Re-layout Chrome OS audio row when headphone connected

ash/common/system/chromeos/audio/volume_view.cc

 // Copyright 2014 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/system/chromeos/audio/volume_view.h"
 
 #include <algorithm>
 
 #include "ash/common/material_design/material_design_controller.h"
 #include "ash/common/metrics/user_metrics_action.h"
@@ skipping 238 matching lines @@
   Update();
   slider_->set_enable_accessibility_events(true);
 }
 
 void VolumeView::UpdateDeviceTypeAndMore() {
   bool show_more = is_default_view_ && audio_delegate_->HasAlternativeSources();
 
   if (!show_more)
     return;
 
+  bool was_visible = device_type_->visible();
+
   // Show output device icon if necessary.
   device_type_->SetVisible(false);
   if (MaterialDesignController::IsSystemTrayMenuMaterial()) {
     const gfx::VectorIcon& device_icon =
         audio_delegate_->GetActiveOutputDeviceVectorIcon();
     if (!device_icon.is_empty()) {
       device_type_->SetImage(
           gfx::CreateVectorIcon(device_icon, kMenuIconColor));
       device_type_->SetVisible(true);
     }
   } else {
     int device_icon = audio_delegate_->GetActiveOutputDeviceIconId();
     if (device_icon != system::TrayAudioDelegate::kNoAudioDeviceIcon) {
       device_type_->SetImage(ui::ResourceBundle::GetSharedInstance()
                                  .GetImageNamed(device_icon)
                                  .ToImageSkia());
       device_type_->SetVisible(true);
     }
   }
+  if (device_type_->visible() != was_visible)
+    device_type_->InvalidateLayout();

[sadrul, 2017/02/02 21:25:34]

Setting the visibility can trigger a repaint. For example, if the View is
visible, then we mark it as hidden first (line 262 above), then make it visible
again. So although we don't actually need to repaint, we end up repainting
anyway.

May I suggest changing this code so this doesn't happen? For example:
  if (!show_more)
    return;
  bool should_be_visible = false;
  if (....) {
    ...
    should_be_visible = true;
  } else {
    ...
    should_be_visible = true;
  }
  if (should_be_visible != device_type_->visible()) {
    device_type_->SetVisible(should_be_visible);
    device_type_->InvalidateLayout();
  }


i.e. set the visibility only if we know that it needs to be changed.

[mohsen, 2017/02/02 21:35:31]

Sure. That makes a lot of sense. Done.

 }
 
 void VolumeView::HandleVolumeUp(int level) {
   audio_delegate_->SetOutputVolumeLevel(level);
   if (audio_delegate_->IsOutputAudioMuted() &&
       level > audio_delegate_->GetOutputDefaultVolumeMuteLevel()) {
     audio_delegate_->SetOutputAudioIsMuted(false);
   }
 }
 
@@ skipping 55 matching lines @@
 void VolumeView::OnBoundsChanged(const gfx::Rect& previous_bounds) {
   // Separator's prefered size is based on set bounds. When an empty bounds is
   // set on first layout this causes BoxLayout to ignore the separator. Reset
   // its height on each bounds change so that it is laid out properly.
   if (separator_)
     separator_->SetSize(gfx::Size(kSeparatorSize, bounds().height()));
 }
 
 }  // namespace tray
 }  // namespace ash