Text in flex items not breaking under specific conditions

https://bugs.webkit.org/show_bug.cgi?id=265252 <rdar://problem/118796634> Reviewed by Antti Koivisto. "zero width space" character (ZWSP) is a non-whitespace space character and is a word boundary. This patch ensures legacy preferred with computation treats "zero width space" as a breakable position. * LayoutTests/fast/text/flexing-content-fails-with-zero-width-space-expected.html: Added. * LayoutTests/fast/text/flexing-content-fails-with-zero-width-space.html: Added. * Source/WebCore/rendering/RenderText.cpp: (WebCore::isSpaceAccordingToStyle): (WebCore::RenderText::computePreferredLogicalWidths): Canonical link: https://commits.webkit.org/271122@main
WebKit · Nov 26, 2023 · 073d844 · 073d844
1 parent 769ad4e
commit 073d844
Show file tree

Hide file tree

Showing 5 changed files with 43 additions and 4 deletions.
diff --git a/LayoutTests/fast/text/flexing-content-fails-with-zero-width-space-expected.html b/LayoutTests/fast/text/flexing-content-fails-with-zero-width-space-expected.html
@@ -0,0 +1,12 @@
+<style>
+body {
+  font-family: Ahem;
+  font-size: 20px;
+}
+
+div {
+  color: green;
+}
+</style>
+<div>X<br>X<br>X</div>
+<br>PASS if no red
diff --git a/LayoutTests/fast/text/flexing-content-fails-with-zero-width-space.html b/LayoutTests/fast/text/flexing-content-fails-with-zero-width-space.html
@@ -0,0 +1,24 @@
+<style>
+body {
+  font-family: Ahem;
+  font-size: 20px;
+}
+
+.test {
+  width: min-content;
+  color: red;
+}
+
+.inline-block {
+  display: inline-block;
+}
+
+.ref {
+  position: absolute;
+  top: 8px;
+  color: green;
+}
+</style>
+<div class=test><div class=inline-block>X</div>X&#8203;<span>X</span></div></div>
+<div class=ref>X<br>X<br>X</div>
+<br>PASS if no red
diff --git a/Source/WebCore/rendering/RenderBlockFlow.cpp b/Source/WebCore/rendering/RenderBlockFlow.cpp
@@ -4695,7 +4695,7 @@ void RenderBlockFlow::computeInlinePreferredLogicalWidths(LayoutUnit& minLogical
 
                 // This text object will not be rendered, but it may still provide a breaking opportunity.
                 if (!widths.hasBreak && !childMax) {
-                    if (autoWrap && (widths.beginWS || widths.endWS)) {
+                    if (autoWrap && (widths.beginWS || widths.endWS || widths.endZeroSpace)) {
                         minLogicalWidth = preferredWidth(minLogicalWidth, inlineMin);
                         inlineMin = 0;
                     }
@@ -4761,8 +4761,8 @@ void RenderBlockFlow::computeInlinePreferredLogicalWidths(LayoutUnit& minLogical
 
                     inlineMin = childMin;
 
-                    if (widths.endWS) {
-                        // We end in whitespace, which means we can end our current line.
+                    if (widths.endWS || widths.endZeroSpace) {
+                        // We end in breakable space, which means we can end our current line.
                         minLogicalWidth = preferredWidth(minLogicalWidth, inlineMin);
                         inlineMin = 0;
                         shouldBreakLineAfterText = false;

diff --git a/Source/WebCore/rendering/RenderText.cpp b/Source/WebCore/rendering/RenderText.cpp
@@ -971,6 +971,8 @@ RenderText::Widths RenderText::trimmedPreferredWidths(float leadWidth, bool& str
     if (!length || (stripFrontSpaces && text().containsOnly<isASCIIWhitespace>()))
         return widths;
 
+    widths.endZeroSpace = text()[length - 1] == zeroWidthSpace;
+
     widths.min = m_minWidth.value_or(-1);
     widths.max = m_maxWidth.value_or(-1);
 
@@ -1260,7 +1262,7 @@ void RenderText::computePreferredLogicalWidths(float leadWidth, WeakHashSet<cons
         bool hasBreak = breakAll || isBreakable(lineBreakIteratorFactory, i, nextBreakable, breakNBSP, canUseLineBreakShortcut, keepAllWords, breakAnywhere);
         bool betweenWords = true;
         unsigned j = i;
-        while (c != '\n' && !isSpaceAccordingToStyle(c, style) && c != '\t' && (c != softHyphen || style.hyphens() == Hyphens::None)) {
+        while (c != '\n' && !isSpaceAccordingToStyle(c, style) && c != '\t' && c != zeroWidthSpace && (c != softHyphen || style.hyphens() == Hyphens::None)) {
             UChar previousCharacter = c;
             j++;
             if (j == length)

diff --git a/Source/WebCore/rendering/RenderText.h b/Source/WebCore/rendering/RenderText.h
@@ -105,6 +105,7 @@ class RenderText : public RenderObject {
         float endMax { 0 };
         bool beginWS { false };
         bool endWS { false };
+        bool endZeroSpace { false };
         bool hasBreakableChar { false };
         bool hasBreak { false };
         bool endsWithBreak { false };