libAfterImage/tutorials/common.h

 Generic Xlib related functionality, common for all the tutorials.

 libAfterImage,
 ASView, ASScale, ASTile, ASMerge, ASGrad, ASFlip, ASText

libAfterImage/tutorials/_XA_WM_DELETE_WINDOW

 _XA_WM_DELETE_WINDOW - stores value of X Atom "WM_DELETE_WINDOW".

 In X all client's top level windows are managed by window manager.
 That includes moving, resizing, decorating, focusing and closing of
 windows. Interactions between window manager and client window are
 governed by ICCCM specification.
 All the parts of this specification are completely optional, but it
 is recommended that the following minimum set of hints be supplied
 for any client window:
 Window's title(WM_NAME), iconified window title(WM_ICON_NAME), class
 hint (WM_CLASS) and supported protocols (WM_PROTOCOLS). It is
 recommended also that WM_DELETE_WINDOW protocol be supported, as
 otherwise there are no way to safely close client window, but to
 kill it.
 All of the above mentioned hints are identified by atoms that have
 standard preset values, except for WM_DELETE_WINDOW. As the result we
 need to obtain WM_DELETE_WINDOW atoms ID explicitly. We use
 _XA_WM_DELETE_WINDOW to store the ID of that atom, so it is accessible
 anywhere from our application.

    Atom _XA_WM_DELETE_WINDOW = None;

libAfterImage/tutorials/create_top_level_window()

 Window create_top_level_window( ASVisual *asv, Window root,
                                 int x, int y,
                                 unsigned int width,
                                 unsigned int height,
                                 unsigned int border_width,
                                 unsigned long attr_mask,
                                 XSetWindowAttributes *attr,
                                 char *app_class );

 asv           - pointer to valid preinitialized ASVisual structure.
 root          - root window of the screen on which to create window.
 x, y          - desired position of the window
 width, height - desired window size.
 border_width  - desired initial border width of the window (may not
                 have any effect due to Window Manager intervention.
 attr_mask     - mask of the attributes that has to be set on the
                 window
 attr          - values of the attributes to be set.
 app_class     - title of the application to be used as its window
                 Title and resources class.

 ID of the created window.

 create_top_level_window() is autyomating process of creating top
 level application window. It creates window for specified ASVisual,
 and then sets up basic ICCCM hints for that window, such as WM_NAME,
 WM_ICON_NAME, WM_CLASS and WM_PROTOCOLS.

    Window
    create_top_level_window( ASVisual *asv, Window root, int x, int y,
                             unsigned int width, unsigned int height,
                             unsigned int border_width, unsigned long attr_mask,
                             XSetWindowAttributes *attr, char *app_class )
    {
        Window w = None;
    #ifndef X_DISPLAY_MISSING
        char *tmp ;
        XTextProperty name;
        XClassHint class1;
    
        w = create_visual_window(asv, root, x, y, width, height, border_width, InputOutput, attr_mask, attr );
    
        tmp = (char*)get_application_name();
        XStringListToTextProperty (&tmp, 1, &name);
    
        class1.res_name = tmp;  /* for future use */
        class1.res_class = app_class;
        XSetWMProtocols (dpy, w, &_XA_WM_DELETE_WINDOW, 1);
        XSetWMProperties (dpy, w, &name, &name, NULL, 0, NULL, NULL, &class1);
        /* final cleanup */
        XFree ((char *) name.value);
    
    #endif /* X_DISPLAY_MISSING */
        return w;
    }

libAfterImage/tutorials/set_window_background_and_free()

 Pixmap set_window_background_and_free( Window w, Pixmap p );

 w - ID of the window background of which we need to set.
 p - Pixmap to set background to.

 None on success. Pixmap ID of original Pixmap on failure.

 set_window_background_and_free() will set window's background to
 specified Pixmap, Then refresh window contents so that background
 is drawn by the server, flush all the requests to force it to be sent
 to server to be processed as fast as possible.

 After Window's background has been set to Pixmap - X server makes
 hidden copy of this Pixmap for later window refreshing. As the result
 original Pixmap is no longer needed and can be freed to conserve
 resources.

    Pixmap
    set_window_background_and_free( Window w, Pixmap p )
    {
    #ifndef X_DISPLAY_MISSING
        if( p != None && w != None )
        {
            XSetWindowBackgroundPixmap( dpy, w, p );
            XClearWindow( dpy, w );
            XFlush( dpy );
            XFreePixmap( dpy, p );
            p = None ;
        }
    #endif /* X_DISPLAY_MISSING */
        return p ;
    }

libAfterImage/tutorials/wait_closedown()

 void wait_closedown( Window w );

 w - ID of the window from which to wait for events.

 User action requesting window to be closed is generally received
 first by Window Manager. Window Manager is then handles it down to
 the window by sending it ClientMessage event with first 32 bit word
 of data set to the value of WM_DELETE_WINDOW Atom.
 Accordingly, all client has to do is wait for such event from X server
 and, when received, it should destroy its window and generally exit.

 It is recommended that XFlush() is issued right after XDestroyWindow()
 as Window Manager itself may attempt to do something with the window
 until it receives DestroyNotify event.

 ICCCM, Window

    void
    wait_closedown( Window w )
    {
    #ifndef X_DISPLAY_MISSING
        if( dpy == NULL || w == None )
            return ;
    
        XSelectInput (dpy, w, (StructureNotifyMask | ButtonPressMask|ButtonReleaseMask));
    
        while(w != None)
        {
            XEvent event ;
            XNextEvent (dpy, &event);
            switch(event.type)
            {
                case ClientMessage:
                    if ((event.xclient.format != 32) ||
                        (event.xclient.data.l[0] != _XA_WM_DELETE_WINDOW))
                        break ;
                case ButtonPress:
                    XDestroyWindow( dpy, w );
                    XFlush( dpy );
                    w = None ;
                    break ;
            }
        }
        XCloseDisplay (dpy);
        dpy = NULL ;
    #endif
    }