Bug 849996. Check the correct frame for transforms in PushAbsoluteContainingBlock --- it might not be the containing block itself. r=bzbarsky

layout/base/nsCSSFrameConstructor.cpp

@@ -791,7 +791,12 @@ public:
   // logic in GetAbsoluteContainingBlock.
   // Also makes aNewAbsoluteContainingBlock the containing block for
   // fixed-pos elements if necessary.
+  // aPositionedFrame is the frame whose style actually makes
+  // aNewAbsoluteContainingBlock a containing block. E.g. for a scrollable element
+  // aPositionedFrame is the element's primary frame and
+  // aNewAbsoluteContainingBlock is the scrolled frame.
   void PushAbsoluteContainingBlock(nsIFrame* aNewAbsoluteContainingBlock,
+                                   nsIFrame* aPositionedFrame,
                                    nsFrameConstructorSaveState& aSaveState);
 
   // Function to push the existing float containing block state and
@@ -1029,6 +1034,7 @@ AdjustAbsoluteContainingBlock(nsIFrame* aContainingBlockIn)
 
 void
 nsFrameConstructorState::PushAbsoluteContainingBlock(nsIFrame* aNewAbsoluteContainingBlock,
+                                                     nsIFrame* aPositionedFrame,
                                                      nsFrameConstructorSaveState& aSaveState)
 {
   aSaveState.mItems = &mAbsoluteItems;
@@ -1044,14 +1050,14 @@ nsFrameConstructorState::PushAbsoluteContainingBlock(nsIFrame* aNewAbsoluteConta
     mFixedItems = mAbsoluteItems;
   }
 
-  mAbsoluteItems = 
+  mAbsoluteItems =
     nsAbsoluteItems(AdjustAbsoluteContainingBlock(aNewAbsoluteContainingBlock));
 
   /* See if we're wiring the fixed-pos and abs-pos lists together.  This happens iff
    * we're a transformed element.
    */
-  mFixedPosIsAbsPos = aNewAbsoluteContainingBlock &&
-    aNewAbsoluteContainingBlock->StyleDisplay()->HasTransform(aNewAbsoluteContainingBlock);
+  mFixedPosIsAbsPos = aPositionedFrame &&
+      aPositionedFrame->StyleDisplay()->HasTransform(aPositionedFrame);
 
   if (aNewAbsoluteContainingBlock) {
     aNewAbsoluteContainingBlock->MarkAsAbsoluteContainingBlock();
@@ -1955,7 +1961,7 @@ nsCSSFrameConstructor::ConstructTable(nsFrameConstructorState& aState,
        (display->HasTransformStyle() &&
         aParentFrame->IsFrameOfType(nsIFrame::eSupportsCSSTransforms))) &&
       !aParentFrame->IsSVGText()) {
-    aState.PushAbsoluteContainingBlock(newFrame, absoluteSaveState);
+    aState.PushAbsoluteContainingBlock(newFrame, newFrame, absoluteSaveState);
   }
   if (aItem.mFCData->mBits & FCDATA_USE_CHILD_ITEMS) {
     ConstructFramesFromItemList(aState, aItem.mChildItems,
@@ -2357,6 +2363,7 @@ nsCSSFrameConstructor::ConstructDocElementFrame(Element*                 aDocEle
     // the root element
     mDocElementContainingBlock->AddStateBits(NS_FRAME_CAN_HAVE_ABSPOS_CHILDREN);
     state.PushAbsoluteContainingBlock(mDocElementContainingBlock,
+                                      mDocElementContainingBlock,
                                       absoluteSaveState);
   }
 
