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virtual | ~VideoOverlay () |
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GstVideoOverlay* | gobj () |
| Provides access to the underlying C GObject. More...
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const GstVideoOverlay* | gobj () const |
| Provides access to the underlying C GObject. More...
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void | set_window_handle (guintptr window_handle) |
| This will call the video overlay's set_window_handle method. More...
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void | got_window_handle (guintptr window_handle) |
| This will post a "have-window-handle" element message on the bus. More...
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void | prepare_window_handle () |
| This will post a "prepare-window-handle" element message on the bus to give applications an opportunity to call gst_video_overlay_set_window_handle() before a plugin creates its own window. More...
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void | expose () |
| Tell an overlay that it has been exposed. More...
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void | handle_events (bool handle_events) |
| Tell an overlay that it should handle events from the window system. More...
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bool | set_render_rectangle (int x, int y, int width, int height) |
| Configure a subregion as a video target within the window set by gst_video_overlay_set_window_handle(). More...
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An interface for setting/getting a Window on elements supporting it.
The VideoOverlay interface is used for 2 main purposes :
- To get a grab on the Window where the video sink element is going to render. This is achieved by either being informed about the Window identifier that the video sink element generated, or by forcing the video sink element to use a specific Window identifier for rendering.
- To force a redrawing of the latest video frame the video sink element displayed on the Window. Indeed if the Pipeline is in STATE_PAUSED state, moving the Window around will damage its content. Application developers will want to handle the Expose events themselves and force the video sink element to refresh the Window's content.
Using the Window created by the video sink is probably the simplest scenario, in some cases, though, it might not be flexible enough for application developers if they need to catch events such as mouse moves and button clicks.
Setting a specific Window identifier on the video sink element is the most flexible solution but it has some issues. Indeed the application needs to set its Window identifier at the right time to avoid internal Window creation from the video sink element. To solve this issue a Message is posted on the bus to inform the application that it should set the Window identifier immediately. Here is an example on how to do that correctly:
#include <gdk/gdkx.h>
...
void PlayerWindow::on_bus_message_sync(
const Glib::RefPtr<Gst::Message>& message)
{
return;
if(!message->get_structure().has_name("prepare-xwindow-id"))
return;
Glib::RefPtr<Gst::Element> element =
Glib::RefPtr<Gst::Element>::cast_dynamic(message->get_source());
Glib::RefPtr< Gst::ElementInterfaced<Gst::XOverlay> > xoverlay =
Gst::Interface::cast <Gst::XOverlay>(element);
if(xoverlay)
{
const gulong xWindowId =
GDK_WINDOW_XID(widget->get_window()->gobj());
xoverlay->set_xwindow_id(xWindowId);
}
}
...
int main (int argc, char *argv[])
{
...
Glib::RefPtr<Gst::Bus> bus = pipeline->get_bus();
bus->enable_sync_message_emission();
bus->signal_sync_message().connect(
sigc::mem_fun(*this, &PlayerWindow::on_bus_message_sync));
...
}