#if 0
mkdir -p build
clang -o build/demo -g x11.c -lX11
exit 0
#endif

/*
** Reading From:
** (1) xlib manual    https://tronche.com/gui/x/xlib/
*/

#include <X11/Xlib.h>

#include <stdio.h>

int main(int argc, char **argv){
  /* (1) /display/opening.html
  ** " The XOpenDisplay() function returns a Display structure that serves
  **   as the connection to the X server and that contains all the 
  **   information about that X server. "
  */
  Display *display = XOpenDisplay(0);
  if (display == 0){
    printf("XOpenDisplay failed\n");
  }
  
  /* (1) /window-information/XInternAtom.html
  ** " returns the atom identifier associated with the specified 
  **   atom_name string "
  */
  Atom atom__WM_DELETE_WINDOW = XInternAtom(display, "WM_DELETE_WINDOW", False);
  
  /* (1) /window/XCreateWindow.html
  ** " The XCreateWindow function creates an unmapped subwindow for a 
  **   specified parent window "
  */
  Window window = 0;
  if (display != 0){
    Window parent = DefaultRootWindow(display);
    int x = 0;
    int y = 0;
    int w = 640;
    int h = 480;
    int border_width = 0;
    int depth = CopyFromParent;
    unsigned int xclass = InputOutput;
    Visual *visual = CopyFromParent;
    unsigned long valuemask = CWEventMask;
    
    XSetWindowAttributes attributes = {0};
    attributes.event_mask = StructureNotifyMask;
    
    window = XCreateWindow(display, parent, x, y, w, h, border_width,
                           depth, xclass, visual, valuemask,
                           &attributes);
    
    if (window == 0){
      printf("XCreateWindow failed\n");
    }
  }
  
  if (window != 0){
    /* (1) /ICC/client-to-window-manager/XStoreName.html
    ** " assigns the name passed to window_name to the specified window "
    */
    XStoreName(display, window, "Example Window");
    
    /* (1) /window/XMapWindow.html
    ** " maps the window and all of its subwindows that have had map requests "
    **~ NOTE: This makes the window visible on the screen.
    */
    XMapWindow(display, window);
    
    /*~ NOTE: Main loop */
    int exit_loop = 0;
    for (;!exit_loop;){
      
      /* (1) /event-handling/XPending.html
      ** " returns the number of events that have been received from the X
      **   server but have not been removed from the event queue "
      **~ NOTE: The docs say this returns the number of events, but it's
      **   easier, and possibly more reliable to just use it to check if
      **   there is at lesat one input.
      */
      for (;XPending(display) > 0;){
        /* (1) /event-handling/manipulating-event-queue/XNextEvent.html
        ** " copies the first event from the event queue into the specified
        **   XEvent structure and then removes it from the queue "
        */
        XEvent event;
        XNextEvent(display, &event);
        
        /* (1) /events/structures.html
        ** " The XEvent structure is a union of the individual structures 
        **   declared for each event type. Depending on the type, you should
        **   access members of each event by using the XEvent union. "
        */
        switch (event.type){
          case ClientMessage: {
            Atom atom = event.xclient.data.l[0];
            if (atom == atom__WM_DELETE_WINDOW){
              exit_loop = 1;
            }
          }break;
        }
      }
    }
  }
  
  /*~ NOTE: Shutdown */
  
  /* (1) /window/XDestroyWindow.html
  ** " destroys the specified window as well as all of its subwindows "
  */
  if (display != 0 && window != 0){
    XDestroyWindow(display, window);
  }
  
  /* (1) /display/closing.html
  ** " To close a display or disconnect from the X server, use
  **   XCloseDisplay(). "
  */
  if (display != 0){
    XCloseDisplay(display);
  }
  
  return(0);
}