Ash magnifier: Check whether the caret bounds were actually moved or not.

ash/magnifier/magnification_controller.cc

 // 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.
 
 #include "ash/magnifier/magnification_controller.h"
 
 #include <memory>
 #include <utility>
 
 #include "ash/common/accelerators/accelerator_controller.h"
@@ skipping 794 matching lines @@
   // caret bounds in screen coordinates.
   const gfx::Rect caret_bounds = client->GetCaretBounds();
   // Note: OnCaretBoundsChanged could be fired OnTextInputTypeChanged during
   // which the caret position is not set a meaning position, and we do not
   // need to adjust the view port position based on the bogus caret position.
   // This is only a transition period, the caret position will be fixed upon
   // focusing right after.
   if (caret_bounds.width() == 0 && caret_bounds.height() == 0)
     return;
 
-  caret_point_ = caret_bounds.CenterPoint();
+  gfx::Point new_caret_point = caret_bounds.CenterPoint();
   // |caret_point_| in |root_window_| coordinates.
-  ::wm::ConvertPointFromScreen(root_window_, &caret_point_);
+  ::wm::ConvertPointFromScreen(root_window_, &new_caret_point);
+
+  // When the caret point was not actually changed, nothing should happen.
+  // OnCaretBoundsChanged could be fired on every event that may change the
+  // caret bounds, in particular a window creation/movement, that may not result
+  // in an actual movement.
+  if (new_caret_point == caret_point_)
+    return;
+  caret_point_ = new_caret_point;
 
   // If the feature for centering the text input focus is disabled, the
   // magnifier window will be moved to follow the focus with a panning margin.
   if (!KeepFocusCentered()) {
     // Visible window_rect in |root_window_| coordinates.
     const gfx::Rect visible_window_rect = GetViewportRect();
     const int panning_margin = kCaretPanningMargin / scale_;
     MoveMagnifierWindowFollowPoint(caret_point_, panning_margin, panning_margin,
                                    visible_window_rect.width() / 2,
                                    visible_window_rect.height() / 2);
@@ skipping 21 matching lines @@
 
 ////////////////////////////////////////////////////////////////////////////////
 // MagnificationController:
 
 // static
 MagnificationController* MagnificationController::CreateInstance() {
   return new MagnificationControllerImpl();
 }
 
 }  // namespace ash