Changeset 239331 in webkit

Timestamp:

Dec 18, 2018 7:23:47 AM (5 years ago)

Author:

Alan Bujtas

Message:

[LFC][BFC][MarginCollapsing] Expand marginAfterCollapsesWithNextSibling and marginBeforeCollapsesWithPreviousSibling collapsing logic
​https://bugs.webkit.org/show_bug.cgi?id=192791

Reviewed by Antti Koivisto.

• layout/blockformatting/BlockMarginCollapse.cpp:

(WebCore::Layout::BlockFormattingContext::Geometry::MarginCollapse::marginBeforeCollapsesWithPreviousSibling):
(WebCore::Layout::BlockFormattingContext::Geometry::MarginCollapse::marginAfterCollapsesWithNextSibling):

Location:

trunk/Source/WebCore

Files:

• ChangeLog (modified) (1 diff)
• layout/blockformatting/BlockMarginCollapse.cpp (modified) (2 diffs)

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2018-12-18  Zalan Bujtas  <zalan@apple.com>
+
+        [LFC][BFC][MarginCollapsing] Expand marginAfterCollapsesWithNextSibling and marginBeforeCollapsesWithPreviousSibling collapsing logic
+        https://bugs.webkit.org/show_bug.cgi?id=192791
+
+        Reviewed by Antti Koivisto.
+
+        * layout/blockformatting/BlockMarginCollapse.cpp:
+        (WebCore::Layout::BlockFormattingContext::Geometry::MarginCollapse::marginBeforeCollapsesWithPreviousSibling):
+        (WebCore::Layout::BlockFormattingContext::Geometry::MarginCollapse::marginAfterCollapsesWithNextSibling):
+
 2018-12-18  Zalan Bujtas  <zalan@apple.com>
 

trunk/Source/WebCore/layout/blockformatting/BlockMarginCollapse.cpp

@@ -291 +291 @@
     ASSERT(layoutBox.isBlockLevelBox());
 
-    if (layoutBox.isFloatingPositioned())
-        return false;
-
-    if (!layoutBox.isPositioned() || layoutBox.isInFlowPositioned())
-        return true;
-
-    // Out of flow positioned.
-    ASSERT(layoutBox.isOutOfFlowPositioned());
-    return layoutBox.style().top().isAuto();
+    if (!layoutBox.previousInFlowSibling())
+        return false;
+
+    auto& previousInFlowSibling = *layoutBox.previousInFlowSibling();
+
+    // Margins between a floated box and any other box do not collapse.
+    if (layoutBox.isFloatingPositioned() || previousInFlowSibling.isFloatingPositioned())
+        return false;
+
+    // Margins of absolutely positioned boxes do not collapse.
+    if ((layoutBox.isOutOfFlowPositioned() && !layoutBox.style().top().isAuto())
+        || (previousInFlowSibling.isOutOfFlowPositioned() && !previousInFlowSibling.style().bottom().isAuto()))
+        return false;
+
+    // Margins of inline-block boxes do not collapse.
+    if (layoutBox.isInlineBlockBox() || previousInFlowSibling.isInlineBlockBox())
+        return false;
+
+    // The bottom margin of an in-flow block-level element always collapses with the top margin of
+    // its next in-flow block-level sibling, unless that sibling has clearance.
+    if (hasClearance(layoutBox))
+        return false;
+
+    return true;
 }
 
@@ -306 +321 @@
     ASSERT(layoutBox.isBlockLevelBox());
 
-    if (layoutBox.isFloatingPositioned())
-        return false;
-
-    if (!layoutBox.isPositioned() || layoutBox.isInFlowPositioned())
-        return true;
-
-    // Out of flow positioned.
-    ASSERT(layoutBox.isOutOfFlowPositioned());
-    return layoutBox.style().bottom().isAuto();
+    if (!layoutBox.nextInFlowSibling())
+        return false;
+
+    return marginBeforeCollapsesWithPreviousSibling(*layoutBox.nextInFlowSibling());
 }