[MPlayer-dev-eng] delete draw_slice stub in vo_corevideo.m

[Reimar Döffinger]

On Tue, Jan 21, 2014 at 01:01:45PM +0900, Zongyao Qu wrote:
> ​when deleting draw_frame , mplayer will crash at filter_video
> 
> I don't have time to look into it. I just thought there must at least one
> draw_ xx function there.​

There should be no such requirement, however a crash is possible
in cases that would have caused incorrect output already before.
Basically not implementing draw_slice is incorrect for all VOs that
support YUV formats, unless they use VOCAP_NOSLICES.
This is the main reason why I decided to go with NULL instead of a stub
function, it should make these kind of bugs fairly obvious.
Except that I see this one does not support YUV formats, so something
else is wrong here.
I suspect the reason is that draw_image incorrect returns 0 when it
should return VO_TRUE on success.
This causes MPlayer to try to draw the frame via the other functions.