Adjust visual overflow rect for rounded/shifted ascent/descent

third_party/WebKit/Source/platform/fonts/FontMetrics.h

 /*
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 28 matching lines @@
         m_descent(0),
         m_lineGap(0),
         m_lineSpacing(0),
         m_xHeight(0),
         m_zeroWidth(0),
         m_underlinethickness(0),
         m_underlinePosition(0),
         m_ascentInt(0),
         m_descentInt(0),
         m_hasXHeight(false),
-        m_hasZeroWidth(false) {}
+        m_hasZeroWidth(false),
+        m_visualOverflowInflationForAscent(0),
+        m_visualOverflowInflationForDescent(0) {}
 
   unsigned unitsPerEm() const { return m_unitsPerEm; }
   void setUnitsPerEm(unsigned unitsPerEm) { m_unitsPerEm = unitsPerEm; }
 
   float floatAscent(FontBaseline baselineType = AlphabeticBaseline) const {
     if (baselineType == AlphabeticBaseline)
       return m_ascent;
     return floatHeight() / 2;
   }
 
   void setAscent(float ascent) {
     m_ascent = ascent;
     m_ascentInt = lroundf(ascent);
+    if (m_ascentInt < ascent)
+      m_visualOverflowInflationForAscent++;

[eae, 2017/04/07 17:41:57]

FontMetrics already stores the rounded and unrounded values, why do we also need
to store the adjustment? Also, why increment here? If setAscent is called twice
why would we want to increment the adjustment, that seems wrong.

[Xianzhu, 2017/04/07 18:02:53]

FontMetrics doesn't store the unrounded values in many cases. See my previous
comment:
https://codereview.chromium.org/2803483002/diff/40001/third_party/WebKit/Sour...

   }
 
   float floatDescent(FontBaseline baselineType = AlphabeticBaseline) const {
     if (baselineType == AlphabeticBaseline)
       return m_descent;
     return floatHeight() / 2;
   }
 
   void setDescent(float descent) {
     m_descent = descent;
     m_descentInt = lroundf(descent);
+    if (m_descentInt < descent)
+      m_visualOverflowInflationForDescent++;
+  }
+
+  void setVisualOverflowInflations(int forAscent, int forDescent) {
+    m_visualOverflowInflationForAscent = forAscent;
+    m_visualOverflowInflationForDescent = forDescent;
+  }
+  int visualOverflowInflationForAscent() const {
+    return m_visualOverflowInflationForAscent;
+  }
+  int visualOverflowInflationForDescent() const {
+    return m_visualOverflowInflationForDescent;
   }
 
   float floatHeight(FontBaseline baselineType = AlphabeticBaseline) const {
     return floatAscent() + floatDescent();
   }
 
   float floatLineGap() const { return m_lineGap; }
   void setLineGap(float lineGap) { m_lineGap = lineGap; }
 
   float floatLineSpacing() const { return m_lineSpacing; }
@@ skipping 76 matching lines @@
     m_ascent = 0;
     m_descent = 0;
     m_ascentInt = 0;
     m_descentInt = 0;
     m_lineGap = 0;
     m_lineSpacing = 0;
     m_xHeight = 0;
     m_hasXHeight = false;
     m_underlinethickness = 0;
     m_underlinePosition = 0;
+    m_visualOverflowInflationForAscent = 0;
+    m_visualOverflowInflationForDescent = 0;
   }
 
   unsigned m_unitsPerEm;
   float m_ascent;
   float m_descent;
   float m_lineGap;
   float m_lineSpacing;
   float m_xHeight;
   float m_zeroWidth;
   float m_underlinethickness;
   float m_underlinePosition;
   int m_ascentInt;
   int m_descentInt;
   bool m_hasXHeight;
   bool m_hasZeroWidth;
+
+  // These are set to non-zero when ascent or descent is rounded or shifted
+  // to be smaller than the actual ascent or descent. When calculating visual
+  // overflows, we should add the inflations.
+  int m_visualOverflowInflationForAscent;
+  int m_visualOverflowInflationForDescent;
 };
 
 }  // namespace blink
 
 #endif  // FontMetrics_h