[LFC] Add margin computation for floating, replaced elements.

https://bugs.webkit.org/show_bug.cgi?id=186337

Reviewed by Antti Koivisto.

If 'margin-left' or 'margin-right' are computed as 'auto', their used value is '0'.

* layout/FormattingContext.h:
* layout/FormattingContextGeometry.cpp:
(WebCore::Layout::FormattingContext::Geometry::floatingReplacedWidthAndMargin):
(WebCore::Layout::FormattingContext::Geometry::inlineReplacedWidthAndMargin):

Canonical link: https://commits.webkit.org/201722@main
git-svn-id: https://svn.webkit.org/repository/webkit/trunk@232541 268f45cc-cd09-0410-ab3c-d52691b4dbfc

Source/WebCore/ChangeLog

@@ -1,3 +1,17 @@
+2018-06-06  Zalan Bujtas  <zalan@apple.com>
+
+        [LFC] Add margin computation for floating, replaced elements.
+        https://bugs.webkit.org/show_bug.cgi?id=186337
+
+        Reviewed by Antti Koivisto.
+
+        If 'margin-left' or 'margin-right' are computed as 'auto', their used value is '0'.
+
+        * layout/FormattingContext.h:
+        * layout/FormattingContextGeometry.cpp:
+        (WebCore::Layout::FormattingContext::Geometry::floatingReplacedWidthAndMargin):
+        (WebCore::Layout::FormattingContext::Geometry::inlineReplacedWidthAndMargin):
+
 2018-06-06  Zalan Bujtas  <zalan@apple.com>
 
         [LFC] Add margin computation for floating, no-replaced elements.

Source/WebCore/layout/FormattingContext.h

@@ -95,7 +95,8 @@ class FormattingContext {
         static LayoutPoint outOfFlowPosition(LayoutContext&, const Box&);
 
         static LayoutUnit inlineReplacedHeight(LayoutContext&, const Box&);
-        static WidthAndMargin inlineReplacedWidthAndMargin(LayoutContext&, const Box&);
+        static WidthAndMargin inlineReplacedWidthAndMargin(LayoutContext&, const Box&, std::optional<LayoutUnit> precomputedMarginLeft = { },
+            std::optional<LayoutUnit> precomputedMarginRight = { });
 
         static Display::Box::Edges computedBorder(LayoutContext&, const Box&);
         static std::optional<Display::Box::Edges> computedPadding(LayoutContext&, const Box&);

Source/WebCore/layout/FormattingContextGeometry.cpp

@@ -255,8 +255,18 @@ FormattingContext::Geometry::WidthAndMargin FormattingContext::Geometry::floatin
     ASSERT(layoutBox.isFloatingPositioned() && layoutBox.replaced());
     // 10.3.6 Floating, replaced elements
     //
-    // The used value of 'width' is determined as for inline replaced elements.
-    return inlineReplacedWidthAndMargin(layoutContext, layoutBox);
+    // 1. If 'margin-left' or 'margin-right' are computed as 'auto', their used value is '0'.
+    // 2. The used value of 'width' is determined as for inline replaced elements.
+    auto& style = layoutBox.style();
+    std::optional<LayoutUnit> computedMarginLeftValue;
+    std::optional<LayoutUnit> computedMarginRightValue;
+
+    if (style.marginLeft().isAuto())
+        computedMarginLeftValue = LayoutUnit { 0 };
+    if (style.marginRight().isAuto())
+        computedMarginRightValue = LayoutUnit { 0 };
+
+    return inlineReplacedWidthAndMargin(layoutContext, layoutBox, computedMarginLeftValue, computedMarginRightValue);
 }
 
 static LayoutPoint outOfFlowNonReplacedPosition(LayoutContext& layoutContext, const Box& layoutBox)
@@ -534,7 +544,8 @@ LayoutUnit FormattingContext::Geometry::inlineReplacedHeight(LayoutContext&, con
     return computedHeightValue;
 }
 
-FormattingContext::Geometry::WidthAndMargin FormattingContext::Geometry::inlineReplacedWidthAndMargin(LayoutContext& layoutContext, const Box& layoutBox)
+FormattingContext::Geometry::WidthAndMargin FormattingContext::Geometry::inlineReplacedWidthAndMargin(LayoutContext& layoutContext, const Box& layoutBox,
+    std::optional<LayoutUnit> precomputedMarginLeft, std::optional<LayoutUnit> precomputedMarginRight)
 {
     ASSERT((layoutBox.isOutOfFlowPositioned() || layoutBox.isFloatingPositioned() || layoutBox.isInFlow()) && layoutBox.replaced());
     // 10.3.2 Inline, replaced elements
@@ -556,19 +567,26 @@ FormattingContext::Geometry::WidthAndMargin FormattingContext::Geometry::inlineR
     // 5. Otherwise, if 'width' has a computed value of 'auto', but none of the conditions above are met, then the used value of 'width' becomes 300px.
     //    If 300px is too wide to fit the device, UAs should use the width of the largest rectangle that has a 2:1 ratio and fits the device instead.
     auto& style = layoutBox.style();
-    LayoutUnit computedWidthValue;
-    LayoutUnit computedMarginLeftValue;
-    LayoutUnit computedMarginRightValue;
+    auto containingBlockWidth = layoutContext.displayBoxForLayoutBox(*layoutBox.containingBlock())->width();
 
-    {
-        auto marginLeft = style.marginLeft();
+    auto computeMarginRight = [&]() {
+        if (precomputedMarginRight)
+            return precomputedMarginRight.value();
         auto marginRight = style.marginRight();
-        auto containingBlockWidth = layoutContext.displayBoxForLayoutBox(*layoutBox.containingBlock())->width();
+        return marginRight.isAuto() ? LayoutUnit { 0 } : valueForLength(marginRight, containingBlockWidth);
+    };
 
-        computedMarginLeftValue = marginLeft.isAuto() ? LayoutUnit(0) : valueForLength(marginLeft, containingBlockWidth);
-        computedMarginRightValue = marginRight.isAuto() ? LayoutUnit(0) : valueForLength(marginRight, containingBlockWidth);
-    }
+    auto computeMarginLeft = [&]() {
+        if (precomputedMarginLeft)
+            return precomputedMarginLeft.value();
+        auto marginLeft = style.marginLeft();
+        return marginLeft.isAuto() ? LayoutUnit { 0 } : valueForLength(marginLeft, containingBlockWidth);
+    };
 
+    LayoutUnit computedMarginLeftValue = computeMarginLeft();
+    LayoutUnit computedMarginRightValue = computeMarginRight();
+
+    LayoutUnit computedWidthValue;
     auto width = style.logicalWidth();
     auto height = style.logicalHeight();
     auto replaced = layoutBox.replaced();