views::Textfield: Implement yank editing command.

ui/views/controls/textfield/textfield_model.cc

 // 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.
 
 #include "ui/views/controls/textfield/textfield_model.h"
 
 #include <algorithm>
 
 #include "base/logging.h"
 #include "base/macros.h"
+#include "base/message_loop/message_loop.h"
 #include "base/stl_util.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "ui/base/clipboard/clipboard.h"
 #include "ui/base/clipboard/scoped_clipboard_writer.h"
 #include "ui/gfx/range/range.h"
 #include "ui/gfx/utf16_indexing.h"
 
 namespace views {
 
@@ skipping 235 matching lines @@
 // there is no such a range.
 gfx::Range GetFirstEmphasizedRange(const ui::CompositionText& composition) {
   for (size_t i = 0; i < composition.underlines.size(); ++i) {
     const ui::CompositionUnderline& underline = composition.underlines[i];
     if (underline.thick)
       return gfx::Range(underline.start_offset, underline.end_offset);
   }
   return gfx::Range::InvalidRange();
 }
 
+// Returns a reference to the kill buffer which holds the text to be inserted on
+// executing yank command. Singleton since it needs to be persisted across
+// multiple textfields.
+// On Mac, the size of the kill ring (no. of buffers) is controlled by
+// NSTextKillRingSize, a text system default. However to keep things simple,
+// the default kill ring size of 1 (i.e. a single buffer) is assumed.
+base::string16& GetKillBuffer() {

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

return a pointer (references are generally restricted to const).

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

Done.

+  CR_DEFINE_STATIC_LOCAL(base::string16, kill_buffer, ());
+  DCHECK(base::MessageLoopForUI::IsCurrent());
+  return kill_buffer;
+}
+
+// Helper method to set the kill buffer.
+void SetKillBuffer(const base::string16& buffer) {
+  base::string16& kill_buffer = GetKillBuffer();
+  kill_buffer = buffer;
+}
+
 }  // namespace
 
 using internal::Edit;
 using internal::DeleteEdit;
 using internal::InsertEdit;
 using internal::ReplaceEdit;
 using internal::MergeType;
 using internal::DO_NOT_MERGE;
 using internal::FORCE_MERGE;
 using internal::MERGEABLE;
@@ skipping 42 matching lines @@
     ConfirmCompositionText();
   size_t save = GetCursorPosition();
   MoveCursor(gfx::LINE_BREAK,
              render_text_->GetVisualDirectionOfLogicalEnd(),
              false);
   InsertText(new_text);
   render_text_->SetCursorPosition(save);
   ClearSelection();
 }
 
-bool TextfieldModel::Delete() {
+bool TextfieldModel::Delete(bool add_to_kill_buffer) {
   if (HasCompositionText()) {
     // No undo/redo for composition text.
     CancelCompositionText();
     return true;
   }
   if (HasSelection()) {
+    if (add_to_kill_buffer)
+      SetKillBuffer(GetSelectedText());
     DeleteSelection();
     return true;
   }
   if (text().length() > GetCursorPosition()) {
     size_t cursor_position = GetCursorPosition();
     size_t next_grapheme_index = render_text_->IndexOfAdjacentGrapheme(
         cursor_position, gfx::CURSOR_FORWARD);
-    ExecuteAndRecordDelete(gfx::Range(cursor_position, next_grapheme_index),
-                           true);
+    gfx::Range range_to_delete(cursor_position, next_grapheme_index);
+    if (add_to_kill_buffer)
+      SetKillBuffer(GetTextFromRange(range_to_delete));
+    ExecuteAndRecordDelete(range_to_delete, true);
     return true;
   }
   return false;
 }
 
-bool TextfieldModel::Backspace() {
+bool TextfieldModel::Backspace(bool add_to_kill_buffer) {
   if (HasCompositionText()) {
     // No undo/redo for composition text.
     CancelCompositionText();
     return true;
   }
   if (HasSelection()) {
+    if (add_to_kill_buffer)
+      SetKillBuffer(GetSelectedText());
     DeleteSelection();
     return true;
   }
   size_t cursor_position = GetCursorPosition();
   if (cursor_position > 0) {
     // Delete one code point, which may be two UTF-16 words.
     size_t previous_char = gfx::UTF16OffsetToIndex(text(), cursor_position, -1);

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

optional nit: |previous_grapheme_index| for consistency with code above.

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

Done.

-    ExecuteAndRecordDelete(gfx::Range(cursor_position, previous_char), true);
+    gfx::Range range_to_delete(cursor_position, previous_char);
+    if (add_to_kill_buffer)
+      SetKillBuffer(GetTextFromRange(range_to_delete));
+    ExecuteAndRecordDelete(range_to_delete, true);
     return true;
   }
   return false;
 }
 
 size_t TextfieldModel::GetCursorPosition() const {
   return render_text_->cursor_position();
 }
 
 void TextfieldModel::MoveCursor(gfx::BreakType break_type,
@@ skipping 176 matching lines @@
 
   SelectRange(gfx::Range(prev, next));
   base::string16 text = GetSelectedText();
   base::string16 transposed_text =
       text.substr(cur - prev) + text.substr(0, cur - prev);
 
   InsertTextInternal(transposed_text, false);
   return true;
 }
 
+bool TextfieldModel::Yank() {
+  const base::string16& kill_buffer = GetKillBuffer();
+  if (!kill_buffer.empty() || HasSelection()) {

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

Why would this try to insert an empty string if there's a selection?

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

That's how Yank works on Mac/Cocoa. Open a new Chrome app instance, select some
text and press Ctrl+Y to yank. The selected text will get deleted (since kill
buffer is empty). 

[msw, 2016/07/25 18:35:49]

Ah, so it's just doing a delete in that case? Okay.

[karandeepb, 2016/07/26 03:45:41]

Yeah!

+    InsertTextInternal(kill_buffer, false);
+    return true;
+  }
+  return false;
+}
+
 bool TextfieldModel::HasSelection() const {
   return !render_text_->selection().is_empty();
 }
 
 void TextfieldModel::DeleteSelection() {
   DCHECK(!HasCompositionText());
   DCHECK(HasSelection());
   ExecuteAndRecordDelete(render_text_->selection(), false);
 }
 
@@ skipping 95 matching lines @@
 
 bool TextfieldModel::HasCompositionText() const {
   return !composition_range_.is_empty();
 }
 
 void TextfieldModel::ClearEditHistory() {
   STLDeleteElements(&edit_history_);
   current_edit_ = edit_history_.end();
 }
 
+// static
+void TextfieldModel::ClearKillBufferForTesting() {
+  SetKillBuffer(base::string16());
+}
+
 /////////////////////////////////////////////////////////////////
 // TextfieldModel: private
 
 void TextfieldModel::InsertTextInternal(const base::string16& new_text,
                                         bool mergeable) {
   if (HasCompositionText()) {
     CancelCompositionText();
     ExecuteAndRecordInsert(new_text, mergeable);
   } else if (HasSelection()) {
     ExecuteAndRecordReplaceSelection(mergeable ? MERGEABLE : DO_NOT_MERGE,
@@ skipping 119 matching lines @@
   ClearComposition();
   if (delete_from != delete_to)
     render_text_->SetText(old_text.erase(delete_from, delete_to - delete_from));
   if (!new_text.empty())
     render_text_->SetText(old_text.insert(new_text_insert_at, new_text));
   render_text_->SetCursorPosition(new_cursor_pos);
   // TODO(oshima): Select text that was just undone, like Mac (but not GTK).
 }
 
 }  // namespace views