adjustable onScreenButtonView alpha(transparency)

Limelight/Input/CustomOSC/OnScreenButtonState.h

@@ -28,6 +28,7 @@ NS_ASSUME_NONNULL_BEGIN
 @property (nonatomic, assign) CGFloat widthFactor; // for OnScreenButtonView
 @property (nonatomic, assign) CGFloat heightFactor; // for OnScreenButtonView
 @property (nonatomic, assign) CGFloat oscLayerSizeFactor; // for OnScreenController CALayer
+@property (nonatomic, assign) CGFloat backgroundAlpha; // for OnScreenController CALayer
 
 // @property (nonatomic, assign) BOOL hasValidPosition;