在PyGI中获取窗口句柄

Question

在我的程序中，我使用PyGObject/PyGI和GStreamer在我的GUI中显示一个视频。视频显示在一个Gtk.DrawingArea中，因此我需要在realize信号处理程序中获得它的窗口句柄。在Linux上，我可以使用以下方法获得这个句柄：

drawing_area.get_property('window').get_xid()

但是我如何获得Windows的句柄呢？

我在互联网上搜索，但只找到了PyGtk使用window.handle的例子，而使用PyGI则不起作用。

GStreamer文档提供了一个示例，它使用GDK_WINDOW_HWND宏获取句柄。这个宏使用AFAIK gdk_win32_drawable_get_handle。但是如何使用PyGI在Python中实现呢？

更新15-07-28:添加(简化)代码

我仍然无法在Windows上播放视频。

问题1:我无法在_on_video_realize()中获得窗口句柄。

问题2:方法_on_player_sync_message()从未被调用。

class MultimediaPlayer:
    def __init__(self):
        # ... some init stuff ...

        self._drawing_area.connect('realize', self._on_video_realize)
        self._drawing_area.connect('unrealize', self._on_video_unrealize)

        # GStreamer setup
        # ---------------
        self._player = Gst.ElementFactory.make('playbin', 'MultimediaPlayer')
        bus = self._player.get_bus()
        bus.add_signal_watch()
        bus.connect('message', self._on_player_message)
        bus.enable_sync_message_emission()
        bus.connect('sync-message::element', self._on_player_sync_message)

    def _on_video_realize(self, widget):
        print('----------> _on_video_realize')
        # The xid must be retrieved first in GUI-thread and before
        # playing pipeline.
        if sys.platform == "win32":
            self._drawing_area.get_property('window').ensure_native()
            # -------------------------------------------------------------
            # TODO [PROBLEM 1] How to get handle here?
            #                  self._drawing_area.GetHandle() does not exist!
            # -------------------------------------------------------------
        else:
            self._wnd_hnd = (self._drawing_area.get_property('window')
                                                                    .get_xid())

    def _on_video_unrealize(self, widget):
        self._player.set_state(Gst.State.NULL)

    def _on_player_message(self, bus, message):
        # ... handle some messages here ...

    def _on_player_sync_message(self, bus, message):
        # ---------------------------------------------------------------------
        # TODO [PROBLEM 2] This method is never called on Windows after opening
        #                  a video_file! But on Linux it is!
        # ---------------------------------------------------------------------

        print('----------> _on_player_sync_message')
        if message.get_structure() is None:
            return True
        if message.get_structure().get_name() == "prepare-window-handle":
            imagesink = message.src
            imagesink.set_property("force-aspect-ratio", True)
            imagesink.set_window_handle(self._wnd_hnd)

    def play(self):
        self._player.set_state(Gst.State.PLAYING)

    def stop(self):
        self._player.set_state(Gst.State.NULL)

    def set_file(self, file):
        # ... 
        self._player.set_property('uri', "file:///" + file)

Answer 1

我终于拿到了。为了解决“窗口句柄”-issue，我使用Marwin (请看这里)的解决方案/黑客：

def _on_video_realize(self, widget):
    # The window handle must be retrieved first in GUI-thread and before
    # playing pipeline.
    video_window = self._drawing_area.get_property('window')
    if sys.platform == "win32":
        if not video_window.ensure_native():
            print("Error - video playback requires a native window")
        ctypes.pythonapi.PyCapsule_GetPointer.restype = ctypes.c_void_p
        ctypes.pythonapi.PyCapsule_GetPointer.argtypes = [ctypes.py_object]
        drawingarea_gpointer = ctypes.pythonapi.PyCapsule_GetPointer(video_window.__gpointer__, None)
        gdkdll = ctypes.CDLL ("libgdk-3-0.dll")
        self._video_window_handle = gdkdll.gdk_win32_window_get_handle(drawingarea_gpointer)
    else:
        self._video_window_handle = video_window.get_xid()

但也有一个问题，就是“同步消息”-handler从未被调用过。我发现并不是所有的视频接收器都支持嵌入式视频，请看这里。例如，d3dvideosink确实支持嵌入式视频，但是我在虚拟机中运行Windows，即使激活了3D硬件加速，它也可能无法工作。在非虚拟化的Windows上运行相同的代码将导致对“同步消息”-handler的回调，在该回调中可以设置以前获取的窗口句柄：

def _on_player_sync_message(self, bus, message):
    if message.get_structure() is None:
        return
    if not GstVideo.is_video_overlay_prepare_window_handle_message(message):
        return
    imagesink = message.src
    imagesink.set_property("force-aspect-ratio", True)
    imagesink.set_window_handle(self._video_window_handle)

Windows上的回放现在运行良好。

Answer 2

你试过：

def OnSyncMessage(self, bus, msg):
    if msg.get_structure() is None:
        return True
    message_name = msg.get_structure().get_name()
    if message_name == 'prepare-window-handle':
        imagesink = msg.src
        imagesink.set_property('force-aspect-ratio', True)
        imagesink.set_window_handle(self.DrawingArea.GetHandle())
    return True