Sometimes you want to activate a window that doesn't belong to you. I wasted way too much time for that knowledge to be lost, so I'm just going to share it here. One would think XRaiseWindow is straightforward enough, but no. Not at all.

#include <X11/Xlib.h>

int WindowBringToFront(unsigned long id)
{
    Display* display = XOpenDisplay(NULL); // you probably want to do this somewhere else

    if (!display)
        return -1;

    XEvent wm_event = { 0 };
    wm_event.xclient.type = ClientMessage;
    wm_event.xclient.send_event = true;
    wm_event.xclient.message_type = XInternAtom(
        display
        "_NET_ACTIVE_WINDOW",
        true
    );
    wm_event.xclient.window = (Window)id;
    wm_event.xclient.format = 32; // man 3 XSendEvent

    Status xresult = XSendEvent(
        display,
        DefaultRootWindow(display),
        false,
        SubstructureRedirectMask
        | SubstructureNotifyMask,
        &wm_event
    );

    if (!xresult)
        return -1;

    return 0;
}

Code released under MIT license. Grab it, fellow corporate code monkey.