Refactored the shortcut dispatcher and bindings to user defaults.

This is a big change that was hard to split into smaller commits. There’s now
a new class to bind shortcuts to actions, a new class to bind user defaults’
keys to actions, and a new way to associate user defaults with the recorder
control (MASShortcutView). I have also updated the demo app to go with the
changes.

The new class to associate shortcuts with actions is called MASShortcutMonitor.
It wraps the Carbon hotkey magic and offers a simple interface to add a
shortcut along with a block that should be run when the shortcut is pressed.
It’s the lowest-level interface.

Since the usual requirement is to store the shortcuts into user defaults,
there’s also a higher-level interface offered by the MASShortcutBinder class.
That takes a defaults key and associates it with a block. When the shortcut
stored under the defaults key changes, the binder automatically switches to the
new shortcut. The class is a wrapper built atop of the previous one, the
MASShortcutMonitor – it simply adds, updates and removes shortcuts as the
user defaults change.

I have removed the special user defaults integration code from the recorder
control (MASShortcutView) and replaced it with a small Cocoa Bindings shim.
This means that in order to keep the recorder control in sync with the defaults
you just have to call the usual bind:toObject:withKeyPath:options: method,
like this:

[_shortcutView bind:MASShortcutBinding
    toObject:[NSUserDefaultsController sharedUserDefaultsController]
    withKeyPath[@"values.ExampleDefaultsKey"
    options:@{NSValueTransformerNameBindingOption:NSKeyedUnarchiveFromDataTransformerName}];

That’s more verbose than the previous solution, but it’s much cleaner and can
be swept under a convenience call if needed. I might also add a dictionaryValue
property later that would make it possible to bind the value to user defaults
directly, without a transformer, and would enable backward compatibility with
Shortcut Recorder.

17 files changed, 381 insertions, 415 deletions

diff --git a/Framework/MASHotKey.h b/Framework/MASHotKey.h
new file mode 100644
index 0000000..1d267e4
--- /dev/null
+++ b/Framework/MASHotKey.h
@@ -0,0 +1,12 @@
+#import "MASShortcut.h"
+
+extern FourCharCode const MASHotKeySignature;
+
+@interface MASHotKey : NSObject
+
+@property(readonly) UInt32 carbonID;
+@property(copy) dispatch_block_t action;
+
++ (instancetype) registeredHotKeyWithShortcut: (MASShortcut*) shortcut;
+
+@end
diff --git a/Framework/MASHotKey.m b/Framework/MASHotKey.m
new file mode 100644
index 0000000..7886440
--- /dev/null
+++ b/Framework/MASHotKey.m
@@ -0,0 +1,44 @@
+#import "MASHotKey.h"
+
+FourCharCode const MASHotKeySignature = 'MASS';
+
+@interface MASHotKey ()
+@property(assign) EventHotKeyRef hotKeyRef;
+@property(assign) UInt32 carbonID;
+@end
+
+@implementation MASHotKey
+
+- (instancetype) initWithShortcut: (MASShortcut*) shortcut
+{
+    self = [super init];
+
+    static UInt32 CarbonHotKeyID = 0;
+
+    _carbonID = ++CarbonHotKeyID;
+    EventHotKeyID hotKeyID = { .signature = MASHotKeySignature, .id = _carbonID };
+
+    OSStatus status = RegisterEventHotKey([shortcut carbonKeyCode], [shortcut carbonFlags],
+        hotKeyID, GetEventDispatcherTarget(), kEventHotKeyExclusive, &_hotKeyRef);
+
+    if (status != noErr) {
+        return nil;
+    }
+
+    return self;
+}
+
++ (instancetype) registeredHotKeyWithShortcut: (MASShortcut*) shortcut
+{
+    return [[self alloc] initWithShortcut:shortcut];
+}
+
+- (void) dealloc
+{
+    if (_hotKeyRef) {
+        UnregisterEventHotKey(_hotKeyRef);
+        _hotKeyRef = NULL;
+    }
+}
+
+@end
diff --git a/Framework/MASShortcut+Monitoring.h b/Framework/MASShortcut+Monitoring.h
deleted file mode 100644
index aa8f224..0000000
--- a/Framework/MASShortcut+Monitoring.h
+++ /dev/null
