use SystemTrayIcon.isVisible() to decide whether to close or minimize jami

Describe your environment

• OS: Guix System, using a minimal window manager (ratpoison)
• Jami version: jami-qt 20210326.1.cfba013
• What build you are using: Guix

Steps to reproduce

• Can you reproduce the bug: at will
• Steps:

1. Configure your system to use a minimal WM (ratpoison, i3, whatever) that lacks a system tray (systray).
2. Launch jami-qt
3. Close the Jami application (on ratpoison that's C-t k)

• Actual result: The jami-qt client process lives on, as can be seen with pgrep jami.
• Expected result: The jami-qt process should be terminated as without a system tray there's no way to bring it back to the foreground. This also affects the GNOME client, but at least the GNOME client offers a way to truly "exit" the application via the user interface.

OK, @sblin pointed to me that there's already an option to prevent the client from staying alive (minimized upon close): Settings -> General -> System -> Keep minimized on close.

That's nice, but I'd suggest instead using the Qt provided QSystemTrayIcon class to check if a systray is available and visible (QSystemTrayIcon.isVisible()) and do the right thing (terminate if no systray is visible, else minimize as it's currently done by default).

quick try: https://review.jami.net/c/jami-client-qt/+/17821

Seems isVisible() return true on gnome even without systray

changed title from jami doesn't terminate when closing its window on systems lacking a systray to automate the decision to close or minimize jami based on systray visibility

changed title from automate the decision to close or minimize jami based on systray visibility to use SystemTrayIcon.isVisible() to decide whether to close or minimize jami

Related #350 (closed) ?

mentioned in issue #903

assigned to @sblin

added SprintTo review UI/UX labels

@mcournoyer I tried a new approach: https://review.jami.net/c/jami-client-qt/+/24730

Will be fixed on next version

closed

removed SprintTo review label

mentioned in commit 316750ad