Question

I need to prevent single touch inside the canvas. But double/multi touch shouch should perform without issue for IOS application

Please find my JS code for touch event

 onTouchStart: function(e, win, eventInfo) {
    if(!this.config.panning) return;
    if(this.config.panning == 'avoid nodes' && (this.dom? this.isLabel(e, win) : eventInfo.getNode())) return;
    this.pressed = true;
    this.pos = eventInfo.getPos();
    var canvas = this.canvas,
        ox = canvas.translateOffsetX,
        oy = canvas.translateOffsetY,
        sx = canvas.scaleOffsetX,
        sy = canvas.scaleOffsetY;
    this.pos.x *= sx;
    this.pos.x += ox;
    this.pos.y *= sy;
    this.pos.y += oy;
  },

  onTouchMove: function(e, win, eventInfo) {
    if(!this.config.panning) return;
    if(!this.pressed) return;
    if(this.config.panning == 'avoid nodes' && (this.dom? this.isLabel(e, win) : eventInfo.getNode())) return;
    var thispos = this.pos, 
        currentPos = eventInfo.getPos(),
        canvas = this.canvas,
        ox = canvas.translateOffsetX,
        oy = canvas.translateOffsetY,
        sx = canvas.scaleOffsetX,
        sy = canvas.scaleOffsetY;
    currentPos.x *= sx;
    currentPos.y *= sy;
    currentPos.x += ox;
    currentPos.y += oy;
    var x = currentPos.x - thispos.x,
        y = currentPos.y - thispos.y;
    this.pos = currentPos;
    this.canvas.translate(x * 1/sx, y * 1/sy);
  },

  onTouchEnd: function(e, win, eventInfo) {
    if(!this.config.panning) return;
    this.pressed = false;
  },
  onTouchCancel: function(e, win, eventInfo) {
        if(!this.config.panning) return;
        this.pressed = false;
      }

From the above code both single touch and multi touch has been perform but I want to do only single touch inside my canvas for IOS app.
Please advice!

Answer 1

per apple documentation Safari Web Connect Guide Handling Touches, you can find the number of touches from the event thus:

    event.touches.length

or, in your case, in the functions of your sample code:

    e.touches.length

if the result of that is 1, you have a single-touch event, and you can simply ignore it. if it is not 1, you have a multi-touch event, and you can process it or pass it on for default handling.