To have keyboard viewer in Debian?

Another name for the *keyboard viewer* is the *special characters keyboard viewer* developed first in OSX, Youtube video here . It is used to visualise the dynamics of typing different key combinations in first-level/second-level/... ways. **Warning** I do not want to have virtual keyboard like shown by the confused answers in the thread Onscreen keyboard? (like OSX's Keyboard Viewer) where the title is about *Onscreen keyboard viewer*, not virtual keyboard. I tested Florence/Onboard/xvkbd/... but the virtual keyboard is risky because it can misconfigure your keyboard settings, forcing you restart your system, so no to virtual keyboards. You can view static keyboard viewer by *Language menu* at top > *Show Keyboard Layout* > Output, or from the settings, *Region & Language* > select an input source > click on the keyboard button in the lower-right-hand corner; this will display the keyboard layout in Fig. 1. This view is static, *i.e.* it displays all accessible characters at once; it does react to key-presses, but only by highlighting the depressed key(s). It would be easier to understand the layout if it showed the characters accessible with the current set of modifiers: *e.g.* the P keycap would show only p by default, and would would change to P if you pressed Shift, ö (on a Dvorak layout) if you pressed AltGr, and Ö if you pressed ShiftAltGr. In OS X, the feature has been 5-10 years, but I have not found anything builtin in any Linux distro nor any program in apt by the following searches. apt search viewer | grep keyboard I think Gnome 3.22 can support such a tool in Linux. I need the tool to better visualise how to typo A with dots/... (ä, ö, ...) in Linux. Fig. 1 Static keyboard layout of Dvorak, an example, Fig. 2 Example of dynamic keyboard viewer in OS X (source ) but video here OS: Debian 9 Gnome: 3.22