WIP new option list

[willmcgugan]

A rewrite of OptionList internals, mostly preserving the original interface. The original was brittle, small changes would break everything. There was also some misguided attempts at doing things lazily, which resulted in doing work multiple times, particularly when first adding the widget. The original would also not be able to report its size accurately, until two or three frames later. An earlier pass partially fixed that, but it still took a frame before the OL could report its size.

• Simplify internal data structures.

• Fix "lazy" operations.

• Integrate better with the new Visual API.

• Replace Separator with None

• Fixes An empty OptionList with width: auto causes a crash in get_content_width #5489

• Fixes When an OptionList has a transparent background option colours can get out of sync (since 0.86.0) #5488

• Fixes The wrap parameter for OptionList no longer works #5418

• Fixes Updating a OptionList that contains separator lines can result in a garbled display (since 0.86.0) #5431

• Fixes Large OptionList widgets are slow to load (since 0.86.0) #5498

[TomJGooding]

I hope you don't mind me sticking my nose in (as usual!), especially since this is still a WiP.

Is it necessary to remove the Separator for this improved version of the OptionList, or is this a design choice? Specifying a separator with None is obviously less intuitive, and it would be a shame to introduce a breaking change if it can be avoided.

[willmcgugan]

I would disagree it is less intuitive. The OptionList intuitively takes a list of options. But a "Separator" is not an option, nor anything that is present in the option list. It is just a way of marking the end of a logical group. I think None does a better job of dividing the options into such groups.

Internally, it does simplify things. There is no need to distinguish between a real option and this special Separator case.

[TomJGooding]

Sorry I didn't spot this before it was merged, from the snapshot it looks like the OptionList height is based on the full height of the prompt rather than the truncated version with nowrap. Is that expected?

[willmcgugan]

Good catch, thanks.