diff --git a/cmenu/popup.c b/cmenu/popup.c
new file mode 100644
index 0000000..1b87c23
--- /dev/null
+++ b/cmenu/popup.c
@@ -0,0 +1,361 @@
+#define _GNU_SOURCE
+
+#include <X11/Xlib.h>
+#include <X11/Xatom.h>
+#include <X11/keysym.h>
+#include <X11/extensions/Xrandr.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+
+static int get_active_window(Display *dpy, Window root, Window *active)
+{
+    Atom prop = XInternAtom(dpy, "_NET_ACTIVE_WINDOW", True);
+
+    if (!prop)
+        return 0;
+
+    Atom actual;
+    int format;
+    unsigned long nitems;
+    unsigned long bytes_after;
+    unsigned char *data = NULL;
+
+    int status = XGetWindowProperty(
+        dpy,
+        root,
+        prop,
+        0,
+        1,
+        False,
+        XA_WINDOW,
+        &actual,
+        &format,
+        &nitems,
+        &bytes_after,
+        &data
+    );
+
+    if (status != Success || !data || nitems == 0) {
+        if (data)
+            XFree(data);
+        return 0;
+    }
+
+    *active = *(Window *)data;
+
+    XFree(data);
+    return 1;
+}
+
+static int get_window_center(
+    Display *dpy,
+    Window window,
+    int *cx,
+    int *cy
+)
+{
+    Window root;
+    Window child;
+
+    int x;
+    int y;
+
+    unsigned int width;
+    unsigned int height;
+    unsigned int border;
+    unsigned int depth;
+
+    if (!XGetGeometry(
+            dpy,
+            window,
+            &root,
+            &x,
+            &y,
+            &width,
+            &height,
+            &border,
+            &depth))
+        return 0;
+
+    int root_x;
+    int root_y;
+
+    if (!XTranslateCoordinates(
+            dpy,
+            window,
+            root,
+            0,
+            0,
+            &root_x,
+            &root_y,
+            &child))
+        return 0;
+
+    *cx = root_x + (int)width / 2;
+    *cy = root_y + (int)height / 2;
+
+    return 1;
+}
+
+int main(void)
+{
+    Display *dpy = XOpenDisplay(NULL);
+
+    if (!dpy) {
+        fprintf(stderr, "popup: cannot open X display\n");
+        return EXIT_FAILURE;
+    }
+
+    int screen = DefaultScreen(dpy);
+    Window root = RootWindow(dpy, screen);
+
+    /*
+     * ------------------------------------------------------------
+     * Find the currently focused window.
+     * ------------------------------------------------------------
+     */
+
+    Window active = None;
+
+    int cursor_x = DisplayWidth(dpy, screen) / 2;
+    int cursor_y = DisplayHeight(dpy, screen) / 2;
+
+    if (get_active_window(dpy, root, &active)) {
+        get_window_center(
+            dpy,
+            active,
+            &cursor_x,
+            &cursor_y
+        );
+    }
+
+    /*
+     * ------------------------------------------------------------
+     * Find the monitor containing the active window.
+     * ------------------------------------------------------------
+     */
+
+    int monitor_x = 0;
+    int monitor_y = 0;
+
+    int monitor_width = DisplayWidth(dpy, screen);
+    int monitor_height = DisplayHeight(dpy, screen);
+
+    int monitor_count = 0;
+
+    XRRMonitorInfo *monitors =
+        XRRGetMonitors(
+            dpy,
+            root,
+            True,
+            &monitor_count
+        );
+
+    if (monitors) {
+
+        for (int i = 0; i < monitor_count; i++) {
+
+            XRRMonitorInfo *m = &monitors[i];
+
+            if (cursor_x >= m->x &&
+                cursor_x < m->x + (int)m->width &&
+                cursor_y >= m->y &&
+                cursor_y < m->y + (int)m->height) {
+
+                monitor_x = m->x;
+                monitor_y = m->y;
+
+                monitor_width = m->width;
+                monitor_height = m->height;
+
+                break;
+            }
+        }
+
+        XRRFreeMonitors(monitors);
+    }
+
+    /*
+     * ------------------------------------------------------------
+     * Desired geometry.
