vo_opengl: allow backends to provide callbacks for custom event loops

Until now, this has been either handled over vo.event_fd (which should
go away), or by putting event handling on a separate thread. The
backends which do the latter do it for a reason and won't need this, but
X11 and Wayland will, in order to get rid of event_fd.

video/out/opengl/context.h

@@ -63,6 +63,11 @@ struct mpgl_driver {
     // This behaves exactly like vo_driver.control().
     int (*control)(struct MPGLContext *ctx, int *events, int request, void *arg);
 
+    // These behave exactly like vo_driver.wakeup/wait_events. They are
+    // optional.
+    void (*wakeup)(struct MPGLContext *ctx);
+    void (*wait_events)(struct MPGLContext *ctx, int64_t until_time_us);
+
     // Destroy the GL context and possibly the underlying VO backend.
     void (*uninit)(struct MPGLContext *ctx);
 };

video/out/vo.c

@@ -610,27 +610,39 @@ static void wait_event_fd(struct vo *vo, int64_t until_time){}
 static void wakeup_event_fd(struct vo *vo){}
 #endif
 
+// VOs which have no special requirements on UI event loops etc. can set the
+// vo_driver.wait_events callback to this (and leave vo_driver.wakeup unset).
+// This function must not be used or called for other purposes.
+void vo_wait_default(struct vo *vo, int64_t until_time)
+{
+    struct vo_internal *in = vo->in;
+
+    pthread_mutex_lock(&in->lock);
+    if (!in->need_wakeup) {
+        struct timespec ts = mp_time_us_to_timespec(until_time);
+        pthread_cond_timedwait(&in->wakeup, &in->lock, &ts);
+    }
+    pthread_mutex_unlock(&in->lock);
+}
+
 // Called unlocked.
 static void wait_vo(struct vo *vo, int64_t until_time)
 {
     struct vo_internal *in = vo->in;
 
     if (vo->event_fd >= 0) {
+        // old/deprecated code path
         wait_event_fd(vo, until_time);
         pthread_mutex_lock(&in->lock);
         in->need_wakeup = false;
         pthread_mutex_unlock(&in->lock);
-    } else if (vo->driver->wait_events) {
-        vo->driver->wait_events(vo, until_time);
-        pthread_mutex_lock(&in->lock);
-        in->need_wakeup = false;
-        pthread_mutex_unlock(&in->lock);
     } else {
-        pthread_mutex_lock(&in->lock);
-        if (!in->need_wakeup) {
-            struct timespec ts = mp_time_us_to_timespec(until_time);
-            pthread_cond_timedwait(&in->wakeup, &in->lock, &ts);
+        if (vo->driver->wait_events) {
+            vo->driver->wait_events(vo, until_time);
+        } else {
+            vo_wait_default(vo, until_time);
         }
+        pthread_mutex_lock(&in->lock);
         in->need_wakeup = false;
         pthread_mutex_unlock(&in->lock);
     }

video/out/vo.h

@@ -282,7 +282,7 @@ struct vo_driver {
      * immediately.
      */
     void (*wakeup)(struct vo *vo);
-    int (*wait_events)(struct vo *vo, int64_t until_time_us);
+    void (*wait_events)(struct vo *vo, int64_t until_time_us);
 
     /*
      * Closes driver. Should restore the original state of the system.
@@ -370,6 +370,7 @@ double vo_get_display_fps(struct vo *vo);
 double vo_get_delay(struct vo *vo);
 
 void vo_wakeup(struct vo *vo);
+void vo_wait_default(struct vo *vo, int64_t until_time);
 
 struct mp_keymap {
   int from;

video/out/vo_drm.c

@@ -253,9 +253,7 @@ static void acquire_vt(void *data)
     crtc_setup(vo);
 }
 
-
-
-static int wait_events(struct vo *vo, int64_t until_time_us)
+static void wait_events(struct vo *vo, int64_t until_time_us)
 {
     struct priv *p = vo->priv;
     if (p->vt_switcher_active) {
@@ -263,7 +261,6 @@ static int wait_events(struct vo *vo, int64_t until_time_us)
         int timeout_ms = MPCLAMP((wait_us + 500) / 1000, 0, 10000);
         vt_switcher_poll(&p->vt_switcher, timeout_ms);
     }
-    return 0;
 }
 
 static void wakeup(struct vo *vo)

video/out/vo_opengl.c

@@ -357,6 +357,23 @@ static int control(struct vo *vo, uint32_t request, void *data)
     return r;
 }
 
+static void wakeup(struct vo *vo)
+{
+    struct gl_priv *p = vo->priv;
+    if (p->glctx->driver->wakeup)
+        p->glctx->driver->wakeup(p->glctx);
+}
+
+static void wait_events(struct vo *vo, int64_t until_time_us)
+{
+    struct gl_priv *p = vo->priv;
+    if (p->glctx->driver->wait_events) {
+        p->glctx->driver->wait_events(p->glctx, until_time_us);
+    } else {
+        vo_wait_default(vo, until_time_us);
+    }
+}
+
 static void uninit(struct vo *vo)
 {
     struct gl_priv *p = vo->priv;
@@ -466,6 +483,8 @@ const struct vo_driver video_out_opengl = {
     .control = control,
     .draw_frame = draw_frame,
     .flip_page = flip_page,
+    .wait_events = wait_events,
+    .wakeup = wakeup,
     .uninit = uninit,
     .priv_size = sizeof(struct gl_priv),
     .options = options,
@@ -481,6 +500,8 @@ const struct vo_driver video_out_opengl_hq = {
     .control = control,
     .draw_frame = draw_frame,
     .flip_page = flip_page,
+    .wait_events = wait_events,
+    .wakeup = wakeup,
     .uninit = uninit,
     .priv_size = sizeof(struct gl_priv),
     .priv_defaults = &(const struct gl_priv){

video/out/vo_sdl.c

@@ -533,7 +533,7 @@ static void wakeup(struct vo *vo)
     SDL_PushEvent(&event);
 }
 
-static int wait_events(struct vo *vo, int64_t until_time_us)
+static void wait_events(struct vo *vo, int64_t until_time_us)
 {
     int64_t wait_us = until_time_us - mp_time_us();
     int timeout_ms = MPCLAMP((wait_us + 500) / 1000, 0, 10000);
@@ -619,8 +619,6 @@ static int wait_events(struct vo *vo, int64_t until_time_us)
             break;
         }
     }
-
-    return 0;
 }
 
 static void uninit(struct vo *vo)