[LFC][IFC] Empty generated content should not prevent margin collapsing

https://bugs.webkit.org/show_bug.cgi?id=243485 Reviewed by Antti Koivisto. In some cases (e.g. pseudo content with '') we construct empty InlineTextItems (they are required so that we keep layout boxes and inline items synced). These truly empty inline items should be collapsed at InlineLine::append so that they don't show up on the line box as (blank) text runs (and make the iterator believe there's content on the line, which in turn prevents margin collapsing). (This makes content: ''; behave as content: ' '; (provided collapsing is allowed)) * LayoutTests/fast/inline/incorrect-content-height-with-empty-generated-content-expected.html: Added. * LayoutTests/fast/inline/incorrect-content-height-with-empty-generated-content.html: Added. * Source/WebCore/layout/formattingContexts/inline/InlineLine.cpp: (WebCore::Layout::Line::appendTextContent): * Source/WebCore/layout/formattingContexts/inline/InlineTextItem.cpp: (WebCore::Layout::InlineTextItem::InlineTextItem): * Source/WebCore/layout/formattingContexts/inline/InlineTextItem.h: (WebCore::Layout::InlineTextItem::isEmpty const): (WebCore::Layout::InlineTextItem::createEmptyItem): Canonical link: https://commits.webkit.org/253079@main
WebKit · Aug 3, 2022 · fe9010d · fe9010d
1 parent febc2b3
commit fe9010d
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Showing 15 changed files with 55 additions and 42 deletions.
diff --git a/LayoutTests/fast/inline/incorrect-content-height-with-empty-generated-content-expected.html b/LayoutTests/fast/inline/incorrect-content-height-with-empty-generated-content-expected.html
@@ -0,0 +1,9 @@
+<style>
+div {
+  width: 100px;
+  height: 100px;
+  background-color: green;
+  padding: 1px;
+}
+</style>
+<div></div>
diff --git a/LayoutTests/fast/inline/incorrect-content-height-with-empty-generated-content.html b/LayoutTests/fast/inline/incorrect-content-height-with-empty-generated-content.html
@@ -0,0 +1,16 @@
+<style>
+div {
+  width: 100px;
+  background-color: green;
+  padding: 1px;
+}
+
+span::before {
+  display: block;
+  content: '';
+  margin-top: 100px;
+  margin-bottom: 100px;
+}
+</style>
+<!-- empty content should not prevent margin collapsing -->
+<div><span></span></div>
diff --git a/LayoutTests/fast/layers/add-layer-with-nested-stacking-expected.txt b/LayoutTests/fast/layers/add-layer-with-nested-stacking-expected.txt
@@ -7,5 +7,4 @@ layer at (8,8) size 784x100
   RenderBlock {DIV} at (0,0) size 784x100
 layer at (8,8) size 100x100
   RenderBlock (generated) at (0,0) size 100x100 [bgcolor=#008000]
-    RenderText at (0,-14) size 0x18
-      text run at (0,-14) width 0: ""
+    RenderText at (0,0) size 0x0
diff --git a/LayoutTests/fast/table/table-section-split-with-after-content-expected.txt b/LayoutTests/fast/table/table-section-split-with-after-content-expected.txt
@@ -11,5 +11,4 @@ layer at (0,0) size 800x16
           RenderTableSection (anonymous) at (0,0) size 0x0
             RenderTableRow (anonymous) at (0,0) size 0x0
               RenderTableCell (anonymous) at (0,0) size 0x0 [r=0 c=0 rs=1 cs=1]
-                RenderText at (0,-40) size 0x50
-                  text run at (0,-40) width 0: ""
+                RenderText at (0,0) size 0x0
diff --git a/LayoutTests/platform/ios/fast/css/acid2-expected.txt b/LayoutTests/platform/ios/fast/css/acid2-expected.txt
@@ -20,11 +20,9 @@ layer at (36,2640) size 764x226
       RenderBlock {DIV} at (12,0) size 144x48 [bgcolor=#FFFF00]
         RenderBlock {DIV} at (60,12) size 24x24 [bgcolor=#FF0000]
           RenderBlock (generated) at (0,0) size 24x12 [border: none (12px solid #FFFF00) (12px solid #000000) (12px solid #FFFF00)]
-            RenderText at (12,-12) size 0x15
-              text run at (12,-12) width 0: ""
+            RenderText at (0,0) size 0x0
           RenderBlock (generated) at (0,12) size 24x12 [border: (12px solid #000000) (12px solid #FFFF00) none (12px solid #FFFF00)]
-            RenderText at (12,0) size 0x15
-              text run at (12,0) width 0: ""
+            RenderText at (0,0) size 0x0
     RenderBlock {DIV} at (87,75) size 590x0
       RenderBlock {DIV} at (48,0) size 518x0
     RenderBlock {DIV} at (48,132) size 668x24

