mjhjmtu

I am trying to develop a chat application whose interface is terminal-based. For that, I've been playing around with both screen and tmux commands.

However, I found a similarity with both of them: my commands do not run in full-screen mode, as in if I scroll up enough in the frames/panels/pane/windows, I can still visualize the history and shell.

How could I make my program to run in full-screen mode just like vi, for instance?

Thanks!

So you want to create a TUI (text-based user interface) application? As the TUI Wikipedia page says:

In Unix-like operating systems, TUIs are often constructed using the
terminal control library curses, or ncurses, a mostly compatible
library.

An easy way to interact with ncurses is with the tput command line tool. And with that we can address your specific question about a "full-screen mode". It is typically done by activating a secondary screen (which should be available in any decent terminal emulator):

tput smcup

The current screen will be hidden away (e.g. you won't be able to scroll up and see previous output) and in the new, "fresh" screen you'll render your application. When that exits revert back to the primary screen with:

tput rmcup

...and everything will be restored to as it was before.

Here is a sampling of other tput capabilities

tput cup 23 4 # move the cursor to row 23, column 4 of your terminal

tput ed # clear to end of screen

tput setaf 2 # set foreground color to bright green

tput cubl # move cursor left one space

tput rev # turn on reverse video mode

tput sc # save the cursor position
tput rc # restore the cursor position

See man tput and man 5 terminfo. For the latter you'll want to scroll down to the Predefined Capabilities section in particular.

And there are plenty of nice resources online to learn more such as http://linuxcommand.org/lc3_adv_tput.php

(Note that none of the above is related to whether or not you are using tmux or the like.)