RenderTextHarfBuzz: Add support for multi line text selection.

ui/gfx/render_text_harfbuzz.h

 // 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.
 
 #ifndef UI_GFX_RENDER_TEXT_HARFBUZZ_H_
 #define UI_GFX_RENDER_TEXT_HARFBUZZ_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 35 matching lines @@
   // value is in run-space (0 corresponds to the first glyph in the run).
   Range CharRangeToGlyphRange(const Range& range) const;
 
   // Returns the number of missing glyphs in the shaped text run.
   size_t CountMissingGlyphs() const;
 
   // Writes the character and glyph ranges of the cluster containing |pos|.
   void GetClusterAt(size_t pos, Range* chars, Range* glyphs) const;
 
   // Returns the grapheme bounds at |text_index|. Handles multi-grapheme glyphs.
-  RangeF GetGraphemeBounds(RenderTextHarfBuzz* render_text, size_t text_index);
+  RangeF GetGraphemeBounds(RenderTextHarfBuzz* render_text,
+                           size_t text_index) const;
 
   // Returns whether the given shaped run contains any missing glyphs.
   bool HasMissingGlyphs() const;
 
+  // Returns the width of the given |char_range| handling grapheme boundaries

[msw, 2016/12/19 22:27:43]

nit: it'd be nice if this were adjacent to GetGraphemeBounds, since the two are
fairly related. It'd be even better if we could combine the two (users of
GetGraphemeBounds would just construct a Range(text_index), and
GetGraphemeWidthForCharRange callers could just get the RangeF::length() of the
returned value), but I'm really not sure that makes sense... don't even bother
if it's nontrivial work to combine them.

[karandeepb, 2016/12/21 14:23:44]

Now they are adjacent. Removed HasMissingGlyphs which did not have any
definition and wasn't being used anywhere. I think we should have a
GetGraphemeBounds method which takes a single index, since it makes sense from
an API point of view. This can be supplemented by a
GetGraphemeBoundsForCharRange or GetGraphemeWidthForCharRange (as done
currently).

+  // within glyphs.
+  float GetGraphemeWidthForCharRange(RenderTextHarfBuzz* render_text,
+                                     const Range& char_range) const;
+
   // Returns the glyph width for the given character range. |char_range| is in
   // text-space (0 corresponds to |GetDisplayText()[0]|).
   SkScalar GetGlyphWidthForCharRange(const Range& char_range) const;
 
   float width;
   float preceding_run_widths;
   Range range;
   bool is_rtl;
   UBiDiLevel level;
   UScriptCode script;
@@ skipping 115 matching lines @@
   // Specify the width of a glyph for test. The width of glyphs is very
   // platform-dependent and environment-dependent. Otherwise multiline test
   // will become really flaky.
   void set_glyph_width_for_test(float test_width) {
     glyph_width_for_test_ = test_width;
   }
 
   // Return the run index that contains the argument; or the length of the
   // |runs_| vector if argument exceeds the text length or width.
   size_t GetRunContainingCaret(const SelectionModel& caret);
-  size_t GetRunContainingXCoord(float x, float* offset) const;
+
+  // Returns the line index for the given argument. |text_y| is relative to
+  // the text bounds. Returns -1 if |text_y| is above the text and
+  // lines().size() if |text_y| is below it.
+  int GetLineContainingYCoord(float text_y);
+
+  // Returns the line segment index for the |line|, |text_x| pair. |text_x| is
+  // relative to text in the given line. Returns -1 if |text_x| is to the left
+  // of text in the line and |line|.segments.size() if it's to the right.
+  // |offset_relative_segment| will contain the offset of |text_x| relative to
+  // the start of the segment it is contained in.
+  int GetLineSegmentContainingXCoord(const internal::Line& line,
+                                     float text_x,
+                                     float* offset_relative_segment);
 
   // Given a |run|, returns the SelectionModel that contains the logical first
   // or last caret position inside (not at a boundary of) the run.
   // The returned value represents a cursor/caret position without a selection.
   SelectionModel FirstSelectionModelInsideRun(
       const internal::TextRunHarfBuzz* run);
   SelectionModel LastSelectionModelInsideRun(
       const internal::TextRunHarfBuzz* run);
 
   // Break the text into logical runs and populate the visual <-> logical maps
@@ skipping 57 matching lines @@
 
   // Fixed width of glyphs. This should only be set in test environments.
   float glyph_width_for_test_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderTextHarfBuzz);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_RENDER_TEXT_HARFBUZZ_H_