# FxOnScreenControl_v4 Defines the methods a plug-in must implement to create parameter controls. ``` protocol FxOnScreenControl_v4 ``` ## Topics ### Instance Methods [`func drawOSC(withWidth: Int, height: Int, activePart: Int, destinationImage: FxImageTile!, at: CMTime)`](/documentation/professional_video_applications/FxOnScreenControl_v4/drawOSC(withWidth:height:activePart:destinationImage:at:)) Draws a control on an image. This is the main method the host application calls to draw a plug-in parameter control. [`func drawingCoordinates() -> FxDrawingCoordinates`](/documentation/professional_video_applications/FxOnScreenControl_v4/drawingCoordinates()) Defines the coordinate space for an event. [`func hitTestOSC(atMousePositionX: Double, mousePositionY: Double, activePart: UnsafeMutablePointer!, at: CMTime)`](/documentation/professional_video_applications/FxOnScreenControl_v4/hitTestOSC(atMousePositionX:mousePositionY:activePart:at:)) Figures out which part of the onscreen control was hit. [`func keyDown(atPositionX: Double, positionY: Double, keyPressed: UInt16, modifiers: FxModifierKeys, forceUpdate: UnsafeMutablePointer!, didHandle: UnsafeMutablePointer!, at: CMTime)`](/documentation/professional_video_applications/FxOnScreenControl_v4/keyDown(atPositionX:positionY:keyPressed:modifiers:forceUpdate:didHandle:at:)) Provides information when a key is pressed. [`func keyUp(atPositionX: Double, positionY: Double, keyPressed: UInt16, modifiers: FxModifierKeys, forceUpdate: UnsafeMutablePointer!, didHandle: UnsafeMutablePointer!, at: CMTime)`](/documentation/professional_video_applications/FxOnScreenControl_v4/keyUp(atPositionX:positionY:keyPressed:modifiers:forceUpdate:didHandle:at:)) Provides information when a key is released. [`func mouseDown(atPositionX: Double, positionY: Double, activePart: Int, modifiers: FxModifierKeys, forceUpdate: UnsafeMutablePointer!, at: CMTime)`](/documentation/professional_video_applications/FxOnScreenControl_v4/mouseDown(atPositionX:positionY:activePart:modifiers:forceUpdate:at:)) Provides information when the left mouse button is pressed and the pointer is on an image with an active plug-in control. [`func mouseDragged(atPositionX: Double, positionY: Double, activePart: Int, modifiers: FxModifierKeys, forceUpdate: UnsafeMutablePointer!, at: CMTime)`](/documentation/professional_video_applications/FxOnScreenControl_v4/mouseDragged(atPositionX:positionY:activePart:modifiers:forceUpdate:at:)) Provides information when the left mouse button is pressed and the pointer is moved with the mouse button still down. [`func mouseEntered(atPositionX: Double, positionY: Double, modifiers: FxModifierKeys, forceUpdate: UnsafeMutablePointer!, at: CMTime)`](/documentation/professional_video_applications/FxOnScreenControl_v4/mouseEntered(atPositionX:positionY:modifiers:forceUpdate:at:)) Provides information when the mouse pointer enters the view. [`func mouseExited(atPositionX: Double, positionY: Double, modifiers: FxModifierKeys, forceUpdate: UnsafeMutablePointer!, at: CMTime)`](/documentation/professional_video_applications/FxOnScreenControl_v4/mouseExited(atPositionX:positionY:modifiers:forceUpdate:at:)) Provides information when the mouse pointer leaves the view. [`func mouseMoved(atPositionX: Double, positionY: Double, activePart: Int, modifiers: FxModifierKeys, forceUpdate: UnsafeMutablePointer!, at: CMTime)`](/documentation/professional_video_applications/FxOnScreenControl_v4/mouseMoved(atPositionX:positionY:activePart:modifiers:forceUpdate:at:)) Provides information when the mouse pointer changes location. [`func mouseUp(atPositionX: Double, positionY: Double, activePart: Int, modifiers: FxModifierKeys, forceUpdate: UnsafeMutablePointer!, at: CMTime)`](/documentation/professional_video_applications/FxOnScreenControl_v4/mouseUp(atPositionX:positionY:activePart:modifiers:forceUpdate:at:)) Provides information when the left mouse button is released. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)