var canvas = new fabric.Canvas('c', { selection: false });
var line, isDown;
canvas.on('mouse:down', function(o){
isDown = true;
var pointer = canvas.getPointer(o.e);
var points = [ pointer.x, pointer.y, pointer.x, pointer.y ];
line = new fabric.Line(points, {
strokeWidth: 5,
fill: 'red',
stroke: 'red',
originX: 'center',
originY: 'center'
});
canvas.add(line);
});
canvas.on('mouse:move', function(o){
if (!isDown) return;
var pointer = canvas.getPointer(o.e);
line.set({ x2: pointer.x, y2: pointer.y });
canvas.renderAll();
});
canvas.on('mouse:up', function(o){
isDown = false;
});
