w32_common: handle media keys

This was attempted before in fc9695e63b, but it was reverted in
1b7ce759b1 because it caused conflicts with other software watching
the same keys (See #2041.) It seems like some PCs ship with OEM software
that watches the volume keys without consuming key events and this
causes them to be handled twice, once by mpv and once by the other
software.

In order to prevent conflicts like this, use the WM_APPCOMMAND message
to handle media keys. Returning TRUE from the WM_APPCOMMAND handler
should indicate to the operating system that we consumed the key event
and it should not be propogated to the shell. Also, we now only listen
for keys that are directly related to multimedia playback (eg. the
APPCOMMAND_MEDIA_* keys.) Keys like APPCOMMAND_VOLUME_* are ignored, so
they can be handled by the shell, or by other mixer software.

DOCS/man/options.rst

@@ -2986,7 +2986,7 @@ Input
     Support depends on the VO in use.
 
 ``--input-media-keys=<yes|no>``
-    (OS X only)
+    (OS X and Windows only)
     Enable/disable media keys support. Enabled by default (except for libmpv).
 
 ``--input-right-alt-gr``, ``--no-input-right-alt-gr``

input/input.c

@@ -200,9 +200,9 @@ const struct m_sub_options input_config = {
         OPT_INTRANGE("input-key-fifo-size", key_fifo_size, 0, 2, 65000),
         OPT_FLAG("input-cursor", enable_mouse_movements, 0),
         OPT_FLAG("input-vo-keyboard", vo_key_input, 0),
+        OPT_FLAG("input-media-keys", use_media_keys, 0),
 #if HAVE_COCOA
         OPT_FLAG("input-appleremote", use_appleremote, 0),
-        OPT_FLAG("input-media-keys", use_media_keys, 0),
 #endif
         OPT_FLAG("window-dragging", allow_win_drag, 0),
         OPT_REPLACED("input-x11-keyboard", "input-vo-keyboard"),
@@ -216,9 +216,9 @@ const struct m_sub_options input_config = {
         .ar_rate = 40,
         .use_alt_gr = 1,
         .enable_mouse_movements = 1,
+        .use_media_keys = 1,
 #if HAVE_COCOA
         .use_appleremote = 1,
-        .use_media_keys = 1,
 #endif
         .default_bindings = 1,
         .vo_key_input = 1,
@@ -1441,6 +1441,14 @@ bool mp_input_use_alt_gr(struct input_ctx *ictx)
     return r;
 }
 
+bool mp_input_use_media_keys(struct input_ctx *ictx)
+{
+    input_lock(ictx);
+    bool r = ictx->opts->use_media_keys;
+    input_unlock(ictx);
+    return r;
+}
+
 struct mp_cmd *mp_input_parse_cmd(struct input_ctx *ictx, bstr str,
                                   const char *location)
 {

input/input.h

@@ -250,6 +250,9 @@ void mp_input_set_cancel(struct input_ctx *ictx, void (*cb)(void *c), void *c);
 // characters. If false, count Right Alt as the modifier Alt key.
 bool mp_input_use_alt_gr(struct input_ctx *ictx);
 
+// Return true if mpv should intercept keyboard media keys
+bool mp_input_use_media_keys(struct input_ctx *ictx);
+
 // Like mp_input_parse_cmd_strv, but also run the command.
 void mp_input_run_cmd(struct input_ctx *ictx, const char **cmd);
 

input/keycodes.c

@@ -159,6 +159,9 @@ static const struct key_name key_names[] = {
   { MP_KEY_SEARCH,      "SEARCH" },
   { MP_KEY_SLEEP,       "SLEEP" },
   { MP_KEY_CANCEL,      "CANCEL" },
+  { MP_KEY_RECORD,      "RECORD" },
+  { MP_KEY_CHANNEL_UP,  "CHANNEL_UP" },
+  { MP_KEY_CHANNEL_DOWN,"CHANNEL_DOWN" },
 
