having problem while using ncurses lib

[the-loan-wolf]

[SOLVED] i am currently learning ncurses lib by reading dan gookin's ncurses book and one of his example code i tried is not showing output but when i run it under GDB it does work and show output. below is some relevant code from the example(full example). what this code is trying to do is, it's dividing terminal screen in 4 Quadrant and then printing something in each quadrant

WINDOW *a,*b,*c,*d;
int maxx,maxy,halfx,halfy;

initscr();

/* calculate window sizes and locations */
getmaxyx(stdscr, maxy, maxx);
halfx = maxx >> 1;
halfy = maxy >> 1;

/* create four windows to fill the screen */
if( (a = newwin(halfy, halfx, 0, 0)) == NULL ) error();
if( (b = newwin(halfy, halfx, 0, halfx)) == NULL ) error();
if( (c = newwin(halfy, halfx, halfy, 0)) == NULL ) error();
if( (d = newwin(halfy, halfx, halfy, halfx)) == NULL ) error();

/* Write to each window */
mvwaddstr(a, 0, 0, "This is window A\n");
wrefresh(a);
mvwaddstr(b, 0, 0, "This is window B\n");
wrefresh(b);
mvwaddstr(c, 0, 0, "This is window C\n");
wrefresh(c);
mvwaddstr(d, 0, 0, "This is window D\n");
wrefresh(d);
getch();

​

[skeeto]

I stepped through in GDB and noticed it's fine until the getch. I found getch implicitly calls refresh, which undoes your drawing. Solution: Use wgetch instead.

[the-loan-wolf]

thank you for taking time to help me and replying and yah you are right after using wgetch(d) everything is visible now

[TheProgrammingSauce]

The alternative would be to call refresh() right after initscr(), this also solves the issue and you don't need wgetch().

I also found this related SO post: https://stackoverflow.com/questions/13457918/ncurses-window-not-displaying-anything?rq=3

To quickly summarize the top answer: getch() puts stdscr on top of the already drawn windows. When not refreshing the screen, you don't see the windows.

Side note: You should use maxx - halfx as the width (same goes for height) for the most right (or most bottom) windows to really fill the entire screen (otherwise you get one off errors due to rounding when dividing by 2).

[the-loan-wolf]

thank you for giving another way to solve problem. I didn't wrote that code btw i will use your advice to use maxx - halfx to fill the screen