player: add --force-window=immediate mode

This creates the window before the first file is loaded. This was
requested a bunch of times, but on the other hand a change to make this
behavior the default was reverted some time ago, because other users
hated it.

DOCS/man/options.rst

@@ -1586,7 +1586,7 @@ Window
     file.mkv normally, then fail to open ``/dev/null``, then exit). (In
     mpv 0.8.0, ``always`` was introduced, which restores the old behavior.)
 
-``--force-window``
+``--force-window=<yes|no|immediate>``
     Create a video output window even if there is no video. This can be useful
     when pretending that mpv is a GUI application. Currently, the window
     always has the size 640x480, and is subject to ``--geometry``,
@@ -1598,7 +1598,9 @@ Window
         window placement still works if the video size is different from the
         ``--force-window`` default window size). This can be a problem if
         initialization doesn't work perfectly, such as when opening URLs with
-        bad network connection, or opening broken video files.
+        bad network connection, or opening broken video files. The ``immediate``
+        mode can be used to create the window always on program start, but this
+        may cause other issues.
 
 ``--ontop``
     Makes the player window stay on top of other windows.

options/options.c

@@ -367,7 +367,8 @@ const m_option_t mp_opts[] = {
     OPT_SETTINGSLIST("ao-defaults", ao_defs, 0, &ao_obj_list),
     OPT_STRING("audio-device", audio_device, 0),
     OPT_STRING("audio-client-name", audio_client_name, 0),
-    OPT_FLAG("force-window", force_vo, 0),
+    OPT_CHOICE("force-window", force_vo, 0,
+               ({"no", 0}, {"yes", 1}, {"immediate", 2})),
     OPT_FLAG("ontop", vo.ontop, M_OPT_FIXED),
     OPT_FLAG("border", vo.border, M_OPT_FIXED),
     OPT_FLAG("on-all-workspaces", vo.all_workspaces, M_OPT_FIXED),

player/main.c

@@ -472,6 +472,8 @@ int mp_initialize(struct MPContext *mpctx, char **options)
                     "the selected video_out (-vo) device.\n");
             return -1;
         }
+        if (opts->force_vo == 2)
+            handle_force_window(mpctx, false);
         mpctx->mouse_cursor_visible = true;
     }