#1795 PageDown does not work correctly for tempo 74 with new JACK transport

[musewhirl]

No one said this was going to be easy, but right of the gate, there's a serious problem with the new jack transport logic. I decided that I might as well create a new ticket, since there is already a separate new bug waiting there.

In one session, I saw two issues:

PageDown key
The PageDown to move the playback pointer forward only works to move it to the end of the current measure. After that it does not appear to work at all. And if at the start of the composition, it moves to the start of measure 2 and then PageDown seems to not work at all...no pointer movement. I tracked this problem to the tempo. I will using 74 as an example below, but this problem is very likely to be restricted to just that.

PageUp key
Even with the default tempo of 70, where both PageUp and PageDown appear to work normally, hitting either repeatedly results in some kind of occasional jitter i.e. what appears to be rapid move in the reverse direction before continuing back again. And ofcourse, with temp 74, this can only be tested with PageUp, but is still observed

These steps are just for the PageDown problem.

Steps to reproduce:

1. Make sure JACK is up.
2. Launch RG
3. Check Use JACK transport
4. Move playback pointer to composition start
5. Change the composition tempo to 74
6. Uncheck New JACK Transport Logic
7. Both PageDown and PageUp work normally i.e. the playback pointer moves forward each PageDown key
8. Now check New JACK Transport Logic
9. Now hit PageDown once and the playback pointer moves forward. After that, it does not work at all
10. You can still PageUp to move back
11. You can also click the playback pointer margin and move the playback pointer anywhere. But from wherever, you only get one PageDown and then that stops working

Of course, I have to uncheck using the New JACK Transport Logic until this is fixed.

Related:
[bugs:#1721]

[Philip Leishman]

Yes - it seems some tempos can cause a rounding error so the position is minimally off what it should be.
The logic for fast forward (PageDown) is move to the end of the current bar so starting from zero the first PageDown works - it moves to the start of the next bar. Unfortunately rounding error in the times caused the time to move to just before the bar line so no further PageDowns worked.
I have a fix for this.
As to the jitter - this is an old problem with an old fix that got broken somewhere down the line. I have included this fix too.

See Codeberg pull request.

[Ted Felix]

Philip's fix pushed as [1366b3]. Please test latest git.

[musewhirl]

Works fine for tempo 74, but from the nature of the bug, I can't comment on all other tempos...except the default of 70. But from the report title itself about tempo=74, it can be closed.