This is another step in the gobjectification of the internal library
of gstreamer-vaapi. Now it is the turn of GstVaapiWindow and its
derivates.
The idea is to minimize the changeset keeping the same design as
much as possible.
GstVaapiWindow is defined as an abstract class with two properties:
the GstVaapiDisplay and the native ID. Thus, many of the
GstVaapiObject macros were copied as GstVaapiWindow macros.
The function gst_vaapi_window_new_internal() is kept as a decorator
of for calling gst_vaapi_window_create() and the possibility of
failure.
The descendant classes, such as glx, still use the private
structures, but through the gobject mechanism.
Since gst_vaapi_window_vpp_convert_internal is created,
GstVaapiWindowX11/Wayland can use it for conversion.
Note that once it chooses to use vpp, it's going to use vpp
until the session is finished.
https://bugzilla.gnome.org/show_bug.cgi?id=759533
Currently, GstVaapiWindowX11/Wayland are not descendants of GstVaapiWindow.
This patch chains them up to GstVaapiWindow to handle common members in GstVaapiWindow.
https://bugzilla.gnome.org/show_bug.cgi?id=759533
Add GstVaapiWindowClass::get_colormap() hook to help determine the
currently active colormap bound to the supplied window, or actually
create it if it does not already exist yet.
Add GstVaapiWindowClass::get_visual_id() function hook to help find
the best suitable visual id for the supplied window. While doing so,
also simplify the process by which an X11 window is created with a
desired Visual, i.e. now use a visual id instead of a Visual object.
Use hardware accelerated XRenderComposite() function, from the RENDER
extension, to blit a pixmap to screen. Besides, this can also support
cropping and scaling.
