Changeset 252143 in webkit

Timestamp:

Nov 6, 2019 1:02:01 PM (4 years ago)

Author:

Alan Bujtas

Message:

[LFC][MarginCollapsing] Add Line::isConsideredEmpty
​https://bugs.webkit.org/show_bug.cgi?id=203800
<rdar://problem/56854192>

Reviewed by Antti Koivisto.

​https://www.w3.org/TR/CSS22/visuren.html#inline-formatting
Line boxes that contain no text, no preserved white space, no inline elements with non-zero margins, padding, or borders,
and no other in-flow content (such as images, inline blocks or inline tables), and do not end with a preserved newline
must be treated as zero-height line boxes for the purposes of determining the positions of any elements inside of them,
and must be treated as not existing for any other purpose.

Note that it does not necessarily mean visually non-empty line
<span style="font-size: 0px">this is still considered non-empty</span>

• layout/blockformatting/BlockMarginCollapse.cpp:

(WebCore::Layout::BlockFormattingContext::MarginCollapse::marginsCollapseThrough const):

• layout/inlineformatting/InlineLine.cpp:

(WebCore::Layout::Line::appendNonBreakableSpace):
(WebCore::Layout::Line::appendTextContent):
(WebCore::Layout::Line::appendNonReplacedInlineBox):
(WebCore::Layout::Line::appendReplacedInlineBox):
(WebCore::Layout::Line::appendLineBreak):

• layout/inlineformatting/InlineLineBox.h:

(WebCore::Layout::LineBox::isConsideredEmpty const):
(WebCore::Layout::LineBox::setIsConsideredNonEmpty):

Location:

trunk/Source/WebCore

Files:

• ChangeLog (modified) (1 diff)
• layout/blockformatting/BlockMarginCollapse.cpp (modified) (1 diff)
• layout/inlineformatting/InlineLine.cpp (modified) (5 diffs)
• layout/inlineformatting/InlineLineBox.h (modified) (2 diffs)

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2019-11-06  Zalan Bujtas  <zalan@apple.com>
+
+        [LFC][MarginCollapsing] Add Line::isConsideredEmpty
+        https://bugs.webkit.org/show_bug.cgi?id=203800
+        <rdar://problem/56854192>
+
+        Reviewed by Antti Koivisto.
+
+        https://www.w3.org/TR/CSS22/visuren.html#inline-formatting
+        Line boxes that contain no text, no preserved white space, no inline elements with non-zero margins, padding, or borders,
+        and no other in-flow content (such as images, inline blocks or inline tables), and do not end with a preserved newline
+        must be treated as zero-height line boxes for the purposes of determining the positions of any elements inside of them,
+        and must be treated as not existing for any other purpose.
+
+        Note that it does not necessarily mean visually non-empty line
+        <span style="font-size: 0px">this is still considered non-empty</span>
+
+        * layout/blockformatting/BlockMarginCollapse.cpp:
+        (WebCore::Layout::BlockFormattingContext::MarginCollapse::marginsCollapseThrough const):
+        * layout/inlineformatting/InlineLine.cpp:
+        (WebCore::Layout::Line::appendNonBreakableSpace):
+        (WebCore::Layout::Line::appendTextContent):
+        (WebCore::Layout::Line::appendNonReplacedInlineBox):
+        (WebCore::Layout::Line::appendReplacedInlineBox):
+        (WebCore::Layout::Line::appendLineBreak):
+        * layout/inlineformatting/InlineLineBox.h:
+        (WebCore::Layout::LineBox::isConsideredEmpty const):
+        (WebCore::Layout::LineBox::setIsConsideredNonEmpty):
+
 2019-11-06  Chris Lord  <clord@igalia.com>
 

