Missing underline after the first character in contenteditable

https://bugs.webkit.org/show_bug.cgi?id=255357
<rdar://107846703>

Reviewed by Antti Koivisto.

RenderText's m_min/m_maxWidth values become stale when we dynamically switch over to IFC preferred width computation.
(and sadly these (cached) values are consulted when RenderText::width is called with [0, text-length] range).

* Source/WebCore/rendering/RenderBlockFlow.cpp:
(WebCore::RenderBlockFlow::tryComputePreferredWidthsUsingModernPath):
* Source/WebCore/rendering/RenderCounter.cpp:
(WebCore::RenderCounter::computePreferredLogicalWidths): (forcedMinMaxWidthComputation is to suppress ASSERT)
* Source/WebCore/rendering/RenderCounter.h:
* Source/WebCore/rendering/RenderText.cpp:
(WebCore::RenderText::minLogicalWidth const):
(WebCore::RenderText::maxLogicalWidth const):
(WebCore::RenderText::computePreferredLogicalWidths):
(WebCore::RenderText::width const):
* Source/WebCore/rendering/RenderText.h:
(WebCore::RenderText::resetMinMaxWidth):

Canonical link: https://commits.webkit.org/262914@main

Source/WebCore/rendering/RenderBlockFlow.cpp

@@ -4927,8 +4927,12 @@ bool RenderBlockFlow::tryComputePreferredWidthsUsingModernPath(LayoutUnit& minLo
     modernLineLayout()->updateInlineContentDimensions();
 
     std::tie(minLogicalWidth, maxLogicalWidth) = modernLineLayout()->computeIntrinsicWidthConstraints();
-    for (auto walker = InlineWalker(*this); !walker.atEnd(); walker.advance())
-        walker.current()->setPreferredLogicalWidthsDirty(false);
+    for (auto walker = InlineWalker(*this); !walker.atEnd(); walker.advance()) {
+        auto* renderer = walker.current();
+        renderer->setPreferredLogicalWidthsDirty(false);
+        if (auto* renderText = dynamicDowncast<RenderText>(renderer))
+            renderText->resetMinMaxWidth();
+    }
     return true;
 }
 

Source/WebCore/rendering/RenderCounter.cpp

@@ -485,7 +485,7 @@ void RenderCounter::updateCounter()
     computePreferredLogicalWidths(0);
 }
 
-void RenderCounter::computePreferredLogicalWidths(float lead)
+void RenderCounter::computePreferredLogicalWidths(float lead, bool forcedMinMaxWidthComputation)
 {
     // FIXME: We shouldn't be modifying the tree in computePreferredLogicalWidths.
     // Instead, we should properly hook the appropriate changes in the DOM and modify
@@ -496,7 +496,7 @@ void RenderCounter::computePreferredLogicalWidths(float lead)
 
     setRenderedText(originalText());
 
-    RenderText::computePreferredLogicalWidths(lead);
+    RenderText::computePreferredLogicalWidths(lead, forcedMinMaxWidthComputation);
 }
 
 static void destroyCounterNodeWithoutMapRemoval(const AtomString& identifier, CounterNode& node)

Source/WebCore/rendering/RenderCounter.h

@@ -53,7 +53,7 @@ class RenderCounter final : public RenderText {
     bool isCounter() const override;
     String originalText() const override;
 
-    void computePreferredLogicalWidths(float leadWidth) override;
+    void computePreferredLogicalWidths(float leadWidth, bool forcedMinMaxWidthComputation = false) override;
 
     RefPtr<CSSCounterStyle> counterStyle() const;
 

Source/WebCore/rendering/RenderText.cpp

@@ -904,15 +904,15 @@ static inline bool isSpaceAccordingToStyle(UChar c, const RenderStyle& style)
 float RenderText::minLogicalWidth() const
 {
     if (preferredLogicalWidthsDirty() || !m_minWidth)
-        const_cast<RenderText*>(this)->computePreferredLogicalWidths(0);
+        const_cast<RenderText*>(this)->computePreferredLogicalWidths(0, !preferredLogicalWidthsDirty());
 
     return *m_minWidth;
 }
 
 float RenderText::maxLogicalWidth() const
 {
     if (preferredLogicalWidthsDirty() || !m_maxWidth)
-        const_cast<RenderText*>(this)->computePreferredLogicalWidths(0);
+        const_cast<RenderText*>(this)->computePreferredLogicalWidths(0, !preferredLogicalWidthsDirty());
 
     return *m_maxWidth;
 }
@@ -935,11 +935,11 @@ LineBreakIteratorMode mapLineBreakToIteratorMode(LineBreak lineBreak)
     return LineBreakIteratorMode::Default;
 }
 
