Add ability to compute text intercepts to Font

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

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2006, 2007, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Holger Hans Peter Freyther
  *
  * 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
@@ skipping 83 matching lines @@
                     CustomFontNotReadyAction,
                     float deviceScaleFactor,
                     const SkPaint&) const;
   void drawEmphasisMarks(SkCanvas*,
                          const TextRunPaintInfo&,
                          const AtomicString& mark,
                          const FloatPoint&,
                          float deviceScaleFactor,
                          const SkPaint&) const;
 
+  // This method follows the behavior and allocation model of the underlying
+  // Skia function: Return the number of intervals that intersect the intercept
+  // along the axis of the advance.  The return count is zero or a multiple of
+  // two, and is at most the number of glyphs * 2 in TextRun part of

[pdr., 2016/10/14 04:40:56]

Super nit: Add "the", remove the second period.
"...number of glyphs * 2 in [the] TextRun part of TextRunPaintInfo."

[drott, 2016/10/14 15:16:44]

I changed the signature of this method and the comment. So this is implicitly
addressed.

+  // TextRunPaintInfo.. The caller may pass nullptr for intervals to determine
+  // the size of the interval array.
+  // TODO(drott): crbug.com/655154 Fix this for upright in vertical.
+  int getTextIntercepts(SkCanvas*,

[f(malita), 2016/10/13 18:09:19]

SkCanvas param doesn't seem needed.

[drott, 2016/10/14 15:15:34]

Ah true, thanks - I initially thought I needed it, that's also why I placed this
on GraphicsContext. Good then.

+                        const TextRunPaintInfo&,
+                        float deviceScaleFactor,
+                        const SkPaint&,
+                        const SkScalar* bounds,
+                        SkScalar* intervals) const;

[f(malita), 2016/10/13 18:09:19]

I'm not necessarily opposed to following Skia's signature here, but it would
also make sense to consider a higher-level, Blink-oriented API.  How about
something like

struct Intercept { float mBegin, mEnd; };

bool getTextIntercepts(const TextRunPaintInfo&,
                       float deviceScaleFactor,
                       const SkPaint&,
                       Vector<Intercept>& intercepts,
                       std::tuple<float, float>& bounds);

Then the caller wouldn't have to invoke twice, but instead the impl can hide
that detail and resize the out vector as needed.

[drott, 2016/10/14 15:15:34]

Good idea, looks better and less alien on the Blink side after changing that.

+
   // Glyph bounds will be the minimum rect containing all glyph strokes, in
   // coordinates using (<text run x position>, <baseline position>) as the
   // origin.
   float width(const TextRun&,
               HashSet<const SimpleFontData*>* fallbackFonts = nullptr,
               FloatRect* glyphBounds = nullptr) const;
 
   int offsetForPosition(const TextRun&,
                         float position,
                         bool includePartialGlyphs) const;
@@ skipping 143 matching lines @@
   // advance an additional tab stop.
   if (distanceToTabStop < fontData.spaceWidth() / 2)
     distanceToTabStop += baseTabWidth;
 
   return distanceToTabStop;
 }
 
 }  // namespace blink
 
 #endif