Proposal: quit Frescobaldi on macOS when the main window is closed

[Federico Bruni]

Hi all,

Following up from:
https://github.com/frescobaldi/frescobaldi/issues/2230#issuecomment-5557640430

DISCLAIMER: This is an AI generated email... sorry for that... to be
honest, I know nothing about macOS so I needed some help to put up this
proposal. But what I'll listen eventually is the input you human users
of Frescobaldi will give in this thread.

================== CHANGE PROPOSAL ===================

I'd like to propose a change to Frescobaldi's behavior on macOS:
closing the main window should quit the application entirely, instead
of leaving it running in the background with just a menu bar, as it
does today.

This currently follows Apple's convention for multi-window document
apps (Safari, TextEdit, Word, and similar apps all behave this way).
But that convention exists to support things a user might still want
after closing all windows — quickly reopening another document, or an
app doing something useful in the background (like a mail or chat
client waiting for notifications). Frescobaldi doesn't do any of that:
once every document is closed, there's nothing happening, and nothing
the user gains by the app staying resident.

Meanwhile, keeping the process alive with no open documents has turned
out to be a real source of bugs. Several error reports — almost
exclusively from macOS users — trace back to background jobs
(LilyPond compilations) that complete after the user has already closed
the relevant document or window, hitting code that assumes a
document/view is still around. @bmjcode just fixed one specific
instance of this, but the underlying condition — the app staying
alive in a state nothing was really designed for — is likely to keep
producing similar bugs over time.

For context: this isn't even a strict Apple mandate. Plenty of macOS
apps (Preview, Lightroom Classic, System Settings, among others)
already quit when their last window closes, and there are well-known
third-party utilities (Swift Quit, RedQuits, Last Window Quits) whose
entire purpose is to force exactly this behavior for apps that don't
— which tells you a fair number of Mac users actively prefer it.

Our plan, if there are no strong objections, is to make Frescobaldi
quit on last-window-close on macOS as well, bringing it in line with
how it already behaves on Windows and Linux. If you rely on the current
background behavior for some workflow we haven't thought of, please let
us know — we'd like to hear about it before making the change.

Thanks
Federico