Hi Ella,

> It'd be nice to have a "Done" button for the script, instead
> of the "click on the viewport" bit, which is a bit too easy to
> trigger accidentally.

Give the version attached here a try - I added a Done button to this version. This one won't exit if you just click with a left-click, you end it by clicking the Done button or using one of the shortcuts for Done (right-click in a viewport or the Enter key).

The line factory part wasn't actually doing anything here, I think it was some left-over remnant from this having started out originally as a modification of the line command or something like that.

The actual meat of creating the construction lines was happening inside the GetPoint() call, which is set up to wait until a point is picked and then return. In this version I replaced that call to a manual event loop so it can respond to getting the "done" event.

Let me know if this one doesn't do what you wanted.

- Michael