Reduce the number of text reshaping in RenderText

ui/gfx/render_text.h

 // Copyright (c) 2012 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_H_
 #define UI_GFX_RENDER_TEXT_H_
 
 #include <algorithm>
 #include <cstring>
 #include <string>
@@ skipping 249 matching lines @@
   void SetMultiline(bool multiline);
 
   // TODO(ckocagil): Add vertical alignment and line spacing support instead.
   int min_line_height() const { return min_line_height_; }
   void SetMinLineHeight(int line_height);
 
   // Set the maximum length of the displayed layout text, not the actual text.
   // A |length| of 0 forgoes a hard limit, but does not guarantee proper
   // functionality of very long strings. Applies to subsequent SetText calls.
   // WARNING: Only use this for system limits, it lacks complex text support.
   void set_truncate_length(size_t length) { truncate_length_ = length; }

[Jun Mukai, 2015/02/12 21:56:46]

Doesn't this have to update the layout text?

[oshima, 2015/02/12 22:09:17]

This is used as safe guard now. I'd like to change this method for test only and
set the hard limit in ctor. msw@, what do you think?

[msw, 2015/02/12 22:45:06]

That's fine with me.

 
   // The layout text will be elided to fit |display_rect| using this behavior.
   // The layout text may be shortened further by the truncate length.
   void SetElideBehavior(ElideBehavior elide_behavior);
   ElideBehavior elide_behavior() const { return elide_behavior_; }
 
-  const base::string16& layout_text() const { return layout_text_; }
-
   const Rect& display_rect() const { return display_rect_; }
   void SetDisplayRect(const Rect& r);
 
   bool background_is_transparent() const { return background_is_transparent_; }
   void set_background_is_transparent(bool transparent) {
     background_is_transparent_ = transparent;
   }
 
   const SelectionModel& selection_model() const { return selection_model_; }
 
@@ skipping 62 matching lines @@
   DirectionalityMode directionality_mode() const {
       return directionality_mode_;
   }
   base::i18n::TextDirection GetTextDirection();
 
   // Returns the visual movement direction corresponding to the logical end
   // of the text, considering only the dominant direction returned by
   // |GetTextDirection()|, not the direction of a particular run.
   VisualCursorDirection GetVisualDirectionOfLogicalEnd();
 
+  // Returns the text used for layout, which may be obscured,
+  // truncated or elided. The subclass may compute elided text on the fly,
+  // or use precomputed the elided text.
+  virtual const base::string16& GetLayoutText() = 0;
+
   // Returns the size required to display the current string (which is the
   // wrapped size in multiline mode). The returned size does not include space
   // reserved for the cursor or the offset text shadows.
   virtual Size GetStringSize() = 0;
 
   // This is same as GetStringSize except that fractional size is returned.
   // The default implementation is same as GetStringSize. Certain platforms that
   // compute the text size as floating-point values, like Mac, will override
   // this method.
   // See comment in Canvas::GetStringWidthF for its usage.
@@ skipping 70 matching lines @@
   // Range will have is_reversed() true.  (This does not return a Rect because a
   // Rect can't have a negative width.)
   virtual Range GetGlyphBounds(size_t index) = 0;
 
   const Vector2d& GetUpdatedDisplayOffset();
   void SetDisplayOffset(int horizontal_offset);
 
  protected:
   RenderText();
 
+  const base::string16& layout_text() const { return layout_text_; }
+  const base::string16& elided_text() const { return elided_text_; }
+  bool text_elided() const { return text_elided_; }
+
   const BreakList<SkColor>& colors() const { return colors_; }
   const std::vector<BreakList<bool> >& styles() const { return styles_; }
 
   const std::vector<internal::Line>& lines() const { return lines_; }
   void set_lines(std::vector<internal::Line>* lines) { lines_.swap(*lines); }
 
   // Returns the baseline of the current text.  The return value depends on
   // the text and its layout while the return value of GetBaseline() doesn't.
   // GetAlignmentOffset() takes into account the difference between them.
   //
@@ skipping 47 matching lines @@
   virtual void SetSelectionModel(const SelectionModel& model);
 
   // Get the visual bounds containing the logical substring within the |range|.
   // If |range| is empty, the result is empty. These bounds could be visually
   // discontinuous if the substring is split by a LTR/RTL level change.
   // These bounds are in local coordinates, but may be outside the visible
   // region if the text is longer than the textfield. Subsequent text, cursor,
   // or bounds changes may invalidate returned values.
   virtual std::vector<Rect> GetSubstringBounds(const Range& range) = 0;
 
-  // Convert between indices into |text_| and indices into |obscured_text_|,
-  // which differ when the text is obscured. Regardless of whether or not the
-  // text is obscured, the character (code point) offsets always match.
-  virtual size_t TextIndexToLayoutIndex(size_t index) const = 0;
-  virtual size_t LayoutIndexToTextIndex(size_t index) const = 0;
+  // Convert between indices into |text_| and indices into
+  // GetLayoutText(), which differ when the text is obscured,
+  // truncated or elided. Regardless of whether or not the text is
+  // obscured, the character (code point) offsets always match.
+  virtual size_t TextIndexToLayoutIndex(size_t index) = 0;
+  virtual size_t LayoutIndexToTextIndex(size_t index) = 0;
 
-  // Reset the layout to be invalid.
-  virtual void ResetLayout() = 0;
+  // Notifies that layout text, or attributes that affects layout text
+  // shape have changed. |text_changed| is true if the content of the
+  // |layouttext_| has changed, not just attributes.

