In GTK dispose can be called before the last ref is reached. This
happens when you close the container window. The dispose will be
explicitly called, and destroyed notify will be fired. This patch
fixes this race by properly tracking the widget state.
In the sink, we now set the widget pointer to NULL, so the widget
will properly get created again if you set your pipeline to NULL
state after the widget was destroy, and set it back to PLAYING.
https://bugzilla.gnome.org/show_bug.cgi?id=751104
Checking for a parent is not enough, it must have a toplevel one.
If widget has no toplevel parent then add it in a GtkWindow, that
make it usable from gst-launch-1.0.
https://bugzilla.gnome.org/show_bug.cgi?id=751104
This patch allow going gst-inspect-1.0 on these elements removing
ugly crash that was previously occurring. The method consist of
making the widget creation as lazy as possible. This way we don't
endup doing gtk_init() before the application. We also ref_sink()
the widget, so we don't crash if the parent widget is discarded,
and cleanly error out with GL if the widget has no parent window,
because calling gtk_widget_realized() can only be done if the widget
has been parented to a window).
