video/out: always support redrawing VO window at any point

Before, a VO could easily refuse to respond to VOCTRL_REDRAW_FRAME,
which means the VO wouldn't redraw OSD and window contents, and the
player would appear frozen to the user. This was a bit stupid, and makes
dealing with some corner cases much harder (think of --keep-open, which
was hard to implement, because the VO gets into this state if there are
no new video frames after a seek reset).

Change this, and require VOs to always react to VOCTRL_REDRAW_FRAME.
There are two aspects of this: First, behavior after a (successful)
vo_reconfig() call, but before any video frame has been displayed.
Second, behavior after a vo_seek_reset().

For the first issue, we define that sending VOCTRL_REDRAW_FRAME after
vo_reconfig() should clear the window with black. This requires minor
changes to some VOs. In particular vaapi makes this horribly
complicated, because OSD rendering is bound to a video surface. We
create a black dummy surface for this purpose.

The second issue is much simpler and works already with most VOs: they
simply redraw whatever has been uploaded previously. The exception is
vdpau, which has a complicated mechanism to track and filter video
frames. The state associated with this mechanism is completely cleared
with vo_seek_reset(), so implementing this to work as expected is not
trivial. For now, we just clear the window with black.

1 files changed, 5 insertions, 2 deletions

diff --git a/video/out/vo_x11.c b/video/out/vo_x11.c
index 98d7a23534..6932cb68f2 100644
--- a/video/out/vo_x11.c
+++ b/video/out/vo_x11.c
@@ -490,8 +490,10 @@ static int redraw_frame(struct vo *vo)
 {
     struct priv *p = vo->priv;
 
-    if (!p->original_image)
+    if (!p->original_image) {
+        vo_x11_clear_background(vo, &(struct mp_rect){0, 0, vo->dwidth, vo->dheight});
         return false;
+    }
 
     draw_image(vo, p->original_image);
     return true;
@@ -628,7 +630,8 @@ static int control(struct vo *vo, uint32_t request, void *data)
         resize(vo);
         return VO_TRUE;
     case VOCTRL_REDRAW_FRAME:
-        return redraw_frame(vo);
+        redraw_frame(vo);
+        return true;
     case VOCTRL_WINDOW_TO_OSD_COORDS: {
         // OSD is rendered into the scaled image
         float *c = data;