[WIP] ScreenManager: Add an external window mode

services/ui/display/screen_manager.h

 // 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.
 
 #ifndef SERVICES_UI_DISPLAY_SCREEN_MANAGER_H_
 #define SERVICES_UI_DISPLAY_SCREEN_MANAGER_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "services/ui/display/screen_manager_delegate.h"
 
 namespace service_manager {
 class InterfaceRegistry;
 }
 
 namespace display {
 
 // ScreenManager provides the necessary functionality to configure all
 // attached physical displays.
 class ScreenManager {
  public:
+  enum WindowMode {
+    WINDOW_MODE_EXTERNAL,

[rjkroege, 2017/01/23 21:19:43]

We've emailed enough to know what these mean but I think it needs a comment.

[fwang, 2017/01/24 17:11:51]

Done.

+    WINDOW_MODE_INTERNAL,
+  };
+
   ScreenManager();
   virtual ~ScreenManager();
 
   // Creates a singleton ScreenManager instance.
   static std::unique_ptr<ScreenManager> Create();
   static ScreenManager* GetInstance();
 
   // Registers Mojo interfaces provided.
   virtual void AddInterfaces(service_manager::InterfaceRegistry* registry) = 0;
 
-  // Triggers initial display configuration to start. On device this will
-  // configuration the connected displays. Off device this will create one or
-  // more fake displays and pretend to configure them. A non-null |delegate|
-  // must be provided that will receive notifications when displays are added,
-  // removed or modified.
-  virtual void Init(ScreenManagerDelegate* delegate) = 0;
+  // If |window_mode| == WINDOW_MODE_EXTERNAL, no initial displays are created
+  // or initialized.  Otherwise, triggers initial display configuration to
+  // start. On device this will configure the connected displays. Off device
+  // this will create one or more fake displays and pretend to configure them. A
+  // non-null |delegate| must be provided that will receive notifications when
+  // displays are added, removed or modified.

[rjkroege, 2017/01/23 21:19:43]

Does external mode need a delegate? I don't remember. The comments should say.

[fwang, 2017/01/24 17:11:51]

Mmh, code in screen manager seems to assume the delegate_ point is non-null so I
would say yes.

+  virtual void Init(ScreenManagerDelegate* delegate,
+                    WindowMode window_mode) = 0;
 
   // Handle requests from the platform to close a display.
   virtual void RequestCloseDisplay(int64_t display_id) = 0;
 
   virtual int64_t GetPrimaryDisplayId() const = 0;
 
  private:
   static ScreenManager* instance_;  // Instance is not owned.
 
   DISALLOW_COPY_AND_ASSIGN(ScreenManager);
 };
 
 }  // namespace display
 
 #endif  // SERVICES_UI_DISPLAY_SCREEN_MANAGER_H_