Strange Curses behaviour

duncs has asked for the wisdom of the Perl Monks concerning the following question:

I am seeing "strange" behaviour when trying to grab user input within Curses v1.32.

I have created a small window and put some text in it, then drawn a box around the window - this works fine until I add the code to get input from the user, after which the box is no longer drawn.

I have seen this on Debian Jessie, Debian Lenny and RHEL-6.

Below is a small code example displaying this behaviour. If you run this code without args a box is drawn around the window. Provide an arg to the script so user input is sought and the box is no longer drawn around the window.

Any Curses guru's shed any light on this for me?

#!/usr/bin/perl
use strict;
use warnings;

use Curses;

END{ endwin(); };

initscr;
curs_set(0);
clear();
noecho();
halfdelay(30);

my $win1 = Curses->new( 7, 30, 5, 5);
$win1->box(ACS_VLINE, ACS_HLINE);

my $char = -1;

while(1) {
        $win1->addstr( 2, 2, scalar(localtime));
        $win1->addstr( 4, 10, "Char: $char ");
        $win1->refresh;

        if(!@ARGV) {
                sleep 3;
        } else {
                $char = getch();
        }
}
[download]

Thanks

Duncs

Comment on Strange Curses behaviour Download Code

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Re: Strange Curses behaviour by Anonymous Monk on Nov 02, 2015 at 19:53 UTC
`#!/usr/bin/perl # http://perlmonks.org/?node_id=1146715 use strict; use warnings; use Curses; END{ endwin(); }; initscr; curs_set(0); clear(); noecho(); halfdelay(30); my $win1 = Curses->new( 7, 30, 5, 5); refresh(); ########################### Curses seems to need this line $win1->box(ACS_VLINE, ACS_HLINE); my $char = -1; while(1) { $win1->addstr( 2, 2, scalar(localtime)); $win1->addstr( 4, 10, "Char: $char "); $win1->refresh; if(!@ARGV) { sleep 3; } else { $char = getch(); } }` [download]	[reply] [d/l]
Re^2: Strange Curses behaviour by duncs (Beadle) on Nov 03, 2015 at 09:05 UTC
Thank you - this has fixed my issue, although I don't understand why :) Using refresh on the window itself exhibits the same behaviour, as though this needs a global screen refresh before doing anything else. Thanks Duncs	[reply]
Re: Strange Curses behaviour by thmsdrew (Scribe) on Nov 02, 2015 at 18:42 UTC
I believe you want to use `getc`. I don't think `getch` is a thing in Perl.	[reply] [d/l] [select]
Re^2: Strange Curses behaviour by Happy-the-monk (Canon) on Nov 02, 2015 at 18:51 UTC
I don't think getch is a thing in Perl. It exists in Curses though. Cheers, Sören Créateur des bugs mobiles - let loose once, run everywhere. (hooked on the Perl Programming language)	[reply]