libobs: Rewrite macOS Hotkeys to use CGEventTap

Using CGEventTapCreate instead of addGlobalMonitorForEventsMatchingMask
to listen to global hotkeys has the advantage of tighter control over
what permissions we need. Since we only listen to and do not modify the
event, it is enough to have "Input Monitoring" instead of the full
"Accessibility" (which would allow modifying the event after catching
it).

cmake/macos/helpers.cmake

@@ -68,6 +68,7 @@ function(set_target_properties_obs target)
                    INFOPLIST_KEY_NSHumanReadableCopyright "(c) 2012-${CURRENT_YEAR} Lain Bailey"
                    INFOPLIST_KEY_NSCameraUsageDescription "OBS needs to access the camera to enable camera sources to work."
                    INFOPLIST_KEY_NSMicrophoneUsageDescription "OBS needs to access the microphone to enable audio input."
+                   INFOPLIST_KEY_NSAppleEventsUsageDescription "OBS needs to access background events to enable hotkeys while not in focus."
       )
 
       get_property(obs_dependencies GLOBAL PROPERTY _OBS_DEPENDENCIES)

libobs/obs-cocoa.m

@@ -421,8 +421,7 @@ static const macOS_glyph_desc_t key_glyphs[(keyCodeMask >> 8)] = {
 
 struct obs_hotkeys_platform {
     volatile long refs;
-    CFTypeRef monitor;
-    CFTypeRef local_monitor;
+    CFMachPortRef eventTap;
     bool is_key_down[OBS_KEY_LAST_VALUE];
     TISInputSourceRef tis;
     CFDataRef layout_data;
@@ -456,14 +455,10 @@ static void hotkeys_release(obs_hotkeys_platform_t *platform)
             platform->layout_data = NULL;
         }
 
-        if (platform->monitor) {
-            [NSEvent removeMonitor:(__bridge id _Nonnull)(platform->monitor)];
-            platform->monitor = NULL;
-        }
-
-        if (platform->local_monitor) {
-            [NSEvent removeMonitor:(__bridge id _Nonnull)(platform->local_monitor)];
-            platform->local_monitor = NULL;
+        if (platform->eventTap) {
+            CGEventTapEnable(platform->eventTap, false);
+            CFRelease(platform->eventTap);
+            platform->eventTap = NULL;
         }
 
         bfree(platform);
@@ -521,20 +516,40 @@ static bool log_layout_name(TISInputSourceRef tis)
 
 // MARK: macOS Hotkey CoreFoundation Callbacks
 
-static void MonitorEventHandlerProc(obs_hotkeys_platform_t *platform, NSEvent *event)
+static CGEventRef KeyboardEventProc(CGEventTapProxy proxy __unused, CGEventType type, CGEventRef event, void *userInfo)
 {
-    NSEventModifierFlags flags = event.modifierFlags;
-    platform->is_key_down[OBS_KEY_CAPSLOCK] = !!(flags & NSEventModifierFlagCapsLock);
-    platform->is_key_down[OBS_KEY_SHIFT] = !!(flags & NSEventModifierFlagShift);
-    platform->is_key_down[OBS_KEY_ALT] = !!(flags & NSEventModifierFlagOption);
-    platform->is_key_down[OBS_KEY_META] = !!(flags & NSEventModifierFlagCommand);
-    platform->is_key_down[OBS_KEY_CONTROL] = !!(flags & NSEventModifierFlagControl);
-
-    if (event.type == NSEventTypeKeyDown || event.type == NSEventTypeKeyUp) {
-        obs_key_t obsKey = obs_key_from_virtual_key(event.keyCode);
-
-        platform->is_key_down[obsKey] = (event.type == NSEventTypeKeyDown);
+    obs_hotkeys_platform_t *platform = userInfo;
+
+    const CGEventFlags flags = CGEventGetFlags(event);
+    platform->is_key_down[OBS_KEY_SHIFT] = !!(flags & kCGEventFlagMaskShift);
+    platform->is_key_down[OBS_KEY_ALT] = !!(flags & kCGEventFlagMaskAlternate);
+    platform->is_key_down[OBS_KEY_META] = !!(flags & kCGEventFlagMaskCommand);
+    platform->is_key_down[OBS_KEY_CONTROL] = !!(flags & kCGEventFlagMaskControl);
+
+    switch (type) {
+        case kCGEventKeyDown: {
+            const int64_t keycode = CGEventGetIntegerValueField(event, kCGKeyboardEventKeycode);
+            platform->is_key_down[obs_key_from_virtual_key(keycode)] = true;
+            break;
+        }
+        case kCGEventKeyUp: {
+            const int64_t keycode = CGEventGetIntegerValueField(event, kCGKeyboardEventKeycode);
+            platform->is_key_down[obs_key_from_virtual_key(keycode)] = false;
+            break;
+        }
+        case kCGEventFlagsChanged: {
+            break;
+        }
+        case kCGEventTapDisabledByTimeout: {
+            blog(LOG_DEBUG, "[hotkeys-cocoa]: Hotkey event tap disabled by timeout. Reenabling...");
+            CGEventTapEnable(platform->eventTap, true);
+            break;
+        }
+        default: {
+            blog(LOG_WARNING, "[hotkeys-cocoa]: Received unexpected event with code '%d'", type);
+        }
     }
+    return event;
 }
 