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

@@ -403 +403 @@
             if (!layoutState.hasFormattingState(layoutContainer))
                 return false;
-            auto& formattingState = downcast<InlineFormattingState>(layoutState.establishedFormattingState(layoutContainer));
-            if (!formattingState.inlineRuns().isEmpty())
-                return false;
-            // Any float box in this formatting context prevents collapsing through.
-            auto& floats = formattingState.floatingState().floats();
-            for (auto& floatItem : floats) {
-                if (floatItem.isDescendantOfFormattingRoot(layoutContainer))
-                    return false;
-            }
-            return true;
+
+            auto isConsideredEmpty = [&] {
+                auto& formattingState = downcast<InlineFormattingState>(layoutState.establishedFormattingState(layoutContainer));
+                for (auto& lineBox : formattingState.lineBoxes()) {
+                    if (!lineBox->isConsideredEmpty())
+                        return false;
+                }
+                // Any float box in this formatting context prevents collapsing through.
+                auto& floats = formattingState.floatingState().floats();
+                for (auto& floatItem : floats) {
+                    if (floatItem.isDescendantOfFormattingRoot(layoutContainer))
+                        return false;
+                }
+                return true;
+            };
+            return isConsideredEmpty();
         }
 

trunk/Source/WebCore/layout/inlineformatting/InlineLine.cpp

@@ -385 +385 @@
     m_runList.append(makeUnique<Run>(inlineItem, Display::Run { inlineItem.style(), logicalRect }));
     m_lineBox.expandHorizontally(logicalRect.width());
+    if (logicalRect.width())
+        m_lineBox.setIsConsideredNonEmpty();
 }
 
@@ -464 +466 @@
     if (collapsesToZeroAdvanceWidth)
         lineRun->setCollapsesToZeroAdvanceWidth();
+    else
+        m_lineBox.setIsConsideredNonEmpty();
+
     if (collapsedRun)
         lineRun->setIsCollapsed();
@@ -489 +494 @@
     m_runList.append(makeUnique<Run>(inlineItem, Display::Run { inlineItem.style(), logicalRect }));
     m_lineBox.expandHorizontally(logicalWidth + horizontalMargin.start + horizontalMargin.end);
+    m_lineBox.setIsConsideredNonEmpty();
     m_trimmableContent.clear();
 }
@@ -497 +503 @@
     // FIXME: Surely replaced boxes behave differently.
     appendNonReplacedInlineBox(inlineItem, logicalWidth);
+    m_lineBox.setIsConsideredNonEmpty();
     if (auto* replaced = inlineItem.layoutBox().replaced(); replaced && replaced->cachedImage())
         m_runList.last()->m_displayRun.setImage(*replaced->cachedImage());
@@ -510 +517 @@
         logicalRect.setHeight(logicalHeight());
     }
+    m_lineBox.setIsConsideredNonEmpty();
     m_runList.append(makeUnique<Run>(inlineItem, Display::Run { inlineItem.style(), logicalRect }));
 }

trunk/Source/WebCore/layout/inlineformatting/InlineLineBox.h

@@ -109 +109 @@
     void shrinkVertically(LayoutUnit delta) { expandVertically(-delta); }
 
+    // https://www.w3.org/TR/CSS22/visuren.html#inline-formatting
+    // Line boxes that contain no text, no preserved white space, no inline elements with non-zero margins, padding, or borders,
+    // and no other in-flow content (such as images, inline blocks or inline tables), and do not end with a preserved newline
+    // must be treated as zero-height line boxes for the purposes of determining the positions of any elements inside of them,
+    // and must be treated as not existing for any other purpose.
+    // Note that it does not necessarily mean visually non-empty line. <span style="font-size: 0px">this is still considered non-empty</span>
+    bool isConsideredEmpty() const { return m_isConsideredEmpty; }
+    void setIsConsideredNonEmpty() { m_isConsideredEmpty = false; }
+
 private:
 #if !ASSERT_DISABLED
@@ -117 +126 @@
     Baseline m_baseline;
     LayoutUnit m_baselineOffset;
+    bool m_isConsideredEmpty { true };
 };