Implement eliding/truncating at end in RenderText

ui/gfx/text_elider.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.
 //
 // This file defines utility functions for eliding and formatting UI text.
 
 #ifndef UI_GFX_TEXT_ELIDER_H_
 #define UI_GFX_TEXT_ELIDER_H_
 
 #include <string>
@@ skipping 10 matching lines @@
 namespace base {
 class FilePath;
 }
 
 namespace gfx {
 class FontList;
 
 GFX_EXPORT extern const char kEllipsis[];
 GFX_EXPORT extern const base::char16 kEllipsisUTF16[];
 
+
+// Helper class to split + elide text, while respecting UTF16 surrogate pairs.
+class StringSlicer {
+ public:
+  StringSlicer(const base::string16& text,
+               const base::string16& ellipsis,
+               bool elide_in_middle);
+
+  // Cuts |text_| to be |length| characters long. If |elide_in_middle_| is true,
+  // the middle of the string is removed to leave equal-length pieces from the
+  // beginning and end of the string; otherwise, the end of the string is
+  // removed and only the beginning remains. If |insert_ellipsis| is true,
+  // then an ellipsis character will be inserted at the cut point.
+  base::string16 CutString(size_t length, bool insert_ellipsis);
+
+ private:
+  // Returns a valid cut boundary at or before/after |index|.
+  size_t FindValidBoundaryBefore(size_t index) const;
+  size_t FindValidBoundaryAfter(size_t index) const;
+
+  // The text to be sliced.
+  const base::string16& text_;
+
+  // Ellipsis string to use.
+  const base::string16& ellipsis_;
+
+  // If true, the middle of the string will be elided.
+  bool elide_in_middle_;
+
+  DISALLOW_COPY_AND_ASSIGN(StringSlicer);
+};
+
 // Elides a well-formed email address (e.g. username@domain.com) to fit into
 // |available_pixel_width| using the specified |font_list|.
 // This function guarantees that the string returned will contain at least one
 // character, other than the ellipses, on either side of the '@'. If it is
 // impossible to achieve these requirements: only an ellipsis will be returned.
 // If possible: this elides only the username portion of the |email|. Otherwise,
 // the domain is elided in the middle so that it splits the available width
 // equally with the elided username (should the username be short enough that it
 // doesn't need half the available width: the elided domain will occupy that
 // extra width).
@@ skipping 19 matching lines @@
                                    const gfx::FontList& font_list,
                                    float available_pixel_width,
                                    const std::string& languages);
 
 enum ElideBehavior {
   // Add ellipsis at the end of the string.
   ELIDE_AT_END,
   // Add ellipsis in the middle of the string.
   ELIDE_IN_MIDDLE,
   // Truncate the end of the string.
-  TRUNCATE_AT_END
+  TRUNCATE_AT_END,
+  // No eliding of the string.
+  NO_ELIDE
 };
 
 // Elides |text| to fit in |available_pixel_width| according to the specified
 // |elide_behavior|.
 GFX_EXPORT base::string16 ElideText(const base::string16& text,
                                     const gfx::FontList& font_list,
                                     float available_pixel_width,
                                     ElideBehavior elide_behavior);
 
 // Elide a filename to fit a given pixel width, with an emphasis on not hiding
@@ skipping 119 matching lines @@
 // the first word break before length, adding the horizontal ellipsis
 // character (unicode character 0x2026) to render ...
 // The supplied string is returned if the string has length characters or
 // less.
 GFX_EXPORT base::string16 TruncateString(const base::string16& string,
                                          size_t length);
 
 }  // namespace gfx
 
 #endif  // UI_GFX_TEXT_ELIDER_H_