Views:: Make Labels support text selection.

ui/views/selection_controller.cc

Index: ui/views/selection_controller.cc
diff --git a/ui/views/selection_controller.cc b/ui/views/selection_controller.cc
index 23e94823add559a08e535d2837cbc01c24913266..6fa77d434baec39b87b71a08c240586774bf13d6 100644
--- a/ui/views/selection_controller.cc
+++ b/ui/views/selection_controller.cc
@@ -32,12 +32,15 @@ bool SelectionController::OnMousePressed(const ui::MouseEvent& event,
     return true;
 
   if (event.IsOnlyLeftMouseButton()) {
-    delegate_->SetTextBeingDragged(false);
+    if (delegate_->SupportsDrag())

[msw, 2016/10/28 06:30:26]

Is this just disabling something that otherwise works or is it entirely not
supported by Labels (and would require non-trivial work to support)? If it's the
former, let's remove the flag and support dragging selected text from labels to
be dropped elsewhere; if it's the latter, then this is fine for now, but we
might want to investigate adding support later (maybe file/cite a bug?).

[karandeepb, 2016/11/01 11:06:25]

To support dragging selected text, Labels would need to implement
DragController. Have added a TODO to Label::SupportsDrag.

The implementation would be almost similar to the Textfield one. It seems that
as you suggested, Textfield and Label can share more code by being in the same
class hierarchy. But again, probably the Label implementation can be simplified
first. 

Will put up a CL subsequently duplicating some of the code in Textfield for
dragging selected text.

+      delegate_->SetTextBeingDragged(false);
+
     switch (aggregated_clicks_) {
       case 0:
         // If the click location is within an existing selection, it may be a
         // potential drag and drop.
-        if (render_text->IsPointInSelection(event.location())) {
+        if (delegate_->SupportsDrag() &&
+            render_text->IsPointInSelection(event.location())) {
           delegate_->SetTextBeingDragged(true);
         } else {
           delegate_->OnBeforePointerAction();
@@ -127,7 +130,9 @@ void SelectionController::OnMouseReleased(const ui::MouseEvent& event) {
         render_text->MoveCursorTo(event.location(), false);
     delegate_->OnAfterPointerAction(false, selection_changed);
   }
-  delegate_->SetTextBeingDragged(false);
+
+  if (delegate_->SupportsDrag())
+    delegate_->SetTextBeingDragged(false);
 
   if (handles_selection_clipboard_ && !render_text->selection().is_empty())
     delegate_->UpdateSelectionClipboard();
@@ -172,7 +177,7 @@ void SelectionController::SelectThroughLastDragLocation() {
   delegate_->OnBeforePointerAction();
 
   // TODO(karandeepb): See if this can be handled at the RenderText level.
-  const bool drags_to_end = PlatformStyle::kTextfieldDragVerticallyDragsToEnd;
+  const bool drags_to_end = PlatformStyle::kTextDragVerticallyDragsToEnd;
   if (drags_to_end && last_drag_location_.y() < 0) {
     render_text->MoveCursor(gfx::LINE_BREAK, gfx::CURSOR_LEFT,
                             gfx::SELECTION_RETAIN);