OpenGL::XScreenSaver(3pm)

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.