scrBresenham

function scrBresenham(x1, y1, x2, y2, grid) {
	var w = x2-x1;
	var h = y2-y1;
	var arr = [];
	var dx1 = 0; var dx2 = 0; var dy1 = 0; var dy2 = 0;
	if (w<0) {dx1 = -1} else if (w > 0) {dx1 = 1};
	if (w<0) {dx2 = -1} else if (w > 0) {dx2 = 1};
	if (h<0) {dy1 = -1} else if (h > 0) {dy1 = 1};
	var longest = abs(w);
	var shortest = abs(h);
	if (!(longest > shortest)) {
		longest = abs(h);
		shortest = abs(w);
		if (h < 0) {dy2 = -1} else if (h > 0) {dy2 = 1}
		dx2 = 0;
	}
	var numerator = longest >> 1;
	for (var i = 0; i <= longest; i++) {
		if (x1 > 0 and y1 > 0 and x1 < ds_grid_width(grid) and y1 < ds_grid_height(grid)) {
			if (ds_grid_get(grid, x1, y1) > 0) {
			    array_push(arr, [x1, y1]);
				numerator += shortest;
				if (!(numerator<longest)){
					numerator -= longest;
					x1 += dx1;
					y1 += dy1;
				} else {
					x1 += dx2;
					y1 += dy2;
				}
			}
		}
	}
	return arr;
}