Paint underline correctly in mixed flow text contexts with truncation

third_party/WebKit/Source/core/paint/InlineTextBoxPainter.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/paint/InlineTextBoxPainter.h"
 
 #include "core/editing/CompositionUnderline.h"
 #include "core/editing/Editor.h"
 #include "core/editing/markers/DocumentMarkerController.h"
 #include "core/frame/LocalFrame.h"
@@ skipping 759 matching lines @@
 {
     if (underline.color == Color::transparent)
         return;
 
     if (m_inlineTextBox.truncation() == cFullTruncation)
         return;
 
     unsigned paintStart = underlinePaintStart(underline);
     unsigned paintEnd = underlinePaintEnd(underline);
 
-    // TODO(crbug.com/636060): Handle mixed-flow contexts correctly.
     // start of line to draw
     float start = paintStart == static_cast<unsigned>(m_inlineTextBox.start()) ? 0 :
         m_inlineTextBox.getLineLayoutItem().width(m_inlineTextBox.start(), paintStart - m_inlineTextBox.start(), m_inlineTextBox.textPos(), m_inlineTextBox.isLeftToRightDirection() ? LTR : RTL, m_inlineTextBox.isFirstLineStyle());
     // how much line to draw
-    float width = (paintStart == static_cast<unsigned>(m_inlineTextBox.start()) && paintEnd == static_cast<unsigned>(m_inlineTextBox.end()) + 1) ? m_inlineTextBox.logicalWidth().toFloat() :
-        m_inlineTextBox.getLineLayoutItem().width(paintStart, paintEnd - paintStart, LayoutUnit(m_inlineTextBox.textPos() + start), m_inlineTextBox.isLeftToRightDirection() ? LTR : RTL, m_inlineTextBox.isFirstLineStyle());
+    float width;
+    bool ltr = m_inlineTextBox.isLeftToRightDirection();
+    bool flowIsLTR = m_inlineTextBox.getLineLayoutItem().style()->isLeftToRightDirection();
+    if (paintStart == static_cast<unsigned>(m_inlineTextBox.start()) && paintEnd == static_cast<unsigned>(m_inlineTextBox.end()) + 1) {
+        width = m_inlineTextBox.logicalWidth().toFloat();
+    } else {
+        width = m_inlineTextBox.getLineLayoutItem().width(ltr == flowIsLTR ? paintStart : paintEnd, ltr == flowIsLTR ? paintEnd - paintStart : m_inlineTextBox.len() - paintEnd, LayoutUnit(m_inlineTextBox.textPos() + start), flowIsLTR ? LTR : RTL, m_inlineTextBox.isFirstLineStyle());
+    }
     // In RTL mode, start and width are computed from the right end of the text box:
     // starting at |logicalWidth| - |start| and continuing left by |width| to
     // |logicalWidth| - |start| - |width|. We will draw that line, but
     // backwards: |logicalWidth| - |start| - |width| to |logicalWidth| - |start|.
-    if (!m_inlineTextBox.isLeftToRightDirection())
+    if (!flowIsLTR)
         start = m_inlineTextBox.logicalWidth().toFloat() - width - start;
 
 
     // Thick marked text underlines are 2px thick as long as there is room for the 2px line under the baseline.
     // All other marked text underlines are 1px thick.
     // If there's not enough space the underline will touch or overlap characters.
     int lineThickness = 1;
     int baseline = m_inlineTextBox.getLineLayoutItem().style(m_inlineTextBox.isFirstLineStyle())->getFontMetrics().ascent();
     if (underline.thick && m_inlineTextBox.logicalHeight() - baseline >= 2)
         lineThickness = 2;
@@ skipping 46 matching lines @@
     GraphicsContext& context = paintInfo.context;
     GraphicsContextStateSaver stateSaver(context);
 
     LayoutRect boxRect(boxOrigin, LayoutSize(m_inlineTextBox.logicalWidth(), m_inlineTextBox.logicalHeight()));
     context.clip(FloatRect(boxRect));
     context.drawHighlightForText(font, run, FloatPoint(boxOrigin), boxRect.height(), color, sPos, ePos);
 }
 
 
 } // namespace blink