[ash-md] Prevents auto-positioning after cancelling overview

ash/common/wm/overview/window_selector.cc

 // Copyright 2013 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/common/wm/overview/window_selector.h"
 
 #include <algorithm>
 #include <functional>
 #include <set>
 #include <utility>
@@ skipping 363 matching lines @@
   WmShell::Get()->accessibility_delegate()->TriggerAccessibilityAlert(
       A11Y_ALERT_WINDOW_OVERVIEW_MODE_ENTERED);
 
   UpdateShelfVisibility();
 }
 
 // NOTE: The work done in Shutdown() is not done in the destructor because it
 // may cause other, unrelated classes, (ie PanelLayoutManager) to make indirect
 // calls to restoring_minimized_windows() on a partially destructed object.
 void WindowSelector::Shutdown() {
+  // Stop observing screen metrics changes first to avoid auto-positioning
+  // windows in response to work area changes from window activation.
+  display::Screen::GetScreen()->RemoveObserver(this);
+
   size_t remaining_items = 0;
   for (std::unique_ptr<WindowGrid>& window_grid : grid_list_) {
     for (WindowSelectorItem* window_selector_item : window_grid->window_list())
       window_selector_item->RestoreWindow();
     remaining_items += window_grid->size();
   }
 
   // Setting focus after restoring windows' state avoids unnecessary animations.
   ResetFocusRestoreWindow(true);
   RemoveAllObservers();
@@ skipping 152 matching lines @@
 
 void WindowSelector::OnDisplayAdded(const display::Display& display) {}
 
 void WindowSelector::OnDisplayRemoved(const display::Display& display) {
   // TODO(flackr): Keep window selection active on remaining displays.
   CancelSelection();
 }
 
 void WindowSelector::OnDisplayMetricsChanged(const display::Display& display,
                                              uint32_t metrics) {
-  // If only the work area changes, there is no need to reposition windows in
-  // overview.
-  if (metrics != DISPLAY_METRIC_WORK_AREA) {

[oshima, 2016/08/09 10:59:56]

Note that we used to ignore work area only metrics change and this was to keep
the same behavior. Are you sure it's safer?

[varkha, 2016/08/09 13:13:39]

Yes, this callback is here to position windows and UI elements while in overview
mode when work area changes. Work area insets such as from the shelf, ChromeVox,
etc. should trigger repositioning. While we attempt to block those insets from
changing in overview I think it is safer to still respond to those changes while
still in overview.
So for instance, if there is some shortcut to activate ChromeVox while in
overview, the new code will deal with it while the old code may allow UI
elements to overlap.

-    PositionWindows(/* animate */ false);
-    RepositionTextFilterOnDisplayMetricsChange();
-  }
+  PositionWindows(/* animate */ false);
+  RepositionTextFilterOnDisplayMetricsChange();
 }
 
 void WindowSelector::OnWindowTreeChanged(WmWindow* window,
                                          const TreeChangeParams& params) {
   // Only care about newly added children of |observed_windows_|.
   if (!observed_windows_.count(window) ||
       !observed_windows_.count(params.new_parent)) {
     return;
   }
 
@@ skipping 141 matching lines @@
   for (size_t i = 0; i <= grid_list_.size() &&
                      grid_list_[selected_grid_index_]->Move(direction, animate);
        i++) {
     selected_grid_index_ =
         (selected_grid_index_ + display_direction + grid_list_.size()) %
         grid_list_.size();
   }
 }
 
 }  // namespace ash