I know that the Raspberry Pi has no power off switch. That you should shutdown your operating system, and only when shutdown has finished, you should turn off or disconnect your power adapter.
But we are using Raspbian with GUI, and when our users shutdown the OS, they only see a black screen.
There is any way of stoping processes, syncing the MicroSD, and show message in the GUI?. Something like "Now you can disconnect your power adapter".