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 118 matching lines @@
  private:
   BreakList<SkColor> colors_;
   std::vector<BreakList<bool> > styles_;
 
   BreakList<SkColor>::const_iterator color_;
   std::vector<BreakList<bool>::const_iterator> style_;
 
   DISALLOW_COPY_AND_ASSIGN(StyleIterator);
 };
 
-// Line segments are slices of the layout text to be rendered on a single line.
+// Line segments are slices of the display text to be rendered on a single line.
 struct LineSegment {
   LineSegment();
   ~LineSegment();
 
   // X coordinates of this line segment in text space.
   Range x_range;
 
   // The character range this segment corresponds to.
   Range char_range;
 
   // The width of this line segment in text space. This could be slightly
   // different from x_range.length().
   // TODO(mukai): Fix Range to support float values and merge it into x_range.
   float width;
 
   // Index of the text run that generated this segment.
   size_t run;
 };
 
-// A line of layout text, comprised of a line segment list and some metrics.
+// A line of display text, comprised of a line segment list and some metrics.
 struct Line {
   Line();
   ~Line();
 
   // Segments that make up this line in visual order.
   std::vector<LineSegment> segments;
 
   // The sum of segment widths and the maximum of segment heights.
   SizeF size;
 
@@ skipping 74 matching lines @@
   bool obscured() const { return obscured_; }
   void SetObscured(bool obscured);
 
   // Makes a char in obscured text at |index| to be revealed. |index| should be
   // a UTF16 text index. If there is a previous revealed index, the previous one
   // is cleared and only the last set index will be revealed. If |index| is -1
   // or out of range, no char will be revealed. The revealed index is also
   // cleared when SetText or SetObscured is called.
   void SetObscuredRevealIndex(int index);
 
-  // Set whether newline characters should be replaced with newline symbols.
-  void SetReplaceNewlineCharsWithSymbols(bool replace);
-
   // TODO(ckocagil): Multiline text rendering is currently only supported on
   // Windows. Support other platforms.
   bool multiline() const { return multiline_; }
   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.
+  // Set the maximum length of the 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; }
 
   // 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 55 matching lines @@
 
   // Returns whether this style is enabled consistently across the entire
   // RenderText.
   bool GetStyle(TextStyle style) const;
 
   // Set or get the text directionality mode and get the text direction yielded.
   void SetDirectionalityMode(DirectionalityMode mode);
   DirectionalityMode directionality_mode() const {
       return directionality_mode_;
   }
-  base::i18n::TextDirection GetTextDirection();
+  base::i18n::TextDirection GetDisplayTextDirection();
 
   // 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.
+  // |GetDisplayTextDirection()|, not the direction of a particular run.
   VisualCursorDirection GetVisualDirectionOfLogicalEnd();
 
+  // Returns the text used to display, 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& GetDisplayText() = 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_; }

[msw, 2015/02/14 00:11:26]

Please add NOTE/WARNING comments for these accessors, as discussed.

[oshima, 2015/02/14 00:40:51]

Hmm, I'm pretty sure I added once, but I probably have undone them while
editing... Sorry. Done.

+  const base::string16& display_text() const { return display_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.
   //
   // We'd like a RenderText to show the text always on the same baseline
   // regardless of the text, so the text does not jump up or down depending
   // on the text.  However, underlying layout engines return different baselines
   // depending on the text.  In general, layout engines determine the minimum
   // bounding box for the text and return the baseline from the top of the
   // bounding box.  So the baseline changes depending on font metrics used to
   // layout the text.
   //
   // For example, suppose there are FontA and FontB and the baseline of FontA
   // is smaller than the one of FontB.  If the text is laid out only with FontA,
   // then the baseline of FontA may be returned.  If the text includes some
   // characters which are laid out with FontB, then the baseline of FontB may
   // be returned.
   //
   // GetBaseline() returns the fixed baseline regardless of the text.
-  // GetLayoutTextBaseline() returns the baseline determined by the underlying
+  // GetDisplayTextBaseline() returns the baseline determined by the underlying
   // layout engine, and it changes depending on the text.  GetAlignmentOffset()
   // returns the difference between them.
-  virtual int GetLayoutTextBaseline() = 0;
+  virtual int GetDisplayTextBaseline() = 0;
 
   void set_cached_bounds_and_offset_valid(bool valid) {
     cached_bounds_and_offset_valid_ = valid;
   }
 
