GML Drawing a partial circle

[IceNineOcean]

In a game I'm making, I want to have a gui timer element similar to the little energy circles used in Breath of the Wild; it starts as a full circle, and as it counts down, the circumference is opened, kinda like a clock. A solution I've come up with is the following:

//x,y are center coordinates
//len is radius
//angle is the calculated current angle of the timer, scaled between 450 and 90, where 450 is the starting time, 90 is 0

for (var i = angle; i>91; i--) {
        draw_line(x+lengthdir_x(len, i), y+lengthdir_y(len, i), x+lengthdir_x(len, i-1), y+lengthdir_y(len, i-1));
}

Is there a better way to do this and not include potentially 360 runs of a loop every single frame? I guess i could decrement by more than 1 and lose resolution on the circle, but that's still a lot of looping.

 

[Slyddar]

Dave's example of doing this works pretty well. Check it out here - http://www.davetech.co.uk/gamemakercircularhealthbars
Note that it does use surfaces though.

 

[IceNineOcean]

Looks helpful, I'll check it out once I'm back at my computer.