haskellterminalio

(How) can I get the character that is currently shown at a given position in the terminal?

(Related to a previous question.)

If I can print a character in the terminal via Prelude.putChar at a position that I've decided via System.Console.ANSI.setCursorPosition, how can I get the charcter at that position?

The use case is that I want to do something like this

do
  setCursorPosition a b
  c <- getTheCharacterHere
  putChar $ if c == 'x' then 'y' else 'z'

where getTheCharacterHere is the desired action of retrieving the character currently shown at the position set via setCursorPosition.

Solution

  • This isn't possible without a framework like ncurses which keeps track of the state of the entire screen. Terminals are write-only by default. See e.g. this question.