Try listening to Bluetooth headphone buttons

Second attempt at getting events from Bluetooth headphone buttons. This
time with some code from KillerDeMouches and Josh Guice.

The magic numbers make no sense to me. Would have loved to have
constants, but hypothesizing that maybe they were gathered from direct
input and event monitoring using Karabiner's event monitor.

Unfortunately, this code didn't work for me. I still have to try it on a
< 10.12 machine, as maybe it'll work there (_hopefully_, as there was
very scarce material online about how to do this). My next attempt is
going to be using `MPRemoteCommandCenter`. Hoping that will work, but
it's only going to be a solution for >= 10.12.

3 files changed, 41 insertions, 0 deletions

diff --git a/DomeKey/AppDelegate.m b/DomeKey/AppDelegate.m
index 3e4f3d8..318aeee 100644
--- a/DomeKey/AppDelegate.m
+++ b/DomeKey/AppDelegate.m
@@ -13,6 +13,7 @@
 - (void)applicationDidFinishLaunching:(NSNotification *)notification
 {
     _headphone_key = [[HeadphoneKey alloc] init];
+    [_headphone_key startMonitoringBluetoothEvents];
 }
 
 @end
diff --git a/DomeKey/HeadphoneKey.h b/DomeKey/HeadphoneKey.h
index 861621f..586c40b 100644
--- a/DomeKey/HeadphoneKey.h
+++ b/DomeKey/HeadphoneKey.h
@@ -29,5 +29,6 @@ static const unsigned int TIMEOUT_MILLISECONDS = 1000;
 
 - (void)handleDeadKey:(HeadphoneButton)button;
 - (void)runAction;
+- (void)startMonitoringBluetoothEvents;
 
 @end
diff --git a/DomeKey/HeadphoneKey.m b/DomeKey/HeadphoneKey.m
index ef90560..5a062fc 100644
--- a/DomeKey/HeadphoneKey.m
+++ b/DomeKey/HeadphoneKey.m
@@ -57,6 +57,45 @@
     }
 }
 
+- (void)startMonitoringBluetoothEvents
+{
+    // https://github.com/jguice/mac-bt-headset-fix/blob/master/Spotify%20Bluetooth%20Headset%20Listener/KDMAppDelegate.m
+    [NSEvent
+        addGlobalMonitorForEventsMatchingMask:(NSKeyDownMask | NSSystemDefinedMask)
+        handler:^(NSEvent *theEvent) {
+            int key_code = (([theEvent data1] & 0xFFFF0000) >> 16);
+            int key_flags = ([theEvent data1] & 0x0000FFFF);
+            int key_state = (((key_flags & 0xFF00) >> 8)) == 0xA;
+
+            // TODO: Fix magic numbers
+            if (key_code == 10 && key_flags == 6972) {
+                switch ([theEvent data2]) {
+                case 786608:
+                case 786637:
+                    NSLog(@"Play");
+
+                    break;
+                case 786611:
+                    NSLog(@"Next");
+
+                    break;
+                case 786612:
+                    NSLog(@"Previous");
+
+                    break;
+                case 786613:
+                    NSLog(@"Fast-forward");
+
+                    break;
+                case 786614:
+                    NSLog(@"Rewind");
+
+                    break;
+                }
+            }
+        }];
+}
+
 - (void)handleDeadKey:(HeadphoneButton)button
 {
     NSNumber *storable_button = [NSNumber numberWithUnsignedInteger:button];