query_sixel.c

#include <poll.h>
#include <stdio.h>
#include <stdlib.h>
#include <termios.h>
#include <unistd.h>

struct termios initial_term_params;

// Check if both stdin and stdout are TTYs.
void check_stdio() {
  if(isatty(STDIN_FILENO) != 1 || isatty(STDOUT_FILENO) != 1) {
    perror("stdio");
    exit(1);
  }
}

// Restore terminal parameters at exit.
void reset_term_params() {
  tcsetattr(STDIN_FILENO, TCSAFLUSH, &initial_term_params);
}

// Disable echo and canonical mode.
void init_tty() {
  struct termios term_params;

  // Get terminal parameters to reset them at exit,
  if (tcgetattr(STDOUT_FILENO, &term_params) == -1) {
    perror("tcgetattr");
    exit(1);
  }

  // Store initial parameters to restore them.
  initial_term_params = term_params;

  term_params.c_lflag &= ~(ICANON|ECHO);
  if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &term_params) == -1) {
    perror("tcsetattr");
    exit(1);
  }

  atexit(reset_term_params);
}

// Send XTSMGRAPHICS and DA1.
void send_query() {
  printf("\033[?1;1;0S\033[c");
  fflush(stdout);
}

// Read response in stdin.
//
// A real program should parse the read data. We are just printing it.
void read_response() {
  char c;
  int timeout;
  int esc_count;
  struct pollfd pollfd = { .fd = 0, .events = POLLIN };

  timeout = 5000;
  esc_count = 0;

  while(poll(&pollfd, 1, timeout) == 1) {
    read(0, &c, 1);

    if(c == 0x1B) {
      esc_count++;

      if(esc_count > 1)
        putc('\n', stdout);
    }

    if(c < ' ')
      printf("\\x%X", (int)c);
    else
      putc(c, stdout);

    // Don't wait after first char is read.
    timeout = 0;
  }

  putc('\n', stdout);
}

int main() {
  check_stdio();
  init_tty();
  send_query();
  read_response();
}