Change outlineItem ID assignment process for major optimization

[emgineering]

This code uses an O(1) process to assign IDs (keep track of the largest ID that has been assigned, and make sure to assign an ID larger than that), compared to the existing O(n^2) process (get a list of all existing IDs, and check every candidate ID starting from 1 until finding one not in the list).

My testing has shown that currently, of all the time spent reading from file, parsing, and setting data, 99.7% of it is spent in the findUniqueID() method. Making this change has led to a speedup from ~18 sec. to ~2 sec on loading my manuscript, while still guaranteeing that any (new) objects have unique IDs.

[TheJackiMonster]

Wow, thanks for fixing that. Existing IDs in old projects won't be replaced using these changes, right? So it's safe to merge, I assume.

Can you squash the commits to one for merging?

[TheJackiMonster]

Does your PR make #777 redundant? I haven't really looked into the details of the ID distribution to see that directly. ^^'

[emgineering]

Squashed.

Existing IDs in old projects won't be replaced using these changes, right?

Should be fine. Previously assigned IDs are read from the file at load time. (In general, calling "setData" with an ID forces the ID assignment, and informs the distributor to not give that ID out again when automatically assigning.)

Does your PR make #777 redundant? I haven't really looked into the details of the ID distribution to see that directly. ^^'

Took a look - as far as I can tell, it's dealing with a separate issue, and would work fine with my changes. (It ultimately calls "setData", which this code has handled.) It does use the slow method for checking for valid IDs, though; all the code there could probably be replaced with item.getUniqueID(recursive=true) to take advantage of the speedups and be more consistent with the rest of the project.

[TheJackiMonster]

Thanks for the insight. I will refer to this PR then in #777. ^^