How to create a straight line in Fabric.Js

Question

I am trying to create a straight line in fabric.js that will switch to line mode using an input checkbox. Problem is, even after I uncheck it, the straight line doesn't stop. How can I make it stop putting out a line after I uncheck?

HTML

<input type="checkbox" id="drawmode">
<canvas id="c" width="500" height="300"></canvas>

JavaScript

    var canvas = new fabric.Canvas('c', { selection: false });
        var line;
        var isDrawing;

document.getElementById('drawmode').addEventListener("click", function(){
        if(this.checked == true){

canvas.on('mouse:down', function (o) {
            isDrawing = true;
            var pointer = canvas.getPointer(o.e);
            var points = [pointer.x, pointer.y, pointer.x, pointer.y];

            line = new fabric.Line(points, {
                strokeWidth: 3,
                stroke: 'black'
            });
            canvas.add(line);
        });


        canvas.on('mouse:move', function (o) {
            if (isDrawing) {
                var pointer = canvas.getPointer(o.e);
                line.set({ x2: pointer.x, y2: pointer.y });
                canvas.renderAll();
            }
        });

        canvas.on('mouse:up', function (o) {
            isDrawing = false;
        });
} 

else if(this.checked == false)
{
  // What should I put here to break out of the line drawing mode??
}

Answer 1

Use canvas.off() to turn off everything, or canvas.off('mouse:down') to turn off all handlers for a certain event, or canvas.off('mouse:down', handler) to turn off a certain handler. In the last case, you'll have to put your handlers in variables.

See also the Fabric.js docs .

You could try something like this:

document.getElementById('drawmode').addEventListener("click", function(){
    if(this.checked) {
        canvas.on('mouse:down', handleMouseDown);
        canvas.on('mouse:move', handleMouseMove);
        canvas.on('mouse:up', handleMouseUp);
    }  else {
        canvas.off('mouse:down', handleMouseDown);
        canvas.off('mouse:move', handleMouseMove);
        canvas.off('mouse:up', handleMouseUp);
    }
}

function handleMouseDown(o) {
    isDrawing = true;
    var pointer = canvas.getPointer(o.e);
    var points = [pointer.x, pointer.y, pointer.x, pointer.y];

    line = new fabric.Line(points, {
        strokeWidth: 3,
        stroke: 'black'
    });
    canvas.add(line);
}

function handleMouseMove(o) {
    if (isDrawing) {
        var pointer = canvas.getPointer(o.e);
        line.set({ x2: pointer.x, y2: pointer.y });
        canvas.renderAll();
    }
}

function handleMouseUp (o) {
    isDrawing = false;
}