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Last active Jul 30, 2022
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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;
// 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);
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);
// draw to our windows
mvwprintw(field, 1, 1, "Field");
mvwprintw(score, 1, 1, "Score");
// refresh each window
return 0;
all: demo
rm -rf demo

There is 100% CPU usage because there is no usleep being used, which is normally common in such loops. You would need it if you're doing any animation.

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wmcbrine commented May 14, 2020

This version:

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

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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().

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