open full screen terminal app in another terminal - c

Question

As an educational project, am I trying to write a simple terminal text editor. Below is a minimal example of my editor. My editor works fine when opening in the same terminal from which the program was run, however I would like to display the editor in a second terminal, leaving the original one free to print logging messages to. In the example below, the editor sucessfully opens in the second terminal, and the logging message about the number of rows and columns is printed in the original terminal. However, I can't work out how to get the editor to receive input from the second terminal, currently I need to close it by pressing ctrl+q in the orginal terminal. How can I get the editor to receive input from the second terminal?
I am compiling with gcc -Wall -Wextra -pedantic -std=c99 -g c_programs/open_alt_screen_in_other_term.c and running with ./a.out -tty /dev/pts/0
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <termios.h>
#include <time.h>
#include <unistd.h>
#define ENTER_ALT_SCREEN "\033[?1049h"
#define EXIT_ALT_SCREEN "\033[?1049l"
#define MOVE_CURSOR_HOME "\033[H"
#define CTRL_KEY(k) ((k)&0x1f)
int UI_OUTPUT_FILENO = STDOUT_FILENO;
int UI_INPUT_FILENO = STDIN_FILENO;
struct termios orig_termios;
void disable_raw_mode();
void enable_raw_mode() {
tcgetattr(UI_INPUT_FILENO, &orig_termios);
atexit(disable_raw_mode);
struct termios raw = orig_termios;
raw.c_iflag &= ~(IXON | ICRNL);
raw.c_oflag &= ~(OPOST);
raw.c_lflag &= ~(ECHO | ICANON | ISIG | IEXTEN);
raw.c_iflag &= ~(BRKINT | INPCK | ISTRIP);
raw.c_cflag |= (CS8);
tcsetattr(UI_INPUT_FILENO, TCSAFLUSH, &raw);
}
void disable_raw_mode() {
tcsetattr(UI_INPUT_FILENO, TCSAFLUSH, &orig_termios);
write(UI_OUTPUT_FILENO, EXIT_ALT_SCREEN, 8);
}
int getWindowSize(int *rows, int *cols) {
struct winsize ws;
if (ioctl(UI_OUTPUT_FILENO, TIOCGWINSZ, &ws) == -1 || ws.ws_col == 0) {
return -1;
} else {
*cols = ws.ws_col;
*rows = ws.ws_row;
return 0;
}
}
int main(int argc, char **argv) {
FILE *lfp = NULL;
for (int a = 1; a < argc; a++) {
if (strcmp(argv[a], "-tty") == 0) {
lfp = fopen(argv[a + 1], "w");
UI_OUTPUT_FILENO = fileno(lfp);
// UI_INPUT_FILENO = UI_OUTPUT_FILENO;
}
}
enable_raw_mode();
write(UI_OUTPUT_FILENO, ENTER_ALT_SCREEN, 8);
write(UI_OUTPUT_FILENO, MOVE_CURSOR_HOME, 3);
int nrows, ncols;
if (getWindowSize(&nrows, &ncols) == -1) return EXIT_FAILURE;
// print logging to original terminal
printf("rows: %d, cols: %d\n", nrows, ncols);
char seq[10] = {0};
while (read(UI_INPUT_FILENO, &seq, 10) != 0) {
if (seq[0] == CTRL_KEY('q')) {
break;
} else if (strlen(seq) == 1) {
write(UI_OUTPUT_FILENO, seq, 1);
}
for (size_t j = 0; j < 10; j++) seq[j] = '\0';
}
// if I clode lfp, the other terminal doesn't exit alt screen
// fclose(lfp);
return 0;
}