You can do it by editing dragdrop.js as mention here:
In Draggables:
register: function(draggable) {
if(this.drags.length == 0) {
this.eventMouseUp = this.endDrag.bindAsEventListener(this);
this.eventMouseMove = this.updateDrag.bindAsEventListener(this);
this.eventKeypress = this.keyPress.bindAsEventListener(this);
Event.observe(document, "mouseup", this.eventMouseUp);
Event.observe(document, "mousemove", this.eventMouseMove);
Event.observe(document, "keypress", this.eventKeypress);
Event.observe(document, "touchstart", this.eventKeypress);
Event.observe(document, "touchmove", this.eventMouseMove);
Event.observe(document, "touchend", this.eventMouseUp);
}
this.drags.push(draggable);
},
unregister: function(draggable) {
this.drags = this.drags.reject(function(d) { return d==draggable });
if(this.drags.length == 0) {
Event.stopObserving(document, "touchstart", this.eventKeypress);
Event.stopObserving(document, "touchmove", this.eventMouseMove);
Event.stopObserving(document, "touchend", this.eventMouseUp);
Event.stopObserving(document, "mouseup", this.eventMouseUp);
Event.stopObserving(document, "mousemove", this.eventMouseMove);
Event.stopObserving(document, "keypress", this.eventKeypress);
}
},
In Draggable:
initialize:
...
this.eventMouseDown = this.initDrag.bindAsEventListener(this);
Event.observe(this.handle, "mousedown", this.eventMouseDown);
Event.observe(this.handle, "touchstart", this.eventMouseDown);
Draggables.register(this);
},
destroy: function() {
Event.stopObserving(this.handle, "mousedown", this.eventMouseDown);
Event.stopObserving(this.handle, "touchstart", this.eventMouseDown);
Draggables.unregister(this);
},
...
initDrag: function(event) {
if(!Object.isUndefined(Draggable._dragging[this.element]) &&
Draggable._dragging[this.element]) return;
if(Event.isLeftClick(event) || event.type == "touchstart") {
Along with editing prototype.js:
function pointerX(event) {
var docElement = document.documentElement,
body = document.body || { scrollLeft: 0 };
if (event.changedTouches) return (event.changedTouches[0].clientX +
(docElement.scrollLeft || body.scrollLeft) -
(docElement.clientLeft || 0));
return event.pageX || (event.clientX +
(docElement.scrollLeft || body.scrollLeft) -
(docElement.clientLeft || 0));
}
function pointerY(event) {
var docElement = document.documentElement,
body = document.body || { scrollTop: 0 };
if (event.changedTouches) return (event.changedTouches[0].clientY +
(docElement.scrollTop || body.scrollTop) -
(docElement.clientTop || 0));
return event.pageY || (event.clientY +
(docElement.scrollTop || body.scrollTop) -
(docElement.clientTop || 0));
}