Windows implementation of multiline RenderText

ui/gfx/render_text.h

Index: ui/gfx/render_text.h
diff --git a/ui/gfx/render_text.h b/ui/gfx/render_text.h
index c10b8abf3d63c2177ee68269b73a0fc9888312a6..11ee680b6e85ecec05c561973b0c45a1fd7b82ec 100644
--- a/ui/gfx/render_text.h
+++ b/ui/gfx/render_text.h
@@ -13,6 +13,7 @@
 
 #include "base/gtest_prod_util.h"
 #include "base/i18n/rtl.h"
+#include "base/memory/scoped_vector.h"
 #include "base/strings/string16.h"
 #include "skia/ext/refptr.h"
 #include "third_party/skia/include/core/SkColor.h"
@@ -111,6 +112,11 @@ class StyleIterator {
   DISALLOW_COPY_AND_ASSIGN(StyleIterator);
 };
 
+struct LineSegment {

[Alexei Svitkine (slow), 2013/07/09 15:35:13]

This should live in the class unless you're planning to expose this externally.

I suggest in the protected section.

[msw, 2013/07/10 04:01:56]

Add a struct comment to describe what this is.
(a reader might wonder how this differs from a run)

[msw, 2013/07/10 04:01:56]

I disagree; SkiaTextRenderer and StyleIterator aren't used elsewhere either, but
we shouldn't make all of these protected to RenderText. I think the internal
namespace is fine for now, and I'd rather eventually see these components moved
to other files, instead of cramming everything in the RenderText class.

[ckocagil, 2013/07/13 16:05:10]

Keeping it in internal namespace for now.

+  ui::Range x_pos; // x coord, in text coordinates
+  ui::Range char_pos;
+};
+
 }  // namespace internal
 
 // RenderText represents an abstract model of styled text and its corresponding
@@ -186,6 +192,9 @@ class UI_EXPORT RenderText {
   bool obscured() const { return obscured_; }
   void SetObscured(bool obscured);
 
+  bool multiline() const { return multiline_; }
+  void set_multiline(bool multiline) { multiline_ = multiline; }
+
   // 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
@@ -288,6 +297,8 @@ class UI_EXPORT RenderText {
   // the margin area of text shadows.
   virtual Size GetStringSize() = 0;
 
+  virtual Size RenderText::GetMultilineTextSize() = 0;

[msw, 2013/07/10 04:01:56]

Remove "RenderText::" and add a comment (explain the width cap).

[ckocagil, 2013/07/13 16:05:10]

Done.

+
   // Returns the width of content, which reserves room for the cursor if
   // |cursor_enabled_| is true.
   int GetContentWidth();
@@ -348,6 +359,27 @@ class UI_EXPORT RenderText {
   const BreakList<SkColor>& colors() const { return colors_; }
   const std::vector<BreakList<bool> >& styles() const { return styles_; }
 
+  const std::vector<size_t>& line_breaks() const { return line_breaks_; }
+
+  const std::vector<ScopedVector<internal::LineSegment> >& lines() const {
+    return lines_;
+  }
+  void set_lines(std::vector<ScopedVector<internal::LineSegment> >* lines) {
+    lines_.swap(*lines);
+  }
+
+  bool lines_valid() const { return lines_valid_; }
+  void set_lines_valid(bool lines_valid) {

[msw, 2013/07/10 04:01:56]

nit: rename the param to |valid| to fit this on one line.

[ckocagil, 2013/07/13 16:05:10]

Actually it fits without renaming.

+    lines_valid_ = lines_valid;
+  }
+
+  int LineWidth(int line) {

[Alexei Svitkine (slow), 2013/07/09 15:35:13]

This is not a trivial method so the implementation should live in the .cc file.

Also, should be named GetLineWidth() and have a comment.

[ckocagil, 2013/07/13 16:05:10]

Removed since we now have a Line struct that caches width.

+    int width = 0;
+    for (size_t i = 0; i < lines()[line].size(); ++i)

[Alexei Svitkine (slow), 2013/07/09 15:35:13]

Add a DCHECK() that |line| is within a valid range.

[ckocagil, 2013/07/13 16:05:10]

This method no longer exists.

+      width += lines()[line][i]->x_pos.length();
+    return width;
+  }
+
   const Vector2d& GetUpdatedDisplayOffset();
 
   void set_cached_bounds_and_offset_valid(bool valid) {
@@ -412,6 +444,8 @@ class UI_EXPORT RenderText {
   // Draw the text.
   virtual void DrawVisualText(Canvas* canvas) = 0;
 
+  virtual void ComputeLines() = 0;

[msw, 2013/07/10 04:01:56]

Add a comment, move this above DrawVisualText (it's more like Layout).

