onPencilDoubleTap(perform:)

Adds an action to perform after the user double-taps their Apple Pencil.

Declaration

nonisolated func onPencilDoubleTap(perform action: @escaping (PencilDoubleTapGestureValue) -> Void) -> some View

Parameters

action:
The action to perform after the user double-taps their Apple Pencil.

Return Value

A view that performs action after the user double-taps their Apple Pencil.

Discussion

You should respect people’s setting for the double-tap gesture by reading the preferredPencilDoubleTapAction environment value, if the setting makes sense in your app. If it doesn’t, consider giving people a way to specify custom behavior in your app instead.

In the example below, double-tapping an Apple Pencil will…

do nothing if this is what the user selected in the Settings app,
switch the tool to ”Lasso” if this is the action they have configured in the app,
switch the tool to ”Eraser” if they haven’t configured a custom action in the app and this is what they selected in the Settings app,
switch the tool to the last used one otherwise.

enum MyDrawingTool: Equatable {
    case brush
    case lasso
    case eraser
    ...
}

enum MyPencilAction: String {
    case switchLasso
    ...
}

@State private var currentTool = MyDrawingTool.brush
@State private var lastTool: MyDrawingTool?

@Environment(\.preferredPencilDoubleTapAction) private var globalAction
@AppStorage("customPencilDoubleTapAction") private var customAction: MyPencilAction?

var body: some View {
    MyDrawingCanvas()
        .onPencilDoubleTap { _ in
            guard globalAction != .ignore else {
                // Respect the user’s preference to ignore the double-tap gesture.
                return
            }
            if let customAction {
                // If a custom action is configured, respect it.
                if customAction == .switchLasso, currentTool != .lasso {
                     (currentTool, lastTool) = (.lasso, currentTool)
                }
            } else if globalAction == .switchEraser, currentTool != .eraser {
                // Switch to eraser if the user prefers it otherwise.
                (currentTool, lastTool) = (.eraser, currentTool)
            } else if let lastTool {
                // Switch to the last used tool by default.
                (currentTool, lastTool) = (lastTool, currentTool)
            }
        }
}

For more information about Apple Pencil double-tap gestures, see Human Interface Guidelines.