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// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <memory>
#include <string>
#include <vector>
#include "build/build_config.h"
#include "content/common/content_export.h"
#include "content/public/common/main_function_params.h"
#include "third_party/abseil-cpp/absl/types/optional.h"
#include "third_party/abseil-cpp/absl/types/variant.h"
namespace variations {
class VariationsIdsProvider;
namespace content {
class ContentBrowserClient;
class ContentClient;
class ContentGpuClient;
class ContentRendererClient;
class ContentUtilityClient;
class ZygoteForkDelegate;
class CONTENT_EXPORT ContentMainDelegate {
// Indicates the delegate is being invoked in the browser process. The
// `kProcessType` switch will be empty.
struct InvokedInBrowserProcess {
// True if running in a test harness.
bool is_running_test = false;
// Indicates the delegate is being invoked in a child process. The
// `kProcessType` switch will hold the precise child process type.
struct InvokedInChildProcess {};
// The context in which a delegate method is invoked, including the process
// type and whether it is in a test harness. Can distinguish between
// the browser process and child processes; for more fine-grained process
// types check the `switches::kProcessType` command-line switch.
using InvokedIn =
absl::variant<InvokedInBrowserProcess, InvokedInChildProcess>;
virtual ~ContentMainDelegate() = default;
// 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 an
// error code if the process should exit afterwards. 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, handling of early exit
// command-line switches can wait until PreBrowserMain at the latest.
virtual absl::optional<int> BasicStartupComplete();
// 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. The embedder may return the
// |main_function_params| back to decline the request and kick-off the
// default behavior or return a non-negative exit code to indicate it handled
// the request.
virtual absl::variant<int, MainFunctionParams> RunProcess(
const std::string& process_type,
MainFunctionParams main_function_params);
// Called right before the process exits.
virtual void ProcessExiting(const std::string& process_type) {}
// 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<ZygoteForkDelegate>>* delegates);
// Called every time the zygote process forks.
virtual void ZygoteForked() {}
// 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();
// 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();
// Allows the embedder to perform platform-specific initialization before
// BrowserMain() is invoked (i.e. before BrowserMainRunner, BrowserMainLoop,
// BrowserMainParts, etc. are created). Return an error code if the process
// should exit afterwards. This is the place for embedder to do the things
// that can shortcut browser execution (i.e. command-line switches).
virtual absl::optional<int> PreBrowserMain();
// 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(InvokedIn invoked_in);
// Returns true if content should initialize Mojo before calling
// PostEarlyInitialization(). Returns true by default. If this returns false,
// the embedder must initialize Mojo. Embedders may wish to override this to
// control when Mojo is initialized; for example, Mojo needs to be initialized
// after FeatureList, so embedders who delay FeatureList setup must also delay
// Mojo setup.
virtual bool ShouldInitializeMojo(InvokedIn invoked_in);
// Creates and returns the VariationsIdsProvider. If null is returned,
// a VariationsIdsProvider is created with a mode of `kUseSignedInState`.
// VariationsIdsProvider is a singleton.
virtual variations::VariationsIdsProvider* CreateVariationsIdsProvider();
// Allows the embedder to perform its own initialization after early content
// initialization.
// At this point, it is possible to post to base::ThreadPool, but the tasks
// won't run until base::ThreadPoolInstance::Start() is called.
// It is also possible to post tasks to the main thread loop via
// base::ThreadTaskRunnerHandle. These tasks won't run until
// base::RunLoop::Run() is called on the main thread, which happens after all
// ContentMainDelegate entry points.
// If ShouldCreateFeatureList() returns true for `invoked_in`, the
// field trials and FeatureList have been initialized. Otherwise, the
// implementation must initialize the field trials and FeatureList before
// returning from PostEarlyInitialization. Return an error code if the process
// should exit afterwards.
virtual absl::optional<int> PostEarlyInitialization(InvokedIn invoked_in);
// Allows the embedder to indicate that console control events (e.g., Ctrl-C,
// Ctrl-break, or closure of the console) are to be handled. By default, these
// events are not handled, leading to process termination. When an embedder
// returns true to indicate that these events are to be handled, the
// embedder's ContentBrowserClient::SessionEnding function will be called
// when a console control event is received. All non-browser processes will
// swallow the event.
virtual bool ShouldHandleConsoleControlEvents();
friend class ContentClientCreator;
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 ContentClient* CreateContentClient();
virtual ContentBrowserClient* CreateContentBrowserClient();
virtual ContentGpuClient* CreateContentGpuClient();
virtual ContentRendererClient* CreateContentRendererClient();
virtual ContentUtilityClient* CreateContentUtilityClient();
} // namespace content