getFlatGraph: rewrite recursion to while loop

[brightman9]

To avoid call stack overflow when the graph has a large nesting depth. For example:

let illo = new Zdog.Illustration({
    element: '.canvas'
});

let parent = illo;
for (let depth = 0; depth < 1000; depth++) {

    let rotateX = new Zdog.Anchor({
        addTo: parent,
        rotate: { x: Zdog.TAU / 4 }
    });

    let rotateY = new Zdog.Anchor({
        addTo: rotateX,
        rotate: { y: Zdog.TAU / 6 }
    });

    let rotateZ = new Zdog.Anchor({
        addTo: rotateY,
        rotate: { z: Zdog.TAU / 8 }
    });

    parent = rotateZ;
}

illo.updateRenderGraph();

[brightman9]

Other recursive functions also have the same problem(Anchor.prototype.update, Anchor.prototype.transform, Anchor.prototype.copyGraph and so on).
I think they could be rewritten to loop in a uniform way.

[desandro]

Add a 👍 reaction to this issue if you would like to see this feature added. Do not add +1 comments — They will be deleted.

[desandro]

Thank you for this contribution. I can see how this could be an improvement, but I see two issues

1. There needs to be a separate fix so it works with Group
2. As it is, I saw worse performance in some of my buggier demos, like Steam Spooky House