@@ -1,8 +0,0 @@
-#import "MASShortcut.h"
-
-@interface MASShortcut (Monitoring)
-
-+ (id)addGlobalHotkeyMonitorWithShortcut:(MASShortcut *)shortcut handler:(void (^)())handler;
-+ (void)removeGlobalHotkeyMonitor:(id)monitor;
-
-@end
diff --git a/Framework/MASShortcut+Monitoring.m b/Framework/MASShortcut+Monitoring.m
deleted file mode 100644
index b6750b4..0000000
--- a/Framework/MASShortcut+Monitoring.m
+++ /dev/null
@@ -1,165 +0,0 @@
-#import "MASShortcut+Monitoring.h"
-
-NSMutableDictionary *MASRegisteredHotKeys(void);
-BOOL InstallCommonEventHandler(void);
-BOOL InstallHotkeyWithShortcut(MASShortcut *shortcut, UInt32 *outCarbonHotKeyID, EventHotKeyRef *outCarbonHotKey);
-void UninstallEventHandler(void);
-
-#pragma mark -
-
-@interface MASShortcutHotKey : NSObject
-
-@property (nonatomic, readonly) MASShortcut *shortcut;
-@property (nonatomic, readonly, copy) void (^handler)();
-@property (nonatomic, readonly) EventHotKeyRef carbonHotKey;
-@property (nonatomic, readonly) UInt32 carbonHotKeyID;
-
-- (id)initWithShortcut:(MASShortcut *)shortcut handler:(void (^)())handler;
-
-@end
-
-#pragma mark -
-
-@implementation MASShortcut (Monitoring)
-
-+ (id)addGlobalHotkeyMonitorWithShortcut:(MASShortcut *)shortcut handler:(void (^)())handler
-{
-    NSString *monitor = [NSString stringWithFormat:@"%@", shortcut.description];
-    if ([MASRegisteredHotKeys() objectForKey:monitor]) return nil;
-
-    MASShortcutHotKey *hotKey = [[MASShortcutHotKey alloc] initWithShortcut:shortcut handler:handler];
-    if (hotKey == nil) return nil;
-
-    [MASRegisteredHotKeys() setObject:hotKey forKey:monitor];
-    return monitor;
-}
-
-+ (void)removeGlobalHotkeyMonitor:(id)monitor
-{
-    if (monitor == nil) return;
-    NSMutableDictionary *registeredHotKeys = MASRegisteredHotKeys();
-    [registeredHotKeys removeObjectForKey:monitor];
-    if (registeredHotKeys.count == 0) {
-        UninstallEventHandler();
-    }
-}
-
-@end
-
-#pragma mark -
-
-@implementation MASShortcutHotKey
-
-@synthesize carbonHotKeyID = _carbonHotKeyID;
-@synthesize handler = _handler;
-@synthesize shortcut = _shortcut;
-@synthesize carbonHotKey = _carbonHotKey;
-
-#pragma mark -
-
-- (id)initWithShortcut:(MASShortcut *)shortcut handler:(void (^)())handler
-{
-    self = [super init];
-    if (self) {
-        _shortcut = shortcut;
-        _handler = [handler copy];
-
-        if (!InstallHotkeyWithShortcut(shortcut, &_carbonHotKeyID, &_carbonHotKey))
-            self = nil;
-    }
-    return self;
-}
-
-- (void)dealloc
-{
-    [self uninstallExisitingHotKey];
-}
-
-- (void)uninstallExisitingHotKey
-{
-    if (_carbonHotKey) {
-        UnregisterEventHotKey(_carbonHotKey);
-        _carbonHotKey = NULL;
-    }
-}
-
-@end
-
-#pragma mark - Carbon magic
-
-NSMutableDictionary *MASRegisteredHotKeys()
-{
-    static NSMutableDictionary *shared = nil;
-    static dispatch_once_t onceToken;
-    dispatch_once(&onceToken, ^{
-        shared = [NSMutableDictionary dictionary];
-    });
-    return shared;
-}
-
-#pragma mark -
-
-FourCharCode const kMASShortcutSignature = 'MASS';
-
-BOOL InstallHotkeyWithShortcut(MASShortcut *shortcut, UInt32 *outCarbonHotKeyID, EventHotKeyRef *outCarbonHotKey)
-{
-    if ((shortcut == nil) || !InstallCommonEventHandler()) return NO;
-
-    static UInt32 sCarbonHotKeyID = 0;
-	EventHotKeyID hotKeyID = { .signature = kMASShortcutSignature, .id = ++ sCarbonHotKeyID };
-    EventHotKeyRef carbonHotKey = NULL;
-    if (RegisterEventHotKey(shortcut.carbonKeyCode, shortcut.carbonFlags, hotKeyID, GetEventDispatcherTarget(), kEventHotKeyExclusive, &carbonHotKey) != noErr) {
-        return NO;
-    }
-
-    if (outCarbonHotKeyID) *outCarbonHotKeyID = hotKeyID.id;
-    if (outCarbonHotKey) *outCarbonHotKey = carbonHotKey;
-    return YES;
-}
-
-static OSStatus CarbonCallback(EventHandlerCallRef inHandlerCallRef, EventRef inEvent, void *inUserData)
