XnView Software

If right-click menu in Viewer has Fullscreen option, why in fullscreen mode option "Exit fullscreen" is absent from said menu?

XnView actually has two fullscreen modes.
You can Add 'Exit' to context menus (Tools » Options... » Interface » Interface). However, both Exit (Ctrl+Q) and Close (Ctrl+W) will quit XnView altogether (cmd_Quit).
I agree that the context menus in both modes should be identical, and that Close should only quit FS mode.

XnTriq wrote: I agree that the context menus in both modes should be identical, and that Close should only quit FS mode.

So Close and Quit entries?

xnview wrote:So Close and Quit entries?

Yes, I think so.

PS: In Mozilla Firefox, it's Exit Full Screen Mode.