block mouse clicks to window by window id

noclickforyou.c

#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <X11/extensions/shape.h>
#include <X11/extensions/Xfixes.h>
#include <X11/Xlib.h>
#include <poll.h>
#include <sys/select.h>

sig_atomic_t running;

void restore(int signum)
{
    (void)signum;
    running = 0;
}

int main(int argc, char **argv)
{
    Display *display;
    Window window;

    if (argc != 2) {
        fprintf(stderr, "Usage: %s <window_id>\n", argv[0]);
        return 1;
    }

    display = XOpenDisplay(NULL);
    if (!display) {
        fprintf(stderr, "Failed to open display\n");
        return 1;
    }

    window = strtoul(argv[1], NULL, 0);

    int event_base, error_base;
    if (!XFixesQueryExtension(display, &event_base, &error_base)) {
        fprintf(stderr, "XFixes extension not available\n");
        XCloseDisplay(display);
        return 1;
    }

    XserverRegion empty_region = XFixesCreateRegion(display, NULL, 0);
    XFixesSetWindowShapeRegion(display, window, ShapeInput, 0, 0, empty_region);
    XFixesDestroyRegion(display, empty_region);

    XSelectInput(display, window, StructureNotifyMask);

    XFlush(display);

    struct pollfd pollFds;
    pollFds.fd = ConnectionNumber(display);
    pollFds.events = POLLIN;
    pollFds.revents = 0;

    signal(SIGINT, restore);
    signal(SIGTERM, restore);

    running = 1;
    while (running) {
        int ready = poll(&pollFds, 1, -1);
        if (ready <= 0) {
            running = 0;
            break;
        }

        // Handle XEvents and flush the input
        while (XPending(display)) {
            XEvent event;
            XNextEvent(display, &event);
            if (event.type == DestroyNotify) {
                window = None;
                running = 0;
            }
        }
    }

    if (window) {
        XFixesSetWindowShapeRegion(display, window, ShapeInput, 0, 0, None);
    }
    XCloseDisplay(display);
}