global shortcuts: fix crash by ignoring duplicate shortcuts

[dec05eba]

hyprland_global_shortcuts_manager_v1_register_shortcut will cause an error if the (app_id, shortcut_id) combination has already been registered. Ignore shortcuts that have already been registered.

When a shortcut is registered again it should also overwrite the session for the keybind to make the shortcut work after restarting an application, otherwise the key can't be used again.

Fixes #236

[dec05eba]

I also noticed that "shortcuts" in CreateSession will never exist since xdg-desktop-portal ignores that key in CreateSession. This means that to make sure shortcuts work applications need to call BindShortcut on program startup. The issue with that is that BindShortcut documentation says that the portal can show a dialog when this happens (https://github.com/flatpak/xdg-desktop-portal/blob/a74c2ee93befca1f8583e86e165dbe90a0e72a15/data/org.freedesktop.portal.GlobalShortcuts.xml#L88) and that is the case with KDE. It will show the global shortcuts dialog where you can setup keys.
That means you cant call BindShortcut on program startup as that would show the dialog everytime. The only solution I know right now is to only call BindShortcut on program startup if the desktop portal running on the system is Hyprland.

KDE handles this differently. It saves the "session_handle_token" (to disk, it remembers it even after you restart your computer) and automatically registers the shortcuts the next time you call CreateSession with the same "session_handle_token". This difference in behavior means programs cant create one global shortcut solution that works with every desktop portal.

[dec05eba]

(I tested these changes with a real program (https://git.dec05eba.com/gpu-screen-recorder-gtk/about/), after allowing it to run on hyprland)

[vaxerski]

thanks!