-{
-	if (GetEventClass(inEvent) != kEventClassKeyboard) return noErr;
-
-	EventHotKeyID hotKeyID;
-	OSStatus status = GetEventParameter(inEvent, kEventParamDirectObject, typeEventHotKeyID, NULL, sizeof(hotKeyID), NULL, &hotKeyID);
-	if (status != noErr) return status;
-
-	if (hotKeyID.signature != kMASShortcutSignature) return noErr;
-
-    [MASRegisteredHotKeys() enumerateKeysAndObjectsUsingBlock:^(id key, MASShortcutHotKey *hotKey, BOOL *stop) {
-        if (hotKeyID.id == hotKey.carbonHotKeyID) {
-            if (hotKey.handler) {
-                hotKey.handler();
-            }
-            *stop = YES;
-        }
-    }];
-
-	return noErr;
-}
-
-#pragma mark -
-
-static EventHandlerRef sEventHandler = NULL;
-
-BOOL InstallCommonEventHandler()
-{
-    if (sEventHandler == NULL) {
-        EventTypeSpec hotKeyPressedSpec = { .eventClass = kEventClassKeyboard, .eventKind = kEventHotKeyPressed };
-        OSStatus status = InstallEventHandler(GetEventDispatcherTarget(), CarbonCallback, 1, &hotKeyPressedSpec, NULL, &sEventHandler);
-        if (status != noErr) {
-            sEventHandler = NULL;
-            return NO;
-        }
-    }
-    return YES;
-}
-
-void UninstallEventHandler()
-{
-    if (sEventHandler) {
-        RemoveEventHandler(sEventHandler);
-        sEventHandler = NULL;
-    }
-}
diff --git a/Framework/MASShortcut+UserDefaults.h b/Framework/MASShortcut+UserDefaults.h
deleted file mode 100644
index 9f2ecb9..0000000
--- a/Framework/MASShortcut+UserDefaults.h
+++ /dev/null
@@ -1,9 +0,0 @@
-#import "MASShortcut.h"
-
-@interface MASShortcut (UserDefaults)
-
-+ (void)registerGlobalShortcutWithUserDefaultsKey:(NSString *)userDefaultsKey handler:(void (^)())handler;
-+ (void)unregisterGlobalShortcutWithUserDefaultsKey:(NSString *)userDefaultsKey;
-+ (void)setGlobalShortcut:(MASShortcut *)shortcut forUserDefaultsKey:(NSString *)userDefaultsKey;
-
-@end
diff --git a/Framework/MASShortcut+UserDefaults.m b/Framework/MASShortcut+UserDefaults.m
deleted file mode 100644
index 006c579..0000000
--- a/Framework/MASShortcut+UserDefaults.m
+++ /dev/null
@@ -1,98 +0,0 @@
-#import "MASShortcut+UserDefaults.h"
-#import "MASShortcut+Monitoring.h"
-
-@interface MASShortcutUserDefaultsHotKey : NSObject
-
-@property (nonatomic, readonly) NSString *userDefaultsKey;
-@property (nonatomic, copy) void (^handler)();
-@property (nonatomic, weak) id monitor;
-
-- (id)initWithUserDefaultsKey:(NSString *)userDefaultsKey handler:(void (^)())handler;
-
-@end
-
-#pragma mark -
-
-@implementation MASShortcut (UserDefaults)
-
-+ (NSMutableDictionary *)registeredUserDefaultsHotKeys
-{
-    static NSMutableDictionary *shared = nil;
-    static dispatch_once_t onceToken;
-    dispatch_once(&onceToken, ^{
-        shared = [NSMutableDictionary dictionary];
-    });
-    return shared;
-}
-
-+ (void)registerGlobalShortcutWithUserDefaultsKey:(NSString *)userDefaultsKey handler:(void (^)())handler
-{
-    MASShortcutUserDefaultsHotKey *hotKey = [[MASShortcutUserDefaultsHotKey alloc] initWithUserDefaultsKey:userDefaultsKey handler:handler];
-    [[self registeredUserDefaultsHotKeys] setObject:hotKey forKey:userDefaultsKey];
-}
-
-+ (void)unregisterGlobalShortcutWithUserDefaultsKey:(NSString *)userDefaultsKey
-{
-    NSMutableDictionary *registeredHotKeys = [self registeredUserDefaultsHotKeys];
-    [registeredHotKeys removeObjectForKey:userDefaultsKey];
-}
-
-+ (void)setGlobalShortcut:(MASShortcut *)shortcut forUserDefaultsKey:(NSString *)userDefaultsKey
-{
-    NSData *shortcutData = [NSArchiver archivedDataWithRootObject:shortcut];
-    if (shortcutData)
-        [[NSUserDefaults standardUserDefaults] setObject:shortcutData forKey:userDefaultsKey];
-    else
-        [[NSUserDefaults standardUserDefaults] removeObjectForKey:userDefaultsKey];
-}
-
-@end
-
-#pragma mark -
-
