+#endif
+    AdjustReflowStateForScrollbars(aReflowState);
+
+  NS_ASSERTION(GetAbsoluteContainingBlock()->GetChildList().IsEmpty() ||
+               (offset.x == 0 && offset.y == 0),
+               "We don't handle correct positioning of fixed frames with "
+               "scrollbars in odd positions");
+
+  // If a scroll position clamping scroll-port size has been set, layout
+  // fixed position elements to this size instead of the computed size.
+  nsRect rect(0, 0, aReflowState->ComputedWidth(), aReflowState->ComputedHeight());
+  nsIPresShell* ps = PresContext()->PresShell();
+  if (ps->IsScrollPositionClampingScrollPortSizeSet()) {
+    rect.SizeTo(ps->GetScrollPositionClampingScrollPortSize());
+  }
+
+  // Make sure content document fixed-position margins are respected.
+  rect.Deflate(ps->GetContentDocumentFixedPositionMargins());
+  return rect;
+}
+
 NS_IMETHODIMP
 ViewportFrame::Reflow(nsPresContext*           aPresContext,
                       nsHTMLReflowMetrics&     aDesiredSize,
@@ -238,28 +263,7 @@ ViewportFrame::Reflow(nsPresContext*           aPresContext,
       reflowState.SetComputedHeight(aDesiredSize.height);
     }
 
-#ifdef DEBUG
-    nsPoint offset =
-#endif
-      AdjustReflowStateForScrollbars(&reflowState);
-
-    NS_ASSERTION(GetAbsoluteContainingBlock()->GetChildList().IsEmpty() ||
-                 (offset.x == 0 && offset.y == 0),
-                 "We don't handle correct positioning of fixed frames with "
-                 "scrollbars in odd positions");
-
-    // If a scroll position clamping scroll-port size has been set, layout
-    // fixed position elements to this size instead of the computed size.
-    nsRect rect(0, 0, reflowState.ComputedWidth(), reflowState.ComputedHeight());
-    if (aPresContext->PresShell()->IsScrollPositionClampingScrollPortSizeSet()) {
-      nsSize size = aPresContext->PresShell()->
-        GetScrollPositionClampingScrollPortSize();
-      rect.width = size.width;
-      rect.height = size.height;
-    }
-
-    // Make sure content document fixed-position margins are respected.
-    rect.Deflate(aPresContext->PresShell()->GetContentDocumentFixedPositionMargins());
+    nsRect rect = AdjustReflowStateAsContainingBlock(&reflowState);
 
     // Just reflow all the fixed-pos frames.
     rv = GetAbsoluteContainingBlock()->Reflow(this, aPresContext, reflowState, aStatus,

layout/generic/nsViewportFrame.h

@@ -24,6 +24,8 @@ class nsPresContext;
   */
 class ViewportFrame : public nsContainerFrame {
 public:
+  NS_DECL_QUERYFRAME_TARGET(ViewportFrame)
+  NS_DECL_QUERYFRAME
   NS_DECL_FRAMEARENA_HELPERS
 
   typedef nsContainerFrame Super;
@@ -68,6 +70,14 @@ public:
    */
   virtual nsIAtom* GetType() const MOZ_OVERRIDE;
 
+  /**
+   * Adjust aReflowState to account for scrollbars and pres shell
+   * GetScrollPositionClampingScrollPortSizeSet and
+   * GetContentDocumentFixedPositionMargins adjustments.
+   * @return the rect to use as containing block rect
+   */
+  nsRect AdjustReflowStateAsContainingBlock(nsHTMLReflowState* aReflowState) const;
+
 #ifdef DEBUG
   NS_IMETHOD GetFrameName(nsAString& aResult) const MOZ_OVERRIDE;
 #endif
@@ -76,6 +86,13 @@ private:
   virtual mozilla::layout::FrameChildListID GetAbsoluteListID() const { return kFixedList; }
 
 protected:
+  /**
+   * Calculate how much room is available for fixed frames. That means
+   * determining if the viewport is scrollable and whether the vertical and/or
+   * horizontal scrollbars are visible.  Adjust the computed width/height and
+   * available width for aReflowState accordingly.
+   * @return the current scroll position, or 0,0 if not scrollable
+   */
   nsPoint AdjustReflowStateForScrollbars(nsHTMLReflowState* aReflowState) const;
 };
 

layout/reftests/bugs/844178-ref.html

@@ -0,0 +1,32 @@
+<!DOCTYPE HTML>
+<html><head>
+    <meta charset="utf-8">
+    <title>Testcase for bug 844178</title>
+    <style type="text/css">
+
+        html,body {
+            color:black; background-color:white; font-size:16px; padding:0; margin:0;
+        }
+	
+body {
+  position: fixed;
+  right: 5px;
+  top: 100px;
+  width: 100px;
+  height: 10px;
+  margin:0;
+  padding:0;
+}
+
+:root { overflow:scroll; }
+
+span {
+    background:lime;
+    display:inline-block;
+    width:100px;
+}
+
+</style>
+</head>
+<body><span>Hello</span></body>
+</html>

layout/reftests/bugs/844178.html

@@ -0,0 +1,40 @@
+<!DOCTYPE HTML>
+<html class="reftest-wait"><head>
+    <meta charset="utf-8">
+    <title>Testcase for bug 844178</title>
+    <style type="text/css">
+
+        html,body {
+            color:black; background-color:white; font-size:16px; padding:0; margin:0;
+        }
+	
+body {
+  position: fixed;
+  right: 0px;
+  top: 100px;
+  width: 100px;
+  height: 10px;
+  margin:0;
+  padding:0;
+}
+
+:root { overflow:scroll; }
+
+span {
+    background:lime;
+    display:inline-block;
+    width:100px;
+}
+
+</style>
+<script>
+function doTest() {
+  document.body.style.right='5px';
+  document.body.offsetHeight;
+  document.documentElement.removeAttribute('class');
+}
+document.addEventListener("MozReftestInvalidate", doTest, false);
+</script>
+</head>
+<body><span>Hello</span></body>
+</html>

layout/reftests/bugs/reftest.list

@@ -1749,6 +1749,7 @@ skip-if(B2G) == 818276-1.html 818276-1-ref.html
 == 827799-1.html about:blank
 == 836844-1.html 836844-1-ref.html
 == 841192-1.html 841192-1-ref.html
+== 844178.html 844178-ref.html
 == 846144-1.html 846144-1-ref.html
 == 847850-1.html 847850-1-ref.html
 == 848421-1.html 848421-1-ref.html