ash/mash: Make sure the right context-factory is used for the views::Widgets.

ash/mus/sysui_application.cc

 // Copyright 2016 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/mus/sysui_application.h"
 
 #include "ash/desktop_background/desktop_background_controller.h"
 #include "ash/host/ash_window_tree_host_init_params.h"
 #include "ash/host/ash_window_tree_host_platform.h"
 #include "ash/mus/shell_delegate_mus.h"
@@ skipping 80 matching lines @@
       views::internal::NativeWidgetDelegate* delegate) {
     std::map<std::string, std::vector<uint8_t>> properties;
     if (params.parent) {
       mash::wm::mojom::Container container = GetContainerId(params.parent);
       if (container != mash::wm::mojom::Container::COUNT) {
         properties[mash::wm::mojom::kWindowContainer_Property] =
             mojo::TypeConverter<const std::vector<uint8_t>, int32_t>::Convert(
                 static_cast<int32_t>(container));
       }
     }
+
+    // AshInit installs a stub implementation of ui::ContextFactory, so that the
+    // AshWindowTreeHost instances created do not actually show anything to the
+    // user. However, when creating a views::Widget instance, the
+    // WindowManagerConnection creates a WindowTreeHostMus instance, which
+    // creates a ui::Compositor, and it needs a real ui::ContextFactory
+    // implementation. So, unset the context-factory here temporarily when
+    // creating NativeWidgetMus. But restore the stub instance afterwards, so
+    // that it is used when new AshWindowTreeHost instances are created (e.g.
+    // when a new monitor is attached).
+    ui::ContextFactory* factory = aura::Env::GetInstance()->context_factory();
+    aura::Env::GetInstance()->set_context_factory(nullptr);
     views::NativeWidgetMus* native_widget =

[sky, 2016/02/10 17:27:43]

I think this code (and NativeWidgetMus too) shows how fragile the static factory
is. Can we explicitly pass in the factory we want to use?

[sadrul, 2016/02/10 17:29:35]

Agree. I started looking at that, but decided to unblock this first. I will land
this, and look into a cleaner solution.

         static_cast<views::NativeWidgetMus*>(
             views::WindowManagerConnection::Get()->CreateNativeWidgetMus(
                 properties, params, delegate));
+    aura::Env::GetInstance()->set_context_factory(factory);
+
     // TODO: Set the correct display id here.
     InitRootWindowSettings(native_widget->GetRootWindow())->display_id =
         Shell::GetInstance()
             ->display_manager()
             ->GetPrimaryDisplayCandidate()
             .id();
     return native_widget;
   }
 
   DISALLOW_COPY_AND_ASSIGN(NativeWidgetFactory);
@@ skipping 35 matching lines @@
     message_center::MessageCenter::Initialize();
 
     ash::ShellInitParams init_params;
     init_params.delegate = ash_delegate_;
     init_params.context_factory = new StubContextFactory;
     init_params.blocking_pool = worker_pool_.get();
     ash::Shell::CreateInstance(init_params);
     ash::Shell::GetInstance()->CreateShelf();
     ash::Shell::GetInstance()->UpdateAfterLoginStatusChange(
         ash::user::LOGGED_IN_USER);
-    // Reset the context factory, so that NativeWidgetMus installs the context
-    // factory for the views::Widgets correctly.
-    aura::Env::GetInstance()->set_context_factory(nullptr);
 
     ash::Shell::GetPrimaryRootWindow()->GetHost()->Show();
     SetupWallpaper(SkColorSetARGB(255, 0, 255, 0));
   }
 
   void SetupWallpaper(SkColor color) {
     SkBitmap bitmap;
     bitmap.allocN32Pixels(16, 16);
     bitmap.eraseColor(color);
 #if !defined(NDEBUG)
@@ skipping 25 matching lines @@
 
 void SysUIApplication::Initialize(mojo::Shell* shell,
                                   const std::string& url,
                                   uint32_t id) {
   ash_init_.reset(new AshInit());
   ash_init_->Initialize(shell);
 }
 
 }  // namespace sysui
 }  // namespace ash