[Accessibility] Gradual tempo changes skipped by Alt+Left and Alt+Right

[shoogle]

Issue type

UI bug

Bug description

Gradual tempo changes, such as "rit.", "rall." and "accel.", are not accessible via the next-element (Alt+Right) or previous-element (Alt+Left) actions

Steps to reproduce

1. Create a score
2. Add a "rit." or "accel." line from the Tempo palette.
3. Click on a nearby note or rest.
4. Try to navigate to the line with Alt+Left or Alt+Right.

Screenshots/Screen recordings

MuseScore Version

Latest nightly (231340304, 0e5a099)

Regression

No.

Operating system

Windows 11

Additional context

No response

[JordanVoets]

I'm gonna check this out

It'll be my first (ever) open-source contribution so I'll probably be back with questions soon.

[cbjeukendrup]

Welcome! You can also ask things in our Discord server: https://discord.gg/HwHhXEbJ4r if you hadn't found it yet. See our Wiki pages (https://github.com/musescore/MuseScore/wiki/Set-up-developer-environment) for the most up-to-date compile instructions.

[JordanVoets]

I apologise for the delay. I have a couple of questions:

1. The EngravingItem::nextElement() method returns the next element with a switch statement based on ElementType. Which element type are these tempo markings classified as?
2. What is the difference between EngravingItem::nextElement() and EngravingItem::nextSegmentElement?

[MarcSabatella]

The overall class for tempo changes is GradualTempoChange. But they are broken into "segments" as they can cross systems, so you might actually be needed GradualTempoChangeSegment. Check to see how other line types are handled, such as hairpins or voltas. Voltas are probably a better match since, like tempo changes, they are system-level elements as opposed to staff. Seems to not be directly in EngravingItem, though. So you'll probably want to single step through as you navigate through voltas to see.

nextSegmentElement is kind of a holdover from n older implementation that I guess we continue to support but probably isn't used much. It doesn't navigate all elements, just ones that actually occupy a segment (a completely different sense of the word "segment" from what happens with lines!) directly. Notes, rests, barlines, clefs - these are all segment elements - contained directly within a segment. Whereas things like articulations etc are attached to the notes, they don't live directly in the segment. So they aren't navigated by the this command. Lines are not segment elements in this sense, so they don't need to be navigated by this command - meaning you can ignore those functions, I think.

[JordanVoets]

Thanks for the detailed answer.

It's interesting to see all the complexity behind Musescore.

I'll try to check how other line types are handled.

[msviolafangirl]

Hi, I am a screen reader user, and I can confirm alt+left and alt+right skips gradual tempo changes.

[JordanVoets]

Spanner* s = firstSpanner(activeStaff);
if (s) {
  return s->spannerSegments().front();
}

I found out that s is true for Volta and s is false for ritardando so something is probably up in the firstSpanner(activeStaff) method.