Skip to content

Instantly share code, notes, and snippets.

@reagent
Last active November 8, 2023 08:53
Show Gist options
  • Save reagent/9819045 to your computer and use it in GitHub Desktop.
Save reagent/9819045 to your computer and use it in GitHub Desktop.
Curses Windowing Example
#include <ncurses.h>
#include <unistd.h>
void draw_borders(WINDOW *screen) {
int x, y, i;
getmaxyx(screen, y, x);
// 4 corners
mvwprintw(screen, 0, 0, "+");
mvwprintw(screen, y - 1, 0, "+");
mvwprintw(screen, 0, x - 1, "+");
mvwprintw(screen, y - 1, x - 1, "+");
// sides
for (i = 1; i < (y - 1); i++) {
mvwprintw(screen, i, 0, "|");
mvwprintw(screen, i, x - 1, "|");
}
// top and bottom
for (i = 1; i < (x - 1); i++) {
mvwprintw(screen, 0, i, "-");
mvwprintw(screen, y - 1, i, "-");
}
}
int main(int argc, char *argv[]) {
int parent_x, parent_y, new_x, new_y;
int score_size = 3;
initscr();
noecho();
curs_set(FALSE);
// set up initial windows
getmaxyx(stdscr, parent_y, parent_x);
WINDOW *field = newwin(parent_y - score_size, parent_x, 0, 0);
WINDOW *score = newwin(score_size, parent_x, parent_y - score_size, 0);
draw_borders(field);
draw_borders(score);
while(1) {
getmaxyx(stdscr, new_y, new_x);
if (new_y != parent_y || new_x != parent_x) {
parent_x = new_x;
parent_y = new_y;
wresize(field, new_y - score_size, new_x);
wresize(score, score_size, new_x);
mvwin(score, new_y - score_size, 0);
wclear(stdscr);
wclear(field);
wclear(score);
draw_borders(field);
draw_borders(score);
}
// draw to our windows
mvwprintw(field, 1, 1, "Field");
mvwprintw(score, 1, 1, "Score");
// refresh each window
wrefresh(field);
wrefresh(score);
}
endwin();
return 0;
}
CFLAGS=-Wall
LDFLAGS=-lncurses
all: demo
clean:
rm -rf demo
@wmcbrine
Copy link

wmcbrine commented May 14, 2020

This version: https://gist.github.com/wmcbrine/f63e83d659cedd5181ae77c56907addb

  1. Loops at 0% CPU; quits on 'q'.
  2. Uses box().
  3. Is compatible with PDCurses as well as ncurses.

@wmcbrine
Copy link

wmcbrine commented May 14, 2020

There is 100% CPU usage because there is no usleep being used, which is normally common in such loops.

While that would be an improvement over the original example, my advice is:

  1. In a curses-based program, don't use usleep() where napms() will suffice. usleep() introduces a POSIX dependency, while napms() is native to curses, so the app may still be portable to non-POSIX systems.
  2. Don't use napms() where a blocking getch() will do. Most curses apps will and should spend most of their time in an idle loop waiting on user input, so you may as well let getch() do the work of idling. In the case of this example, even resize events are reported as KEY_RESIZE key events by ncurses and PDCurses. And even in cases where a non-blocking getch() is needed, you can often rely on mechanisms like halfdelay() or timeout() instead of resorting to an explicit napms().

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment