content/public/app/content_main_delegate.h

// 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.

#ifndef CONTENT_PUBLIC_APP_CONTENT_MAIN_DELEGATE_H_
#define CONTENT_PUBLIC_APP_CONTENT_MAIN_DELEGATE_H_

#include <memory>
#include <string>
#include <vector>

#include "base/callback_forward.h"
#include "build/build_config.h"
#include "content/common/content_export.h"
#include "services/service_manager/embedder/process_type.h"

namespace base {
class CommandLine;
}

namespace service_manager {
class BackgroundServiceManager;
class Identity;
class ZygoteForkDelegate;
}  // namespace service_manager

namespace content {

class ContentBrowserClient;
class ContentGpuClient;
class ContentRendererClient;
class ContentUtilityClient;
struct MainFunctionParams;

class CONTENT_EXPORT ContentMainDelegate {
 public:
  virtual ~ContentMainDelegate() {}

  // Tells the embedder that the absolute basic startup has been done, i.e.
  // it's now safe to create singletons and check the command line. Return true
  // if the process should exit afterwards, and if so, |exit_code| should be
  // set. This is the place for embedder to do the things that must happen at
  // the start. Most of its startup code should be in the methods below.
  virtual bool BasicStartupComplete(int* exit_code);

  // This is where the embedder puts all of its startup code that needs to run
  // before the sandbox is engaged.
  virtual void PreSandboxStartup() {}

  // This is where the embedder can add startup code to run after the sandbox
  // has been initialized.
  virtual void SandboxInitialized(const std::string& process_type) {}

  // Asks the embedder to start a process. Return -1 for the default behavior.
  virtual int RunProcess(
      const std::string& process_type,
      const MainFunctionParams& main_function_params);

  // Called right before the process exits.
  virtual void ProcessExiting(const std::string& process_type) {}

#if defined(OS_MACOSX)
  // Returns true if the process registers with the system monitor, so that we
  // can allocate an IO port for it before the sandbox is initialized. Embedders
  // are called only for process types that content doesn't know about.
  virtual bool ProcessRegistersWithSystemProcess(
      const std::string& process_type);

  // Allows the embedder to override initializing the sandbox. This is needed
  // because some processes might not want to enable it right away or might not
  // want it at all.
  virtual bool DelaySandboxInitialization(const std::string& process_type);

#elif defined(OS_LINUX)
  // Tells the embedder that the zygote process is starting, and allows it to
  // specify one or more zygote delegates if it wishes by storing them in
  // |*delegates|.
  virtual void ZygoteStarting(
      std::vector<std::unique_ptr<service_manager::ZygoteForkDelegate>>*
          delegates);

  // Called every time the zygote process forks.
  virtual void ZygoteForked() {}
#endif  // defined(OS_LINUX)

  // Allows the embedder to prevent locking the scheme registry. The scheme
  // registry is the list of URL schemes we recognize, with some additional
  // information about each scheme such as whether it expects a host. The
  // scheme registry is not thread-safe, so by default it is locked before any
  // threads are created to ensure single-threaded access. An embedder can
  // override this to prevent the scheme registry from being locked during
  // startup, but if they do so then they are responsible for making sure that
  // the registry is only accessed in a thread-safe way, and for calling
  // url::LockSchemeRegistries() when initialization is complete. If possible,
  // prefer registering additional schemes through
  // ContentClient::AddAdditionalSchemes over preventing the scheme registry
  // from being locked.
  virtual bool ShouldLockSchemeRegistry();

  // Fatal errors during initialization are reported by this function, so that
  // the embedder can implement graceful exit by displaying some message and
  // returning initialization error code. Default behavior is CHECK(false).
  virtual int TerminateForFatalInitializationError();

  // Overrides the Service Manager process type to use for the currently running
  // process.
  virtual service_manager::ProcessType OverrideProcessType();

  // Allows the content embedder to adjust arbitrary command line arguments for
  // any service process started by the Service Manager.
  virtual void AdjustServiceProcessCommandLine(
      const service_manager::Identity& identity,
      base::CommandLine* command_line);

  // Allows the embedder to perform arbitrary initialization within the Service
  // Manager process immediately before the Service Manager runs its main loop.
  //
  // |quit_closure| is a callback the embedder may retain and invoke at any time
  // to cleanly terminate Service Manager execution.
  virtual void OnServiceManagerInitialized(
      const base::Closure& quit_closure,
      service_manager::BackgroundServiceManager* service_manager);

  // Allows the embedder to perform platform-specific initialization before
  // creating the main message loop.
  virtual void PreCreateMainMessageLoop() {}

  // Returns true if content should create field trials and initialize the
  // FeatureList instance for this process. Default implementation returns true.
  // Embedders that need to control when and/or how FeatureList should be
  // created should override and return false.
  virtual bool ShouldCreateFeatureList();

  // Allows the embedder to perform initialization once field trials/FeatureList
  // initialization has completed if ShouldCreateFeatureList() returns true.
  // Otherwise, the embedder is responsible for calling this method once feature
  // list initialization is complete.
  virtual void PostFieldTrialInitialization() {}

  // Allows the embedder to perform its own initialization after early content
  // initialization. At this point, it is possible to post to base::ThreadPool
  // or to the main thread loop via base::ThreadTaskRunnerHandle, but the tasks
  // won't run immediately.
  //
  // If ShouldCreateFeatureList() returns true, the field trials and FeatureList
  // have been initialized. Otherwise, the implementation must initialize the
  // field trials and FeatureList and call PostFieldTrialInitialization().
  //
  // |is_running_tests| indicates whether it is running in tests.
  virtual void PostEarlyInitialization(bool is_running_tests) {}

 protected:
  friend class ContentClientInitializer;
  friend class BrowserTestBase;

  // Called once per relevant process type to allow the embedder to customize
  // content. If an embedder wants the default (empty) implementation, don't
  // override this.
  virtual ContentBrowserClient* CreateContentBrowserClient();
  virtual ContentGpuClient* CreateContentGpuClient();
  virtual ContentRendererClient* CreateContentRendererClient();
  virtual ContentUtilityClient* CreateContentUtilityClient();
};

}  // namespace content

#endif  // CONTENT_PUBLIC_APP_CONTENT_MAIN_DELEGATE_H_