Implement eliding/truncating at end in 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 8696d690560e6fddc28da3a59740d725c88a8e57..24afd113291ac3d30904bb76d6a98a556f0eff3e 100644
--- a/ui/gfx/render_text.h
+++ b/ui/gfx/render_text.h
@@ -27,6 +27,7 @@
 #include "ui/gfx/shadow_value.h"
 #include "ui/gfx/size_f.h"
 #include "ui/gfx/text_constants.h"
+#include "ui/gfx/text_elider.h"
 #include "ui/gfx/vector2d.h"
 
 class SkCanvas;
@@ -227,6 +228,11 @@ class GFX_EXPORT RenderText {
   // WARNING: Only use this for system limits, it lacks complex text support.
   void set_truncate_length(size_t length) { truncate_length_ = length; }
 
+  // Elides the text to fit in |available_pixel_width| according to the
+  // specified |elide_behavior|. Only one of elide or truncate should be used.

[msw, 2013/12/11 08:10:14]

We should support simultaneous truncation and eliding, since the Windows
implementation of RenderText uses a 10k code point truncation limit by default
to avoid performance degradation. I posted a comment in the implementation of
UpdateLayoutText about how to accomplish this.

[Anuj, 2013/12/11 18:41:32]

The second part of the comment mentions what will happen if both are used. I was
just trying to recommend ("should") that only one should be used.

[msw, 2013/12/11 19:39:57]

Then this says elide shouldn't be used on windows, since truncate is always
used. I think clarifying the interaction of the two limitations is good, but the
advice against using both simultaneously is probably unnecessary.

[Anuj, 2013/12/12 08:08:41]

Done.

+  // If both are specified, the shorter of the two will be applicable.
+  void Elide(float available_pixel_width, ElideBehavior elide_behavior);

[msw, 2013/12/11 08:10:14]

I would rather this function be SetElideBehavior(ElideBehavior elide_behavior),
and the available pixel width is simply the width of |display_rect_|, that
avoids requiring clients to deal with two RenderText widths when eliding text.

[Anuj, 2013/12/11 18:41:32]

So I will need to add UpdateLayoutText to both of SetElideBehavior and
SetDisplayRect. Does that seem ok to you? Just confirming.

[msw, 2013/12/11 19:39:57]

I think that'll be okay, but you'll only need to UpdateLayoutText on
SetDisplayRect if the ElideBehavior is not NO_ELIDE.

[Anuj, 2013/12/12 08:08:41]

Done.

+
   const Rect& display_rect() const { return display_rect_; }
   void SetDisplayRect(const Rect& r);
 
@@ -556,6 +562,11 @@ class GFX_EXPORT RenderText {
   // Updates |layout_text_| if the text is obscured or truncated.
   void UpdateLayoutText();
 
+  // Elides |text| to fit in the |available_pixel_width_| with given
+  // |elide_behavior_|.
+  // See ElideText in ui/gfx/text_elider.cc for reference.
+  base::string16 ElideText(const base::string16& text);
+
   // Update the cached bounds and display offset to ensure that the current
   // cursor is within the visible display area.
   void UpdateCachedBoundsAndOffset();
@@ -628,6 +639,12 @@ class GFX_EXPORT RenderText {
   // The maximum length of text to display, 0 forgoes a hard limit.
   size_t truncate_length_;
 
+  // The maxmium width available to display the text.

[msw, 2013/12/11 08:10:14]

nit: "  // The maximum width used for eliding, disjoint from the display_rect
width."... but I hope this goes away.

[Anuj, 2013/12/12 08:08:41]

Done.

+  float available_pixel_width_;
+
+  // The behavior for eliding or truncating.
+  ElideBehavior elide_behavior_;
+
   // The obscured and/or truncated text that will be displayed.
   base::string16 layout_text_;