   // Get the selection model that visually neighbors |position| by |break_type|.
   // The returned value represents a cursor/caret position without a selection.
   SelectionModel GetAdjacentSelectionModel(const SelectionModel& current,
                                            BreakType break_type,
                                            VisualCursorDirection direction);
@@ skipping 18 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
+  // GetDisplayText(), 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 TextIndexToDisplayIndex(size_t index) = 0;
+  virtual size_t DisplayIndexToTextIndex(size_t index) = 0;
 
-  // Reset the layout to be invalid.
-  virtual void ResetLayout() = 0;
+  // Notifies that layout text, or attributes that affect the layout text
+  // shape have changed. |text_changed| is true if the content of the
+  // |layout_text_| has changed, not just attributes.
+  virtual void OnLayoutTextAttributeChanged(bool text_changed) = 0;
+
+  // Notifies that attributes that affect the display text shape have changed.
+  virtual void OnDisplayTextAttributeChanged() = 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 display text.
+  void UpdateDisplayText(float text_width);
 
-  // Returns layout text positions that are suitable for breaking lines.
+  // Returns display 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.
   Vector2d GetLineOffset(size_t line_number);
 
@@ skipping 10 matching lines @@
 
   // Returns the line offset from the origin, accounts for text alignment only.
   Vector2d GetAlignmentOffset(size_t line_number);
 
   // Applies fade effects to |renderer|.
   void ApplyFadeEffects(internal::SkiaTextRenderer* renderer);
 
   // Applies text shadows to |renderer|.
   void ApplyTextShadows(internal::SkiaTextRenderer* renderer);
 
+  // Get the text direction for the current directionality mode and given
+  // |text|.
+  base::i18n::TextDirection GetTextDirection(const base::string16& text);
+
   // A convenience function to check whether the glyph attached to the caret
   // is within the given range.
   static bool RangeContainsCaret(const Range& range,
                                  size_t caret_pos,
                                  LogicalCursorDirection caret_affinity);
 
  private:
   friend class RenderTextTest;
   FRIEND_TEST_ALL_PREFIXES(RenderTextTest, DefaultStyle);
   FRIEND_TEST_ALL_PREFIXES(RenderTextTest, SetColorAndStyle);
@@ skipping 24 matching lines @@
   FRIEND_TEST_ALL_PREFIXES(RenderTextTest, PangoAttributes);
   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.
-  void UpdateLayoutText();
+  // Updates |layout_text_| and |display_text_| as needed (or marks them dirty).
+  void 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 40 matching lines @@
   // The background color used for drawing the selection when focused.
   SkColor selection_background_focused_color_;
 
   // The focus state of the text.
   bool focused_;
 
   // Composition text range.
   Range composition_range_;
 
   // Color and style breaks, used to color and stylize ranges of text.
-  // BreakList positions are stored with text indices, not layout indices.
+  // BreakList positions are stored with text indices, not display indices.
   // TODO(msw): Expand to support cursor, selection, background, etc. colors.
   BreakList<SkColor> colors_;
   std::vector<BreakList<bool> > styles_;
 
   // Breaks saved without temporary composition and selection styling.
   BreakList<SkColor> saved_colors_;
   BreakList<bool> saved_underlines_;
   bool composition_and_selection_styles_applied_;
 
   // A flag to obscure actual text with asterisks for password fields.
   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 obscured and/or truncated text used to layout the text to display.
+  base::string16 layout_text_;
+
+  // The elided text displayed visually. This is empty if the text
+  // does not have to be elided, or became empty as a result of eliding.
+  // TODO(oshima): When the text is elided, painting can be done only with
+  // display text info, so it should be able to clear the |layout_text_| and
+  // associated information.
+  base::string16 display_text_;
+
   // The behavior for eliding, fading, or truncating.
   ElideBehavior elide_behavior_;
 
-  // The obscured and/or truncated text that will be displayed.
-  base::string16 layout_text_;
-
-  // Whether newline characters should be replaced with newline symbols.
-  bool replace_newline_chars_with_symbols_;
+  // True if the text is elided given the current behavior and display area.
+  bool text_elided_;
 
   // 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_;
 
   // Is the background transparent (either partially or fully)?
   bool background_is_transparent_;
@@ skipping 16 matching lines @@
   // centered.
   int baseline_;
 
   // The cached bounds and offset are invalidated by changes to the cursor,
   // 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.
+  // A list of valid display text line break positions.
   BreakList<size_t> line_breaks_;
 
-  // Lines computed by EnsureLayout. These should be invalidated with
-  // ResetLayout and on |display_rect_| changes.
+  // Lines computed by EnsureLayout. These should be invalidated upon
+  // OnLayoutTextAttributeChanged and OnDisplayTextAttributeChanged calls.
   std::vector<internal::Line> lines_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderText);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_RENDER_TEXT_H_