Bug 1305957 part 3 - Add IsStickyPositioned() method to nsStyleDisplay. r=emilio

This commit is used in a later commit to exclude frames that are sticky positioned
from being scroll anchors.

Differential Revision: https://phabricator.services.mozilla.com/D13266

--HG--
extra : rebase_source : 50cddce18bbc0164bfff70bf00ab698354ede375
extra : histedit_source : 7cad7389e6958d3107e43e5f915139f6682c168d

layout/generic/nsIFrame.h

@@ -3848,6 +3848,7 @@ class nsIFrame : public nsQueryFrame {
   inline bool IsAbsPosContainingBlock() const;
   inline bool IsFixedPosContainingBlock() const;
   inline bool IsRelativelyPositioned() const;
+  inline bool IsStickyPositioned() const;
   inline bool IsAbsolutelyPositioned(
       const nsStyleDisplay* aStyleDisplay = nullptr) const;
 

layout/generic/nsIFrameInlines.h

@@ -47,6 +47,10 @@ bool nsIFrame::IsRelativelyPositioned() const {
   return StyleDisplay()->IsRelativelyPositioned(this);
 }
 
+bool nsIFrame::IsStickyPositioned() const {
+  return StyleDisplay()->IsStickyPositioned(this);
+}
+
 bool nsIFrame::IsAbsolutelyPositioned(
     const nsStyleDisplay* aStyleDisplay) const {
   const nsStyleDisplay* disp = StyleDisplayWithOptionalParam(aStyleDisplay);

layout/style/nsStyleStruct.h

@@ -2109,6 +2109,9 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleDisplay {
     return NS_STYLE_POSITION_RELATIVE == mPosition ||
            NS_STYLE_POSITION_STICKY == mPosition;
   }
+  bool IsStickyPositionedStyle() const {
+    return NS_STYLE_POSITION_STICKY == mPosition;
+  }
   bool IsPositionForcingStackingContext() const {
     return NS_STYLE_POSITION_STICKY == mPosition ||
            NS_STYLE_POSITION_FIXED == mPosition;
@@ -2230,6 +2233,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleDisplay {
   inline mozilla::StyleDisplay GetDisplay(const nsIFrame* aContextFrame) const;
   inline bool IsFloating(const nsIFrame* aContextFrame) const;
   inline bool IsRelativelyPositioned(const nsIFrame* aContextFrame) const;
+  inline bool IsStickyPositioned(const nsIFrame* aContextFrame) const;
   inline bool IsAbsolutelyPositioned(const nsIFrame* aContextFrame) const;
 
   // These methods are defined in nsStyleStructInlines.h.

layout/style/nsStyleStructInlines.h

@@ -211,6 +211,13 @@ bool nsStyleDisplay::IsRelativelyPositioned(
          !nsSVGUtils::IsInSVGTextSubtree(aContextFrame);
 }
 
+bool nsStyleDisplay::IsStickyPositioned(const nsIFrame* aContextFrame) const {
+  NS_ASSERTION(aContextFrame->StyleDisplay() == this,
+               "unexpected aContextFrame");
+  return IsStickyPositionedStyle() &&
+         !nsSVGUtils::IsInSVGTextSubtree(aContextFrame);
+}
+
 bool nsStyleDisplay::IsAbsolutelyPositioned(
     const nsIFrame* aContextFrame) const {
   NS_ASSERTION(aContextFrame->StyleDisplay() == this,