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, 2 insertions, 3 deletions

diff --git a/video/out/vo.c b/video/out/vo.c
index 6f876d1898..a069c442df 100644
--- a/video/out/vo.c
+++ b/video/out/vo.c
@@ -202,7 +202,7 @@ void vo_queue_image(struct vo *vo, struct mp_image *mpi)
 
 int vo_redraw_frame(struct vo *vo)
 {
-    if (!vo->config_ok || !vo->hasframe)
+    if (!vo->config_ok)
         return -1;
     if (vo_control(vo, VOCTRL_REDRAW_FRAME, NULL) == true) {
         vo->want_redraw = false;
@@ -214,7 +214,7 @@ int vo_redraw_frame(struct vo *vo)
 
 bool vo_get_want_redraw(struct vo *vo)
 {
-    if (!vo->config_ok || !vo->hasframe)
+    if (!vo->config_ok)
         return false;
     return vo->want_redraw;
 }
@@ -289,7 +289,6 @@ void vo_seek_reset(struct vo *vo)
 {
     vo_control(vo, VOCTRL_RESET, NULL);
     vo->frame_loaded = false;
-    vo->hasframe = false;
     mp_image_unrefp(&vo->waiting_mpi);
 }