Make GTK and Aura parts orthogonal to OS parts

content/public/browser/browser_main_parts.h

+// Copyright (c) 2011 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 CONTENT_PUBLIC_BROWSER_BROWSER_MAIN_PARTS_H_
+#define CONTENT_PUBLIC_BROWSER_BROWSER_MAIN_PARTS_H_
+#pragma once
+
+#include "base/basictypes.h"
+#include "content/common/content_export.h"
+
+namespace content {
+
+// This class contains different "stages" to be executed by |BrowserMain()|,
+// Each stage is represented by a single BrowserMainParts method, called from
+// the corresponding method in |BrowserMainLoop| (e.g., EarlyInitialization())
+// which does the following:
+//  - calls a method (e.g., "PreEarlyInitialization()") for each member of
+//    |parts_|. Parts will implement platform or tookit specific code for that
+//    stage.
+//  - calls various methods for things common to all platforms (for that stage).
+//  - calls a method (e.g., "PostEarlyInitialization()") for platform-specific
+//    code to be called after the common code.
+//
+// Stages:
+//  - EarlyInitialization: things which should be done as soon as possible on
+//    program start (such as setting up signal handlers) and things to be done
+//    at some generic time before the start of the main message loop.
+//  - MainMessageLoopStart: things beginning with the start of the main message
+//    loop and ending with initialization of the main thread; platform-specific
+//    things which should be done immediately before the start of the main
+//    message loop should go in |PreMainMessageLoopStart()|.
+//  - RunMainMessageLoopParts:  things to be done before and after invoking the
+//    main message loop run method (e.g. MessageLoopForUI::current()->Run()).
+//
+// How to add stuff (to existing parts):
+//  - Figure out when your new code should be executed. What must happen
+//    before/after your code is executed? Are there performance reasons for
+//    running your code at a particular time? Document these things!
+//  - Split out any platform-specific bits. Please avoid #ifdefs it at all
+//    possible. You have two choices for platform-specific code: (1) Execute it
+//    from one of the platform-specific |Pre/Post...()| methods; do this if the
+//    code is unique to a platform type. Or (2) execute it from one of the
+//    "parts" (e.g., |EarlyInitialization()|) and provide platform-specific
+//    implementations of your code (in a virtual method); do this if you need to
+//    provide different implementations across most/all platforms.
+//  - Unless your new code is just one or two lines, put it into a separate
+//    method with a well-defined purpose. (Likewise, if you're adding to an
+//    existing chunk which makes it longer than one or two lines, please move
+//    the code out into a separate method.)
+//
+// There can be any number of "Parts". These should be constructed in
+// ContentBrowserClient::CreateBrowserMainParts. Each stage will be called
+// for each part in the order it was added. Destruction is in the inverse order.
+class CONTENT_EXPORT BrowserMainParts {
+ public:
+  BrowserMainParts() {}
+  virtual ~BrowserMainParts() {}
+
+  virtual void PreEarlyInitialization() = 0;
+
+  virtual void PostEarlyInitialization() = 0;
+
+  virtual void PreMainMessageLoopStart() = 0;
+
+  // Allows an embedder to do any extra toolkit initialization.
+  virtual void ToolkitInitialized() = 0;
+
+  virtual void PostMainMessageLoopStart() = 0;
+
+  virtual void PreMainMessageLoopRun() = 0;
+
+  // Returns true if the message loop was run, false otherwise.
+  // May set |result_code|, which will be returned by |BrowserMain()|.
+  // If no BrowserMainParts implementations return true, the default
+  // implementation will be run.
+  virtual bool MainMessageLoopRun(int* result_code) = 0;
+
+  virtual void PostMainMessageLoopRun() = 0;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(BrowserMainParts);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_BROWSER_BROWSER_MAIN_PARTS_H_