No output from ncurses without second getch

Question

I am having a similar problem to Ncurses No Output. Just I am having a getch call before exiting. I don't see any output when I don't add a second getch call before outputting anything. The following is a collection of all relevant code parts copied together in one routine exhibiting the same problem as my complete program. So some calls look superfluous but I find those necessary in the local context.

#include <glib.h>
#include <stdlib.h>

#define bool ncbool
#include <ncurses.h>
#undef bool


gint32 main ( gint32 argc, gchar * argv [] )
{
    initscr ();
    keypad ( stdscr, FALSE );
    nonl ();
    cbreak ();
    nodelay ( stdscr, FALSE );
    noecho ();

    /*
    gint zch_extra;
    zch_extra = getch ();
    */

    WINDOW* w;
    w = newwin ( 5, 10, 3, 3 );
    box ( w, 0, 0 );
    wnoutrefresh ( w );

    mvwaddstr ( w, 1, 1, "huhu" );
    wnoutrefresh ( w );
    doupdate ();

    mvwaddstr ( w, 2, 1, "<cont>" );
    wrefresh ( w );

    gint zch;
    zch = getch ();

    clear ();
    refresh ();

    nl ();
    nocbreak ();
    echo ();

    endwin ();

    return 1;
}

I only see output when I add the extra getch commented out in the code.

Compilation commands:

gcc -I /usr/include/ncurses -I /home/mkiever/include -I/usr/include/glib-2.0 -I/usr/lib/i386-linux-gnu/glib-2.0/include  -ansi -ggdb -c -o main.o main.c
gcc -o test main.o -lncurses `pkg-config --libs glib-2.0`

Platform (uname -a): Linux Pirx 3.16.0-4-686-pae #1 SMP Debian 3.16.7-ckt11-1 (2015-05-24) i686 GNU/Linux

What am I doing wrong? I guess, it's my combination of different refresh calls, but I don't have a clue where exactly the problem is.

Thanks for taking a look.

btw, main returns int, and the argument argc is an int too; using gint32 instead can never be "more correct" — Antti Haapala
@AnttiHaapala Possibly gone a bit too far using GLib, true that. — mkiever

Thomas Dickey Thomas Dickey · Accepted Answer · 2017-04-30T14:37:29

curses starts up wanting to clear the screen stdscr (as noted in the manual page for initscr):

initscr also causes the first call to refresh(3x) to clear the screen.

Doing that requires a refresh, sometime after the call to initscr. getch does a refresh of stdscr. In the non-working case, the program creates, modifies and refreshes the other window, but when you call getch, curses refreshes stdscr (again, in the manual), overwriting that window.

It does those steps internally, no need to show the result until the program requests input via getch.

No output from ncurses without second getch

1 Answers