[ckocagil, 2013/07/13 16:05:10]

I moved this to render_text_win since we now call EnsureLayout to compute the
lines.

+
   // Returns the text used for layout, which may be |obscured_text_|.
   const base::string16& GetLayoutText() const;
 
@@ -421,16 +455,18 @@ class UI_EXPORT RenderText {
 
   // Returns the text offset from the origin after applying text alignment and
   // display offset.
-  Vector2d GetTextOffset();
+  Vector2d GetTextOffset(int line_width);

[msw, 2013/07/10 04:01:56]

Comment on what |line_width| is used for here. It's needed to get the offsets of
individually centered lines, right? But it's also used to get the more general
offset for a whole block of left/right-aligned text with GetContentWidth, right?
Rename this and the param for GetAlignmentOffset |text_width| or simply |width|.
I would really suggest that you leave these functions as-is and make per-line
offsets a separate matter dealt with elsewhere (like each Line storing it's
bounds, etc.).

[ckocagil, 2013/07/13 16:05:10]

I renamed this to |GetLineOffset| and it now takes a line number.
|GetAlignmentOffset| now takes a line number as well. These should make things
easier since I aim for making everything line-oriented and make the single-line
mode use mostly the same code paths as multi-line. I would rather not have each
Line store its own view bounds to keep the struct simple. Sounds good?

[msw, 2013/07/17 06:47:18]

Sounds good.

 
   // Convert points from the text space to the view space and back.
   // Handles the display area, display offset, and the application LTR/RTL mode.
   Point ToTextPoint(const Point& point);
   Point ToViewPoint(const Point& point);
 
+  std::vector<Rect> RangeToViewRects(const ui::Range& x, int y);

[msw, 2013/07/10 04:01:56]

nit: Comment on what this does and what the args are.
|y| is only ever 0 so far, is it needed?

[ckocagil, 2013/07/13 16:05:10]

Comment added, |y| removed.

+
   // Returns the text offset from the origin, taking into account text alignment
   // only.
-  Vector2d GetAlignmentOffset();
+  Vector2d GetAlignmentOffset(int line_width);

[msw, 2013/07/10 04:01:56]

Ditto comment from GetTextOffset: Comment and rename.

[ckocagil, 2013/07/13 16:05:10]

This method now takes a line number.

 
   // Applies fade effects to |renderer|.
   void ApplyFadeEffects(internal::SkiaTextRenderer* renderer);
@@ -545,6 +581,9 @@ class UI_EXPORT RenderText {
   // The index at which the char should be revealed in the obscured text.
   int obscured_reveal_index_;
 
+  // Whether we should break the text to multiple lines.

[msw, 2013/07/10 04:01:56]

optional nit: I prefer avoiding "we" in comments.
Consider "Whether the text should be broken into multiple lines."
Constider mentioning the use of the display rect's width.

[ckocagil, 2013/07/13 16:05:10]

Done.

+  bool multiline_;
+
   // Fade text head and/or tail, if text doesn't fit into |display_rect_|.
   bool fade_head_;
   bool fade_tail_;
@@ -572,6 +611,14 @@ class UI_EXPORT RenderText {
   // Text shadows to be drawn.
   ShadowValues text_shadows_;
 
+  // Positions at which we can break the line.
+  std::vector<size_t> line_breaks_;
+
+  // Lines computed by ComputeLines().
+  std::vector<ScopedVector<internal::LineSegment> > lines_;

[Alexei Svitkine (slow), 2013/07/09 15:35:13]

Can you use a regular vector instead of a ScopedVector to represent a line? (I
guess you can't because there's a platform specific subclass of LineSegment).

Also, consider making a typedef Line.

[msw, 2013/07/10 04:01:56]

I'm wondering if it might help in the long run to use a BreakList for
merging/splitting existing lines rather than frequently reconstructing the
Lines/LineSegments. I don't have a solid recommendation but maybe you already
thought about this.

[ckocagil, 2013/07/13 16:05:10]

I can't, we need pointers as long as we have LineSegmentWin.
We now have a Line struct.

[ckocagil, 2013/07/13 16:05:10]

I'm not sure how this would work but I'm adding a TODO to the document in Google
Docs and I'll give it some thought later.

+
+  bool lines_valid_;

[Alexei Svitkine (slow), 2013/07/09 15:35:13]

Add a comment.

[ckocagil, 2013/07/13 16:05:10]

Done.

+
   DISALLOW_COPY_AND_ASSIGN(RenderText);
 };