player: add --screen-name and --fs-screen-name

Simple groundwork for adding a couple of user options that allow
selecting the screen with a string name. The next two commits implements
these options for xorg and wayland.

DOCS/interface-changes.rst

@@ -26,6 +26,9 @@ Interface changes
 
 ::
 
+ --- mpv 0.34.0 ---
+    - add `--screen-name` and `--fs-screen-name` flags to allow selecting the 
+      screen by its name instead of the index
  --- mpv 0.33.0 ---
     - add `--d3d11-exclusive-fs` flag to enable D3D11 exclusive fullscreen mode
       when the player enters fullscreen.

DOCS/man/options.rst

@@ -2839,6 +2839,12 @@ Window
 
     See also ``--fs-screen``.
 
+``--screen-name=<string>``
+    In multi-monitor configurations, this option tells mpv which screen to
+    display the video on based on the screen name from the video backend. The
+    same caveats in the ``--screen`` option also apply here. This option is
+    ignored and does nothing if ``--screen`` is explicitly set.
+
 ``--fullscreen``, ``--fs``
     Fullscreen playback.
 
@@ -2859,6 +2865,12 @@ Window
 
     See also ``--screen``.
 
+``--fs-screen-name=<string>``
+    In multi-monitor configurations, this option tells mpv which screen to go
+    fullscreen to based on the screen name from the video backend. The same
+    caveats in the ``--fs-screen`` option also apply here. This option is
+    ignored and does nothing if ``--fs-screen`` is explicitly set.
+
 ``--keep-open=<yes|no|always>``
     Do not terminate when playing or seeking beyond the end of the file, and
     there is not next file to be played (and ``--loop`` is not used).

options/options.c

@@ -147,8 +147,10 @@ static const m_option_t mp_vo_opt_list[] = {
         {"no", 0}, {"yes", 1}, {"downscale-big", 2})},
     {"wid", OPT_INT64(WinID)},
     {"screen", OPT_CHOICE(screen_id, {"default", -1}), M_RANGE(0, 32)},
+    {"screen-name", OPT_STRING(screen_name)},
     {"fs-screen", OPT_CHOICE(fsscreen_id, {"all", -2}, {"current", -1}),
         M_RANGE(0, 32)},
+    {"fs-screen-name", OPT_STRING(fsscreen_name)},
     {"keepaspect", OPT_FLAG(keepaspect)},
     {"keepaspect-window", OPT_FLAG(keepaspect_window)},
     {"hidpi-window-scale", OPT_FLAG(hidpi_window_scale)},

options/options.h

@@ -22,7 +22,9 @@ typedef struct mp_vo_opts {
     bool focus_on_open;
 
     int screen_id;
+    char *screen_name;
     int fsscreen_id;
+    char *fsscreen_name;
     char *winname;
     char *appid;
     int x11_netwm;