[msw, 2015/02/12 22:45:06]

nit: |layout_text_|

[oshima, 2015/02/13 00:29:43]

Done.

+  virtual void OnLayoutTextShapeChanged(bool text_changed) = 0;
+
+  // Notifies that attributes that affects elided text shape has changed.

[msw, 2015/02/12 22:45:06]

nit: s/affects/affect/ and s/has/have/

[oshima, 2015/02/13 00:29:43]

Done.

+  virtual void OnElidedTextShapeChanged() = 0;
 
   // Ensure the text is laid out, lines are computed, and |lines_| is valid.
   virtual void EnsureLayout() = 0;
 
   // Draw the text.
   virtual void DrawVisualText(Canvas* canvas) = 0;
 
-  // Returns the text used for layout, which may be obscured or truncated.
-  const base::string16& GetLayoutText() const;
+  // Update the elided text.
+  void UpdateElidedText(float visual_width);
 
   // Returns layout text positions that are suitable for breaking lines.
   const BreakList<size_t>& GetLineBreaks();
 
   // Apply (and undo) temporary composition underlines and selection colors.
   void ApplyCompositionAndSelectionStyles();
   void UndoCompositionAndSelectionStyles();
 
   // Returns the line offset from the origin after applying the text alignment
   // and the display offset.
@@ skipping 57 matching lines @@
   FRIEND_TEST_ALL_PREFIXES(RenderTextTest, StringFitsOwnWidth);
 
   // Set the cursor to |position|, with the caret trailing the previous
   // grapheme, or if there is no previous grapheme, leading the cursor position.
   // If |select| is false, the selection start is moved to the same position.
   // If the |position| is not a cursorable position (not on grapheme boundary),
   // it is a NO-OP.
   void MoveCursorTo(size_t position, bool select);
 
   // Updates |layout_text_| if the text is obscured or truncated.
+  // This will triggers |elided_text_| update.

[msw, 2015/02/12 22:45:06]

nit: merge the comments to something simpler, like "Updates |layout_text_| and
|elided_text_| as needed."

[oshima, 2015/02/13 00:29:43]

Done.

   void UpdateLayoutText();

[msw, 2015/02/12 22:45:06]

I like the pattern of On*Changed, and I could see this being renamed
OnText[Content|Attribute]Changed or maybe OnLayoutAttributeChanged or similar.
WDYT?

[oshima, 2015/02/13 00:29:43]

Changed to OnTextAttributeChanged

 
   // Elides |text| as needed to fit in the |available_width| using |behavior|.
+  // |text_width| is the pre-calculated width of the text shaped by this render
+  // text, or pass 0 if the width is unknown.
   base::string16 Elide(const base::string16& text,
+                       float text_width,
                        float available_width,
                        ElideBehavior behavior);
 
   // Elides |email| as needed to fit the |available_width|.
   base::string16 ElideEmail(const base::string16& email, float available_width);
 
   // Update the cached bounds and display offset to ensure that the current
   // cursor is within the visible display area.
   void UpdateCachedBoundsAndOffset();
 
@@ skipping 61 matching lines @@
   bool obscured_;
   // The index at which the char should be revealed in the obscured text.
   int obscured_reveal_index_;
 
   // The maximum length of text to display, 0 forgoes a hard limit.
   size_t truncate_length_;
 
   // The behavior for eliding, fading, or truncating.
   ElideBehavior elide_behavior_;
 
-  // The obscured and/or truncated text that will be displayed.
+  // The obscured and/or truncated text, before elided.

[msw, 2015/02/12 22:45:06]

Rename this, it doesn't match the semantics of GetLayoutText, which elides the
text as needed... Perhaps rename them as an intermediate |unelided_layout_text_|
and a definitive |layout_text_|, or some other pattern.

[oshima, 2015/02/13 00:29:43]

kept layout_text_ and changed elided_text_ to display_text_ as discussed
offline. let me know if you misunderstood something.

   base::string16 layout_text_;
 
+  // The elided text. This is empty if the text does not have to be elided.
+  base::string16 elided_text_;

[msw, 2015/02/12 22:45:06]

nit: reorder |elide_behavior_| to come immediately before |elided_text_| and
|text_elided_|.

[oshima, 2015/02/13 00:29:43]

Done.

+
+  bool text_elided_;

[msw, 2015/02/12 22:45:06]

nit: add a comment like "True if the text is elided given the current behavior
and display area."

[oshima, 2015/02/13 00:29:43]

Done.

+
   // Whether newline characters should be replaced with newline symbols.
   bool replace_newline_chars_with_symbols_;
 
   // The minimum height a line should have.
   int min_line_height_;
 
   // Whether the text should be broken into multiple lines. Uses the width of
   // |display_rect_| as the width cap.
   bool multiline_;
 
@@ skipping 22 matching lines @@
   // selection, font, and other operations that adjust the visible text bounds.
   bool cached_bounds_and_offset_valid_;
 
   // Text shadows to be drawn.
   ShadowValues shadows_;
 
   // A list of valid layout text line break positions.
   BreakList<size_t> line_breaks_;
 
   // Lines computed by EnsureLayout. These should be invalidated with
   // ResetLayout and on |display_rect_| changes.

[msw, 2015/02/12 22:45:06]

nit: Update the comment referencing ResetLayout.

   std::vector<internal::Line> lines_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderText);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_RENDER_TEXT_H_