Ready. Set. Go!

.gitignore

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+main

Makefile

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+CFLAGS=-Wall -Wextra -std=c11 -pedantic -ggdb
+LIBS=-lX11 -lXext
+
+main: main.c
+	$(CC) $(CFLAGS) -o main main.c $(LIBS)

main.c

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+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <X11/Xlib.h>
+
+#include <unistd.h>
+
+#define WIDTH 800
+#define HEIGHT 600
+#define FPS 120
+
+int main(void)
+{
+    Display *display = XOpenDisplay(NULL);
+    if (display == NULL) {
+        fprintf(stderr, "ERROR: could not open the default display\n");
+        exit(1);
+    }
+
+    Window window = XCreateSimpleWindow(
+                        display,
+                        XDefaultRootWindow(display),
+                        0, 0,
+                        WIDTH, HEIGHT,
+                        0,
+                        0,
+                        0);
+
+    XWindowAttributes wa = {0};
+    XGetWindowAttributes(display, window, &wa);
+
+    GC gc = XCreateGC(display, window, 0, NULL);
+
+    Atom wm_delete_window = XInternAtom(display, "WM_DELETE_WINDOW", False);
+    XSetWMProtocols(display, window, &wm_delete_window, 1);
+
+    XSelectInput(display, window, KeyPressMask);
+
+    XMapWindow(display, window);
+
+    XSetForeground(display, gc, 0xFF0000);
+
+    int rect_x = 0;
+    int rect_y = 0;
+
+    int quit = 0;
+    while (!quit) {
+        while (XPending(display) > 0) {
+            XEvent event = {0};
+            XNextEvent(display, &event);
+            switch (event.type) {
+            case KeyPress: {
+                switch (XLookupKeysym(&event.xkey, 0)) {
+                case 'q':
+                    quit = 1;
+                    break;
+                default:
+                {}
+                }
+            } break;
+            case ClientMessage: {
+                if ((Atom) event.xclient.data.l[0] == wm_delete_window) {
+                    quit = 1;
+                }
+            }
+            break;
+            }
+        }
+
+        XClearArea(display, window, 0, 0, WIDTH, HEIGHT, False);
+        XFillRectangle(display, window, gc, rect_x, rect_y, 100, 100);
+
+        rect_x += 1;
+        rect_y += 1;
+
+        usleep(1000*1000/FPS);
+    }
+
+    XCloseDisplay(display);
+    return 0;
+}