Changeset 239334 in webkit

Timestamp:

Dec 18, 2018 7:27:09 AM (5 years ago)

Author:

Alan Bujtas

Message:

[LFC][BFC][MarginCollapsing] Implement marginAfterCollapsesWithParentMarginBefore
​https://bugs.webkit.org/show_bug.cgi?id=192798

Reviewed by Antti Koivisto.

• layout/blockformatting/BlockFormattingContext.h:
• layout/blockformatting/BlockFormattingContextGeometry.cpp:

(WebCore::Layout::BlockFormattingContext::Geometry::inFlowNonReplacedHeightAndMargin):

• layout/blockformatting/BlockMarginCollapse.cpp:

(WebCore::Layout::BlockFormattingContext::Geometry::MarginCollapse::collapsedMarginAfterFromLastChild):
(WebCore::Layout::BlockFormattingContext::Geometry::MarginCollapse::marginAfterCollapsesWithParentMarginBefore):
(WebCore::Layout::BlockFormattingContext::Geometry::MarginCollapse::marginAfterCollapsesWithParentMarginAfter):
(WebCore::Layout::BlockFormattingContext::Geometry::MarginCollapse::marginAfter):

Location:

trunk/Source/WebCore

Files:

• ChangeLog (modified) (1 diff)
• layout/blockformatting/BlockFormattingContext.h (modified) (2 diffs)
• layout/blockformatting/BlockFormattingContextGeometry.cpp (modified) (1 diff)
• layout/blockformatting/BlockMarginCollapse.cpp (modified) (4 diffs)

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2018-12-18  Zalan Bujtas  <zalan@apple.com>
+
+        [LFC][BFC][MarginCollapsing] Implement marginAfterCollapsesWithParentMarginBefore
+        https://bugs.webkit.org/show_bug.cgi?id=192798
+
+        Reviewed by Antti Koivisto.
+
+        * layout/blockformatting/BlockFormattingContext.h:
+        * layout/blockformatting/BlockFormattingContextGeometry.cpp:
+        (WebCore::Layout::BlockFormattingContext::Geometry::inFlowNonReplacedHeightAndMargin):
+        * layout/blockformatting/BlockMarginCollapse.cpp:
+        (WebCore::Layout::BlockFormattingContext::Geometry::MarginCollapse::collapsedMarginAfterFromLastChild):
+        (WebCore::Layout::BlockFormattingContext::Geometry::MarginCollapse::marginAfterCollapsesWithParentMarginBefore):
+        (WebCore::Layout::BlockFormattingContext::Geometry::MarginCollapse::marginAfterCollapsesWithParentMarginAfter):
+        (WebCore::Layout::BlockFormattingContext::Geometry::MarginCollapse::marginAfter):
+
 2018-12-18  Zalan Bujtas  <zalan@apple.com>
 

trunk/Source/WebCore/layout/blockformatting/BlockFormattingContext.h

@@ -91 +91 @@
 
             static bool marginBeforeCollapsesWithParentMarginAfter(const Box&);
-            static bool marginAfterCollapsesWithParentMarginAfter(const Box&);
+            static bool marginAfterCollapsesWithParentMarginAfter(const LayoutState&, const Box&);
 
         private:
@@ -107 +107 @@
             static bool marginAfterCollapsesWithNextSibling(const Box&);
             static bool marginAfterCollapsesWithSiblingMarginBeforeWithClearance(const Box&);
-            static bool marginAfterCollapsesWithParentMarginBefore(const Box&);
+            static bool marginAfterCollapsesWithParentMarginBefore(const LayoutState&, const Box&);
             static bool marginsCollapseThrough(const LayoutState&, const Box&);
         };

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

@@ -85 +85 @@
         auto* lastInFlowChild = downcast<Container>(layoutBox).lastInFlowChild();
         ASSERT(lastInFlowChild);
-        if (!MarginCollapse::marginAfterCollapsesWithParentMarginAfter(*lastInFlowChild)) {
+        if (!MarginCollapse::marginAfterCollapsesWithParentMarginAfter(layoutState, *lastInFlowChild)) {
             auto& lastInFlowDisplayBox = layoutState.displayBoxForLayoutBox(*lastInFlowChild);
             return { lastInFlowDisplayBox.bottom() + lastInFlowDisplayBox.marginAfter() - borderAndPaddingTop, { nonCollapsedMargin, collapsedMargin } };

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

@@ -168 +168 @@
     // FIXME: Check for collapsed through margin.
     auto& lastInFlowChild = *downcast<Container>(layoutBox).lastInFlowChild();
-    if (!marginAfterCollapsesWithParentMarginAfter(lastInFlowChild))
+    if (!marginAfterCollapsesWithParentMarginAfter(layoutState, lastInFlowChild))
         return 0;
 
@@ -231 +231 @@
 }
 
-bool BlockFormattingContext::Geometry::MarginCollapse::marginAfterCollapsesWithParentMarginBefore(const Box&)
-{
+bool BlockFormattingContext::Geometry::MarginCollapse::marginAfterCollapsesWithParentMarginBefore(const LayoutState& layoutState, const Box& layoutBox)
+{
+    // 1. This is the first in-flow child and its margins collapse through and the margin before collapses with parent's margin before or
+    // 2. This box's margin before collapses with the previous sibling's margin after and that sibling collapses through and
+    // we can get to the first in-flow child like that.
+    auto* firstInFlowChild = layoutBox.parent()->firstInFlowChild();
+    for (auto* currentBox = &layoutBox; currentBox; currentBox = currentBox->previousInFlowSibling()) {
+        if (!marginsCollapseThrough(layoutState, *currentBox))
+            return false;
+        if (currentBox == firstInFlowChild)
+            return marginBeforeCollapsesWithParentMarginBefore(layoutState, *currentBox); 
+        if (!marginBeforeCollapsesWithPreviousSibling(*currentBox))
+            return false;
+    }
+    ASSERT_NOT_REACHED();
     return false;
 }
 
-bool BlockFormattingContext::Geometry::MarginCollapse::marginAfterCollapsesWithParentMarginAfter(const Box& layoutBox)
+bool BlockFormattingContext::Geometry::MarginCollapse::marginAfterCollapsesWithParentMarginAfter(const LayoutState& layoutState, const Box& layoutBox)
 {
     if (layoutBox.isAnonymous())
@@ -282 +295 @@
     // nor (if the box's min-height is non-zero) with the box's top margin.
     auto computedMinHeight = parent.style().logicalMinHeight();
-    if (!computedMinHeight.isAuto() && computedMinHeight.value() && marginAfterCollapsesWithParentMarginBefore(layoutBox))
+    if (!computedMinHeight.isAuto() && computedMinHeight.value() && marginAfterCollapsesWithParentMarginBefore(layoutState, layoutBox))
         return false;
 
@@ -407 +420 @@
 
     // TODO: take _hasAdjoiningMarginBeforeAndBottom() into account.
-    if (marginAfterCollapsesWithParentMarginAfter(layoutBox))
+    if (marginAfterCollapsesWithParentMarginAfter(layoutState, layoutBox))
         return 0;