@@ -2443,7 +2450,8 @@ nsCSSFrameConstructor::ConstructDocElementFrame(Element*                 aDocEle
                                               mDocElementContainingBlock),
                      mDocElementContainingBlock, styleContext,
                      &contentFrame, frameItems,
-                     display->IsPositioned(contentFrame), nullptr);
+                     display->IsPositioned(contentFrame) ? contentFrame : nullptr,
+                     nullptr);
       newFrame = frameItems.FirstChild();
       NS_ASSERTION(frameItems.OnlyChild(), "multiple root element frames");
     }
@@ -3064,7 +3072,7 @@ nsCSSFrameConstructor::ConstructFieldSetFrame(nsFrameConstructorState& aState,
 
   newFrame->AddStateBits(NS_FRAME_CAN_HAVE_ABSPOS_CHILDREN);
   if (newFrame->IsPositioned()) {
-    aState.PushAbsoluteContainingBlock(newFrame, absoluteSaveState);
+    aState.PushAbsoluteContainingBlock(newFrame, newFrame, absoluteSaveState);
   }
 
   ProcessChildren(aState, content, styleContext, blockFrame, true,
@@ -3615,7 +3623,7 @@ nsCSSFrameConstructor::ConstructFrameFromItemInternal(FrameConstructionItem& aIt
     nsFrameConstructorSaveState absoluteSaveState;
 
     if (bits & FCDATA_FORCE_NULL_ABSPOS_CONTAINER) {
-      aState.PushAbsoluteContainingBlock(nullptr, absoluteSaveState);
+      aState.PushAbsoluteContainingBlock(nullptr, nullptr, absoluteSaveState);
     } else if (!(bits & FCDATA_SKIP_ABSPOS_PUSH)) {
       nsIFrame* cb = maybeAbsoluteContainingBlock;
       cb->AddStateBits(NS_FRAME_CAN_HAVE_ABSPOS_CHILDREN);
@@ -3624,7 +3632,7 @@ nsCSSFrameConstructor::ConstructFrameFromItemInternal(FrameConstructionItem& aIt
            (maybeAbsoluteContainingBlockDisplay->HasTransformStyle() &&
             cb->IsFrameOfType(nsIFrame::eSupportsCSSTransforms))) &&
           !cb->IsSVGText()) {
-        aState.PushAbsoluteContainingBlock(cb, absoluteSaveState);
+        aState.PushAbsoluteContainingBlock(cb, primaryFrame, absoluteSaveState);
       }
     }
 
@@ -4359,7 +4367,7 @@ nsCSSFrameConstructor::ConstructScrollableBlock(nsFrameConstructorState& aState,
   ConstructBlock(aState, scrolledContentStyle->StyleDisplay(), content,
                  newFrame, newFrame, scrolledContentStyle,
                  &scrolledFrame, blockItem,
-                 aDisplay->IsPositioned(scrolledFrame),
+                 aDisplay->IsPositioned(newFrame) ? newFrame : nullptr,
                  aItem.mPendingBinding);
 
   NS_ASSERTION(blockItem.FirstChild() == scrolledFrame,
@@ -4402,7 +4410,8 @@ nsCSSFrameConstructor::ConstructNonScrollableBlock(nsFrameConstructorState& aSta
   ConstructBlock(aState, aDisplay, aItem.mContent,
                  aState.GetGeometricParent(aDisplay, aParentFrame),
                  aParentFrame, styleContext, &newFrame,
-                 aFrameItems, aDisplay->IsPositioned(newFrame),
+                 aFrameItems,
+                 aDisplay->IsPositioned(newFrame) ? newFrame : nullptr,
                  aItem.mPendingBinding);
   return newFrame;
 }
@@ -10892,7 +10901,7 @@ nsCSSFrameConstructor::ConstructBlock(nsFrameConstructorState& aState,
                                       nsStyleContext*          aStyleContext,
                                       nsIFrame**               aNewFrame,
                                       nsFrameItems&            aFrameItems,
-                                      bool                     aAbsPosContainer,
+                                      nsIFrame*                aPositionedFrameForAbsPosContainer,
                                       PendingBinding*          aPendingBinding)
 {
   // Create column wrapper if necessary
@@ -10937,9 +10946,9 @@ nsCSSFrameConstructor::ConstructBlock(nsFrameConstructorState& aState,
   // in nsBlockFrame::CalculateContainingBlockSizeForAbsolutes.
   nsFrameConstructorSaveState absoluteSaveState;
   (*aNewFrame)->AddStateBits(NS_FRAME_CAN_HAVE_ABSPOS_CHILDREN);
-  if (aAbsPosContainer) {
+  if (aPositionedFrameForAbsPosContainer) {
     //    NS_ASSERTION(aRelPos, "should have made area frame for this");
-    aState.PushAbsoluteContainingBlock(*aNewFrame, absoluteSaveState);
+    aState.PushAbsoluteContainingBlock(*aNewFrame, aPositionedFrameForAbsPosContainer, absoluteSaveState);
   }
 