diff --git a/LayoutTests/platform/ios/fast/css/acid2-pixel-expected.txt b/LayoutTests/platform/ios/fast/css/acid2-pixel-expected.txt
@@ -20,11 +20,9 @@ layer at (36,72) size 764x226
       RenderBlock {DIV} at (12,0) size 144x48 [bgcolor=#FFFF00]
         RenderBlock {DIV} at (60,12) size 24x24 [bgcolor=#FF0000]
           RenderBlock (generated) at (0,0) size 24x12 [border: none (12px solid #FFFF00) (12px solid #000000) (12px solid #FFFF00)]
-            RenderText at (12,-12) size 0x15
-              text run at (12,-12) width 0: ""
+            RenderText at (0,0) size 0x0
           RenderBlock (generated) at (0,12) size 24x12 [border: (12px solid #000000) (12px solid #FFFF00) none (12px solid #FFFF00)]
-            RenderText at (12,0) size 0x15
-              text run at (12,0) width 0: ""
+            RenderText at (0,0) size 0x0
     RenderBlock {DIV} at (87,75) size 590x0
       RenderBlock {DIV} at (48,0) size 518x0
     RenderBlock {DIV} at (48,132) size 668x24

diff --git a/LayoutTests/platform/ios/http/tests/misc/acid2-expected.txt b/LayoutTests/platform/ios/http/tests/misc/acid2-expected.txt
@@ -20,11 +20,9 @@ layer at (36,2640) size 764x226
       RenderBlock {DIV} at (12,0) size 144x48 [bgcolor=#FFFF00]
         RenderBlock {DIV} at (60,12) size 24x24 [bgcolor=#FF0000]
           RenderBlock (generated) at (0,0) size 24x12 [border: none (12px solid #FFFF00) (12px solid #000000) (12px solid #FFFF00)]
-            RenderText at (12,-12) size 0x15
-              text run at (12,-12) width 0: ""
+            RenderText at (0,0) size 0x0
           RenderBlock (generated) at (0,12) size 24x12 [border: (12px solid #000000) (12px solid #FFFF00) none (12px solid #FFFF00)]
-            RenderText at (12,0) size 0x15
-              text run at (12,0) width 0: ""
+            RenderText at (0,0) size 0x0
     RenderBlock {DIV} at (87,75) size 590x0
       RenderBlock {DIV} at (48,0) size 518x0
     RenderBlock {DIV} at (48,132) size 668x24

diff --git a/LayoutTests/platform/ios/http/tests/misc/acid2-pixel-expected.txt b/LayoutTests/platform/ios/http/tests/misc/acid2-pixel-expected.txt
@@ -20,11 +20,9 @@ layer at (36,72) size 764x226
       RenderBlock {DIV} at (12,0) size 144x48 [bgcolor=#FFFF00]
         RenderBlock {DIV} at (60,12) size 24x24 [bgcolor=#FF0000]
           RenderBlock (generated) at (0,0) size 24x12 [border: none (12px solid #FFFF00) (12px solid #000000) (12px solid #FFFF00)]
-            RenderText at (12,-12) size 0x15
-              text run at (12,-12) width 0: ""
+            RenderText at (0,0) size 0x0
           RenderBlock (generated) at (0,12) size 24x12 [border: (12px solid #000000) (12px solid #FFFF00) none (12px solid #FFFF00)]
-            RenderText at (12,0) size 0x15
-              text run at (12,0) width 0: ""
+            RenderText at (0,0) size 0x0
     RenderBlock {DIV} at (87,75) size 590x0
       RenderBlock {DIV} at (48,0) size 518x0
     RenderBlock {DIV} at (48,132) size 668x24

