ScaleRotateGestureHandler

Use the ScaleRotateGestureHandler to handle pinch and rotation gestures from trackpads or touchscreens. Recognition is limited to the element’s geometry.

export component Example inherits Window {
    width: 400px;
    height: 400px;

    property <float> start-scale;
    property <angle> start-rotation;

    gesture := ScaleRotateGestureHandler {
        started => {
            start-scale = rect.current-scale;
            start-rotation = rect.current-rotation;
        }
        updated => {
            rect.current-scale = start-scale * self.scale;
            rect.current-rotation = start-rotation + self.rotation;
        }

        rect := Rectangle {
            background: @radial-gradient(circle, #4488ff, #224488);
            border-radius: 8px;

            property <float> current-scale: 1.0;
            property <angle> current-rotation: 0deg;
            width: 200px * self.current-scale;
            height: 200px * self.current-scale;
            x: (parent.width - self.width) / 2;
            y: (parent.height - self.height) / 2;

            Text {
                text: "Pinch & rotate";
                color: white;
            }
        }
    }
}

slint

The scale property provides a cumulative scale factor relative to the start of the gesture (starting at 1.0). The rotation property provides a cumulative rotation angle (starting at 0deg). Use the started callback to capture your initial state, then multiply by scale and add rotation in the updated callback to apply the gesture.

On macOS and iOS, the handler responds to trackpad pinch and rotation gestures (platform gesture events). On other platforms, it processes raw two-finger touch input for pinch and rotation.

Properties

enabled

bool default: true

When disabled, the ScaleRotateGestureHandler doesn’t recognize any gestures and any on-going gesture is cancelled.

active

bool (out) default: false

true while a gesture is being recognized, false otherwise.

scale

float (out) default: 1.0

The cumulative scale factor of the gesture. Always starts at 1.0 when the gesture begins. A value greater than 1.0 means zooming in, less than 1.0 means zooming out. When the gesture is not active, the value is 1.0.

rotation

angle (out) default: 0deg

The cumulative rotation angle of the gesture. Always starts at 0deg when the gesture begins. Positive values indicate clockwise rotation, negative values indicate counter-clockwise rotation. When the gesture is not active, the value is 0deg.

center

struct Point (out) default: a struct with all default values

The center point of the gesture, in the coordinate system of the ScaleRotateGestureHandler. For two-finger touch input, this is the midpoint between the two fingers. For trackpad gestures, this is the mouse cursor position.

Point

This structure represents a point with x and y coordinate

• x (length):
• y (length):

Callbacks

started()

Invoked when a gesture begins. Use this to capture the initial state you want to transform.

updated()

Invoked whenever the scale, rotation, or center changes during the gesture.

ended()

Invoked when the gesture completes normally (fingers lifted).

cancelled()

Invoked when the gesture is cancelled, for example when the handler is disabled during an active gesture or the window loses focus.