-@implementation MASShortcutUserDefaultsHotKey {
-    NSString *_observableKeyPath;
-}
-
-void *MASShortcutUserDefaultsContext = &MASShortcutUserDefaultsContext;
-
-- (id)initWithUserDefaultsKey:(NSString *)userDefaultsKey handler:(void (^)())handler
-{
-    self = [super init];
-    if (self) {
-        _userDefaultsKey = userDefaultsKey.copy;
-        _handler = [handler copy];
-        _observableKeyPath = [@"values." stringByAppendingString:_userDefaultsKey];
-        [[NSUserDefaultsController sharedUserDefaultsController] addObserver:self forKeyPath:_observableKeyPath options:NSKeyValueObservingOptionInitial context:MASShortcutUserDefaultsContext];
-    }
-    return self;
-}
-
-- (void)dealloc
-{
-    [[NSUserDefaultsController sharedUserDefaultsController] removeObserver:self forKeyPath:_observableKeyPath context:MASShortcutUserDefaultsContext];
-    [MASShortcut removeGlobalHotkeyMonitor:self.monitor];
-}
-
-#pragma mark -
-
-- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
-{
-    if (context == MASShortcutUserDefaultsContext) {
-        [MASShortcut removeGlobalHotkeyMonitor:self.monitor];
-        [self installHotKeyFromUserDefaults];
-    }
-    else {
-        [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
-    }
-}
-
-- (void)installHotKeyFromUserDefaults
-{
-    NSData *data = [[NSUserDefaults standardUserDefaults] dataForKey:_userDefaultsKey];
-    MASShortcut *shortcut = [NSKeyedUnarchiver unarchiveObjectWithData:data];
-    if (shortcut == nil) return;
-    self.monitor = [MASShortcut addGlobalHotkeyMonitorWithShortcut:shortcut handler:self.handler];
-}
-
-@end
diff --git a/Framework/MASShortcutBinder.h b/Framework/MASShortcutBinder.h
new file mode 100644
index 0000000..74842f3
--- /dev/null
+++ b/Framework/MASShortcutBinder.h
@@ -0,0 +1,10 @@
+#import "MASShortcutMonitor.h"
+
+@interface MASShortcutBinder : NSObject
+
+@property(strong) MASShortcutMonitor *shortcutMonitor;
+
+- (void) bindShortcutWithDefaultsKey: (NSString*) defaultsKeyName toAction: (dispatch_block_t) action;
+- (void) breakBindingWithDefaultsKey: (NSString*) defaultsKeyName;
+
+@end
diff --git a/Framework/MASShortcutBinder.m b/Framework/MASShortcutBinder.m
new file mode 100644
index 0000000..d6249a8
--- /dev/null
+++ b/Framework/MASShortcutBinder.m
@@ -0,0 +1,83 @@
+#import "MASShortcutBinder.h"
+#import "MASShortcut.h"
+
+@interface MASShortcutBinder ()
+@property(strong) NSMutableDictionary *actions;
+@property(strong) NSMutableDictionary *shortcuts;
+@end
+
+@implementation MASShortcutBinder
+
+#pragma mark Initialization
+
+- (id) init
+{
+    self = [super init];
+    [self setActions:[NSMutableDictionary dictionary]];
+    [self setShortcuts:[NSMutableDictionary dictionary]];
+    return self;
+}
+
+- (void) dealloc
+{
+    for (NSString *bindingName in [_actions allKeys]) {
+        [self unbind:bindingName];
+    }
+}
+
+#pragma mark Bindings
+
+- (void) bindShortcutWithDefaultsKey: (NSString*) defaultsKeyName toAction: (dispatch_block_t) action
+{
+    [_actions setObject:[action copy] forKey:defaultsKeyName];
+    NSDictionary *bindingOptions = @{NSValueTransformerNameBindingOption: NSKeyedUnarchiveFromDataTransformerName};
+    [self bind:defaultsKeyName toObject:[NSUserDefaultsController sharedUserDefaultsController]
+        withKeyPath:[@"values." stringByAppendingString:defaultsKeyName] options:bindingOptions];
+}
+
+- (void) breakBindingWithDefaultsKey: (NSString*) defaultsKeyName
+{
+    [_shortcutMonitor unregisterShortcut:[_shortcuts objectForKey:defaultsKeyName]];
+    [_shortcuts removeObjectForKey:defaultsKeyName];
+    [_actions removeObjectForKey:defaultsKeyName];
+    [self unbind:defaultsKeyName];
+}
+
+- (BOOL) isRegisteredAction: (NSString*) name
+{
+    return !![_actions objectForKey:name];
+}
+
+- (id) valueForUndefinedKey: (NSString*) key
+{
+    return [self isRegisteredAction:key] ?
