X11 window with basic writing and input

.gitignore

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+/.idea/
+/bt

Makefile

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+P=bt
+OBJECTS=
+CFLAGS=-g -Wall -Wextra -pedantic -O0
+LDLIBS=
+CC=gcc
+RM=rm -vf
+
+bt: clean
+	$(CC) $(CFLAGS) -lX11 $(P).c -o $(P)
+
+clean:
+	$(RM) $(P)
+
+run:bt
+	./$(P)
+
+all:$(P)

bt.c

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+#include <X11/X.h>
+#include <X11/Xlib.h>
+#include <X11/Xutil.h>
+#include <X11/Xos.h>
+#include <asm-generic/ioctls.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <pty.h>
+#include <ctype.h>
+
+// PTY
+int master;
+int slave;
+
+// X11
+Display *display;
+int screen;
+Window win;
+GC gc;
+int x11fd;
+
+// Scrollback
+char *scrollback;
+
+void init_x(void) {
+    unsigned long black,white;
+    display = XOpenDisplay((char *) 0);
+    screen = DefaultScreen(display);
+    black = BlackPixel(display, screen);
+    white = WhitePixel(display, screen);
+
+    win = XCreateSimpleWindow(display, DefaultRootWindow(display), 0, 0, 500, 800, 5, white, black);
+
+    XSetStandardProperties(display, win, "The window", "Hello", None, NULL, 0, NULL);
+    XSelectInput(display, win, ExposureMask|KeyPressMask);
+    gc = XCreateGC(display, win, 0, 0);
+    XSetBackground(display, gc, white);
+    XSetForeground(display, gc, black);
+    x11fd = ConnectionNumber(display);
+    XClearWindow(display, win);
+    XMapRaised(display, win);
+}
+
+void close_x(void) {
+    XFreeGC(display, gc);
+    XDestroyWindow(display, win);
+    XCloseDisplay(display);
+    exit(0);
+}
+
+void spawn(void) {
+    openpty(&master, &slave, NULL, NULL, NULL);
+    pid_t p = fork();
+    if (p == 0) {
+        close(master);
+
+        setsid();
+        ioctl(slave, TIOCSCTTY, NULL);
+        dup2(slave, 0);
+        dup2(slave, 1);
+        dup2(slave, 2);
+
+        close(slave);
+
+        execle("/bin/dash", "-/bin/dash", (char *)NULL, (char *[]){ "TERM=dumb", NULL });
+        exit(0);
+    } else {
+        close(slave);
+    }
+}
+
+void update(void) {
+    XEvent event;
+    KeySym key;
+    char buf[1];
+    char x11inputbuf[255];
+    fd_set readable;
+    /* char tmp[512]; */
+    scrollback = malloc(2048);
+    scrollback[0] = '\0';
+    int sbcount = 0;
+    int maxfd = master > x11fd ? master : x11fd;
+
+    for (;;) {
+        FD_ZERO(&readable);
+        FD_SET(master, &readable);
+        FD_SET(x11fd, &readable);
+        select(maxfd + 1, &readable, NULL, NULL, NULL);
+        if (FD_ISSET(master, &readable)) {
+            read(master, buf, 1);
+            scrollback[sbcount++] = *buf;
+            scrollback[sbcount] = '\0';
+            XClearWindow(display, win);
+            char *curr = scrollback;
+            while (*curr) {
+                if (!iscntrl(*curr)) {
+                    XSetForeground(display, gc, 255);
+                    XDrawString(display, win, gc, 10, 10, curr, sbcount);
+                }
+                curr++;
+            }
+        }
+        while (XPending(display)) {
+            XNextEvent(display, &event);
+            switch (event.type) {
+                // This gets called when the window is resized
+                case Expose: // Resized
+                    XClearWindow(display, win);
+                    break;
+                case KeyPress:
+                    if (XLookupString(&event.xkey,x11inputbuf,255,&key,0) == 1) {
+                        switch (x11inputbuf[0]) {
+                            case 'q':
+                                close_x();
+                                break;
+                            default:
+                                write(master, &x11inputbuf[0], 1);
+                        }
+                    }
+                    break;
+            }
+        }
+    }
+}
+
+int main(void) {
+    init_x();
+    spawn();
+
+    update();
+    return 0;
+}
+