player: add --force-render option

mpv has an internal optimization on a couple of platforms where it will
not render any frames if the window is minimized or hidden. There's at
least once possible use case for wanting to force a render anyway
(screensharing with pipeware) so let's just add a simple switch for
this that always forces mpv to render. Closes #10846.

DOCS/interface-changes.rst

@@ -26,6 +26,8 @@ Interface changes
 
 ::
 
+ --- mpv 0.36.0 ---
+    - add `--force-render`
  --- mpv 0.35.0 ---
     - add the `--vo=gpu-next` video output driver, as well as the options
       `--allow-delayed-peak-detect`, `--builtin-scalers`,

DOCS/man/options.rst

@@ -3243,6 +3243,12 @@ Window
     depending on GPU drivers and hardware. For other VOs, this just makes
     rendering slower.
 
+``--force-render``
+    Forces mpv to always render frames regardless of the visibility of the
+    window. Currently only affects X11 and Wayland VOs since they are the
+    only ones that have this optimization (i.e. everything else always renders
+    regardless of visibility).
+
 ``--force-window-position``
     Forcefully move mpv's video output window to default location whenever
     there is a change in video parameters, video stream or file. This used to

options/options.c

@@ -126,6 +126,7 @@ static const m_option_t mp_vo_opt_list[] = {
     {"window-minimized", OPT_FLAG(window_minimized)},
     {"window-maximized", OPT_FLAG(window_maximized)},
     {"focus-on-open", OPT_BOOL(focus_on_open)},
+    {"force-render", OPT_FLAG(force_render)},
     {"force-window-position", OPT_FLAG(force_window_position)},
     {"x11-name", OPT_STRING(winname)},
     {"wayland-app-id", OPT_STRING(appid)},

options/options.h

@@ -56,6 +56,7 @@ typedef struct mp_vo_opts {
 
     float force_monitor_aspect;
     float monitor_pixel_aspect;
+    int force_render;
     int force_window_position;
 
     char *mmcss_profile;

video/out/wayland_common.c

@@ -1754,7 +1754,7 @@ int vo_wayland_allocate_memfd(struct vo *vo, size_t size)
 bool vo_wayland_check_visible(struct vo *vo)
 {
     struct vo_wayland_state *wl = vo->wl;
-    bool render = !wl->hidden || wl->opts->disable_vsync;
+    bool render = !wl->hidden || wl->vo_opts->force_render;
     wl->frame_wait = true;
     return render;
 }

video/out/x11_common.c

@@ -1972,7 +1972,8 @@ bool vo_x11_check_visible(struct vo *vo) {
     struct vo_x11_state *x11 = vo->x11;
     struct mp_vo_opts *opts = x11->opts;
 
-    bool render = !x11->hidden || VS_IS_DISP(opts->video_sync);
+    bool render = !x11->hidden || opts->force_render ||
+                  VS_IS_DISP(opts->video_sync);
     return render;
 }