+        [_shortcuts objectForKey:key] :
+        [super valueForUndefinedKey:key];
+}
+
+- (void) setValue: (id) value forUndefinedKey: (NSString*) key
+{
+    if (![self isRegisteredAction:key]) {
+        [super setValue:value forUndefinedKey:key];
+        return;
+    }
+
+    MASShortcut *newShortcut = value;
+    MASShortcut *currentShortcut = [_shortcuts objectForKey:key];
+
+    // Unbind previous shortcut if any
+    if (currentShortcut != nil) {
+        [_shortcutMonitor unregisterShortcut:currentShortcut];
+    }
+
+    // Just deleting the old shortcut
+    if (newShortcut == nil) {
+        return;
+    }
+
+    // Bind new shortcut
+    [_shortcuts setObject:newShortcut forKey:key];
+    [_shortcutMonitor registerShortcut:newShortcut withAction:[_actions objectForKey:key]];
+}
+
+@end
diff --git a/Framework/MASShortcutBinderTests.m b/Framework/MASShortcutBinderTests.m
new file mode 100644
index 0000000..f416304
--- /dev/null
+++ b/Framework/MASShortcutBinderTests.m
@@ -0,0 +1,82 @@
+#import "MASShortcutBinder.h"
+
+static NSString *const SampleDefaultsKey = @"sampleShortcut";
+
+@interface MASShortcutBinderTests : XCTestCase
+@property(strong) MASShortcutBinder *binder;
+@property(strong) MASShortcutMonitor *monitor;
+@property(strong) NSUserDefaults *defaults;
+@end
+
+@implementation MASShortcutBinderTests
+
+- (void) setUp
+{
+    [super setUp];
+
+    [self setBinder:[[MASShortcutBinder alloc] init]];
+    [self setMonitor:[[MASShortcutMonitor alloc] init]];
+    [_binder setShortcutMonitor:_monitor];
+
+    [self setDefaults:[[NSUserDefaults alloc] init]];
+    [_defaults removeObjectForKey:SampleDefaultsKey];
+}
+
+- (void) tearDown
+{
+    [self setMonitor:nil];
+    [self setDefaults:nil];
+    [self setBinder:nil];
+    [super tearDown];
+}
+
+- (void) testInitialValueReading
+{
+    MASShortcut *shortcut = [MASShortcut shortcutWithKeyCode:1 modifierFlags:1];
+    [_defaults setObject:[NSKeyedArchiver archivedDataWithRootObject:shortcut] forKey:SampleDefaultsKey];
+    [_binder bindShortcutWithDefaultsKey:SampleDefaultsKey toAction:^{}];
+    XCTAssertTrue([_monitor isShortcutRegistered:shortcut],
+        @"Pass the initial shortcut from defaults to shortcut monitor.");
+}
+
+- (void) testValueChangeReading
+{
+    MASShortcut *shortcut = [MASShortcut shortcutWithKeyCode:1 modifierFlags:1];
+    [_binder bindShortcutWithDefaultsKey:SampleDefaultsKey toAction:^{}];
+    [_defaults setObject:[NSKeyedArchiver archivedDataWithRootObject:shortcut] forKey:SampleDefaultsKey];
+    XCTAssertTrue([_monitor isShortcutRegistered:shortcut],
+        @"Pass the shortcut from defaults to shortcut monitor after defaults change.");
+}
+
+- (void) testValueClearing
+{
+    MASShortcut *shortcut = [MASShortcut shortcutWithKeyCode:1 modifierFlags:1];
+    [_binder bindShortcutWithDefaultsKey:SampleDefaultsKey toAction:^{}];
+    [_defaults setObject:[NSKeyedArchiver archivedDataWithRootObject:shortcut] forKey:SampleDefaultsKey];
+    [_defaults removeObjectForKey:SampleDefaultsKey];
+    XCTAssertFalse([_monitor isShortcutRegistered:shortcut],
+        @"Unregister shortcut from monitor after value is cleared from defaults.");
+}
+
+- (void) testBindingRemoval
+{
+    MASShortcut *shortcut = [MASShortcut shortcutWithKeyCode:1 modifierFlags:1];
+    [_binder bindShortcutWithDefaultsKey:SampleDefaultsKey toAction:^{}];
+    [_defaults setObject:[NSKeyedArchiver archivedDataWithRootObject:shortcut] forKey:SampleDefaultsKey];
+    [_binder breakBindingWithDefaultsKey:SampleDefaultsKey];
+    XCTAssertFalse([_monitor isShortcutRegistered:shortcut],
+        @"Unregister shortcut from monitor after binding was removed.");
+}
+
+- (void) testRebinding
+{
+    MASShortcut *shortcut = [MASShortcut shortcutWithKeyCode:1 modifierFlags:1];
+    [_defaults setObject:[NSKeyedArchiver archivedDataWithRootObject:shortcut] forKey:SampleDefaultsKey];
+    [_binder bindShortcutWithDefaultsKey:SampleDefaultsKey toAction:^{}];
