/* This example:
 *  - creates X11 container window;
 *  - executes child process (container window id is appended to argv);
 *  - handles child window requests;
 *  - propagates container window events to child window.
 *
 * Usage:
 *   gcc -o xlib_container xlib_container.c -lX11
 *   ./xlib_container xterm -into
 *   ./xlib_container mplayer video.mp4 -wid
 */
#include <X11/Xlib.h>
#include <X11/Xutil.h>

#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#include <sys/signal.h>
#include <sys/wait.h>

#define WIDTH   400
#define HEIGHT  200

static const char *event_names[] = {
   "",
   "",
   "KeyPress",
   "KeyRelease",
   "ButtonPress",
   "ButtonRelease",
   "MotionNotify",
   "EnterNotify",
   "LeaveNotify",
   "FocusIn",
   "FocusOut",
   "KeymapNotify",
   "Expose",
   "GraphicsExpose",
   "NoExpose",
   "VisibilityNotify",
   "CreateNotify",
   "DestroyNotify",
   "UnmapNotify",
   "MapNotify",
   "MapRequest",
   "ReparentNotify",
   "ConfigureNotify",
   "ConfigureRequest",
   "GravityNotify",
   "ResizeRequest",
   "CirculateNotify",
   "CirculateRequest",
   "PropertyNotify",
   "SelectionClear",
   "SelectionRequest",
   "SelectionNotify",
   "ColormapNotify",
   "ClientMessage",
   "MappingNotify"
};

int main(int argc, char** argv) {
    if (argc < 2) {
        fprintf(stderr, "usage: %s child_program child_arguments..\n", argv[0]);
        exit(1);
    }

    Display* display = XOpenDisplay(NULL);
    if (display == NULL) {
        fprintf(stderr, "error: can't open display!\n");
        exit(1);
    }

    int screen = DefaultScreen(display);

    Colormap colormap = DefaultColormap(display, screen);

    XColor blue;
    XAllocNamedColor(display, colormap, "blue", &blue, &blue);

    // Initialize container window attributes
    XSetWindowAttributes attrs;

    attrs.event_mask
        = SubstructureRedirectMask // handle child window requests      (MapRequest)
        | SubstructureNotifyMask   // handle child window notifications (DestroyNotify)
        | StructureNotifyMask      // handle container notifications    (ConfigureNotify)
        | ExposureMask             // handle container redraw           (Expose)
        ;

    attrs.do_not_propagate_mask = 0; // do not hide any events from child window

    attrs.background_pixel = blue.pixel; // background color

    unsigned long attrs_mask = CWEventMask  // enable attrs.event_mask
                             | NoEventMask  // enable attrs.do_not_propagate_mask
                             | CWBackPixel  // enable attrs.background_pixel
                             ;

    // Create and map container window
    Window container_window = XCreateWindow(display, RootWindow(display, screen),
                                            0,
                                            0,
                                            WIDTH,
                                            HEIGHT,
                                            1,
                                            CopyFromParent,
                                            InputOutput,
                                            CopyFromParent,
                                            attrs_mask,
                                            &attrs);

    // Make window visible
    XMapWindow(display, container_window);

    // Set window title
    XStoreName(display, container_window, "XLIB container");

    // Get WM_DELETE_WINDOW atom
    Atom wm_delete = XInternAtom(display, "WM_DELETE_WINDOW", True);

    // Subscribe WM_DELETE_WINDOW message
    XSetWMProtocols(display, container_window, &wm_delete, 1);

    // Create child process
    int child_pid = fork();

    if (child_pid == 0) {
        char window_id[64];
        sprintf(window_id, "%lu", container_window);

        char** child_argv = calloc(argc + 1, sizeof(char* ));
        int a;
        for (a = 1; a < argc; ++a) {
            child_argv[a - 1] = argv[a];
        }

        child_argv[argc - 1] = window_id;
        execvp(child_argv[0], child_argv);

        fprintf(stderr, "error: can't execute child process!\n");
        exit(1);
    }

    // Child window ID and its display
    Display* child_display = NULL;
    Window child_window = 0;

    // Container window event loop
    for (;;) {
        XEvent event;
        XNextEvent(display, &event);

        printf("container_event: %s\n", event_names[event.type]);

        // Map child window when it requests and store its display and window id
        if (event.type == MapRequest) {
            XMapWindow(event.xmaprequest.display, event.xmaprequest.window);

            child_display = event.xmaprequest.display;
            child_window = event.xmaprequest.window;
        }

        // Propagate resize event to child window, and also resize it after MapRequest
        if (event.type == ConfigureNotify || event.type == MapRequest) {
            if (child_window) {
                // Get container window attributes
                XWindowAttributes attrs;
                XGetWindowAttributes(display, container_window, &attrs);

                // Move and resize child
                XMoveResizeWindow(child_display,
                                  child_window,
                                  2, 2, attrs.width - 6, attrs.height - 6);
            }
        }

        // Refresh container window
        if (event.type == Expose) {
            XClearWindow(display, container_window);
        }

        // Exit if child window was destroyed
        if (event.type == DestroyNotify) {
            fprintf(stderr, "child window destroyed, exiting\n");
            break;
        }

        // Close button
        if (event.type == ClientMessage) {
            if (event.xclient.data.l[0] == wm_delete) {
                break;
            }
        }
    }

    // Kill child process
    kill(child_pid, SIGTERM);
    wait(0);

    XCloseDisplay(display);
    return 0;
}