input: add new keys: Back, Tools, ZoomIn, ZoomOut

These were the only keys missing to support mapping all keycodes on a
[popular RF Remote][1] used with Linux HTPC apps.

Note that X11/XWayland + xkbcomp still warns about keycodes > 255, due
to the 8-bit limit in Xorg but `mpv` on Wayland is able to handle these.
For X11 users, there are [a couple options][2]:

- [Gianni Ceccarelli's patched `xf86-input-evdev`][3]
- [Use udev hwdb to map scancodes to keycodes][4]

[1]: https://www.mythtv.org/wiki/Air_mouse_rf_remote
[2]: https://unix.stackexchange.com/a/436233/7688
[3]: https://www.thenautilus.net/SW/xf86-input-evdev/
[4]: https://wiki.archlinux.org/title/Map_scancodes_to_keycodes

etc/input.conf

@@ -62,7 +62,9 @@
 #Alt+up    add video-pan-y  0.1         # move the video down
 #Alt+down  add video-pan-y -0.1         # move the video up
 #Alt++     add video-zoom   0.1         # zoom in
+#ZOOMIN    add video-zoom   0.1         # zoom in
 #Alt+-     add video-zoom  -0.1         # zoom out
+#ZOOMOUT   add video-zoom  -0.1         # zoom out
 #Alt+BS set video-zoom 0 ; set video-pan-x 0 ; set video-pan-y 0 # reset zoom and pan settings
 #PGUP add chapter 1                     # seek to the next chapter
 #PGDWN add chapter -1                   # seek to the previous chapter

input/keycodes.c

@@ -165,6 +165,10 @@ static const struct key_name key_names[] = {
   { MP_KEY_CHANNEL_DOWN,"CHANNEL_DOWN" },
   { MP_KEY_PLAYONLY,    "PLAYONLY" },
   { MP_KEY_PAUSEONLY,   "PAUSEONLY" },
+  { MP_KEY_BACK,        "BACK" },
+  { MP_KEY_TOOLS,       "TOOLS" },
+  { MP_KEY_ZOOMIN,      "ZOOMIN" },
+  { MP_KEY_ZOOMOUT,     "ZOOMOUT" },
 
   // These are kept for backward compatibility
   { MP_KEY_PAUSE,   "XF86_PAUSE" },

input/keycodes.h

@@ -82,6 +82,10 @@
 #define MP_KEY_CHANNEL_DOWN     (MP_KEY_MM_BASE+22)
 #define MP_KEY_PLAYONLY         (MP_KEY_MM_BASE+23)
 #define MP_KEY_PAUSEONLY        (MP_KEY_MM_BASE+24)
+#define MP_KEY_BACK             (MP_KEY_MM_BASE+25)
+#define MP_KEY_TOOLS            (MP_KEY_MM_BASE+26)
+#define MP_KEY_ZOOMIN           (MP_KEY_MM_BASE+27)
+#define MP_KEY_ZOOMOUT          (MP_KEY_MM_BASE+28)
 
 /*  Function keys  */
 #define MP_KEY_F (MP_KEY_BASE+0x40)

video/out/wayland_common.c

@@ -132,6 +132,8 @@ static const struct mp_keymap keymap[] = {
     {XKB_KEY_XF86HomePage, MP_KEY_HOMEPAGE}, {XKB_KEY_XF86WWW, MP_KEY_WWW},
     {XKB_KEY_XF86Mail, MP_KEY_MAIL}, {XKB_KEY_XF86Favorites, MP_KEY_FAVORITES},
     {XKB_KEY_XF86Search, MP_KEY_SEARCH}, {XKB_KEY_XF86Sleep, MP_KEY_SLEEP},
+    {XKB_KEY_XF86Back, MP_KEY_BACK}, {XKB_KEY_XF86Tools, MP_KEY_TOOLS},
+    {XKB_KEY_XF86ZoomIn, MP_KEY_ZOOMIN}, {XKB_KEY_XF86ZoomOut, MP_KEY_ZOOMOUT},
 
     {0, 0}
 };

video/out/x11_common.c

@@ -753,6 +753,8 @@ static const struct mp_keymap keymap[] = {
     {XF86XK_HomePage, MP_KEY_HOMEPAGE}, {XF86XK_WWW, MP_KEY_WWW},
     {XF86XK_Mail, MP_KEY_MAIL}, {XF86XK_Favorites, MP_KEY_FAVORITES},
     {XF86XK_Search, MP_KEY_SEARCH}, {XF86XK_Sleep, MP_KEY_SLEEP},
+    {XF86XK_Back, MP_KEY_BACK}, {XF86XK_Tools, MP_KEY_TOOLS},
+    {XF86XK_ZoomIn, MP_KEY_ZOOMIN}, {XF86XK_ZoomOut, MP_KEY_ZOOMOUT},
 
     {0, 0}
 };