core, vo: modify OSD redraw architecture, support EOSD

Previously the core sent VFCTRL_REDRAW_OSD to change OSD contents over
the current frame. Change this to VFCTRL_REDRAW_FRAME followed by
normal EOSD and OSD drawing calls, then vo_flip_page(). The new
version supports changing EOSD contents for libass-rendered subtitles
and simplifies the redraw support code needed per VO. vo_xv doesn't
support EOSD changes because it relies on vf_ass to render EOSD
contents earlier in the filter chain.

vo_xv logic is additionally simplified because the previous commit
removed the need to track the status of current and next images
separately (now each frame is guaranteed to become "visible" soon
after we receive it as "next", with no VO code running in the interval
between).

1 files changed, 2 insertions, 4 deletions

diff --git a/libmpcodecs/vf_expand.c b/libmpcodecs/vf_expand.c
index 95580b9f26..a640108e0e 100644
--- a/libmpcodecs/vf_expand.c
+++ b/libmpcodecs/vf_expand.c
@@ -452,10 +452,6 @@ static int control(struct vf_instance *vf, int request, void* data){
     case VFCTRL_DRAW_OSD:
 	if(vf->priv->osd_enabled) return CONTROL_TRUE;
         break;
-    case VFCTRL_REDRAW_OSD:
-        if (vf->priv->osd_enabled)
-            return false;
-        break;
     }
 #endif
     return vf_next_control(vf,request,data);
@@ -481,6 +477,8 @@ static int vf_open(vf_instance_t *vf, char *args){
     vf->priv->osd_enabled,
     vf->priv->aspect,
     vf->priv->round);
+    if (vf->priv->osd_enabled)
+        vf->default_caps = VFCAP_OSD_FILTER;
     return 1;
 }