Fix handling multiples of the same MIDI note (fixes bug brought up in issue #10199)

[jakobkg]

Description

This change makes it so that MIDI note on messages are sent every time a MIDI key is pressed, but the MIDI note off message is only sent once all instances of the same MIDI note have been released. This issue would make it so that if you have a keymap with several MIDI chords, where the chords had overlapping notes, the common notes would be turned off once one chord was released even if another chord containing the same note is still being held. This PR fixes that.

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout/userspace (addition or update)
• Documentation

Issues Fixed or Closed by This PR

• [MIDI] Sustain effect when same notes are played. #10199

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).

[jakobkg]

An issue I've noticed while playing some with this change applied is that if I change octaves on the keyboard while a note is held, the note is sustained as the note off message being sent when hte key is released is an octave off from the note on message that was sent when the key was pressed. I would optimally try to map the registered presses to physical keys rather than keycodes, but since that would be layout dependent I'm assuming it can't be done in core so I'll have to think of a different solution. I assume this also applies to transpositions.
Example: I press a key with keycode MI_C and while holding it, I press a key with MI_OCTU. Now when I release the first key the note off message does not get sent, and the original C is sustained until I press and release the same note elsewhere on the keyboard, or transpose back down an octave to press and release the same key again.

[jakobkg]

Failing build is addressed in PR #11652

[stale]

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[3araht]

Hi @jakobkg.
Sorry that I couldn't comment on this pull request before the merge.
Somehow this update brought back the sutain issue again on my keyboard.

If I tried the previous version (c66df16) by the following command, the problems can be solved.
git checkout c66df16 quantum/process_keycode/process_midi.c

Could you check it at your enviromnent?