Get bounding box off all objects on a fabric canvas

bounding_box_fabricjs.js

getBoardBoundingBox: function(canvas) {

            var minX = Number.MAX_VALUE;
            var maxX = Number.MIN_VALUE;
            var minY = Number.MAX_VALUE;
            var maxY = Number.MIN_VALUE;

            canvas.forEachObject(function(o){
                var rad = o.angle * Math.PI/180;
                var w = o.width * o.scaleX;
                var h = o.height * o.scaleY;
                // xmax = x * w/2 * |cos(theta)| + h/2 * |sin(theta)|
                var omaxX = o.left +((w/2) * Math.abs(Math.cos(rad))) + ((h/2) * Math.abs(Math.sin(rad)));
                var ominX = o.left - (omaxX - o.left);
                // ymax = y * w/2 * |sin(theta)| + h/2 * |cos(theta)|
                var omaxY = o.top + ((w/2) * Math.abs(Math.sin(rad))) + ((h/2) * Math.abs(Math.cos(rad)));
                var ominY = o.top - (omaxY - o.top);

                if (ominX < minX)
                    minX = ominX;
                if (omaxX > maxX)
                    maxX = omaxX;
                if (ominY < minY)
                    minY = ominY;
                if (omaxY > maxY)
                    maxY = omaxY;
            
            });
            var box = {
                "x": minX,
                "y": minY,
                "w": maxX - minX,
                "h": maxY - minY
            };
            return box;
        }
    });

It's much simpler to use object's oCoords field

 canvas.forEachObject (o) ->
    cords = o.oCoords
    omaxX = Math.max(cords.tl.x, cords.tr.x, cords.bl.x, cords.br.x)
    ominX = Math.min(cords.tl.x, cords.tr.x, cords.bl.x, cords.br.x)
    omaxY = Math.max(cords.tl.y, cords.tr.y, cords.bl.y, cords.br.y)
    ominY = Math.min(cords.tl.y, cords.tr.y, cords.bl.y, cords.br.y)

    if (ominX < minX)
        minX = ominX
    if (omaxX > maxX)
        maxX = omaxX
    if (ominY < minY)
        minY = ominY
    if (omaxY > maxY)
        maxY = omaxY

In my case the @coulix solution it's better than @everdance because you can calculate the bounding box without have the items already pushed in the canvas, because the only way to have the oCoords is to have the item inserted in the canvas, and I want to prepare the canvas size before have the items inserted.