vo: don't update zoom and pan while changing file

When the current playlist entry changes, or when quitting, and
file-local options values are reset, the VO re-renders the current file
with the new option values before rendering the next file, if any,
causing flicker.

Fix this for zoom/pan-related options by not making VO drivers resize
while changing file until the next frame arrives.

Manually sending VOCTRL_SET_PANSCAN for the new file is only necessary
when navigating between images with the same dimensions, else VOs resize
automatically on reconfig.

The VO can still re-render while changing file to print new OSD
messages, only resizing and panning the image is delayed.

Fixes #7293
Fixes #7675
Fixes Dudemanguy/mpv-manga-reader#12

Author: guidocella

player/loadfile.c

@@ -1991,8 +1991,11 @@ static void play_current_file(struct MPContext *mpctx)
                      current && current->reloading;
     if (current)
         current->reloading = false;
-    if (!reloading)
+    if (!reloading) {
+        if (mpctx->video_out)
+            vo_set_changing_file(mpctx->video_out);
         m_config_restore_backups(mpctx->mconfig);
+    }
 
     TA_FREEP(&mpctx->filter_root);
     talloc_free(mpctx->filtered_tags);

video/out/vo.c

@@ -139,6 +139,7 @@ struct vo_internal {
     bool paused;
     bool visible;
     bool wakeup_on_done;
+    bool changing_file;
     int queued_events;              // event mask for the user
     int internal_events;            // event mask for us
 
@@ -237,12 +238,25 @@ static void read_opts(struct vo *vo)
 static void update_opts(void *p)
 {
     struct vo *vo = p;
+    struct vo_internal *in = vo->in;
 
     if (m_config_cache_update(vo->opts_cache)) {
         read_opts(vo);
         vo->driver->control(vo, VOCTRL_VO_OPTS_CHANGED, NULL);
-        // "Legacy" update of video position related options.
-        // Unlike VOCTRL_VO_OPTS_CHANGED, often not propagated to backends.
+        if (!in->changing_file) {
+            // "Legacy" update of video position related options.
+            // Unlike VOCTRL_VO_OPTS_CHANGED, often not propagated to backends.
+            vo->driver->control(vo, VOCTRL_SET_PANSCAN, NULL);
+        }
+    }
+}
+
+static void handle_file_change(struct vo *vo)
+{
+    struct vo_internal *in = vo->in;
+
+    if (in->changing_file) {
+        in->changing_file = false;
         vo->driver->control(vo, VOCTRL_SET_PANSCAN, NULL);
     }
 }
@@ -1012,6 +1026,8 @@ static bool render_frame(struct vo *vo)
 
         stats_time_start(in->stats, "video-flip");
 
+        handle_file_change(vo);
+
         vo->driver->flip_page(vo);
 
         struct vo_vsync_info vsync = {
@@ -1236,6 +1252,13 @@ void vo_set_paused(struct vo *vo, bool paused)
     mp_mutex_unlock(&in->lock);
 }
 
+void vo_set_changing_file(struct vo *vo)
+{
+    mp_mutex_lock(&vo->in->lock);
+    vo->in->changing_file = true;
+    mp_mutex_unlock(&vo->in->lock);
+}
+
 int64_t vo_get_drop_count(struct vo *vo)
 {
     mp_mutex_lock(&vo->in->lock);

video/out/vo.h

@@ -542,6 +542,7 @@ bool vo_want_redraw(struct vo *vo);
 void vo_seek_reset(struct vo *vo);
 void vo_destroy(struct vo *vo);
 void vo_set_paused(struct vo *vo, bool paused);
+void vo_set_changing_file(struct vo *vo);
 int64_t vo_get_drop_count(struct vo *vo);
 void vo_increment_drop_count(struct vo *vo, int64_t n);
 int64_t vo_get_delayed_count(struct vo *vo);