Tracking text selection on the browser side in OOPIF.

content/browser/renderer_host/render_widget_host_view_base.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.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_BASE_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_BASE_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 414 matching lines @@
   // While the mouse is locked, the cursor is hidden from the user. Mouse events
   // are still generated. However, the position they report is the last known
   // mouse position just as mouse lock was entered; the movement they report
   // indicates what the change in position of the mouse would be had it not been
   // locked.
   bool mouse_locked_;
 
   // Whether we are showing a context menu.
   bool showing_context_menu_;
 
+// TODO(ekaramad): In aura, text selection tracking for IME is done through the
+// TextInputManager. We still need the following variables for other platforms.
+// Remove them when tracking is done by TextInputManager on all platforms
+// (https://crbug.com/578168).
+#if !defined(USE_AURA)
   // A buffer containing the text inside and around the current selection range.
   base::string16 selection_text_;
 
   // The offset of the text stored in |selection_text_| relative to the start of
   // the web page.
   size_t selection_text_offset_;
 
   // The current selection range relative to the start of the web page.
   gfx::Range selection_range_;
+#endif
 
   // The scale factor of the display the renderer is currently on.
   float current_device_scale_factor_;
 
   // The orientation of the display the renderer is currently on.
   display::Display::Rotation current_display_rotation_;
 
   // Whether pinch-to-zoom should be enabled and pinch events forwarded to the
   // renderer.
   bool pinch_zoom_enabled_;
 
   // A reference to current TextInputManager instance this RWHV is registered
   // with. This is initially nullptr until the first time the view calls
   // GetTextInputManager(). It also becomes nullptr when TextInputManager is
   // destroyed before the RWHV is destroyed.
   TextInputManager* text_input_manager_;
 
  private:
   void FlushInput();
 
+  // The non-const implementation of RenderWidgetHostView::GetSelectedText().

[kenrb, 2016/07/12 19:15:25]

Why is this needed? There is only one caller, which can access the selected text
directly.

[EhsanK, 2016/07/12 19:33:48]

The idea was to remove |selection_text_|, |selection_text_offset_|, and
|selection_range_| from this into TextInputManager. The only reason I have not
remove them yet is that Mac uses them so I will have to wait until I start
working on Mac code. Then these will be removed. So for this CL, I pretend they
do not exist and the state is only tracked at TextInputManager.

Now to implement RenderWidgetHostView::GetSelectedText(), I cannot simply call
GetTextInputManager() since GetSelectedText() is const but GetTextInputManager()
and TextInputManager::GetTextSelection are not. So I implemented this extra
method which is not const, and then I call it, after const_cast, from
GetSelectedText().

I am not particularly happy with this const_cast myself, but I could not come up
with a less messy way of getting around this problem.

[kenrb, 2016/07/12 20:15:17]

Yeah, this isn't good. Basically it is trying to cheat on this method being
const.

It looks like TextInputManager::GetTextSelection() should be const to begin
with, which is part of the problem. GetTextInputManager() could almost be const,
but it can lazily create the TextInputManager. Can you make
GetTextInputManager() const if you make text_input_manager_ mutable? That seems
like the right way to do this.

[EhsanK, 2016/07/18 15:21:29]

So basically we ended up removing const from this method altogether (in a
separate CL). So the new version does not have the same issue.

+  base::string16 GetSelectedTextFromTextInputManager();
+
   gfx::Rect current_display_area_;
 
   uint32_t renderer_frame_number_;
 
   base::OneShotTimer flush_input_timer_;
 
   base::ObserverList<RenderWidgetHostViewBaseObserver> observers_;
 
   base::WeakPtrFactory<RenderWidgetHostViewBase> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostViewBase);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_BASE_H_