Dual monitor, separated workspaces?

I have a question quite crazy... I know.
I have dual monitor with a hdmi projector connected: i wish to clone only one workspace (desktop) between primary monitor and projector.
I see on the web that exist some windows managers called "tiling wm" (i.e: i3) that can do this, but I don't want to change wm, Mate + Marco is my preferred, furthermore those windows managers are programmers and/or sysadmins oriented.
I explored xrandr and mate-display-properties, I can achieve an extension of the monitor, but is not useful for my task, because the user can't see from the primary monitor what is passing on the projected image.
Somebody can help me, please?