| // Copyright 2015 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 UI_ACCELERATED_WIDGET_MAC_WINDOW_RESIZE_HELPER_MAC_H_ |
| #define UI_ACCELERATED_WIDGET_MAC_WINDOW_RESIZE_HELPER_MAC_H_ |
| |
| #include "base/lazy_instance.h" |
| #include "base/macros.h" |
| #include "base/memory/ref_counted.h" |
| #include "ui/accelerated_widget_mac/accelerated_widget_mac_export.h" |
| |
| namespace base { |
| class SingleThreadTaskRunner; |
| class TimeDelta; |
| class WaitableEvent; |
| } |
| |
| namespace ui { |
| |
| // WindowResizeHelperMac is used to make resize appear smooth. That is to |
| // say, make sure that the window size and the size of the contents being drawn |
| // in that window are resized in lock-step. This is accomplished by waiting |
| // inside AppKit drawing routines on the UI thread for the compositor to produce |
| // a frame of same size as the NSView that hosts an AcceleratedWidgetMac. When a |
| // resize occurs, the view controller can wait for a frame of the correct size |
| // by calling WindowResizeHelperMac::WaitForSingleTaskToRun() until a timeout |
| // occurs, or the corresponding AcceleratedWidgetMac has a renderer frame of the |
| // same size as its NSView. |
| // |
| // By posting tasks to the custom task_runner(), other threads indicate tasks |
| // that are required to pick up a new frame. In the ordinary run of things these |
| // would be posted to the |target_task_runner|; the UI thread given as an |
| // argument to Init(). Posting instead to task_runner() will cause the tasks to |
| // be posted to the UI thread (as usual), and will also enqueue them into a |
| // queue which will be read and run in WaitForSingleTaskToRun(), potentially |
| // before the task posted to the UI thread is run. Some care is taken (see |
| // WrappedTask) to make sure that the messages are only executed once. |
| // |
| // This is further complicated because, in order for a frame to appear, it is |
| // also necessary to run tasks posted by the ui::Compositor. To accomplish this, |
| // the task_runner() that WindowResizeHelperMac provides can be used to |
| // construct a ui::Compositor. When the Compositor posts tasks to it, they are |
| // enqueued in the aforementioned queue, which may be pumped by |
| // WindowResizeHelperMac::WaitForSingleTaskToRun(). |
| class ACCELERATED_WIDGET_MAC_EXPORT WindowResizeHelperMac { |
| public: |
| static WindowResizeHelperMac* Get(); |
| |
| // Initializes the pumpable task_runner(), providing it with the task runner |
| // for UI thread tasks. task_runner() will be null before Init() is called, |
| // and WaitForSingleTaskToRun() will immediately return false. |
| void Init( |
| const scoped_refptr<base::SingleThreadTaskRunner>& target_task_runner); |
| |
| // Because this class is global, many tests may want to do this setup |
| // repeatedly, so need some way to uninitialize as well. |
| void ShutdownForTests(); |
| |
| scoped_refptr<base::SingleThreadTaskRunner> task_runner() const; |
| |
| // UI THREAD ONLY ----------------------------------------------------------- |
| |
| // Waits at most |max_delay| for a task to run. Returns true if a task ran, |
| // false if no task ran. |
| bool WaitForSingleTaskToRun(const base::TimeDelta& max_delay); |
| |
| private: |
| friend struct base::DefaultLazyInstanceTraits<WindowResizeHelperMac>; |
| WindowResizeHelperMac(); |
| ~WindowResizeHelperMac(); |
| |
| // This helper is needed to create a ScopedAllowWait inside the scope of a |
| // class where it is allowed. |
| static void EventTimedWait(base::WaitableEvent* event, base::TimeDelta delay); |
| |
| // The task runner to which the helper will post tasks. This also maintains |
| // the task queue and does the actual work for WaitForSingleTaskToRun. |
| scoped_refptr<base::SingleThreadTaskRunner> task_runner_; |
| |
| DISALLOW_COPY_AND_ASSIGN(WindowResizeHelperMac); |
| }; |
| |
| } // namespace ui |
| |
| #endif // UI_ACCELERATED_WIDGET_MAC_WINDOW_RESIZE_HELPER_MAC_H_ |