diff --git a/LayoutTests/platform/mac/fast/css/acid2-expected.txt b/LayoutTests/platform/mac/fast/css/acid2-expected.txt
@@ -20,11 +20,9 @@ layer at (36,2638) size 764x226
       RenderBlock {DIV} at (12,0) size 144x48 [bgcolor=#FFFF00]
         RenderBlock {DIV} at (60,12) size 24x24 [bgcolor=#FF0000]
           RenderBlock (generated) at (0,0) size 24x12 [border: none (12px solid #FFFF00) (12px solid #000000) (12px solid #FFFF00)]
-            RenderText at (12,-11) size 0x14
-              text run at (12,-11) width 0: ""
+            RenderText at (0,0) size 0x0
           RenderBlock (generated) at (0,12) size 24x12 [border: (12px solid #000000) (12px solid #FFFF00) none (12px solid #FFFF00)]
-            RenderText at (12,1) size 0x14
-              text run at (12,1) width 0: ""
+            RenderText at (0,0) size 0x0
     RenderBlock {DIV} at (87,75) size 590x0
       RenderBlock {DIV} at (48,0) size 518x0
     RenderBlock {DIV} at (48,132) size 668x24

diff --git a/LayoutTests/platform/mac/fast/css/acid2-pixel-expected.txt b/LayoutTests/platform/mac/fast/css/acid2-pixel-expected.txt
@@ -20,11 +20,9 @@ layer at (36,72) size 764x226
       RenderBlock {DIV} at (12,0) size 144x48 [bgcolor=#FFFF00]
         RenderBlock {DIV} at (60,12) size 24x24 [bgcolor=#FF0000]
           RenderBlock (generated) at (0,0) size 24x12 [border: none (12px solid #FFFF00) (12px solid #000000) (12px solid #FFFF00)]
-            RenderText at (12,-11) size 0x14
-              text run at (12,-11) width 0: ""
+            RenderText at (0,0) size 0x0
           RenderBlock (generated) at (0,12) size 24x12 [border: (12px solid #000000) (12px solid #FFFF00) none (12px solid #FFFF00)]
-            RenderText at (12,1) size 0x14
-              text run at (12,1) width 0: ""
+            RenderText at (0,0) size 0x0
     RenderBlock {DIV} at (87,75) size 590x0
       RenderBlock {DIV} at (48,0) size 518x0
     RenderBlock {DIV} at (48,132) size 668x24

diff --git a/LayoutTests/platform/mac/http/tests/misc/acid2-expected.txt b/LayoutTests/platform/mac/http/tests/misc/acid2-expected.txt
@@ -20,11 +20,9 @@ layer at (36,2638) size 764x226
       RenderBlock {DIV} at (12,0) size 144x48 [bgcolor=#FFFF00]
         RenderBlock {DIV} at (60,12) size 24x24 [bgcolor=#FF0000]
           RenderBlock (generated) at (0,0) size 24x12 [border: none (12px solid #FFFF00) (12px solid #000000) (12px solid #FFFF00)]
-            RenderText at (12,-11) size 0x14
-              text run at (12,-11) width 0: ""
+            RenderText at (0,0) size 0x0
           RenderBlock (generated) at (0,12) size 24x12 [border: (12px solid #000000) (12px solid #FFFF00) none (12px solid #FFFF00)]
-            RenderText at (12,1) size 0x14
-              text run at (12,1) width 0: ""
+            RenderText at (0,0) size 0x0
     RenderBlock {DIV} at (87,75) size 590x0
       RenderBlock {DIV} at (48,0) size 518x0
     RenderBlock {DIV} at (48,132) size 668x24

diff --git a/LayoutTests/platform/mac/http/tests/misc/acid2-pixel-expected.txt b/LayoutTests/platform/mac/http/tests/misc/acid2-pixel-expected.txt
@@ -20,11 +20,9 @@ layer at (36,72) size 764x226
       RenderBlock {DIV} at (12,0) size 144x48 [bgcolor=#FFFF00]
         RenderBlock {DIV} at (60,12) size 24x24 [bgcolor=#FF0000]
           RenderBlock (generated) at (0,0) size 24x12 [border: none (12px solid #FFFF00) (12px solid #000000) (12px solid #FFFF00)]
-            RenderText at (12,-11) size 0x14
-              text run at (12,-11) width 0: ""
+            RenderText at (0,0) size 0x0
           RenderBlock (generated) at (0,12) size 24x12 [border: (12px solid #000000) (12px solid #FFFF00) none (12px solid #FFFF00)]
-            RenderText at (12,1) size 0x14
-              text run at (12,1) width 0: ""
+            RenderText at (0,0) size 0x0
     RenderBlock {DIV} at (87,75) size 590x0
       RenderBlock {DIV} at (48,0) size 518x0
     RenderBlock {DIV} at (48,132) size 668x24