-void RenderText::computePreferredLogicalWidths(float leadWidth)
+void RenderText::computePreferredLogicalWidths(float leadWidth, bool forcedMinMaxWidthComputation)
 {
     HashSet<const Font*> fallbackFonts;
     GlyphOverflow glyphOverflow;
-    computePreferredLogicalWidths(leadWidth, fallbackFonts, glyphOverflow);
+    computePreferredLogicalWidths(leadWidth, fallbackFonts, glyphOverflow, forcedMinMaxWidthComputation);
     if (fallbackFonts.isEmpty() && !glyphOverflow.left && !glyphOverflow.right && !glyphOverflow.top && !glyphOverflow.bottom)
         m_knownToHaveNoOverflowAndNoFallbackFonts = true;
 }
@@ -1004,9 +1004,9 @@ float RenderText::maxWordFragmentWidth(const RenderStyle& style, const FontCasca
     return std::max(maxFragmentWidth, suffixWidth);
 }
 
-void RenderText::computePreferredLogicalWidths(float leadWidth, HashSet<const Font*>& fallbackFonts, GlyphOverflow& glyphOverflow)
+void RenderText::computePreferredLogicalWidths(float leadWidth, HashSet<const Font*>& fallbackFonts, GlyphOverflow& glyphOverflow, bool forcedMinMaxWidthComputation)
 {
-    ASSERT(m_hasTab || preferredLogicalWidthsDirty() || !m_knownToHaveNoOverflowAndNoFallbackFonts);
+    ASSERT_UNUSED(forcedMinMaxWidthComputation, m_hasTab || preferredLogicalWidthsDirty() || forcedMinMaxWidthComputation || !m_knownToHaveNoOverflowAndNoFallbackFonts);
 
     m_minWidth = 0;
     m_beginMinWidth = 0;
@@ -1642,6 +1642,9 @@ float RenderText::width(unsigned from, unsigned length, const FontCascade& fontC
                     if (fallbackFonts->isEmpty() && !glyphOverflow->left && !glyphOverflow->right && !glyphOverflow->top && !glyphOverflow->bottom)
                         m_knownToHaveNoOverflowAndNoFallbackFonts = true;
                 }
+                // The rare case of when we switch between IFC and legacy preferred width computation.
+                if (!m_maxWidth)
+                    width = maxLogicalWidth();
                 width = *m_maxWidth;
             } else
                 width = maxLogicalWidth();

Source/WebCore/rendering/RenderText.h

@@ -182,8 +182,10 @@ class RenderText : public RenderObject {
 
     static std::optional<bool> emphasisMarkExistsAndIsAbove(const RenderText&, const RenderStyle&);
 
+    void resetMinMaxWidth();
+
 protected:
-    virtual void computePreferredLogicalWidths(float leadWidth);
+    virtual void computePreferredLogicalWidths(float leadWidth, bool forcedMinMaxWidthComputation = false);
     void willBeDestroyed() override;
 
     virtual void setRenderedText(const String&);
@@ -206,7 +208,7 @@ class RenderText : public RenderObject {
     LayoutRect selectionRectForRepaint(const RenderLayerModelObject* repaintContainer, bool clipToVisibleContent = true) final;
     LayoutRect clippedOverflowRect(const RenderLayerModelObject* repaintContainer, VisibleRectContext) const final;
 
-    void computePreferredLogicalWidths(float leadWidth, HashSet<const Font*>& fallbackFonts, GlyphOverflow&);
+    void computePreferredLogicalWidths(float leadWidth, HashSet<const Font*>& fallbackFonts, GlyphOverflow&, bool forcedMinMaxWidthComputation = false);
 
     bool computeCanUseSimpleFontCodePath() const;
 
@@ -316,6 +318,12 @@ inline RenderText* Text::renderer() const
     return downcast<RenderText>(Node::renderer());
 }
 
+inline void RenderText::resetMinMaxWidth()
+{
+    m_minWidth = { };
+    m_maxWidth = { };
+}
+
 } // namespace WebCore
 
 SPECIALIZE_TYPE_TRAITS_RENDER_OBJECT(RenderText, isText())