1 files changed, 97 insertions, 0 deletions
diff --git a/gfx/layers/ipc/CanvasThread.h b/gfx/layers/ipc/CanvasThread.h
new file mode 100644
index 0000000000..ebcd4bc8d5
--- /dev/null
+++ b/gfx/layers/ipc/CanvasThread.h
@@ -0,0 +1,97 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_layers_CanvasThread_h
+#define mozilla_layers_CanvasThread_h
+
+#include "mozilla/layers/CompositorThread.h"
+#include "mozilla/DataMutex.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/TaskQueue.h"
+#include "nsIThreadPool.h"
+
+namespace mozilla {
+namespace layers {
+
+/**
+ * The CanvasThreadHolder is used to manage the lifetime of the canvas
+ * thread (IPC) and workers and also provides methods for using them.
+ */
+class CanvasThreadHolder final {
+  // We only AddRef/Release on the Compositor thread.
+  NS_INLINE_DECL_REFCOUNTING(CanvasThreadHolder)
+
+ public:
+  /**
+   * Ensures that the canvas thread and workers are created.
+   * This must be called on the compositor thread.
+   * @return a CanvasThreadHolder
+   */
+  static already_AddRefed<CanvasThreadHolder> EnsureCanvasThread();
+
+  /**
+   * Used to release CanvasThreadHolder references, which must be released on
+   * the compositor thread.
+   * @param aCanvasThreadHolder the reference to release
+   */
+  static void ReleaseOnCompositorThread(
+      already_AddRefed<CanvasThreadHolder> aCanvasThreadHolder);
+
+  /**
+   * @return true if in the canvas thread
+   */
+  static bool IsInCanvasThread();
+
+  /**
+   * @return true if in a canvas worker thread
+   */
+  static bool IsInCanvasWorker();
+
+  /**
+   * @return true if in the canvas thread or worker
+   */
+  static bool IsInCanvasThreadOrWorker();
+
+  /**
+   * Static method to dispatch a runnable to the canvas thread. If there is no
+   * canvas thread this will just release aRunnable.
+   * @param aRunnable the runnable to dispatch
+   */
+  static void MaybeDispatchToCanvasThread(
+      already_AddRefed<nsIRunnable> aRunnable);
+
+  /**
+   * Dispatch a runnable to the canvas thread.
+   * @param aRunnable the runnable to dispatch
+   */
+  void DispatchToCanvasThread(already_AddRefed<nsIRunnable> aRunnable);
+
+  /**
+   * Create a TaskQueue for the canvas worker threads. This must be shutdown
+   * before the reference to CanvasThreadHolder is dropped.
+   * @return a TaskQueue that dispatches to the canvas worker threads
+   */
+  already_AddRefed<TaskQueue> CreateWorkerTaskQueue();
+
+ private:
+  static StaticDataMutex<StaticRefPtr<CanvasThreadHolder>> sCanvasThreadHolder;
+
+  CanvasThreadHolder(already_AddRefed<nsISerialEventTarget> aCanvasThread,
+                     already_AddRefed<nsIThreadPool> aCanvasWorkers);
+
+  ~CanvasThreadHolder();
+
+  nsCOMPtr<nsISerialEventTarget> mCanvasThread;
+  RefPtr<nsIThreadPool> mCanvasWorkers;
+
+  // Hold a reference to prevent the compositor thread ending.
+  RefPtr<CompositorThreadHolder> mCompositorThreadKeepAlive;
+};
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif  // mozilla_layers_CanvasThread_h