FIX: Grey out format options when calendar applet uses…

[carsteneu]

Fixes #13447 - Grey out date/time format settings when calendar applet uses custom format

When the calendar applet has "Use a custom date format" enabled, the system date/time format settings in cinnamon-settings are now disabled with an info banner explaining why they don't apply.

Problem reported in #13447

Users were confused when toggling "Display the date" or "Display seconds" in Date/Time Settings had no effect. This happened because the calendar applet's "Use a custom date format" option overrides all system format settings, but there was no visual indication of this in the settings UI.

Solution

• Added a new "Custom Format Active" section that appears when any calendar applet instance has custom format enabled
• Shows a Gtk.InfoBar explaining the situation and how to resolve it
• Disables the affected format switches:
  • Use 24h clock
  • Display the date
  • Display seconds
• Uses the same pattern as KeybindingTable.py for reading applet configurations from ~/.config/cinnamon/spices/

Screenshots

before

after

Tested in VM with Linux Mint 22.3, Cinnamon 6.6.6:

• Settings display normally when custom format is disabled
• Info section appears when custom format is enabled
• All three affected switches are greyed out
• "First day of week" remains active (not affected by custom format as far as i know)
• Graceful handling when no calendar applet is present
• Should work with multiple calendar applet instances - but normally there should only be one

Technical Details

• Uses standard Gtk.InfoBar widget (consistent with cs_startup.py, cs_user.py)
• Should be a robust error handling for missing config files or malformed JSON
• No changes to calendar applet itself - pure settings UI enhancement

[mtwebster]

This is wrong - see my comment in the other issue.

[carsteneu]

Ah yes, maybe a hint above the settings may be an option, that was already my first idea.