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QLabKit is an Objective-C library for controlling QLab over the OSC API in QLab 3 or later. QLabKit requires macOS 10.9+ or iOS 8.4+.

NOTE: This library is under active development and the API may change.


All the files for the library are in the lib folder. Copy all the files from that folder into your project. Make sure you also include the code in the F53OSC folder which is a submodule. You'll also need to link against Security.framework and GLKit.framework. All files in QLabKit and F53OSC use ARC.

QLabKit can also be installed on iOS using CocoaPods by adding the following to your podfile:

pod 'F53OSC', :git => ''
pod 'QLabKit', :git => ''


There are four primary classes you will use for talking to QLab:

  • QLKBrowser - automatically discover QLab instances on the network
  • QLKServer - represents an individual QLab server with a name, host, and port
  • QLKWorkspace - a single workspace on a server
  • QLKCue - a simplified representation of a cue. A cue list cue is also represented as a cue

There are other classes in QLabKit that these classes rely on that you need not worry about. Read the headers of these primary classes for more usage information. All classes in QLabKit use ARC.


The first thing you need to do is to get a QLKWorkspace instance to communicate with a single workspace from QLab. You can get this in one of two ways:


QLab advertises itself using Bonjour. This allows for the automatic discovery of all QLab machines on the same local network. The QLKBrowser class handles this for you like so:

Create a browser object and give it a delegate that implements QLKBrowserDelegate protocol:

QLKBrowser *browser = [[QLKBrowser alloc] init];
browser.delegate = self;
[browser start];

// Optional: continuously refresh every 5 seconds
[browser enableAutoRefreshWithInterval:5];

Implement the required QLKBrowserDelegate methods. The browser has a servers property that is an array of QLKServer objects. Each QLKServer has a workspaces property that holds an array of QLKWorkspace objects discovered on the network.

- (void) browserDidUpdateServers:(QLKBrowser *)browser
    // Browser has a servers property
    for ( QLKServer *aServer in browser.servers ) 
        for ( QLKWorkspace *aWorkspace in aServer.workspaces ) 
            // do something with the servers and workspaces, i.e. add to a selection UI, etc


If you don't want to automatically discover QLab, you can also do it manually by first creating a server:

NSString *hostIP = @"";
NSInteger port = 53000;
QLKServer *server = [[QLKServer alloc] initWithHost:hostIP port:port];
[server refreshWorkspacesWithCompletion:^(NSArray<QLKWorkspace *> * _Nonnull workspaces) {
    // server now has workspaces
    for ( QLKWorkspace *aWorkspace in workspaces )
        // ... do something with aWorkspace

Once you have a workspace, you can send commands to and get data from QLab. The first thing is to connect to the workspace:

QLKWorkspace *workspace; // assume this exists as a result of one of the earlier methods

// Connect to workspace
[workspace connect];

// Tell workspace to GO
[workspace go];


// Update name of a cue, assuming you have a cue object = @"New name";

QLKWorkspace exposes higher level methods so you don't have to directly deal with formatting the correct message and address. However, there may be API calls that the workspace class doesn't currently support, and you can use the lower-level methods to manually send a message.

NSString *address = [NSString stringWithFormat:@"/workspace/%@/cue_id/%@/name", workspace.uniqueID, cue.uid];
[workspace sendMessage:@"New Name" toAddress:address];

There is also working demo project that shows how you might hook all of this together to find servers on the network, show their workspaces, connect to a workspace, and finally fetch and display all the cues. Open QLabKit.xcodeproj and run the QLabKitDemo project to learn more.

Migrating from 0.0.3 to 0.0.4

QLabKit 0.0.4 requires macOS 10.9+ or iOS 8.4+.


  • Fixes the class method cueTypeIsAudio: so that it now correctly returns NO for the following cue types: Fade, Camera, Text/Titles.
  • Fixes panicCue: so that the QLKOSCIsPanickingKey property is only updated when connected to QLab 4.0 or later (which is the minimum QLab version that supports the /isPanicking OSC method).
  • Adds convenience getters isOverridden, isBroken, isTailingOut, and isPanicking which also take into account the property values of child cues in Group, Cue List, and Cue Cart cues.
  • When using propertyForKey: to get the quaternion of a Video or Fade cue, the value is no longer transformed to NSValue and is now returned as an array of NSNumbers (representing the X, Y, Z, and W components of the quaternion). The convenience property quaternion remains unchanged and gets/sets a GLKQuaternion struct, and the new convenience setter setQuaternion:tellQLab: also accepts a GLKQuaternion struct.


  • Colors and colorspaces are now more consistent between iOS and macOS.
  • The name property and the class method +[QLKColor colorWithName:] now return an empty QLKColor object for undefined color names. Subclasses or categories can override the name property to define additional colors.


