scriou.c

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/** @file scriou.c
    @brief Screen IO Support for MENU
    @author Bill Waller
    Copyright (c) 2025
    MIT License
    billxwaller@gmail.com
    @date 2026-02-09
 */
 
/** Terminal Handling
    @defgroup screen_io Screen IO Support
    @brief Provides Terminal Settings for C-MENU Applications and Restores
    Terminal State on Exit
 */
 
#include <cm.h>
#include <stdbool.h>
#include <stdio.h>
#include <termios.h>
#include <unistd.h>
 
struct termios shell_tioctl;
struct termios curses_tioctl;
bool f_have_shell_tioctl = false;
bool f_have_curses_tioctl = false;
bool capture_shell_tioctl();
bool restore_shell_tioctl();
bool capture_curses_tioctl();
bool restore_curses_tioctl();
bool set_sane_tioctl(struct termios *);
bool mk_raw_tioctl(struct termios *);
char di_getch();
 
struct termios shell_tioctl, curses_tioctl;
struct termios shell_in_tioctl, curses_in_tioctl;
struct termios shell_out_tioctl, curses_out_tioctl;
struct termios shell_err_tioctl, curses_err_tioctl;
 
/** @brief capture_shell_tioctl() - capture shell terminal settings
    @ingroup screen_io
    @return - true on success
    @note - captures terminal settings for stdin, stdout, and stderr */
bool capture_shell_tioctl() {
    if (f_have_shell_tioctl)
        return true;
    tcgetattr(0, &shell_in_tioctl);
    tcgetattr(1, &shell_out_tioctl);
    tcgetattr(2, &shell_err_tioctl);
    f_have_shell_tioctl = true;
    return true;
}
/** @brief restore_shell_tioctl() - restore shell terminal settings
    @ingroup screen_io
    @return - true on success
    @note - restores terminal settings for stdin, stdout, and stderr */
bool restore_shell_tioctl() {
    if (!f_have_shell_tioctl)
        return false;
    tcsetattr(0, TCSANOW, &shell_in_tioctl);
    tcsetattr(1, TCSANOW, &shell_out_tioctl);
    tcsetattr(2, TCSANOW, &shell_err_tioctl);
    return true;
}
/** @brief capture_curses_tioctl() - capture curses terminal settings
    @ingroup screen_io
    @return - true on success
    @note - captures terminal settings for stdin, stdout, and stderr */
bool capture_curses_tioctl() {
    if (f_have_curses_tioctl)
        return true;
    tcgetattr(0, &curses_in_tioctl);
    tcgetattr(1, &curses_out_tioctl);
    tcgetattr(2, &curses_err_tioctl);
    f_have_curses_tioctl = true;
    return true;
}
/** @brief restore_curses_tioctl() - restore curses terminal settings
    @ingroup screen_io
    @return - true on success
    @note - restores terminal settings for stdin, stdout, and stderr */
bool restore_curses_tioctl() {
    if (!f_have_curses_tioctl)
        return false;
    tcsetattr(0, TCSANOW, &curses_in_tioctl);
    tcsetattr(1, TCSANOW, &curses_out_tioctl);
    tcsetattr(2, TCSANOW, &curses_err_tioctl);
 
    return true;
}
/** @brief set_sane_tioctl() - set terminal to sane settings for C-MENU
    @ingroup screen_io
    @param t_p - pointer to termios structure to modify
    @return - true on success
     @note - sets terminal to sane settings for C-MENU applications */
bool set_sane_tioctl(struct termios *t_p) {
    tcgetattr(0, t_p);
    t_p->c_iflag &= ~(IGNBRK | BRKINT | PARMRK | INPCK | ISTRIP | INLCR |
                      IGNCR | ICRNL | IXON | IXOFF);
    t_p->c_iflag |= IUTF8;
    t_p->c_oflag |= OPOST | ONLCR;
    t_p->c_lflag &= ~(ECHO | ECHONL | ICANON | IEXTEN);
    t_p->c_lflag |= (ISIG | ICANON | IEXTEN | ECHO | ECHOE | ECHOK);
    t_p->c_cflag &= ~(CSIZE | PARENB);
    t_p->c_cflag |= CS8 | CLOCAL | CREAD;
    tcsetattr(0, TCSANOW, t_p);
    return true;
}
/** @brief mk_raw_tioctl() - set terminal to raw mode
    @ingroup screen_io
    @param t_p - pointer to termios structure to modify
    @return - true on success
    @note - unlike cfmakeraw(), this leaves ISIG enabled.
    @note - cfmakeraw() disables ISIG, which prevents C-MENU from handling
   signals like Ctrl-C. Instead of using cfmakeraw(), we manually set the
   terminal to raw mode while leaving ISIG enabled.
    @note - the following code is equivalent to cfmakeraw() but with ISIG left
   enabled:
    @code
    t_p->c_iflag &= ~(IGNBRK | BRKINT | PARMRK | INPCK | ISTRIP | INLCR |
                   IGNCR | ICRNL | IXON | IXOFF);
    t_p->c_lflag &= ~(ECHO | ECHONL | ICANON | IEXTEN);
    t_p->c_cflag &= ~(CSIZE | PARENB);
    t_p->c_cflag |= CS8 | CLOCAL;
    @endcode
   */
bool mk_raw_tioctl(struct termios *t_p) {
    tcgetattr(0, t_p);
    t_p->c_lflag |= ISIG;
    t_p->c_lflag &= ~(ECHO | ICANON);
    t_p->c_cc[VMIN] = 1;
    t_p->c_cc[VTIME] = 0;
    tcsetattr(0, TCSAFLUSH, t_p);
    return true;
}
/** @brief  sget single character from terminal in raw mode
    @ingroup screen_io
    @return - the character read from terminal
    @note restores terminal settings */
char di_getch() {
    struct termios org_tioctl, new_tioctl;
    char buf;
 
    if (tcgetattr(2, &org_tioctl) == -1) {
        fprintf(stderr, "\ndi_getch: tcgetattr failed\n");
        return (0);
    }
    new_tioctl = org_tioctl;
    new_tioctl.c_lflag &= ~(ECHO | ICANON);
    new_tioctl.c_cc[VMIN] = 1;
    new_tioctl.c_cc[VTIME] = 0;
    tcsetattr(2, TCSAFLUSH, &new_tioctl);
    read(2, &buf, 1);
    tcsetattr(2, TCSAFLUSH, &org_tioctl);
    return (buf);
}