Bug 1484360 - Remove UNSET_DISPLAY in nsCSSFrameConstructor. r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D3686

--HG--
extra : moz-landing-system : lando

layout/base/nsCSSFrameConstructor.cpp

@@ -6240,17 +6240,15 @@ nsCSSFrameConstructor::AppendFramesToParent(nsFrameConstructorState&       aStat
   InsertFrames(aParentFrame, kPrincipalList, aPrevSibling, aFrameList);
 }
 
-#define UNSET_DISPLAY static_cast<StyleDisplay>(255)
-
 // This gets called to see if the frames corresponding to aSibling and aContent
 // should be siblings in the frame tree. Although (1) rows and cols, (2) row
 // groups and col groups, (3) row groups and captions, (4) legends and content
 // inside fieldsets, (5) popups and other kids of the menu are siblings from a
 // content perspective, they are not considered siblings in the frame tree.
 bool
-nsCSSFrameConstructor::IsValidSibling(nsIFrame*              aSibling,
-                                      nsIContent*            aContent,
-                                      StyleDisplay&          aDisplay)
+nsCSSFrameConstructor::IsValidSibling(nsIFrame* aSibling,
+                                      nsIContent* aContent,
+                                      Maybe<StyleDisplay>& aDisplay)
 {
   nsIFrame* parentFrame = aSibling->GetParent();
   LayoutFrameType parentType = parentFrame->Type();
@@ -6265,7 +6263,7 @@ nsCSSFrameConstructor::IsValidSibling(nsIFrame*              aSibling,
       LayoutFrameType::Menu == parentType) {
     // if we haven't already, resolve a style to find the display type of
     // aContent.
-    if (UNSET_DISPLAY == aDisplay) {
+    if (aDisplay.isNothing()) {
       if (aContent->IsComment() || aContent->IsProcessingInstruction()) {
         // Comments and processing instructions never have frames, so we should
         // not try to generate styles for them.
@@ -6274,11 +6272,13 @@ nsCSSFrameConstructor::IsValidSibling(nsIFrame*              aSibling,
       // FIXME(emilio): This is buggy some times, see bug 1424656.
       RefPtr<ComputedStyle> computedStyle = ResolveComputedStyle(aContent);
       const nsStyleDisplay* display = computedStyle->StyleDisplay();
-      aDisplay = display->mDisplay;
+      aDisplay.emplace(display->mDisplay);
     }
+
+    StyleDisplay display = aDisplay.value();
     if (LayoutFrameType::Menu == parentType) {
       return
-        (StyleDisplay::MozPopup == aDisplay) ==
+        (StyleDisplay::MozPopup == display) ==
         (StyleDisplay::MozPopup == siblingDisplay);
     }
     // To have decent performance we want to return false in cases in which
@@ -6294,15 +6294,15 @@ nsCSSFrameConstructor::IsValidSibling(nsIFrame*              aSibling,
     // siblings of each other.  Treating a column or colgroup as a valid
     // sibling of a non-table-related frame will just mean we end up reframing.
     if ((siblingDisplay == StyleDisplay::TableCaption) !=
-        (aDisplay == StyleDisplay::TableCaption)) {
+        (display == StyleDisplay::TableCaption)) {
       // One's a caption and the other is not.  Not valid siblings.
       return false;
     }
 
     if ((siblingDisplay == StyleDisplay::TableColumnGroup ||
          siblingDisplay == StyleDisplay::TableColumn) !=
-        (aDisplay == StyleDisplay::TableColumnGroup ||
-         aDisplay == StyleDisplay::TableColumn)) {
+        (display == StyleDisplay::TableColumnGroup ||
+         display == StyleDisplay::TableColumn)) {
       // One's a column or column group and the other is not.  Not valid
       // siblings.
       return false;
@@ -6336,7 +6336,7 @@ nsIFrame*
 nsCSSFrameConstructor::FindSiblingInternal(
   FlattenedChildIterator& aIter,
   nsIContent* aTargetContent,
-  StyleDisplay& aTargetContentDisplay)
+  Maybe<StyleDisplay>& aTargetContentDisplay)
 {
   auto adjust = [&](nsIFrame* aPotentialSiblingFrame) -> nsIFrame* {
     return AdjustSiblingFrame(
@@ -6397,7 +6397,7 @@ nsIFrame*
 nsCSSFrameConstructor::AdjustSiblingFrame(
   nsIFrame* aSibling,
   nsIContent* aTargetContent,
-  mozilla::StyleDisplay& aTargetContentDisplay,
+  Maybe<StyleDisplay>& aTargetContentDisplay,
   SiblingDirection aDirection)
 {
   if (!aSibling) {
@@ -6431,14 +6431,14 @@ nsCSSFrameConstructor::AdjustSiblingFrame(
 
 nsIFrame*
 nsCSSFrameConstructor::FindPreviousSibling(const FlattenedChildIterator& aIter,
-                                           StyleDisplay& aTargetContentDisplay)
+                                           Maybe<StyleDisplay>& aTargetContentDisplay)
 {
   return FindSibling<SiblingDirection::Backward>(aIter, aTargetContentDisplay);
 }
 
