Force calling PostDisplayConfigurationChange() even if earyling out in UpdateDisplays

ash/display/display_manager.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/display/display_manager.h"
 
 #include <algorithm>
 #include <cmath>
 #include <set>
 #include <string>
@@ skipping 866 matching lines @@
       InsertAndUpdateDisplayInfo(*new_info_iter);
       new_displays.push_back(
           CreateDisplayFromDisplayInfoById(new_info_iter->id()));
       ++new_info_iter;
     }
   }
 
   scoped_ptr<NonDesktopDisplayUpdater> non_desktop_display_updater(
       new NonDesktopDisplayUpdater(this, delegate_));
 
-  // Do not update |displays_| if there's nothing to be updated. Without this,
-  // it will not update the display layout, which causes the bug
-  // http://crbug.com/155948.
-  if (display_changes.empty() && added_display_indices.empty() &&
-      removed_displays.empty()) {
-    return;
-  }
   // Clear focus if the display has been removed, but don't clear focus if
   // the destkop has been moved from one display to another
   // (mirror -> docked, docked -> single internal).
   bool clear_focus =
       !removed_displays.empty() &&
       !(removed_displays.size() == 1 && added_display_indices.size() == 1);
   if (delegate_)
     delegate_->PreDisplayConfigurationChange(clear_focus);
 
+  // Do not update |displays_| if there's nothing to be updated. Without this,
+  // it will not update the display layout, which causes the bug
+  // http://crbug.com/155948.
+  if (display_changes.empty() && added_display_indices.empty() &&
+      removed_displays.empty()) {
+    // When changing from software mirroring mode to sinlge display mode, it
+    // is possible there is no need to update |displays_| and we early out
+    // here. But we still want to run the PostDisplayConfigurationChange()
+    // cause there are some clients need to act on this, e.g.
+    // TouchTransformerController needs to adjust the TouchTransformer when
+    // switching from dual displays to single display.
+    if (delegate_)
+      delegate_->PostDisplayConfigurationChange();
+    return;
+  }
+
   size_t updated_index;
   if (UpdateSecondaryDisplayBoundsForLayout(&new_displays, &updated_index) &&
       std::find(added_display_indices.begin(),
                 added_display_indices.end(),
                 updated_index) == added_display_indices.end()) {
     uint32_t metrics = gfx::DisplayObserver::DISPLAY_METRIC_BOUNDS |
                        gfx::DisplayObserver::DISPLAY_METRIC_WORK_AREA;
     if (display_changes.find(updated_index) != display_changes.end())
       metrics |= display_changes[updated_index];
 
@@ skipping 346 matching lines @@
       new_secondary_origin.Offset(-secondary_bounds.width(), offset);
       break;
   }
   gfx::Insets insets = secondary_display->GetWorkAreaInsets();
   secondary_display->set_bounds(
       gfx::Rect(new_secondary_origin, secondary_bounds.size()));
   secondary_display->UpdateWorkAreaFromInsets(insets);
 }
 
 }  // namespace ash