+    [_binder breakBindingWithDefaultsKey:SampleDefaultsKey];
+    [_binder bindShortcutWithDefaultsKey:SampleDefaultsKey toAction:^{}];
+    XCTAssertTrue([_monitor isShortcutRegistered:shortcut],
+        @"Bind after unbinding.");
+}
+
+@end
diff --git a/Framework/MASShortcutMonitor.h b/Framework/MASShortcutMonitor.h
new file mode 100644
index 0000000..c29747c
--- /dev/null
+++ b/Framework/MASShortcutMonitor.h
@@ -0,0 +1,9 @@
+#import "MASShortcut.h"
+
+@interface MASShortcutMonitor : NSObject
+
+- (void) registerShortcut: (MASShortcut*) shortcut withAction: (dispatch_block_t) action;
+- (BOOL) isShortcutRegistered: (MASShortcut*) shortcut;
+- (void) unregisterShortcut: (MASShortcut*) shortcut;
+
+@end
diff --git a/Framework/MASShortcutMonitor.m b/Framework/MASShortcutMonitor.m
new file mode 100644
index 0000000..f1c7e9c
--- /dev/null
+++ b/Framework/MASShortcutMonitor.m
@@ -0,0 +1,84 @@
+#import "MASShortcutMonitor.h"
+#import "MASHotKey.h"
+
+@interface MASShortcutMonitor ()
+@property(assign) EventHandlerRef eventHandlerRef;
+@property(strong) NSMutableDictionary *hotKeys;
+@end
+
+static OSStatus MASCarbonEventCallback(EventHandlerCallRef, EventRef, void*);
+
+@implementation MASShortcutMonitor
+
+- (instancetype) init
+{
+    self = [super init];
+    [self setHotKeys:[NSMutableDictionary dictionary]];
+    EventTypeSpec hotKeyPressedSpec = { .eventClass = kEventClassKeyboard, .eventKind = kEventHotKeyPressed };
+    OSStatus status = InstallEventHandler(GetEventDispatcherTarget(), MASCarbonEventCallback,
+        1, &hotKeyPressedSpec, (__bridge void*)self, &_eventHandlerRef);
+    if (status != noErr) {
+        return nil;
+    }
+    return self;
+}
+
+- (void) dealloc
+{
+    if (_eventHandlerRef) {
+        RemoveEventHandler(_eventHandlerRef);
+        _eventHandlerRef = NULL;
+    }
+}
+
+#pragma mark Registration
+
+- (void) registerShortcut: (MASShortcut*) shortcut withAction: (dispatch_block_t) action
+{
+    MASHotKey *hotKey = [MASHotKey registeredHotKeyWithShortcut:shortcut];
+    [hotKey setAction:action];
+    [_hotKeys setObject:hotKey forKey:shortcut];
+}
+
+- (void) unregisterShortcut: (MASShortcut*) shortcut
+{
+    [_hotKeys removeObjectForKey:shortcut];
+}
+
+- (BOOL) isShortcutRegistered: (MASShortcut*) shortcut
+{
+    return !![_hotKeys objectForKey:shortcut];
+}
+
+#pragma mark Event Handling
+
+- (void) handleEvent: (EventRef) event
+{
+	if (GetEventClass(event) != kEventClassKeyboard) {
+        return;
+    }
+
+	EventHotKeyID hotKeyID;
+	OSStatus status = GetEventParameter(event, kEventParamDirectObject, typeEventHotKeyID, NULL, sizeof(hotKeyID), NULL, &hotKeyID);
+	if (status != noErr || hotKeyID.signature != MASHotKeySignature) {
+        return;
+    }
+
+    [_hotKeys enumerateKeysAndObjectsUsingBlock:^(MASShortcut *shortcut, MASHotKey *hotKey, BOOL *stop) {
+        if (hotKeyID.id == [hotKey carbonID]) {
+            if ([hotKey action]) {
+                dispatch_async(dispatch_get_main_queue(), [hotKey action]);
+            }
+            *stop = YES;
+        }
+    }];
+}
+
+@end
+
+static OSStatus MASCarbonEventCallback(EventHandlerCallRef _, EventRef event, void *context)
+{
+    MASShortcutMonitor *dispatcher = (__bridge id)context;
+    [dispatcher handleEvent:event];
+    return noErr;
+}
diff --git a/Framework/MASShortcutView+UserDefaults.h b/Framework/MASShortcutView+UserDefaults.h
deleted file mode 100644
index 05d3c5b..0000000
--- a/Framework/MASShortcutView+UserDefaults.h
+++ /dev/null
@@ -1,7 +0,0 @@
-#import "MASShortcutView.h"
-
-@interface MASShortcutView (UserDefaults)
-
-@property (nonatomic, copy) NSString *associatedUserDefaultsKey;
-
-@end
diff --git a/Framework/MASShortcutView+UserDefaults.m b/Framework/MASShortcutView+UserDefaults.m
deleted file mode 100644
index 55584f4..0000000
--- a/Framework/MASShortcutView+UserDefaults.m
+++ /dev/null
@@ -1,125 +0,0 @@
-#import "MASShortcutView+UserDefaults.h"
-#import "MASShortcut.h"
-#import <objc/runtime.h>
-
-@interface MASShortcutDefaultsObserver : NSObject
