kanshi/event-loop.c

#define _POSIX_C_SOURCE 200809L
#include <errno.h>
#include <fcntl.h>
#include <poll.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "kanshi.h"

static int set_pipe_flags(int fd) {
	int flags = fcntl(fd, F_GETFL);
	if (flags == -1) {
		perror("fnctl F_GETFL failed");
		return -1;
	}
	flags |= O_NONBLOCK;
	if (fcntl(fd, F_SETFL, flags) == -1) {
		perror("fnctl F_SETFL failed");
		return -1;
	}
	flags = fcntl(fd, F_GETFD);
	if (flags == -1) {
		perror("fnctl F_GETFD failed");
		return -1;
	}
	flags |= O_CLOEXEC;
	if (fcntl(fd, F_SETFD, flags) == -1) {
		perror("fnctl F_SETFD failed");
		return -1;
	}
	return 0;
}

static int signal_pipefds[2];

static void signal_handler(int signum) {
	if (write(signal_pipefds[1], &signum, sizeof(signum)) == -1) {
		abort();
	}
}

enum readfds_type {
	FD_WAYLAND,
	FD_SIGNAL,
	FD_COUNT,
};

int kanshi_main_loop(struct kanshi_state *state) {
	if (pipe(signal_pipefds) == -1) {
		perror("read from signalfd failed");
		return EXIT_FAILURE;
	}
	if (set_pipe_flags(signal_pipefds[0]) == -1) {
		return EXIT_FAILURE;
	}
	if (set_pipe_flags(signal_pipefds[1]) == -1) {
		return EXIT_FAILURE;
	}

	struct sigaction action;
	sigfillset(&action.sa_mask);
	action.sa_flags = 0;
	action.sa_handler = signal_handler;
	sigaction(SIGINT, &action, NULL);
	sigaction(SIGQUIT, &action, NULL);
	sigaction(SIGTERM, &action, NULL);
	sigaction(SIGHUP, &action, NULL);

	struct pollfd readfds[FD_COUNT] = {0};
	readfds[FD_WAYLAND].fd = wl_display_get_fd(state->display);
	readfds[FD_WAYLAND].events = POLLIN;
	readfds[FD_SIGNAL].fd = signal_pipefds[0];
	readfds[FD_SIGNAL].events = POLLIN;

	while (state->running) {
		while (wl_display_prepare_read(state->display) != 0) {
			if (wl_display_dispatch_pending(state->display) == -1) {
				return EXIT_FAILURE;
			}
		}

		int ret;

		while (true) {
			ret = wl_display_flush(state->display);
			if (ret != -1 || errno != EAGAIN) {
				break;
			}
		}

		if (ret < 0 && errno != EPIPE) {
			goto read_error;
		}

		do {
			ret = poll(readfds, sizeof(readfds) / sizeof(readfds[0]), -1);
		} while (ret == -1 && errno == EINTR);
		/* will only be -1 if errno wasn't EINTR */
		if (ret == -1) {
			goto read_error;
		}

		if (wl_display_read_events(state->display) == -1) {
			return EXIT_FAILURE;
		}

		if (readfds[FD_SIGNAL].revents & POLLIN) {
			for (;;) {
				int signum;
				ssize_t s
					= read(readfds[FD_SIGNAL].fd, &signum, sizeof(signum));
				if (s == 0) {
					break;
				}
				if (s < 0) {
					if (errno == EAGAIN) {
						break;
					}
					perror("read from signal pipe failed");
					return EXIT_FAILURE;
				}
				if (s < (ssize_t) sizeof(signum)) {
					fprintf(stderr, "read too few bytes from signal pipe\n");
					return EXIT_FAILURE;
				}
				switch (signum) {
				case SIGHUP:
					kanshi_reload_config(state);
					break;
				default:
					/* exiting after signal considered successful */
					return EXIT_SUCCESS;
				}
			}
		}

		if (wl_display_dispatch_pending(state->display) == -1) {
			return EXIT_FAILURE;
		}
	}

	return EXIT_SUCCESS;

read_error:
	wl_display_cancel_read(state->display);
	return EXIT_FAILURE;
}