views::Textfield: Implement yank editing command.

ui/views/controls/textfield/textfield_model.cc

Index: ui/views/controls/textfield/textfield_model.cc
diff --git a/ui/views/controls/textfield/textfield_model.cc b/ui/views/controls/textfield/textfield_model.cc
index 297ea1978cb84132388d102cbef5833fa8ade271..e3095e648bbe4e3388819257af63289ac4a97969 100644
--- a/ui/views/controls/textfield/textfield_model.cc
+++ b/ui/views/controls/textfield/textfield_model.cc
@@ -251,6 +251,13 @@ class DeleteEdit : public Edit {
 
 namespace {
 
+// Buffer containing the text to be inserted on executing yank command. This
+// is a 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 g_kill_buffer_;

[tapted, 2016/07/06 01:46:37]

This will add a static initializer, which isn't allowed. I don't *think* there
are thread safety issues, so something like the following probably has the least
overhead

base::string16& GetKillBuffer() {
  CR_DEFINE_STATIC_LOCAL(base::string16, kill_buffer, ());
  DCHECK(base::MessageLoopForUI::IsCurrent());
  return kill_buffer;
}

An alternative to this is to place the buffer as a data member of
views::ViewsDelegate. And, in fact, this may even be a requirement since
toolkit-views technically has some threading support (it might get used for
Mus.. but I doubt it will come up for Mac). A data member of ViewsDelegate also
has the advantage of not leaving around global state in tests :)

[karandeepb, 2016/07/19 07:04:40]

Added as a member of ViewsDelegate.

+
 // Returns the first segment that is visually emphasized. Usually it's used for
 // representing the target clause (on Windows). Returns an invalid range if
 // there is no such a range.
@@ -325,13 +332,15 @@ void TextfieldModel::Append(const base::string16& new_text) {
   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)
+      g_kill_buffer_ = GetSelectedText();
     DeleteSelection();
     return true;
   }
@@ -339,20 +348,24 @@ bool TextfieldModel::Delete() {
     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)
+      g_kill_buffer_ = 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)
+      g_kill_buffer_ = GetSelectedText();
     DeleteSelection();
     return true;
   }
@@ -360,7 +373,10 @@ bool TextfieldModel::Backspace() {
   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);
-    ExecuteAndRecordDelete(gfx::Range(cursor_position, previous_char), true);
+    gfx::Range range_to_delete(cursor_position, previous_char);
+    if (add_to_kill_buffer)
+      g_kill_buffer_ = GetTextFromRange(range_to_delete);
+    ExecuteAndRecordDelete(range_to_delete, true);
     return true;
   }
   return false;
@@ -557,6 +573,14 @@ bool TextfieldModel::Transpose() {
   return true;
 }
 
+bool TextfieldModel::Yank() {
+  if (!g_kill_buffer_.empty() || HasSelection()) {
+    InsertTextInternal(g_kill_buffer_, false);
+    return true;
+  }
+  return false;
+}
+
 bool TextfieldModel::HasSelection() const {
   return !render_text_->selection().is_empty();
 }