diff --git a/Source/WebCore/layout/formattingContexts/inline/InlineLine.cpp b/Source/WebCore/layout/formattingContexts/inline/InlineLine.cpp
@@ -293,6 +293,10 @@ void Line::appendInlineBoxEnd(const InlineItem& inlineItem, const RenderStyle& s
 void Line::appendTextContent(const InlineTextItem& inlineTextItem, const RenderStyle& style, InlineLayoutUnit logicalWidth)
 {
     auto willCollapseCompletely = [&] {
+        if (m_runs.isEmpty() && inlineTextItem.isEmpty()) {
+            // Some generated content initiates empty text items. They are truly collapsible.
+            return true;
+        }
         if (!inlineTextItem.isWhitespace()) {
             auto isLeadingCollapsibleNonBreakingSpace = [&] {
                 // Let's check for leading non-breaking space collapsing to match legacy line layout quirk.

diff --git a/Source/WebCore/layout/formattingContexts/inline/InlineTextItem.cpp b/Source/WebCore/layout/formattingContexts/inline/InlineTextItem.cpp
@@ -50,8 +50,8 @@ InlineTextItem::InlineTextItem(const InlineTextBox& inlineTextBox, unsigned star
     m_textItemType = textItemType;
 }
 
-InlineTextItem::InlineTextItem(const InlineTextBox& inlineTextBox, UBiDiLevel bidiLevel)
-    : InlineItem(inlineTextBox, Type::Text, bidiLevel)
+InlineTextItem::InlineTextItem(const InlineTextBox& inlineTextBox)
+    : InlineItem(inlineTextBox, Type::Text, UBIDI_DEFAULT_LTR)
 {
 }
 

diff --git a/Source/WebCore/layout/formattingContexts/inline/InlineTextItem.h b/Source/WebCore/layout/formattingContexts/inline/InlineTextItem.h
@@ -41,12 +41,13 @@ class InlineTextItem : public InlineItem {
 public:
     static InlineTextItem createWhitespaceItem(const InlineTextBox&, unsigned start, unsigned length, UBiDiLevel, bool isWordSeparator, std::optional<InlineLayoutUnit> width);
     static InlineTextItem createNonWhitespaceItem(const InlineTextBox&, unsigned start, unsigned length, UBiDiLevel, bool hasTrailingSoftHyphen, std::optional<InlineLayoutUnit> width);
-    static InlineTextItem createEmptyItem(const InlineTextBox&, UBiDiLevel = UBIDI_DEFAULT_LTR);
+    static InlineTextItem createEmptyItem(const InlineTextBox&);
 
     unsigned start() const { return m_startOrPosition; }
     unsigned end() const { return start() + length(); }
     unsigned length() const { return m_length; }
 
+    bool isEmpty() const { return !length() && m_textItemType == TextItemType::Undefined; }
     bool isWhitespace() const { return m_textItemType == TextItemType::Whitespace; }
     bool isWordSeparator() const { return m_isWordSeparator; }
     bool isZeroWidthSpaceSeparator() const;
@@ -68,7 +69,7 @@ class InlineTextItem : public InlineItem {
     InlineTextItem split(size_t leftSideLength);
 
     InlineTextItem(const InlineTextBox&, unsigned start, unsigned length, UBiDiLevel, bool hasTrailingSoftHyphen, bool isWordSeparator, std::optional<InlineLayoutUnit> width, TextItemType);
-    explicit InlineTextItem(const InlineTextBox&, UBiDiLevel);
+    explicit InlineTextItem(const InlineTextBox&);
 };
 
 inline InlineTextItem InlineTextItem::createWhitespaceItem(const InlineTextBox& inlineTextBox, unsigned start, unsigned length, UBiDiLevel bidiLevel, bool isWordSeparator, std::optional<InlineLayoutUnit> width)
@@ -82,9 +83,10 @@ inline InlineTextItem InlineTextItem::createNonWhitespaceItem(const InlineTextBo
     return { inlineTextBox, start, length, bidiLevel, hasTrailingSoftHyphen, false, width, TextItemType::NonWhitespace };
 }
 
-inline InlineTextItem InlineTextItem::createEmptyItem(const InlineTextBox& inlineTextBox, UBiDiLevel bidiLevel)
+inline InlineTextItem InlineTextItem::createEmptyItem(const InlineTextBox& inlineTextBox)
 {
-    return InlineTextItem { inlineTextBox, bidiLevel };
+    ASSERT(!inlineTextBox.content().length());
+    return InlineTextItem { inlineTextBox };
 }
 
 }