NAME

       OpenGL::XScreenSaver - prepare environment for writing OpenGL-based XScreenSaver hacks

SYNOPSIS

        use OpenGL qw(:all);
        use OpenGL::XScreenSaver;

        OpenGL::XScreenSaver::init();
        # GetOptions(...); # parse your own options, if any

        OpenGL::XScreenSaver::start();

        while (1) {
            glClear(...);
            # draw your scene here
            OpenGL::XScreenSaver::update();
        }

DESCRIPTION

       This module allows you to write OpenGL XScreenSaver hacks in Perl. It prepares the GL to
       be used with XScreenSaver.

       Read the synopsis for how your program might look.

   Description of functions
       The init() function will return a true value if a window to draw on has been found, and a
       false value if a window will have to be created. This value can be ignored unless you want
       to make sure that your screenhack cannot be executed outside XScreenSaver (e.g. if your
       standalone version comes as an extra binary with keyboard control, which would be useless
       in a screensaver).

       The start() function will open the connection to the X server and bind to the window ID or
       create a new window to draw on (depends on if it was called standalone or from
       XScreenSaver).

       The update() function should be called when you finished rendering the frame. It will
       flush output and swap the buffers. In the future it might also handle a minimal set of X
       events when run in standalone mode (like window deletion requests by the window manager).

       The dimensions() function returns a list with the width and the height of the currently
       used window.

   About screenhacks
       What follows is a short description of how it works and what XScreenSaver expects a
       screenhack to do.

       XScreenSaver tells the hack on startup what window ID the hack shall draw to.  This is
       either a small window mapping to the screen in the preview dialog, or a fullscreen window.
       The window ID is passed either via the -window-id option or via the XSCREENSAVER_WINDOW
       environment variable. init() of this module checks both of these.

       XScreenSaver handles all user input including exiting and pausing the screensaver. The
       process is sent a SIGSTOP when the unlock screen is displayed, obviously a SIGCONT when it
       is dismissed, and when the pointing device is moved or the screen gets unlocked
       XScreenSaver sends a SIGTERM. This means that no event handling is required by your
       screenhack whatsoever. This again keeps the design of a screenhack dead simple.

SEE ALSO

       OpenGL

AUTHORS & COPYRIGHTS

       Made 2010 by Lars Stoltenow.  OpenGL::XScreenSaver is free software; you may redistribute
       it and/or modify it under the same terms as Perl itself.