Changeset 237452 in webkit

Timestamp:

Oct 26, 2018, 7:29:22 AM (8 years ago)

Author:

Alan Bujtas

Message:

[LFC][IFC] Find floating constraints for a given vertical position
​https://bugs.webkit.org/show_bug.cgi?id=190928

Reviewed by Antti Koivisto.

​https://www.w3.org/TR/CSS22/visuren.html#inline-formatting

"In general, the left edge of a line box touches the left edge of its containing block and the right edge touches the right edge of its containing block.
However, floating boxes may come between the containing block edge and the line box edge.
Thus, although line boxes in the same inline formatting context generally have the same width
(that of the containing block), they may vary in width if available horizontal space is reduced due to floats."

This patch adds support for retrieving left/right constraints for a given line (vertical position).

• layout/floats/FloatingState.cpp:

(WebCore::Layout::FloatingState::constraints const):

• layout/floats/FloatingState.h:

Location:

trunk/Source/WebCore

Files:

• ChangeLog (modified) (1 diff)
• layout/floats/FloatingState.cpp (modified) (1 diff)
• layout/floats/FloatingState.h (modified) (1 diff)

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2018-10-26  Zalan Bujtas  <zalan@apple.com>
+
+        [LFC][IFC] Find floating constraints for a given vertical position
+        https://bugs.webkit.org/show_bug.cgi?id=190928
+
+        Reviewed by Antti Koivisto.
+
+        https://www.w3.org/TR/CSS22/visuren.html#inline-formatting
+
+        "In general, the left edge of a line box touches the left edge of its containing block and the right edge touches the right edge of its containing block.
+        However, floating boxes may come between the containing block edge and the line box edge.
+        Thus, although line boxes in the same inline formatting context generally have the same width
+        (that of the containing block), they may vary in width if available horizontal space is reduced due to floats."
+
+        This patch adds support for retrieving left/right constraints for a given line (vertical position).
+
+        * layout/floats/FloatingState.cpp:
+        (WebCore::Layout::FloatingState::constraints const):
+        * layout/floats/FloatingState.h:
+
 2018-10-26  Zalan Bujtas  <zalan@apple.com>
 

trunk/Source/WebCore/layout/floats/FloatingState.cpp

@@ -87 +87 @@
 }
 
+FloatingState::Constraints FloatingState::constraints(LayoutUnit verticalPosition, const Box& formattingContextRoot) const
+{
+    if (isEmpty())
+        return { };
+
+    // 1. Convert vertical position if this floating context is inherited.
+    // 2. Find the inner left/right floats at verticalPosition.
+    // 3. Convert left/right positions back to formattingContextRoot's cooridnate system.
+    auto coordinateMappingIsRequired = &root() != &formattingContextRoot;
+    auto adjustedPosition = Position { 0, verticalPosition };
+
+    if (coordinateMappingIsRequired)
+        adjustedPosition = FormattingContext::mapCoordinateToAncestor(m_layoutContext, adjustedPosition, downcast<Container>(formattingContextRoot), downcast<Container>(root()));
+
+    Constraints constraints;
+    for (int index = m_floats.size() - 1; index >= 0; --index) {
+        auto& floatItem = m_floats[index];
+
+        if (constraints.left && floatItem.isLeftPositioned())
+            continue;
+
+        if (constraints.right && !floatItem.isLeftPositioned())
+            continue;
+
+        auto rect = floatItem.rectWithMargin();
+        if (!(rect.top() <= verticalPosition && verticalPosition < rect.bottom()))
+            continue;
+
+        if (floatItem.isLeftPositioned())
+            constraints.left = rect.right();
+        else
+            constraints.right = rect.left();
+
+        if (constraints.left && constraints.right)
+            break;
+    }
+
+    if (coordinateMappingIsRequired) {
+        if (constraints.left)
+            constraints.left = *constraints.left - adjustedPosition.x;
+
+        if (constraints.right)
+            constraints.right = *constraints.right - adjustedPosition.x;
+    }
+
+    return constraints;
+}
+
 std::optional<LayoutUnit> FloatingState::bottom(const Box& formattingContextRoot, Clear type) const
 {

trunk/Source/WebCore/layout/floats/FloatingState.h

@@ -58 +58 @@
     std::optional<LayoutUnit> rightBottom(const Box& formattingContextRoot) const;
     std::optional<LayoutUnit> bottom(const Box& formattingContextRoot) const;
+
+    struct Constraints {
+        std::optional<LayoutUnit> left;
+        std::optional<LayoutUnit> right;
+    };
+    Constraints constraints(LayoutUnit verticalPosition, const Box& formattingContextRoot) const;
 
     class FloatItem {