   // These are kept for backward compatibility
   { MP_KEY_PAUSE,   "XF86_PAUSE" },

input/keycodes.h

@@ -73,6 +73,9 @@
 #define MP_KEY_SEARCH           (MP_KEY_MM_BASE+17)
 #define MP_KEY_SLEEP            (MP_KEY_MM_BASE+18)
 #define MP_KEY_CANCEL           (MP_KEY_MM_BASE+19)
+#define MP_KEY_RECORD           (MP_KEY_MM_BASE+20)
+#define MP_KEY_CHANNEL_UP       (MP_KEY_MM_BASE+21)
+#define MP_KEY_CHANNEL_DOWN     (MP_KEY_MM_BASE+22)
 
 /*  Function keys  */
 #define MP_KEY_F (MP_KEY_BASE+0x40)

osdep/w32_keyboard.c

@@ -69,6 +69,21 @@ static const struct keymap vk_map[] = {
     {0, 0}
 };
 
+static const struct keymap appcmd_map[] = {
+    {APPCOMMAND_MEDIA_NEXTTRACK,     MP_KEY_NEXT},
+    {APPCOMMAND_MEDIA_PREVIOUSTRACK, MP_KEY_PREV},
+    {APPCOMMAND_MEDIA_STOP,          MP_KEY_STOP},
+    {APPCOMMAND_MEDIA_PLAY_PAUSE,    MP_KEY_PLAYPAUSE},
+    {APPCOMMAND_MEDIA_PLAY,          MP_KEY_PLAY},
+    {APPCOMMAND_MEDIA_PAUSE,         MP_KEY_PAUSE},
+    {APPCOMMAND_MEDIA_RECORD,        MP_KEY_RECORD},
+    {APPCOMMAND_MEDIA_FAST_FORWARD,  MP_KEY_FORWARD},
+    {APPCOMMAND_MEDIA_REWIND,        MP_KEY_REWIND},
+    {APPCOMMAND_MEDIA_CHANNEL_UP,    MP_KEY_CHANNEL_UP},
+    {APPCOMMAND_MEDIA_CHANNEL_DOWN,  MP_KEY_CHANNEL_DOWN},
+    {0, 0}
+};
+
 static int lookup_keymap(const struct keymap *map, int key)
 {
     while (map->from && map->from != key) map++;
@@ -89,3 +104,8 @@ int mp_w32_vkey_to_mpkey(UINT vkey, bool extended)
 
     return mpkey;
 }
+
+int mp_w32_appcmd_to_mpkey(UINT appcmd)
+{
+    return lookup_keymap(appcmd_map, appcmd);
+}

osdep/w32_keyboard.h

@@ -23,4 +23,7 @@
 /* Convert a Windows virtual key code to an mpv key */
 int mp_w32_vkey_to_mpkey(UINT vkey, bool extended);
 
+/* Convert a WM_APPCOMMAND value to an mpv key */
+int mp_w32_appcmd_to_mpkey(UINT appcmd);
+
 #endif

video/out/w32_common.c

@@ -354,6 +354,17 @@ static int decode_key(struct vo_w32_state *w32, UINT vkey, UINT scancode)
     return c;
 }
 
+static bool handle_appcommand(struct vo_w32_state *w32, UINT cmd)
+{
+    if (!mp_input_use_media_keys(w32->input_ctx))
+        return false;
+    int mpkey = mp_w32_appcmd_to_mpkey(cmd);
+    if (!mpkey)
+        return false;
+    mp_input_put_key(w32->input_ctx, mpkey | mod_state(w32));
+    return true;
+}
+
 static void handle_key_down(struct vo_w32_state *w32, UINT vkey, UINT scancode)
 {
     // Ignore key repeat
@@ -1020,6 +1031,10 @@ static LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam,
                                         GET_Y_LPARAM(lParam));
         }
         break;
+    case WM_APPCOMMAND:
+        if (handle_appcommand(w32, GET_APPCOMMAND_LPARAM(lParam)))
+            return TRUE;
+        break;
     case WM_SYSKEYDOWN:
         // Open the window menu on Alt+Space. Normally DefWindowProc opens the
         // window menu in response to WM_SYSCHAR, but since mpv translates its