function onCanvasEnter( event ) {
    /**
     * Raised when a pointer enters the {@link OpenSeadragon.Viewer#canvas} element.
     *
     * @event canvas-enter
     * @memberof OpenSeadragon.Viewer
     * @type {object}
     * @property {OpenSeadragon.Viewer} eventSource - A reference to the Viewer which raised this event.
     * @property {OpenSeadragon.MouseTracker} tracker - A reference to the MouseTracker which originated this event.
     * @property {String} pointerType - "mouse", "touch", "pen", etc.
     * @property {OpenSeadragon.Point} position - The position of the event relative to the tracked element.
     * @property {Number} buttons - Current buttons pressed. A combination of bit flags 0: none, 1: primary (or touch contact), 2: secondary, 4: aux (often middle), 8: X1 (often back), 16: X2 (often forward), 32: pen eraser.
     * @property {Number} pointers - Number of pointers (all types) active in the tracked element.
     * @property {Boolean} insideElementPressed - True if the left mouse button is currently being pressed and was initiated inside the tracked element, otherwise false.
     * @property {Boolean} buttonDownAny - Was the button down anywhere in the screen during the event. <span style="color:red;">Deprecated. Use buttons instead.</span>
     * @property {Object} originalEvent - The original DOM event.
     * @property {?Object} userData - Arbitrary subscriber-defined object.
     */
    this.raiseEvent( 'canvas-enter', {
        tracker: event.eventSource,
        pointerType: event.pointerType,
        position: event.position,
        buttons: event.buttons,
        pointers: event.pointers,
        insideElementPressed: event.insideElementPressed,
        buttonDownAny: event.buttonDownAny,
        originalEvent: event.originalEvent
    });
}
Raised when a mouse or touch drag operation ends on the {@link OpenSeadragon.Viewer#canvas} element.

@event canvas-drag-end
@memberof OpenSeadragon.Viewer
@type {object}
@property {OpenSeadragon.Viewer} eventSource - A reference to the Viewer which raised this event.
@property {OpenSeadragon.MouseTracker} tracker - A reference to the MouseTracker which originated this event.
@property {String} pointerType - "mouse", "touch", "pen", etc.
@property {OpenSeadragon.Point} position - The position of the event relative to the tracked element.
@property {Number} speed - Speed at the end of a drag gesture, in pixels per second.
@property {Number} direction - Direction at the end of a drag gesture, expressed as an angle counterclockwise relative to the positive X axis (-pi to pi, in radians). Only valid if speed > 0.
@property {Boolean} shift - True if the shift key was pressed during this event.
@property {Object} originalEvent - The original DOM event.
@property {Boolean} preventDefaultAction - Set to true to prevent default drag-end flick behaviour. Default: false.
@property {?Object} userData - Arbitrary subscriber-defined object.