Linux: Add multi-threaded message loop support (issue #2512)

tests/cefclient/browser/main_message_loop_multithreaded_gtk.cc

@@ -0,0 +1,155 @@
+// Copyright (c) 2018 The Chromium Embedded Framework 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 "tests/cefclient/browser/main_message_loop_multithreaded_gtk.h"
+
+#include <X11/Xlib.h>
+#include <gtk/gtkmain.h>
+
+#include "include/base/cef_bind.h"
+#include "include/base/cef_logging.h"
+#include "include/wrapper/cef_closure_task.h"
+
+namespace client {
+
+namespace {
+
+base::Lock g_global_lock;
+base::PlatformThreadId g_global_lock_thread = kInvalidPlatformThreadId;
+
+void lock_enter() {
+  // The GDK lock is not reentrant, so check that we're using it correctly.
+  // See comments on ScopedGdkThreadsEnter.
+  base::PlatformThreadId current_thread = base::PlatformThread::CurrentId();
+  CHECK(current_thread != g_global_lock_thread);
+
+  g_global_lock.Acquire();
+  g_global_lock_thread = current_thread;
+}
+
+void lock_leave() {
+  g_global_lock_thread = kInvalidPlatformThreadId;
+  g_global_lock.Release();
+}
+
+// Same as g_idle_add() but specifying the GMainContext.
+guint idle_add(GMainContext* main_context,
+               GSourceFunc function,
+               gpointer data) {
+  GSource* source = g_idle_source_new();
+  g_source_set_callback(source, function, data, nullptr);
+  guint id = g_source_attach(source, main_context);
+  g_source_unref(source);
+  return id;
+}
+
+// Same as g_timeout_add() but specifying the GMainContext.
+guint timeout_add(GMainContext* main_context,
+                  guint interval,
+                  GSourceFunc function,
+                  gpointer data) {
+  GSource* source = g_timeout_source_new(interval);
+  g_source_set_callback(source, function, data, nullptr);
+  guint id = g_source_attach(source, main_context);
+  g_source_unref(source);
+  return id;
+}
+
+}  // namespace
+
+MainMessageLoopMultithreadedGtk::MainMessageLoopMultithreadedGtk()
+    : thread_id_(base::PlatformThread::CurrentId()) {
+  // Initialize Xlib support for concurrent threads. This function must be the
+  // first Xlib function a multi-threaded program calls, and it must complete
+  // before any other Xlib call is made.
+  CHECK(XInitThreads() != 0);
+
+  // Initialize GDK thread support. See comments on ScopedGdkThreadsEnter.
+  gdk_threads_set_lock_functions(lock_enter, lock_leave);
+  gdk_threads_init();
+}
+
+MainMessageLoopMultithreadedGtk::~MainMessageLoopMultithreadedGtk() {
+  DCHECK(RunsTasksOnCurrentThread());
+  DCHECK(queued_tasks_.empty());
+}
+
+int MainMessageLoopMultithreadedGtk::Run() {
+  DCHECK(RunsTasksOnCurrentThread());
+
+  // Chromium uses the default GLib context so we create our own context and
+  // make it the default for this thread.
+  main_context_ = g_main_context_new();
+  g_main_context_push_thread_default(main_context_);
+
+  main_loop_ = g_main_loop_new(main_context_, TRUE);
+
+  // Check the queue when GTK is idle, or at least every 100ms.
+  // TODO(cef): It might be more efficient to use input functions
+  // (gdk_input_add) and trigger by writing to an fd.
+  idle_add(main_context_, MainMessageLoopMultithreadedGtk::TriggerRunTasks,
+           this);
+  timeout_add(main_context_, 100,
+              MainMessageLoopMultithreadedGtk::TriggerRunTasks, this);
+
+  // Block until g_main_loop_quit().
+  g_main_loop_run(main_loop_);
+
+  // Release GLib resources.
+  g_main_loop_unref(main_loop_);
+  main_loop_ = nullptr;
+
+  g_main_context_pop_thread_default(main_context_);
+  g_main_context_unref(main_context_);
+  main_context_ = nullptr;
+
+  return 0;
+}
+
+void MainMessageLoopMultithreadedGtk::Quit() {
+  PostTask(CefCreateClosureTask(base::Bind(
+      &MainMessageLoopMultithreadedGtk::DoQuit, base::Unretained(this))));
+}
+
+void MainMessageLoopMultithreadedGtk::PostTask(CefRefPtr<CefTask> task) {
+  base::AutoLock lock_scope(lock_);
+
+  // Queue the task.
+  queued_tasks_.push(task);
+}
+
+bool MainMessageLoopMultithreadedGtk::RunsTasksOnCurrentThread() const {
+  return (thread_id_ == base::PlatformThread::CurrentId());
+}
+
+// static
+int MainMessageLoopMultithreadedGtk::TriggerRunTasks(void* self) {
+  static_cast<MainMessageLoopMultithreadedGtk*>(self)->RunTasks();
+  return G_SOURCE_CONTINUE;
+}
+
+void MainMessageLoopMultithreadedGtk::RunTasks() {
+  DCHECK(RunsTasksOnCurrentThread());
+
+  std::queue<CefRefPtr<CefTask>> tasks;
+
+  {
+    base::AutoLock lock_scope(lock_);
+    tasks.swap(queued_tasks_);
+  }
+
+  // Execute all queued tasks.
+  while (!tasks.empty()) {
+    CefRefPtr<CefTask> task = tasks.front();
+    tasks.pop();
+    task->Execute();
+  }
+}
+
+void MainMessageLoopMultithreadedGtk::DoQuit() {
+  DCHECK(RunsTasksOnCurrentThread());
+  g_main_loop_quit(main_loop_);
+}
+
+}  // namespace client