osx: improve Media Keys support

This commit addresses some issues with the users had with the previous
implementation in commit c39efb9. Here's the changes:

  * Use Quartz Event Taps to remove Media Key events mpv handles from
    the global OS X queue. This prevents conflicts with iTunes. I did this on
    the main thread since it is mostly idling. It's the playloop thread that
    actually does all the work so there is no danger of blocking the event tap
    callback.
  * Introduce `--no-media-keys` switch so that users can disable all of mpv's
    media key handling at runtime (some prefer iTunes for example).
  * Use mpv's bindings so that users can customize what the media keys do via
    input.conf. Current bindings are:

      MK_PLAY cycle pause
      MK_PREV playlist_prev
      MK_NEXT playlist_next

An additional benefit of this implementation is that it is completly handled
by the `macosx_events` file instead of `macosx_application` making the
project organization more straightforward.

1 files changed, 98 insertions, 15 deletions

diff --git a/osdep/macosx_events.m b/osdep/macosx_events.m
index 86d0ebaa3e..7970f0b5d5 100644
--- a/osdep/macosx_events.m
+++ b/osdep/macosx_events.m
@@ -92,18 +92,67 @@ static int convert_key(unsigned key, unsigned charcode)
     return charcode;
 }
 
-void cocoa_start_apple_remote(void)
+void cocoa_init_apple_remote(void)
 {
     Application *app = mpv_shared_app();
     [app.eventsResponder startAppleRemote];
 }
 
-void cocoa_stop_apple_remote(void)
+void cocoa_uninit_apple_remote(void)
 {
     Application *app = mpv_shared_app();
     [app.eventsResponder stopAppleRemote];
 }
 
+static CGEventRef tap_event_callback(CGEventTapProxy proxy, CGEventType type,
+                                     CGEventRef event, void *ctx)
+{
+    EventsResponder *responder = ctx;
+
+    if (type == kCGEventTapDisabledByTimeout) {
+        // The Mach Port receiving the taps became unresponsive for some
+        // reason, restart listening on it.
+        [responder restartMediaKeys];
+        return event;
+    }
+
+    if (type == kCGEventTapDisabledByUserInput)
+        return event;
+
+    NSEvent *nse = [NSEvent eventWithCGEvent:event];
+
+    if ([nse type] != NSSystemDefined || [nse subtype] != 8)
+        // This is not a media key
+        return event;
+
+    // It's a media key! Handle it specially. The magic numbers are reverse
+    // engineered and found on several blog posts. Unfortunately there is
+    // no public API for this. F-bomb.
+    int code  = (([nse data1] & 0xFFFF0000) >> 16);
+    int flags = ([nse data1] & 0x0000FFFF);
+    int down  = (((flags & 0xFF00) >> 8)) == 0xA;
+
+    if (down && [responder handleMediaKey:code]) {
+        // Handled this event, return nil so that it is removed from the
+        // global queue.
+        return nil;
+    } else {
+        // Was a media key but we were not interested in it. Leave it in the
+        // global queue by returning the original event.
+        return event;
+    }
+}
+
+void cocoa_init_media_keys(void) {
+    Application *app = mpv_shared_app();
+    [app.eventsResponder startMediaKeys];
+}
+
+void cocoa_uninit_media_keys(void) {
+    Application *app = mpv_shared_app();
+    [app.eventsResponder stopMediaKeys];
+}
+
 void cocoa_check_events(void)
 {
     Application *app = mpv_shared_app();
@@ -117,7 +166,9 @@ void cocoa_put_key(int keycode)
     [mpv_shared_app().iqueue push:keycode];
 }
 
-@implementation EventsResponder
+@implementation EventsResponder {
+    CFMachPortRef _mk_tap_port;
+}
 - (void)startAppleRemote
 {
     dispatch_async(dispatch_get_main_queue(), ^{
@@ -135,24 +186,56 @@ void cocoa_put_key(int keycode)
         [self.remote stopRemoteControl];
     });
 }
+- (void)restartMediaKeys
+{
+    CGEventTapEnable(self->_mk_tap_port, true);
+}
+- (void)startMediaKeys
+{
+    dispatch_async(dispatch_get_main_queue(), ^{
+        // Install a Quartz Event Tap. This will notify mpv through the
+        // returned Mach Port and cause mpv to execute the `tap_event_callback`
+        // function.
+        self->_mk_tap_port = CGEventTapCreate(kCGSessionEventTap,
+            kCGHeadInsertEventTap,
+            kCGEventTapOptionDefault,
+            CGEventMaskBit(NX_SYSDEFINED),
+            tap_event_callback,
+            self);
+
+        assert(self->_mk_tap_port != nil);
+
+        NSMachPort *port = (NSMachPort *)self->_mk_tap_port;
+        [[NSRunLoop mainRunLoop] addPort:port forMode:NSRunLoopCommonModes];
+    });
+}
+- (void)stopMediaKeys
+{
+    dispatch_async(dispatch_get_main_queue(), ^{
+        NSMachPort *port = (NSMachPort *)self->_mk_tap_port;
+        [[NSRunLoop mainRunLoop] removePort:port forMode:NSRunLoopCommonModes];
+        CFRelease(self->_mk_tap_port);
+        self->_mk_tap_port = nil;
+    });
+}
 - (NSArray *) keyEquivalents
 {
     return @[@"h", @"q", @"Q", @"0", @"1", @"2"];
 }
-- (void)handleMediaKey:(int)key
+- (BOOL)handleMediaKey:(int)key
 {
-    switch (key) {
-        case NX_KEYTYPE_PLAY:
-            cocoa_put_key(MP_KEY_PLAY);
-            break;
-
-        case NX_KEYTYPE_FAST:
-            cocoa_put_key(MP_KEY_NEXT);
-            break;
+    NSDictionary *keymap = @{
+        @(NX_KEYTYPE_PLAY):    @(MP_MK_PLAY),
+        @(NX_KEYTYPE_REWIND):  @(MP_MK_PREV),
+        @(NX_KEYTYPE_FAST):    @(MP_MK_NEXT),
+    };
 
-        case NX_KEYTYPE_REWIND:
-            cocoa_put_key(MP_KEY_PREV);
-            break;
+    int mpkey = [keymap[@(key)] intValue];
+    if (mpkey > 0) {
+        cocoa_put_key(mpkey);
+        return YES;
+    } else {
+        return NO;
     }
 }
 - (NSEvent*)handleKeyDown:(NSEvent *)event