views::Textfield: Implement yank editing command.

ui/views/controls/textfield/textfield_model.h

 // Copyright 2014 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_VIEWS_CONTROLS_TEXTFIELD_TEXTFIELD_MODEL_H_
 #define UI_VIEWS_CONTROLS_TEXTFIELD_TEXTFIELD_MODEL_H_
 
 #include <stddef.h>
 
 #include <list>
@@ skipping 77 matching lines @@
   void ReplaceChar(base::char16 c) {
     ReplaceTextInternal(base::string16(&c, 1), true);
   }
 
   // Appends the text.
   // The current composition text will be confirmed.
   void Append(const base::string16& new_text);
 
   // Deletes the first character after the current cursor position (as if, the
   // the user has pressed delete key in the textfield). Returns true if
-  // the deletion is successful.
+  // the deletion is successful. If |add_to_kill_buffer| is true, the deleted
+  // text is copied to the kill buffer.
   // If there is composition text, it'll be deleted instead.
-  bool Delete();
+  bool Delete(bool add_to_kill_buffer = false);

[msw, 2016/07/22 17:44:03]

I thought chromium generally discouraged default parameters, but I don't see
anything in our style guide, and the Google style guide says they're allowed
here (albeit with a long list of cons), so I guess this is fine.

 
   // Deletes the first character before the current cursor position (as if, the
   // the user has pressed backspace key in the textfield). Returns true if
-  // the removal is successful.
+  // the removal is successful. If |add_to_kill_buffer| is true, the deleted
+  // text is copied to the kill buffer.
   // If there is composition text, it'll be deleted instead.
-  bool Backspace();
+  bool Backspace(bool add_to_kill_buffer = false);
 
   // Cursor related methods.
 
   // Returns the current cursor position.
   size_t GetCursorPosition() const;
 
   // Moves the cursor, see RenderText for additional details.
   // The current composition text will be confirmed.
   void MoveCursor(gfx::BreakType break_type,
                   gfx::VisualCursorDirection direction,
@@ skipping 58 matching lines @@
 
   // Pastes text from the clipboard at current cursor position. Returns true
   // if any text is pasted.
   bool Paste();
 
   // Transposes the characters to either side of the insertion point and
   // advances the insertion point past both of them. Returns true if text is
   // changed.
   bool Transpose();
 
+  // Pastes text from the kill buffer at the current cursor position or
+  // selection.

[msw, 2016/07/22 17:44:03]

nit: What does "or selection" mean? Just that a current selection would be
replaced, similar to the standard paste behavior? If so, you can probably nix
that tidbit, otherwise please clarify.

[karandeepb, 2016/07/25 06:38:11]

Done. Yeah it follows the standard paste behavior. 

+  bool Yank();
+
   // Tells if any text is selected, even if the selection is in composition
   // text.
   bool HasSelection() const;
 
   // Deletes the selected text. This method shouldn't be called with
   // composition text.
   void DeleteSelection();
 
   // Deletes the selected text (if any) and insert text at given position.
   void DeleteSelectionAndInsertTextAt(const base::string16& new_text,
@@ skipping 21 matching lines @@
 
   // Retrieves the range of current composition text.
   void GetCompositionTextRange(gfx::Range* range) const;
 
   // Returns true if there is composition text.
   bool HasCompositionText() const;
 
   // Clears all edit history.
   void ClearEditHistory();
 
+  // Clears the kill buffer. Exposed to clear global state between tests.
+  static void ClearKillBufferForTesting();

[sky, 2016/07/22 15:22:49]

How about friending the helper and moving this to private? Having a bunch of
FooForTesting results in an ugly API.

[karandeepb, 2016/07/25 06:38:11]

Done. But friending BridgedNativeWidgetTest here seems slightly ugly. 

[sky, 2016/07/25 15:26:27]

Another option is to friend a class that is used by all test. These are commonly
called TestApi, eg TextfieldModelTestApi.

+
  private:
   friend class internal::Edit;
 
   FRIEND_TEST_ALL_PREFIXES(TextfieldModelTest, UndoRedo_BasicTest);
   FRIEND_TEST_ALL_PREFIXES(TextfieldModelTest, UndoRedo_CutCopyPasteTest);
   FRIEND_TEST_ALL_PREFIXES(TextfieldModelTest, UndoRedo_ReplaceTest);
 
   // Insert the given |new_text|. |mergeable| indicates if this insert operation
   // can be merged with previous edits in the history.
   void InsertTextInternal(const base::string16& new_text, bool mergeable);
@@ skipping 58 matching lines @@
   //   2) new edit is added. (redo history is cleared)
   //   3) redone all undone edits.
   EditHistory::iterator current_edit_;
 
   DISALLOW_COPY_AND_ASSIGN(TextfieldModel);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_CONTROLS_TEXTFIELD_TEXTFIELD_MODEL_H_