 nsIFrame*
 nsCSSFrameConstructor::FindNextSibling(const FlattenedChildIterator& aIter,
-                                       StyleDisplay& aTargetContentDisplay)
+                                       Maybe<StyleDisplay>& aTargetContentDisplay)
 {
   return FindSibling<SiblingDirection::Forward>(aIter, aTargetContentDisplay);
 }
@@ -6446,7 +6446,7 @@ nsCSSFrameConstructor::FindNextSibling(const FlattenedChildIterator& aIter,
 template<nsCSSFrameConstructor::SiblingDirection aDirection>
 nsIFrame*
 nsCSSFrameConstructor::FindSibling(const FlattenedChildIterator& aIter,
-                                   StyleDisplay& aTargetContentDisplay)
+                                   Maybe<StyleDisplay>& aTargetContentDisplay)
 {
   nsIContent* targetContent = aIter.Get();
   FlattenedChildIterator siblingIter = aIter;
@@ -6535,7 +6535,7 @@ nsCSSFrameConstructor::GetInsertionPrevSibling(InsertionPoint* aInsertion,
 
   // Note that FindPreviousSibling is passed the iterator by value, so that
   // the later usage of the iterator starts from the same place.
-  StyleDisplay childDisplay = UNSET_DISPLAY;
+  Maybe<StyleDisplay> childDisplay;
   nsIFrame* prevSibling = FindPreviousSibling(iter, childDisplay);
 
   // Now, find the geometric parent so that we can handle
@@ -6566,7 +6566,7 @@ nsCSSFrameConstructor::GetInsertionPrevSibling(InsertionPoint* aInsertion,
     }
   }
 
-  *aIsRangeInsertSafe = (childDisplay == UNSET_DISPLAY);
+  *aIsRangeInsertSafe = childDisplay.isNothing();
   return prevSibling;
 }
 
@@ -6933,7 +6933,7 @@ nsCSSFrameConstructor::FindNextSiblingForAppend(const InsertionPoint& aInsertion
     FlattenedChildIterator iter(aInsertion.mContainer,
                                 /* aStartAtBeginning = */ false);
     iter.GetPreviousChild(); // Prime the iterator.
-    StyleDisplay unused = UNSET_DISPLAY;
+    Maybe<StyleDisplay> unused;
     return FindNextSibling(iter, unused);
   };
 

layout/base/nsCSSFrameConstructor.h

@@ -15,6 +15,7 @@
 #include "mozilla/ArenaAllocator.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/LinkedList.h"
+#include "mozilla/Maybe.h"
 #include "mozilla/RestyleManager.h"
 #include "mozilla/ScrollStyles.h"
 
@@ -2062,12 +2063,11 @@ private:
    * @param aIter should be positioned such that aIter.GetPreviousChild()
    *          is the first content to search for frames
    * @param aTargetContentDisplay the CSS display enum for the content aIter
-   *          points to if already known, UNSET_DISPLAY otherwise. It will be
-   *          filled in if needed.
+   *          points to if already known. It will be filled in if needed.
    */
   template<SiblingDirection>
   nsIFrame* FindSibling(const mozilla::dom::FlattenedChildIterator& aIter,
-                        mozilla::StyleDisplay& aTargetContentDisplay);
+                        mozilla::Maybe<mozilla::StyleDisplay>& aTargetContentDisplay);
 
   // Helper for the implementation of FindSibling.
   //
@@ -2076,14 +2076,14 @@ private:
   nsIFrame* FindSiblingInternal(
     mozilla::dom::FlattenedChildIterator&,
     nsIContent* aTargetContent,
-    mozilla::StyleDisplay& aTargetContentDisplay);
+    mozilla::Maybe<mozilla::StyleDisplay>& aTargetContentDisplay);
 
   // An alias of FindSibling<SiblingDirection::Forward>.
   nsIFrame* FindNextSibling(const mozilla::dom::FlattenedChildIterator& aIter,
-                            mozilla::StyleDisplay& aTargetContentDisplay);
+                            mozilla::Maybe<mozilla::StyleDisplay>& aTargetContentDisplay);
   // An alias of FindSibling<SiblingDirection::Backwards>.
   nsIFrame* FindPreviousSibling(const mozilla::dom::FlattenedChildIterator& aIter,
-                                mozilla::StyleDisplay& aTargetContentDisplay);
+                                mozilla::Maybe<mozilla::StyleDisplay>& aTargetContentDisplay);
 
   // Given a potential first-continuation sibling frame for aTargetContent,
   // verify that it is an actual valid sibling for it, and return the
@@ -2091,7 +2091,7 @@ private:
   // inserted next to.
   nsIFrame* AdjustSiblingFrame(nsIFrame* aSibling,
                                nsIContent* aTargetContent,
-                               mozilla::StyleDisplay& aTargetContentDisplay,
+                               mozilla::Maybe<mozilla::StyleDisplay>& aTargetContentDisplay,
                                SiblingDirection aDirection);
 
   // Find the right previous sibling for an insertion.  This also updates the
@@ -2120,7 +2120,7 @@ private:
   // may be constructed based on tag, not based on aDisplay!
   bool IsValidSibling(nsIFrame*              aSibling,
                       nsIContent*            aContent,
-                      mozilla::StyleDisplay& aDisplay);
+                      mozilla::Maybe<mozilla::StyleDisplay>& aDisplay);
 
   void QuotesDirty();
   void CountersDirty();