-
-@property (nonatomic, readonly) NSString *userDefaultsKey;
-@property (nonatomic, readonly, weak) MASShortcutView *shortcutView;
-
-- (id)initWithShortcutView:(MASShortcutView *)shortcutView userDefaultsKey:(NSString *)userDefaultsKey;
-
-@end
-
-#pragma mark -
-
-@implementation MASShortcutView (UserDefaults)
-
-void *MASAssociatedDefaultsObserver = &MASAssociatedDefaultsObserver;
-
-- (NSString *)associatedUserDefaultsKey
-{
-    MASShortcutDefaultsObserver *defaultsObserver = objc_getAssociatedObject(self, MASAssociatedDefaultsObserver);
-    return defaultsObserver.userDefaultsKey;
-}
-
-- (void)setAssociatedUserDefaultsKey:(NSString *)associatedUserDefaultsKey
-{
-    // First, stop observing previous shortcut view
-    objc_setAssociatedObject(self, MASAssociatedDefaultsObserver, nil, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
-
-    if (associatedUserDefaultsKey.length == 0) return;
-
-    // Next, start observing current shortcut view
-    MASShortcutDefaultsObserver *defaultsObserver = [[MASShortcutDefaultsObserver alloc] initWithShortcutView:self userDefaultsKey:associatedUserDefaultsKey];
-    objc_setAssociatedObject(self, MASAssociatedDefaultsObserver, defaultsObserver, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
-}
-
-@end
-
-#pragma mark -
-
-@implementation MASShortcutDefaultsObserver {
-    MASShortcut *_originalShortcut;
-    BOOL _internalPreferenceChange;
-    BOOL _internalShortcutChange;
-}
-
-- (id)initWithShortcutView:(MASShortcutView *)shortcutView userDefaultsKey:(NSString *)userDefaultsKey
-{
-    self = [super init];
-    if (self) {
-        _originalShortcut = shortcutView.shortcutValue;
-        _shortcutView = shortcutView;
-        _userDefaultsKey = userDefaultsKey.copy;
-        [self startObservingShortcutView];
-    }
-    return self;
-}
-
-- (void)dealloc
-{
-    // __weak _shortcutView is not yet deallocated because it refers MASShortcutDefaultsObserver
-    [self stopObservingShortcutView];
-}
-
-#pragma mark -
-
-void *kShortcutValueObserver = &kShortcutValueObserver;
-
-- (void)startObservingShortcutView
-{
-    // Read initial shortcut value from user preferences
-    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
-    NSData *data = [defaults dataForKey:_userDefaultsKey];
-    _shortcutView.shortcutValue = [NSKeyedUnarchiver unarchiveObjectWithData:data];
-
-    // Observe user preferences to update shortcut value when it changed
-    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(userDefaultsDidChange:) name:NSUserDefaultsDidChangeNotification object:defaults];
-
-    // Observe the keyboard shortcut that user inputs by hand
-    [_shortcutView addObserver:self forKeyPath:@"shortcutValue" options:0 context:kShortcutValueObserver];
-}
-
-- (void)userDefaultsDidChange:(NSNotification *)note
-{
-    // Ignore notifications posted from -[self observeValueForKeyPath:]
-    if (_internalPreferenceChange) return;
-
-    _internalShortcutChange = YES;
-    NSData *data = [note.object dataForKey:_userDefaultsKey];
-    _shortcutView.shortcutValue = [NSKeyedUnarchiver unarchiveObjectWithData:data];
-    _internalShortcutChange = NO;
-}
-
-- (void)stopObservingShortcutView
-{
-    // Stop observing keyboard hotkeys entered by user in the shortcut view
-    [_shortcutView removeObserver:self forKeyPath:@"shortcutValue" context:kShortcutValueObserver];
-
-    // Stop observing user preferences
-    [[NSNotificationCenter defaultCenter] removeObserver:self name:NSUserDefaultsDidChangeNotification object:[NSUserDefaults standardUserDefaults]];
-
-    // Restore original hotkey in the shortcut view
-    _shortcutView.shortcutValue = _originalShortcut;
-}
-
-- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
-{
-    if (context == kShortcutValueObserver) {
-        if (_internalShortcutChange) return;
-        MASShortcut *shortcut = [object valueForKey:keyPath];
-        _internalPreferenceChange = YES;
-
-        NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
