A VERY Obscure and Harmless Bug

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john

18 Nov, 2017 01:04 PM

Frederik,

Attached are two simple networks: redraw good and redraw bad. Both are almost identical. Both work just fine.

But here is something strange: if you open redraw bad in a text editor and look at the definition of the "slice1" node on line 19, you will see that it has no position.

For comparison, open redraw good and, on line 19, you will see that "slice1" does have a position: 4.00,5.00.

That is the only difference between the two files: the position of the slice1 node. Moreover, if you open redraw good, move the slice1 node up 1 unit, and save, it's position will disappear! Position 4.00,4.00 is like the Bermuda Triangle: move this particular node to that spot and its position disappears. This doesn't seem to happen if I drag other nodes into that position however.

None of this has any noticeable effect. Both networks display properly in the composition pane, and both function correctly. And if the problem appears all you have to do is move the affected node one unit and re-save.

This phenomenon is not a one-time occurrence. I have now spotted similar missing positions on a half-dozen other networks. It strikes at random, very rarely, and affects a different kind of node each time. I see no obvious common factor across the other networks.

You might wonder how I even spotted it. Just for fun I decided to do a survey of the 282 NodeBox networks I've created to date. I wrote a quick network using the new import_text node to suck in all the ndbx files and spit out a table showing every node in every network (more than 76,000 altogether). For each node I show name, category, type, position and level (for subnetworks). It all worked wonderfully except that, every now and then, one of my nodes had a missing position.

Since this bug is harmless (except for screwing up my survey) I don't think there is any urgent need for you to try to fix it. But having found such a strange and obscure bug I had to at least report it. Sometimes tracking down harmless bugs like this reveals deeper issues.

What a strange bug!

John

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