Adding the touchend event listener through the HTML DOM within Amazon Sumerian.

AnchorPositioning.js

// Add an event listener for touch events anywhere on the screen.
// Note: the MouseUpAction of Sumerian doesn't provide the coordinates
// -> use the HTML DOM event directly. This is accessible through
// the Renderer.
this.internalWorld.sumerianRunner.renderer.domElement.addEventListener('touchend', performHitTestCallback);
// Phones use touch events. To also develop / test on a PC (or on
// a mobile device with a mouse attached), you can also register for
// mouse events.
//this.internalWorld.sumerianRunner.renderer.domElement.addEventListener('mouseup', performHitTestCallback);