-        [defaults setObject:[NSKeyedArchiver archivedDataWithRootObject:shortcut] forKey:_userDefaultsKey];
-        [defaults synchronize];
-
-        _internalPreferenceChange = NO;
-    }
-    else {
-        [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
-    }
-}
-
-@end
diff --git a/Framework/MASShortcutView.h b/Framework/MASShortcutView.h
index 5d788b9..8cff0ca 100644
--- a/Framework/MASShortcutView.h
+++ b/Framework/MASShortcutView.h
@@ -1,5 +1,7 @@
 @class MASShortcut, MASShortcutValidator;
 
+extern NSString *const MASShortcutBinding;
+
 typedef enum {
     MASShortcutViewAppearanceDefault = 0,  // Height = 19 px
     MASShortcutViewAppearanceTexturedRect, // Height = 25 px
diff --git a/Framework/MASShortcutView.m b/Framework/MASShortcutView.m
index 6f562a5..d03efbc 100644
--- a/Framework/MASShortcutView.m
+++ b/Framework/MASShortcutView.m
@@ -1,6 +1,8 @@
 #import "MASShortcutView.h"
 #import "MASShortcutValidator.h"
 
+NSString *const MASShortcutBinding = @"shortcutValue";
+
 #define HINT_BUTTON_WIDTH 23.0
 #define BUTTON_FONT_SIZE 11.0
 #define SEGMENT_CHROME_WIDTH 6.0
@@ -149,6 +151,7 @@
     _shortcutValue = shortcutValue;
     [self resetToolTips];
     [self setNeedsDisplay:YES];
+    [self propagateValue:shortcutValue forBinding:@"shortcutValue"];
 
     if (self.shortcutValueChange) {
         self.shortcutValueChange(self);
@@ -462,4 +465,51 @@ void *kUserDataHint = &kUserDataHint;
     }
 }
 
+#pragma mark Bindings
+
+// http://tomdalling.com/blog/cocoa/implementing-your-own-cocoa-bindings/
+-(void) propagateValue:(id)value forBinding:(NSString*)binding;
+{
+	NSParameterAssert(binding != nil);
+
+	//WARNING: bindingInfo contains NSNull, so it must be accounted for
+	NSDictionary* bindingInfo = [self infoForBinding:binding];
+	if(!bindingInfo)
+		return; //there is no binding
+
+	//apply the value transformer, if one has been set
+	NSDictionary* bindingOptions = [bindingInfo objectForKey:NSOptionsKey];
+	if(bindingOptions){
+		NSValueTransformer* transformer = [bindingOptions valueForKey:NSValueTransformerBindingOption];
+		if(!transformer || (id)transformer == [NSNull null]){
+			NSString* transformerName = [bindingOptions valueForKey:NSValueTransformerNameBindingOption];
+			if(transformerName && (id)transformerName != [NSNull null]){
+				transformer = [NSValueTransformer valueTransformerForName:transformerName];
+			}
+		}
+
+		if(transformer && (id)transformer != [NSNull null]){
+			if([[transformer class] allowsReverseTransformation]){
+				value = [transformer reverseTransformedValue:value];
+			} else {
+				NSLog(@"WARNING: binding \"%@\" has value transformer, but it doesn't allow reverse transformations in %s", binding, __PRETTY_FUNCTION__);
+			}
+		}
+	}
+
+	id boundObject = [bindingInfo objectForKey:NSObservedObjectKey];
+	if(!boundObject || boundObject == [NSNull null]){
+		NSLog(@"ERROR: NSObservedObjectKey was nil for binding \"%@\" in %s", binding, __PRETTY_FUNCTION__);
+		return;
+	}
+
+	NSString* boundKeyPath = [bindingInfo objectForKey:NSObservedKeyPathKey];
+	if(!boundKeyPath || (id)boundKeyPath == [NSNull null]){
+		NSLog(@"ERROR: NSObservedKeyPathKey was nil for binding \"%@\" in %s", binding, __PRETTY_FUNCTION__);
+		return;
+	}
+
+	[boundObject setValue:value forKeyPath:boundKeyPath];
+}
+
 @end
diff --git a/Framework/Prefix.pch b/Framework/Prefix.pch
index 7f2c544..3e71c31 100644
--- a/Framework/Prefix.pch
+++ b/Framework/Prefix.pch
@@ -1 +1,2 @@
 #import <AppKit/AppKit.h>
+#import <Carbon/Carbon.h>
\ No newline at end of file
diff --git a/Framework/Shortcut.h b/Framework/Shortcut.h
index 3087a51..dce07a5 100644
--- a/Framework/Shortcut.h
+++ b/Framework/Shortcut.h
@@ -1,4 +1,5 @@
 #import "MASShortcut.h"
-#import "MASShortcutView+UserDefaults.h"
-#import "MASShortcut+UserDefaults.h"
-#import "MASShortcut+Monitoring.h"
\ No newline at end of file
+#import "MASShortcutValidator.h"
+#import "MASShortcutMonitor.h"
+#import "MASShortcutBinder.h"
+#import "MASShortcutView.h"