  • Fixes an issue where replies from individual OSC getter methods (i.e. calls from cue:valueForKey:block:) were not being processed.
  • The internal F53OSCClient used by QLKClient now performs its TCP/UDP communication with QLab on a background thread. F53OSCClient ensures that its F53OSCClientDelegate methods continue to be called on the main thread. However, be aware that custom implementations of GCDAsyncSocketDelegate or GCDAsyncUdpSocketDelegate methods in any subclasses of QLKClient or F53OSCClient will now be called on a background thread and must dispatch back to the main thread when necessary.
  • Adds QLKClientDelegate methods:
    • workspaceDisconnected (required) which is now called when a QLKClient receives an OSC /update/workspace/{id}/disconnect message from QLab. This replaces the previous behavior in which clientConnectionErrorOccurred was called. This new delegate method now makes it possible for a client app to distinguish between the QLab workspace proactively notifying the client it should disconnect (e.g. because the QLab workspace was closed) and some other issue with the network connection. Connection errors continue to trigger a call to clientConnectionErrorOccurred.
    • clientShouldDisconnectOnError (optional) - If the delegate implements this method and returns NO, the QLKClient will no longer immediately disconnect after a connection error is reported by its internal F53OSCClient. Instead, the delegate is responsible for disconnecting and tearing down the client at some point in the future. If this method returns YES or is not implemented, the QLKClient will behave as before and immediately call disconnect in response to a connection error.
    • lightDashboardUpdated: (optional) - When connected to QLab 4.2 or later, this notifies the delegate when the state of the Light Dashboard has updated.
    • preferencesUpdated: (optional) - When connected to QLab 4.2 or later, this notifies the delegate when certain application preferences in QLab are updated, namely liveFadePreview. To respond to changes made to workspace-level settings, continue to use workspaceSettingsUpdated:.


  • QLKWorkspace now posts a QLKWorkspaceDidDisconnectNotification only after receiving an affirmative /disconnect update message from QLab. QLKWorkspace also no longer posts a redundant QLKWorkspaceDidDisconnectNotification when disconnecting itself from QLab. All other connection errors, e.g. failed attempts to connect due to an incorrect OSC passcode or other network problems, post a QLKWorkspaceConnectionErrorNotification so that observers can evaluate whether to attempt to reconnect or not.
  • The connect method is deprecated because it does not support connecting to workspaces with an OSC passcode. Instead, use connectWithPasscode:completion: and pass nil for the passcode parameter to connect to a workspace whose hasPasscode property is NO.
  • The method connectWithPasscode:completion: now caches the passcode in the workspace only upon a successful connection.
  • Adds a property attemptToReconnect which QLKWorkspace uses in its implementation of the new QLKClientDelegate method clientShouldDisconnectOnError. After receiving a connection error notification, QLKWorkspace uses the value of the attemptToReconnect property to determine whether to attempt to reestablish a connection to the current workspace or to disconnect immediately.
  • The methods startHeartbeat and stopHeartbeat are now public and can be used to actively monitor the network connection. When the heartbeat is running, a network timeout will cause the workspace to post a QLKWorkspaceConnectionErrorNotification.
  • Adds two new methods deferFetchingPropertiesForCue: and resumeFetchingPropertiesForCue: which can be used to reduce network traffic and significantly improve performance when connected to large workspaces. Selective use of these methods allows a workspace to consolidate update requests on a cue-by-cue basis, enabling a client app to send requests for data only when it is actually needed (e.g. when a cue is about to become visible in the UI). When a workspace is set to defer fetching the properties of a given cue, all QLKWorkspace methods prefixed with fetch will cache the property key(s) from any request for that cue instead of sending an OSC message to QLab. When the workspace later is set to resume fetching the properties for that cue, a single /valuesForKeys message will be sent to QLab requesting values for all previously-cached property keys, and all fetch methods will once again transmit OSC requests for that cue immediately when called.
  • Adds a property defaultDeferFetchingPropertiesForNewCues. Set this property to YES to cause the workspace to defer fetching properties for all new cues immediately upon creation. For example, this can be used to avoid flooding the network with OSC update requests when first connecting to QLab. The default for this property is NO, meaning new cues created by the workspace will not defer fetching properties (the "resume" behavior).
  • Adds a QLKWorkspaceDidUpdateLightDashboardNotification which is posted by the QLKWorkspace implementation of QLKClientDelegate method lightDashboardUpdated: when connected to QLab 4.2 or later.
  • Adds a QLKQLabDidUpdatePreferencesNotification which is posted by the QLKWorkspace implementation of QLKClientDelegate method preferencesUpdated: when connected to QLab 4.2 or later.
  • The methods fetchChildrenForCue:block: and fetchAudioLevelsForCue:block: are deprecated because their block parameters are not compatible with the new deferred property fetching mechanism. Instead, request these values using cue:valueForKey:block: with the keys children and sliderLevels, respectively.
  • The values of the following NSString constants are updated to follow the convention of the value matching the name. Any code that directly accesses the value of one of these constants, e.g. comparing to another string using isEqual: or isEqualToString:, should update to use the new string values:
    • QLKWorkspaceDidConnectNotification
    • QLKWorkspaceDidDisconnectNotification
    • QLKWorkspaceConnectionErrorNotification

Migrating from 0.0.2 to 0.0.3

QLabKit 0.0.3 requires macOS 10.9+ or iOS 8.4+.


