Adjust visual overflow rect for rounded/shifted ascent/descent

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

Index: third_party/WebKit/Source/platform/fonts/FontMetrics.h
diff --git a/third_party/WebKit/Source/platform/fonts/FontMetrics.h b/third_party/WebKit/Source/platform/fonts/FontMetrics.h
index ce51ee9aaa7a49f9a04ef249568865c9ce5ee38d..5d9e13a3b4acfcc971c2b09e04e68889083bf92d 100644
--- a/third_party/WebKit/Source/platform/fonts/FontMetrics.h
+++ b/third_party/WebKit/Source/platform/fonts/FontMetrics.h
@@ -46,7 +46,9 @@ class FontMetrics {
         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; }
@@ -60,6 +62,8 @@ class FontMetrics {
   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 {
@@ -71,6 +75,19 @@ class FontMetrics {
   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 {
@@ -167,6 +184,8 @@ class FontMetrics {
     m_hasXHeight = false;
     m_underlinethickness = 0;
     m_underlinePosition = 0;
+    m_visualOverflowInflationForAscent = 0;
+    m_visualOverflowInflationForDescent = 0;
   }
 
   unsigned m_unitsPerEm;
@@ -182,6 +201,12 @@ class FontMetrics {
   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