Re: "erase" vs "clear" question

[Brian Raiter]

> What exactly is the difference between the functions "erase" and
> "clear"? From what I understand, they both have the same effective
> expungement result but the latter in addition repaints the window. I
> don't see the point of having both available---in what situations
> would it be more apt to use one over the other?

The difference is that clear() also calls clearok(). clearok()
basically tells ncurses to forget whatever it knows about the current
terminal contents, so that when refresh() is called, it will actually
begin by clearing the entire terminal screen before redrawing any of
it.

erase() on the other hand, just clears the screen (the internal
object, not the terminal screen). When refresh() is later called,
ncurses will still compute the minimum number of characters to send to
update the terminal.

Thus, for example, I typically call erase() at the start of my
rendering function. I then render the entire screen in its current
state, and let ncurses optimize the actual output. I typically call
clear() in response to the user pressing ctrl-R (a popular keystroke
used to request a redraw of the screen after some other process has
modified it), or when the program resumes after being suspended by
ctrl-Z (since the terminal's contents are now completely unknown).

b