NetBSD Problem Report #56664

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Date: Mon, 24 Jan 2022 07:59:53 +0000 (UTC)
From: ak@akkartik.com
Reply-To: ak@akkartik.com
To: gnats-bugs@NetBSD.org
Subject: curses getch() doesn't wait for keystroke when cursor is at bottom right of window
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>Number:         56664
>Category:       lib
>Synopsis:       curses getch() doesn't wait for keystroke when cursor is at bottom right of window
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    blymn
>State:          closed
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Jan 24 08:00:01 +0000 2022
>Closed-Date:    Thu May 05 07:25:37 +0000 2022
>Last-Modified:  Thu May 05 12:55:01 +0000 2022
>Originator:     Kartik Agaram
>Release:        9.2
>Organization:
>Environment:
NetBSD rosa.tilde.pink 9.2 NetBSD 9.2 (GENERIC) #0: Wed May 12 13:15:55 UTC 2021  mkrepro@mkrepro.NetBSD.org:/usr/src/sys/arch/amd64/compile/GENERIC amd64
>Description:
By default, C programs linked with the curses library wait for a keystroke when getch() is called. However, when the cursor is at the bottom right they do not.

I don't see this behavior documented at http://wiki.netbsd.org/curses_in_netbsd
>How-To-Repeat:
Example program

$ cat x.c
#include<curses.h>
int main() {
  initscr();
  move(LINES-1, COLS-1);
  getch();
  endwin();
}

Steps to reproduce:

$ gcc x.c -lcurses
$ ./a.out

Expected behavior: terminal window is clear, cursor at bottom right of window. Upon a keystroke the program exits and returns to shell prompt.

Observed behavior: program immediately exits without waiting for keystroke.

Replacing COLS-1 with COLS-2 yields expected behavior.
>Fix:

>Release-Note:

>Audit-Trail:

Responsible-Changed-From-To: lib-bug-people->blymn
Responsible-Changed-By: blymn@NetBSD.org
Responsible-Changed-When: Tue, 03 May 2022 22:23:16 +0000
Responsible-Changed-Why:
I will claim this bug.


State-Changed-From-To: open->closed
State-Changed-By: blymn@NetBSD.org
State-Changed-When: Thu, 05 May 2022 07:25:37 +0000
State-Changed-Why:
This is not a bug but expected behaviour.  The sample code positions
the curses at the bottom right of the window, scrolling is turned off and
getch is expected to echo a character which it cannot do.


From: "Kartik Agaram" <ak@akkartik.com>
To: gnats-bugs@netbsd.org, blymn@netbsd.org, netbsd-bugs@netbsd.org,
 gnats-admin@netbsd.org
Cc: 
Subject: Re: lib/56664 (curses getch() doesn't wait for keystroke when cursor is at
 bottom right of window)
Date: Thu, 05 May 2022 05:50:26 -0700

 Thank you for looking into it.

 On some other platforms (albeit with ncurses) I see a cursor blinking at the bottom right of the page until I press a key. I was assuming my keypress would be echoed where the cursor is displayed. Did you mean there's no place to display the cursor after echoing the current keypress?

>Unformatted:

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