  • The QLKBrowserDelegate method serverDidUpdateWorkspaces: is renamed to browserServerDidUpdateWorkspaces: to avoid collision with the QLKServerDelegate method of the same name.
  • The selector called by the NSTimer scheduled in enableAutoRefreshWithInterval: is changed from the public method refreshAllWorkspaces to a new private method _refreshAllWorkspaces:.


  • Color values are updated to match the color scheme of QLab 4.
  • Helper class methods colorWithRed:green:blue:alpha: and colorWithWhite:alpha: are deprecated in favor of specific values for NSColor/UIColor for better color matching between Mac and iOS.
  • The "type" property for the object returned by class method defaultColor now has the string value "default" instead of "none".
  • startColor and endColor are deprecated since QLab 4 no longer displays cue colors with gradients. Use lightColor and darkColor instead.
  • lightBlueColor, panelColor and navBarColor are no longer used in QLab 4 and are deprecated.


  • playbackPositionUpdated: is changed to cueListUpdated:withPlaybackPositionID: to allow updating the playback position individually for each cue list cue.


  • Class method iconForType: now returns the string value "mic" for Mic cues to match QLab conventions.
  • pushUpProperty:forKey: is deprecated. Use setProperty:forKey:tellQLab: instead, with the tellQLab parameter set to YES.
  • triggerPushDownPropertyForKey: is deprecated. Use pullDownPropertyForKey:block: instead.
  • pushDownProperty:forKey: is deprecated. Use setProperty:forKey:tellQLab: instead.
  • String constant QLKCueHasNewDataNotification is removed because the method which posted this notification is now deprecated.
  • The unique ID of each cue list cue's playback position can now be accessed using the playbackPositionID property and set using setPlaybackPositionID:tellQLab:. View controllers should now observe QLKCueListDidChangePlaybackPositionIDNotification notifications to respond to playback position changes on a per-cue list basis.
  • QLKCue property getters and setters are now thread-safe and updates are processed on a background queue.


  • QLKActiveCueListIdentifier is renamed to QLKActiveCuesIdentifier for clarity.
  • QLKCueTypeMicrophone is renamed to QLKCueTypeMic to match QLab conventions.


  • The property browser is removed. QLKBrowser now conforms to QLKServerProtocol so an existing browser instance can now be set as the delegate of QLKServer instead of needing to have a dedicated browser property on the server itself.


  • uniqueId property is renamed to uniqueID to unify capitalization of "ID".
  • fetchMainPropertiesForCue: is renamed to fetchDefaultCueListPropertiesForCue:.
  • A QLKCueUpdatedNotification notification is now posted only when cue data has actually changed.
  • String constant QLKWorkspaceDidChangePlaybackPositionNotification is replaced by QLKCueListDidChangePlaybackPositionIDNotification. (See QLKCue above.)
  • String constant QLKWorkspaceDidUpdateCuesNotification has been removed and is replaced with QLKCueUpdatedNotification. Observers of QLKCueUpdatedNotification notifications can now inspect the notification object, which is the cue that was updated, and react accordingly. For example, the notification object will be the QLKWorkspace root after adding a cue list to the workspace. Test the notification object cue for isCueList to determine if the child cues of a particular cue list have changed.
  • All method parameters of type QLKMessageHandlerBlock are renamed to "block" to distinguish from the various styles of other "completion" blocks:
    • cue:valueForKey:completion: is renamed to cue:valueForKey:block:.
    • fetchCueListsWithCompletion: is renamed to fetchCueListsWithBlock:.
    • fetchPlaybackPositionForCue:completion: is renamed to fetchPlaybackPositionForCue:block:.
    • fetchChildrenForCue:completion: is renamed to fetchChildrenForCue:block:.
    • fetchAudioLevelsForCue:completion: is renamed to fetchAudioLevelsForCue:block:.
  • The "type" property for the __root__ and __active__ cue list cues are changed from QLKCueTypeGroup to QLKCueTypeCueList.


QLabKit © copyright 2014-2018 Figure 53, LLC.

QLabKit is licensed under the MIT license.


An Objective C library for controlling QLab using the OSC API introduced in QLab 3.



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