Enabled the piano roll and automation editor buttons only when not empty

[clemetayer]

This PR aims to resolve issue #1132 by enabling the piano roll and automation editor only if they have associated data.

Changes

• Enable/disable the piano roll and automation editor depending on whether they have associated data

Notes

• I'm new and don't have much experience with QT/C++, so I kept the dev simple.
  • By the way, I find the documentation good for a newcomer. I was able to quickly start compiling/testing (on Linux Mint).
• I didn't use a formatter because it made too many changes compared to what I actually changed. Please let me know if I made any formatting mistakes.
• I thought about only displaying these buttons if they have data, but that tended to result in a weird display and broke the keyboard shortcuts.
• currentClipChanged from AutomationEditorWindow was not enough to handle all cases. So I also had to integrate currentClipChanged from AutomationEditor.

Questions

• I'm not sure if accessing automationEditor directly via getGUI()->automationEditor()->m_editor is a good idea. Is there a better way to do this?
• Should I add tests to my dev or is that overkill?

[Monospace-V]

#6295 created an empty clip on the first instrument if there were no clips already, but was unfortunately reverted. You might be interested in looking at that pr and its approaches, the follow-up issue and reverting pr, and other possible approaches to the basic problem of a button able to open up an empty box.

[Monospace-V]

#6295 created an empty clip on the first instrument if there were no clips already, but was unfortunately reverted.

My concern is that your approach, unlike the current approach or #6295, may not indicate to users that there is any possible way to use the piano roll or that it even exists.

[clemetayer]

The "No valid clip" window can still appear, especially in the same scenario as #8148 (I think this is the revert linked to #6295 you mentionned ?), but it will only appear if you previously had opened at least one clip and kept the window opened somewhere.

However, I do agree that seeing these two buttons disabled by default might be confusing for newcomers. Maybe I should change the tooltip to make it clearer ?