+     *
+     * Half the monitor width and half the monitor height,
+     * centered on that monitor.
+     * ------------------------------------------------------------
+     */
+
+    int width = monitor_width / 2;
+    int height = monitor_height / 2;
+
+    int x = monitor_x + (monitor_width - width) / 2;
+    int y = monitor_y + (monitor_height - height) / 2;
+
+    /*
+     * ------------------------------------------------------------
+     * Create the window.
+     *
+     * override_redirect means the window manager does not manage
+     * this window. This prevents it from moving/resizing it.
+     * ------------------------------------------------------------
+     */
+
+    XSetWindowAttributes attributes;
+
+    attributes.override_redirect = True;
+    attributes.background_pixel =
+        BlackPixel(dpy, screen);
+
+    attributes.event_mask =
+        KeyPressMask |
+        FocusChangeMask |
+        StructureNotifyMask;
+
+    Window window = XCreateWindow(
+        dpy,
+        root,
+
+        x,
+        y,
+
+        width,
+        height,
+
+        0,
+
+        CopyFromParent,
+        InputOutput,
+        CopyFromParent,
+
+        CWOverrideRedirect |
+        CWBackPixel |
+        CWEventMask,
+
+        &attributes
+    );
+
+    if (!window) {
+        fprintf(stderr, "popup: XCreateWindow failed\n");
+        XCloseDisplay(dpy);
+        return EXIT_FAILURE;
+    }
+
+    /*
+     * ------------------------------------------------------------
+     * Map the window.
+     * ------------------------------------------------------------
+     */
+
+    XMapRaised(dpy, window);
+    XFlush(dpy);
+
+    /*
+     * ------------------------------------------------------------
+     * Wait until the X server has actually mapped the window.
+     *
+     * Calling XSetInputFocus() before this can result in:
+     *
+     *     BadMatch (invalid parameter attributes)
+     *
+     * ------------------------------------------------------------
+     */
+
+    for (;;) {
+
+        XEvent event;
+
+        XNextEvent(dpy, &event);
+
+        if (event.type == MapNotify &&
+            event.xmap.window == window) {
+            break;
+        }
+    }
+
+    /*
+     * ------------------------------------------------------------
+     * Now that the window is viewable, take keyboard focus.
+     * ------------------------------------------------------------
+     */
+
+    XSetInputFocus(
+        dpy,
+        window,
+        RevertToParent,
+        CurrentTime
+    );
+
+    XRaiseWindow(dpy, window);
+
+    XFlush(dpy);
+
+    /*
+     * ------------------------------------------------------------
+     * Event loop.
+     *
+     * Escape:
+     *     exit
+     *
+     * FocusOut:
+     *     exit
+     *
+     * The window is override-redirect, so the WM won't resize or
+     * reposition it.
+     * ------------------------------------------------------------
+     */
+
+    for (;;) {
+
+        XEvent event;
+
+        XNextEvent(dpy, &event);
+
+        switch (event.type) {
+
+        case KeyPress:
+        {
+            KeySym key =
+                XLookupKeysym(
+                    &event.xkey,
+                    0
+                );
+
+            if (key == XK_Escape) {
+
+                XDestroyWindow(
+                    dpy,
+                    window
+                );
+
+                XCloseDisplay(dpy);
+
+                return EXIT_SUCCESS;
+            }
+
+            break;
+        }
+
+        case FocusOut:
+        {
+            /*
+             * Any loss of keyboard focus causes the popup
+             * to immediately terminate.
+             */
+
+            XDestroyWindow(
+                dpy,
+                window
+            );
+
+            XCloseDisplay(dpy);
+
+            return EXIT_SUCCESS;
+        }
+
+        default:
+            break;
+        }
+    }
+
+    return EXIT_SUCCESS;
+}