Implement eliding/truncating at end 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>
 #include <utility>
 #include <vector>
 
 #include "base/gtest_prod_util.h"
 #include "base/i18n/rtl.h"
 #include "base/strings/string16.h"
 #include "skia/ext/refptr.h"
 #include "third_party/skia/include/core/SkColor.h"
 #include "third_party/skia/include/core/SkPaint.h"
 #include "third_party/skia/include/core/SkRect.h"
 #include "ui/gfx/break_list.h"
 #include "ui/gfx/font_list.h"
 #include "ui/gfx/point.h"
 #include "ui/gfx/range/range.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/selection_model.h"
 #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;
 class SkDrawLooper;
 struct SkPoint;
 class SkShader;
 class SkTypeface;
 
 namespace gfx {
 
@@ skipping 180 matching lines @@
   // Windows. Support other platforms.
   bool multiline() const { return multiline_; }
   void SetMultiline(bool multiline);
 
   // 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; }
 
+  // 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);
 
   void set_fade_head(bool fade_head) { fade_head_ = fade_head; }
   bool fade_head() const { return fade_head_; }
   void set_fade_tail(bool fade_tail) { fade_tail_ = fade_tail; }
   bool fade_tail() const { return fade_tail_; }
 
   bool background_is_transparent() const { return background_is_transparent_; }
   void set_background_is_transparent(bool transparent) {
@@ skipping 309 matching lines @@
   // 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();
 
+  // 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();
 
   // Draw the selection.
   void DrawSelection(Canvas* canvas);
 
   // Logical UTF-16 string data to be drawn.
   base::string16 text_;
 
@@ skipping 52 matching lines @@
   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 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_;
 
   // Whether the text should be broken into multiple lines. Uses the width of
   // |display_rect_| as the width cap.
   bool multiline_;
 
   // Fade text head and/or tail, if text doesn't fit into |display_rect_|.
   bool fade_head_;
   bool fade_tail_;
@@ skipping 32 matching lines @@
   // Lines computed by EnsureLayout. These should be invalidated with
   // ResetLayout and on |display_rect_| changes.
   std::vector<internal::Line> lines_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderText);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_RENDER_TEXT_H_