Changeset 249590 in webkit

Timestamp:

Sep 6, 2019 1:51:21 PM (5 years ago)

Author:

Alan Bujtas

Message:

[LFC] A formatting context root is always a containing block for relative: static boxes.
​https://bugs.webkit.org/show_bug.cgi?id=201554
<rdar://problem/55123295>

Reviewed by Antti Koivisto.

"For other elements, if the element's position is 'relative' or 'static', the containing block is formed by the content
edge of the nearest ancestor box that is a block container or which establishes a formatting context."

• layout/layouttree/LayoutBox.cpp:

(WebCore::Layout::Box::containingBlock const):

• page/FrameViewLayoutContext.cpp:

(WebCore::layoutUsingFormattingContext):

Location:

trunk/Source/WebCore

Files:

• ChangeLog (modified) (1 diff)
• layout/layouttree/LayoutBox.cpp (modified) (2 diffs)

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2019-09-06  Zalan Bujtas  <zalan@apple.com>
+
+        [LFC] A formatting context root is always a containing block for relative: static boxes.
+        https://bugs.webkit.org/show_bug.cgi?id=201554
+        <rdar://problem/55123295>
+
+        Reviewed by Antti Koivisto.
+
+        "For other elements, if the element's position is 'relative' or 'static', the containing block is formed by the content
+        edge of the nearest ancestor box that is a block container or which establishes a formatting context."
+
+        * layout/layouttree/LayoutBox.cpp:
+        (WebCore::Layout::Box::containingBlock const):
+        * page/FrameViewLayoutContext.cpp:
+        (WebCore::layoutUsingFormattingContext):
+
 2019-09-06  Sihui Liu  <sihui_liu@apple.com>
 

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

@@ -189 +189 @@
     // The containing block in which the root element lives is a rectangle called the initial containing block.
     // For other elements, if the element's position is 'relative' or 'static', the containing block is formed by the
-    // content edge of the nearest block container ancestor box.
+    // content edge of the nearest block container ancestor box or which establishes a formatting context.
     // If the element has 'position: fixed', the containing block is established by the viewport
     // If the element has 'position: absolute', the containing block is established by the nearest ancestor with a
@@ -197 +197 @@
 
     if (!isPositioned() || isInFlowPositioned()) {
-        auto* nearestBlockContainer = parent();
-        for (; nearestBlockContainer->parent() && !nearestBlockContainer->isBlockContainerBox(); nearestBlockContainer = nearestBlockContainer->parent()) { }
-        return nearestBlockContainer;
+        for (auto* nearestBlockContainerOrFormattingContextRoot = parent(); nearestBlockContainerOrFormattingContextRoot; nearestBlockContainerOrFormattingContextRoot = nearestBlockContainerOrFormattingContextRoot->parent()) {
+            if (nearestBlockContainerOrFormattingContextRoot->isBlockContainerBox() || nearestBlockContainerOrFormattingContextRoot->establishesFormattingContext())
+                return nearestBlockContainerOrFormattingContextRoot; 
+        }
+        // We should always manage to find the ICB.
+        ASSERT_NOT_REACHED();
+        return nullptr;
     }