Fix envelope point navigation getting stuck on a point or skipping points when there are multiple points at the same position.

[jcsteh]

Fixes #1242.

[jcsteh]

@LeonarddeR, I'd love a review on this if you have the time, but I totally understand if you don't. I really tried to come up with a simpler or cleaner way to do this, but I just couldn't. Is this readable? Am I missing a simpler approach? Thanks.

[github-actions]

Build 122 succeeded!

• Download for Windows
• Download for Mac

[github-actions]

Build 123 succeeded!

• Download for Windows
• Download for Mac

[LeonarddeR]

I will have a look over the weekend.

[LeonarddeR]

I must admit that this is not the easiest code to read. The most important thing seems to me that it works. That said, could using a random access iterator, just as with MIDI events, improve readability? Or is that a totally wrong way of thinking?

[LeonarddeR]

It occurs to me that this extra call is superfluous when the call at line 278/279 doesn't result in a skip. is that correct?

[jcsteh]

You're quite correct. I originally thought that there were code paths that can reach here where the time, etc. hasn't been fetched yet. However, I'm now thinking that might be incorrect, so I might be able to move this inside the if block.

[jcsteh]

Thanks for the suggestion. I spent some time thinking about this just now, but I don't think a random access iterator will help here. There are a few key differences between envelope points and MIDI events. For envelope points:

1. There are multiple possible start points. If we previously moved to a point at the cursor, then we always want to move (unless we can't). On the other hand, if we didn't previously move to a point at the cursor, we only want to move from the start point if it isn't at the cursor.
2. We only have one dimension of navigation for envelope points. With MIDI, we have separate commands for notes and chords. For envelope points, next and previous move even through points at the same position.
3. REAPER has an API call to get the envelope point nearest the cursor. That means we only need to increment (or decrement) once at most. In contrast, with MIDI events, we potentially have to increment many times to find the event we want, which increases the utility (and justifies the complexity) of an iterator.
4. For envelope points, we want next and previous to move to the point at the cursor if they can't move any further. That is where a lot of the edge cases here come from. We don't do that for MIDI events, though arguably we should; see MIDI Editor: broken the chords preview moving throughby #897. I suspect fixing that will increase the complexity there too.

[jcsteh]

I'm happy for someone to take a stab at rewriting this if they have a better idea; I'm not particularly fond of this code. That said, I really don't see how I can make this better despite more thinking about it today; I don't think an iterator is going to make the edge cases any simpler, but maybe I'm missing something. I'll merge it for now.

[github-actions]

Build 126 succeeded!

• Download for Windows
• Download for Mac