 static void InputMethodChangedProc(CFNotificationCenterRef center __unused, void *observer,
@@ -577,19 +592,26 @@ bool obs_hotkeys_platform_init(struct obs_core_hotkeys *hotkeys)
 
     obs_hotkeys_platform_t *platform = bzalloc(sizeof(obs_hotkeys_platform_t));
 
-    platform->monitor =
-        (__bridge CFTypeRef)([NSEvent addGlobalMonitorForEventsMatchingMask:NSEventMaskKeyUp | NSEventMaskKeyDown
-                                                                    handler:^(NSEvent *_Nonnull event) {
-                                                                        MonitorEventHandlerProc(platform, event);
-                                                                    }]);
-
-    platform->local_monitor = (__bridge CFTypeRef)([NSEvent
-        addLocalMonitorForEventsMatchingMask:NSEventMaskKeyUp | NSEventMaskKeyDown
-                                     handler:^NSEvent *_Nullable(NSEvent *_Nonnull event) {
-                                         MonitorEventHandlerProc(platform, event);
+    const bool has_event_access = CGPreflightListenEventAccess();
+    if (has_event_access) {
+        platform->eventTap = CGEventTapCreate(kCGHIDEventTap, kCGHeadInsertEventTap, kCGEventTapOptionListenOnly,
+                                              CGEventMaskBit(kCGEventKeyDown) | CGEventMaskBit(kCGEventKeyUp) |
+                                                  CGEventMaskBit(kCGEventFlagsChanged),
+                                              KeyboardEventProc, platform);
+        if (!platform->eventTap) {
+            blog(LOG_WARNING, "[hotkeys-cocoa]: Couldn't create hotkey event tap.");
+            hotkeys_release(platform);
+            platform = NULL;
+            return false;
+        }
+        CFRunLoopSourceRef source = CFMachPortCreateRunLoopSource(kCFAllocatorDefault, platform->eventTap, 0);
+        CFRunLoopAddSource(CFRunLoopGetCurrent(), source, kCFRunLoopCommonModes);
+        CFRelease(source);
 
-                                         return event;
-                                     }]);
+        CGEventTapEnable(platform->eventTap, true);
+    } else {
+        blog(LOG_WARNING, "[hotkeys-cocoa]: No event permissions, could not add global hotkeys.");
+    }
 
     platform->tis = TISCopyCurrentKeyboardLayoutInputSource();
     platform->layout_data = (CFDataRef) TISGetInputSourceProperty(platform->tis, kTISPropertyUnicodeKeyLayoutData);