Changeset 247198 in webkit

Timestamp:

Jul 7, 2019 6:47:26 AM (5 years ago)

Author:

Alan Bujtas

Message:

[LFC] Fix formatting context root for inflow positioned inline containers
​https://bugs.webkit.org/show_bug.cgi?id=199551
<rdar://problem/52728868>

Reviewed by Antti Koivisto.

Relatively positioned (inflow) inline container lives in the formatting context where its parent lives unless
the parent establishes a formatting context. This is slightly different from the usual behavior which is containing block driven.

div id=outer style="position: absolute">><div id=inner><span style="position: relative">content</span></div></div>

While the relatively positioned inline container (span) is placed relative to its containing block "outer", it lives in the inline formatting context established by "inner".

• layout/FormattingContext.cpp:

(WebCore::Layout::FormattingContext::layoutOutOfFlowDescendants const):

• layout/layouttree/LayoutBox.cpp:

(WebCore::Layout::Box::formattingContextRoot const):

• layout/layouttree/LayoutBox.h:
• layout/layouttree/LayoutInlineContainer.cpp:

(WebCore::Layout::InlineContainer::formattingContextRoot const):

• layout/layouttree/LayoutInlineContainer.h:

Location:

trunk/Source/WebCore

Files:

• ChangeLog (modified) (1 diff)
• layout/FormattingContext.cpp (modified) (1 diff)
• layout/layouttree/LayoutBox.cpp (modified) (1 diff)
• layout/layouttree/LayoutBox.h (modified) (1 diff)
• layout/layouttree/LayoutInlineContainer.cpp (modified) (1 diff)
• layout/layouttree/LayoutInlineContainer.h (modified) (1 diff)

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2019-07-07  Zalan Bujtas  <zalan@apple.com>
+
+        [LFC] Fix formatting context root for inflow positioned inline containers
+        https://bugs.webkit.org/show_bug.cgi?id=199551
+        <rdar://problem/52728868>
+
+        Reviewed by Antti Koivisto.
+
+        Relatively positioned (inflow) inline container lives in the formatting context where its parent lives unless
+        the parent establishes a formatting context. This is slightly different from the usual behavior which is containing block driven.
+
+        div id=outer style="position: absolute">><div id=inner><span style="position: relative">content</span></div></div>
+
+        While the relatively positioned inline container (span) is placed relative to its containing block "outer", it lives in the inline formatting context established by "inner".
+
+        * layout/FormattingContext.cpp:
+        (WebCore::Layout::FormattingContext::layoutOutOfFlowDescendants const):
+        * layout/layouttree/LayoutBox.cpp:
+        (WebCore::Layout::Box::formattingContextRoot const):
+        * layout/layouttree/LayoutBox.h:
+        * layout/layouttree/LayoutInlineContainer.cpp:
+        (WebCore::Layout::InlineContainer::formattingContextRoot const):
+        * layout/layouttree/LayoutInlineContainer.h:
+
 2019-07-06  Simon Fraser  <simon.fraser@apple.com>
 

trunk/Source/WebCore/layout/FormattingContext.cpp

@@ -136 +136 @@
 void FormattingContext::layoutOutOfFlowDescendants(const Box& layoutBox) const
 {
-    // Initial containing block by definition is a containing block.
-    if (!layoutBox.isPositioned() && !layoutBox.isInitialContainingBlock())
-        return;
-
     if (!is<Container>(layoutBox))
         return;

trunk/Source/WebCore/layout/layouttree/LayoutBox.cpp

@@ -175 +175 @@
 const Container& Box::formattingContextRoot() const
 {
-    for (auto* ancestor = containingBlock(); ancestor; ancestor = ancestor->containingBlock()) {
-        if (ancestor->establishesFormattingContext())
-            return *ancestor;
-    }
-
-    // Initial containing block always establishes a formatting context.
-    if (isInitialContainingBlock())
-        return downcast<Container>(*this);
-
-    RELEASE_ASSERT_NOT_REACHED();
+    // We should never need to ask this question on the ICB.
+    ASSERT(!isInitialContainingBlock());
+    // A box lives in the same formatting context as its containing block unless the containing block establishes a formatting context.
+    auto& containingBlock = *this->containingBlock();
+    if (containingBlock.establishesFormattingContext())
+        return containingBlock;
+    return containingBlock.formattingContextRoot();
 }
 

trunk/Source/WebCore/layout/layouttree/LayoutBox.h

@@ -98 +98 @@
 
     const Container* containingBlock() const;
-    const Container& formattingContextRoot() const;
+    virtual const Container& formattingContextRoot() const;
     const Container& initialContainingBlock() const;
 

trunk/Source/WebCore/layout/layouttree/LayoutInlineContainer.cpp

@@ -55 +55 @@
 }
 
+const Container& InlineContainer::formattingContextRoot() const
+{
+    // Relatively positioned (inflow) inline container lives in the formatting context where its parent lives unless
+    // the parent establishes a formatting context. This is slightly different from the usual behavior which is containing block driven.
+    //
+    // <div id=outer style="position: absolute">><div id=inner><span style="position: relative">content</span></div></div>
+    // While the relatively positioned inline container (span) is placed relative to its containing block "outer", it lives in the inline
+    // formatting context established by "inner".
+    auto& ancestor = isInFlowPositioned() ? *parent() : *containingBlock();
+    if (ancestor.establishesFormattingContext())
+        return ancestor;
+    return ancestor.formattingContextRoot();
+}
+
 }
 }

trunk/Source/WebCore/layout/layouttree/LayoutInlineContainer.h

@@ -43 +43 @@
 
     bool establishesInlineFormattingContext() const final;
+    const Container& formattingContextRoot() const final;
 };