Change pinch-zoom sensitivity in fabric.js

Question

I have a custom built fabric.js bundle with touch support. Now I can scale any object with the pinch-zoom gesture. The problem is the zoom is really really sensitive, I barely move my fingers and the object is hugely scaled.

I couldn't find much information in the documents about how I can change the sensitivity. I know Event.js is used to handle the touch events within fabric.js. Is there any way I can change this sensitivity?

Answer 1

Ok, I ended up implementing touch controls myself, this is the code I made. This code was placed on the added event of my custom fabric.js object.

////////////////////////////// Touch event handlers
// Add listener event for pinch-zoom
var bbScope = this;
var hammer = new Hammer.Manager(this.canvas.upperCanvasEl);
var pinch = new Hammer.Pinch();
hammer.add([pinch]);

hammer.on('pinch', function (ev) {
    // Set the scale and render only if we have a valid pinch (inside the object)
    if (bbScope._validPinch) {
        bbScope.set('scaleX', ev.scale);
        bbScope.set('scaleY', ev.scale);
        bbScope.canvas.renderAll();
    }
});
hammer.on('pinchend', function (ev) {
    bbScope._validPinch = false;
});
hammer.on('pinchcancel', function (ev) {
    bbScope._validPinch = false;
});
hammer.on('pinchstart', function (ev) {
    // Convert mouse coordinates to canvas coordinates
    ev.clientX = ev.center.x;
    ev.clientY = ev.center.y;

    // Check if the pinch was started inside this object
    if (bbScope.canvas) {
        var p = bbScope.canvas.getPointer(ev);
        bbScope._validPinch = bbScope.containsPoint(p);
    }
    else {
        bbScope._validPinch = false;
    }
});