   // Process the child content
@@ -11038,7 +11047,7 @@ nsCSSFrameConstructor::ConstructInline(nsFrameConstructorState& aState,
   if (positioned) {
     // Relatively positioned frames becomes a container for child
     // frames that are positioned
-    aState.PushAbsoluteContainingBlock(newFrame, absoluteSaveState);
+    aState.PushAbsoluteContainingBlock(newFrame, newFrame, absoluteSaveState);
   }
 
   // Process the child content

layout/base/nsCSSFrameConstructor.h

@@ -1582,6 +1582,9 @@ private:
   // block
   // @param aContentParent is the parent the block would have if it
   // were in-flow
+  // @param aPositionedFrameForAbsPosContainer if non-null, then the new
+  // block should be an abs-pos container and aPositionedFrameForAbsPosContainer
+  // is the frame whose style is making this block an abs-pos container.
   // @param aPendingBinding the pending binding  from this block's frame
   // construction item.
   void ConstructBlock(nsFrameConstructorState& aState,
@@ -1592,7 +1595,7 @@ private:
                       nsStyleContext*          aStyleContext,
                       nsIFrame**               aNewFrame,
                       nsFrameItems&            aFrameItems,
-                      bool                     aAbsPosContainer,
+                      nsIFrame*                aPositionedFrameForAbsPosContainer,
                       PendingBinding*          aPendingBinding);
 
   nsIFrame* ConstructInline(nsFrameConstructorState& aState,

layout/reftests/bugs/849996-1-ref.html

@@ -0,0 +1,23 @@
+<!DOCTYPE html>
+<html>
+<head>
+<style>
+#parent {
+  width: 200px;
+  height: 200px;
+  margin-left: 10px;
+  background: green;
+}
+#child {
+  width: 90px;
+  height: 90px;
+  background: red;
+}
+</style>
+</head>
+<body>
+<div id="parent">
+  <div id="child"></div>
+</div>
+</body>
+</html>

layout/reftests/bugs/849996-1.html

@@ -0,0 +1,27 @@
+<!DOCTYPE html>
+<html>
+<head>
+<style>
+#parent {
+  width: 200px;
+  height: 200px;
+  overflow: hidden;
+  transform: translateX(10px);
+  background: green;
+}
+#child {
+  position: fixed;
+  top: -10px;
+  left: -10px;
+  width: 100px;
+  height: 100px;
+  background: red;
+}
+</style>
+</head>
+<body>
+<div id="parent">
+  <div id="child"></div>
+</div>
+</body>
+</html>

layout/reftests/bugs/reftest.list

@@ -1753,5 +1753,6 @@ skip-if(B2G) == 818276-1.html 818276-1-ref.html
 == 847850-1.html 847850-1-ref.html
 == 848421-1.html 848421-1-ref.html
 test-pref(layout.css.flexbox.enabled,true) == 849407-1.html 849407-1-ref.html
+== 849996-1.html 849996-1-ref.html
 == 858803-1.html 858803-1-ref.html
 != 860370.html 860370-notref.html