Changeset 232154 in webkit

Timestamp:

May 24, 2018, 9:57:24 AM (8 years ago)

Author:

Alan Bujtas

Message:

[LFC] Implement position computation for inflow positioned elements
​https://bugs.webkit.org/show_bug.cgi?id=185936

Reviewed by Antti Koivisto.

• layout/blockformatting/BlockFormattingContext.cpp:

(WebCore::Layout::BlockFormattingContext::computeInFlowPositionedPosition const):

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

(WebCore::Layout::BlockFormattingContext::Geometry::inFlowPositionedPosition):

Location:

trunk/Source/WebCore

Files:

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

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2018-05-24  Zalan Bujtas  <zalan@apple.com>
+
+        [LFC] Implement position computation for inflow positioned elements
+        https://bugs.webkit.org/show_bug.cgi?id=185936
+
+        Reviewed by Antti Koivisto.
+
+        * layout/blockformatting/BlockFormattingContext.cpp:
+        (WebCore::Layout::BlockFormattingContext::computeInFlowPositionedPosition const):
+        * layout/blockformatting/BlockFormattingContext.h:
+        * layout/blockformatting/BlockFormattingContextGeometry.cpp:
+        (WebCore::Layout::BlockFormattingContext::Geometry::inFlowPositionedPosition):
+
 2018-05-24  Zalan Bujtas  <zalan@apple.com>
 

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

@@ -135 +135 @@
 }
 
+void BlockFormattingContext::computeInFlowPositionedPosition(LayoutContext& layoutContext, const Box& layoutBox, Display::Box& displayBox) const
+{
+    auto topLeft = Geometry::inFlowPositionedPosition(layoutContext, layoutBox);
+    displayBox.setTopLeft(topLeft);
+}
+
 void BlockFormattingContext::computeInFlowHeight(LayoutContext& layoutContext, const Box& layoutBox, Display::Box& displayBox) const
 {

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

@@ -53 +53 @@
 private:
     void computeStaticPosition(LayoutContext&, const Box&, Display::Box&) const override;
+    void computeInFlowPositionedPosition(LayoutContext&, const Box&, Display::Box&) const override;
     void computeInFlowWidth(LayoutContext&, const Box&, Display::Box&) const override;
     void computeInFlowHeight(LayoutContext&, const Box&, Display::Box&) const override;
@@ -66 +67 @@
 
         static LayoutPoint staticPosition(LayoutContext&, const Box&);
+        static LayoutPoint inFlowPositionedPosition(LayoutContext&, const Box&);
     };
 };

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

@@ -138 +138 @@
 }
 
+LayoutPoint BlockFormattingContext::Geometry::inFlowPositionedPosition(LayoutContext& layoutContext, const Box& layoutBox)
+{
+    ASSERT(layoutBox.isInFlowPositioned());
+    // 9.4.3 Relative positioning
+    //
+    // The 'top' and 'bottom' properties move relatively positioned element(s) up or down without changing their size.
+    // Top' moves the boxes down, and 'bottom' moves them up. Since boxes are not split or stretched as a result of 'top' or 'bottom', the used values are always: top = -bottom.
+    //
+    // 1. If both are 'auto', their used values are both '0'.
+    // 2. If one of them is 'auto', it becomes the negative of the other.
+    // 3. If neither is 'auto', 'bottom' is ignored (i.e., the used value of 'bottom' will be minus the value of 'top').
+    auto& displayBox = *layoutContext.displayBoxForLayoutBox(layoutBox);
+    auto& style = layoutBox.style();
+
+    auto top = style.logicalTop();
+    auto bottom = style.logicalBottom();
+    LayoutUnit topDelta;
+
+    if (top.isAuto() && bottom.isAuto()) {
+        // #1
+        topDelta = 0;
+    } else if (top.isAuto()) {
+        // #2
+        topDelta = -bottom.value();
+    } else if (bottom.isAuto()) {
+        // #3 #4
+        topDelta = top.value();
+    }
+
+    // For relatively positioned elements, 'left' and 'right' move the box(es) horizontally, without changing their size.
+    // 'Left' moves the boxes to the right, and 'right' moves them to the left.
+    // Since boxes are not split or stretched as a result of 'left' or 'right', the used values are always: left = -right.
+    //
+    // 1. If both 'left' and 'right' are 'auto' (their initial values), the used values are '0' (i.e., the boxes stay in their original position).
+    // 2. If 'left' is 'auto', its used value is minus the value of 'right' (i.e., the boxes move to the left by the value of 'right').
+    // 3. If 'right' is specified as 'auto', its used value is minus the value of 'left'.
+    // 4. If neither 'left' nor 'right' is 'auto', the position is over-constrained, and one of them has to be ignored.
+    //    If the 'direction' property of the containing block is 'ltr', the value of 'left' wins and 'right' becomes -'left'.
+    //    If 'direction' of the containing block is 'rtl', 'right' wins and 'left' is ignored.
+    //
+    auto left = style.logicalLeft();
+    auto right = style.logicalRight();
+    LayoutUnit leftDelta;
+
+    if (left.isAuto() && right.isAuto()) {
+        // #1
+        leftDelta = 0;
+    } else if (left.isAuto()) {
+        // #2
+        leftDelta = -right.value();
+    } else if (right.isAuto()) {
+        // #3
+        leftDelta = left.value();
+    } else {
+        // #4
+        // FIXME: take direction into account
+        leftDelta = left.value();
+    }
+
+    return { displayBox.left() + leftDelta, displayBox.top() + topDelta };
+}
+
 }
 }