From http://www.jwz.org/xscreensaver/xscreensaver-5.18.tar.gz

[xscreensaver] / README.hacking

diff --git a/README.hacking b/README.hacking
index 72489a2d5504c065180a4ba2bfd5858e1bd829d8..718cae2b150804629081a0982048c5c2bfea079a 100644 (file)
--- a/README.hacking
+++ b/README.hacking
@@ -5,6 +5,19 @@
 
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+Any program that can be made to render on an X window created by another
+process can be used as a screen saver.  Just get the window ID out of
+$XSCREENSAVER_WINDOW, draw on that, and you're done.
+
+In theory, you can write a screen saver in any language you like.  In
+practice, however, languages other than C or C++ tend not to allow you to
+draw to windows that they did not create themselves.  Unfortunately, this
+means that if you want to write a screen saver, you must write it in C.
+
+Given that you're going to be writing in C, you might as well take
+advantage of the various utility functions that I have written to make
+that easier.  Writing a new screen saver in C using the frameworks
+included with xscreensaver simplifies things enormously.

 
 Generally, the best way to learn how to do something is to find a similar
 program, and play around with it until you understand it.  Another
 
 Generally, the best way to learn how to do something is to find a similar
 program, and play around with it until you understand it.  Another


@@ -14,8 +27,8 @@ xscreensaver demos, included in the "hacks/" directory, rename the file,
 and edit it until it does what you want.
 
 The "Greynetic" and "Deluxe" hacks are probably good ones to start with,
 and edit it until it does what you want.
 
 The "Greynetic" and "Deluxe" hacks are probably good ones to start with,

-since they are so very simple.  For GL programs, "DangerBall" is a good
-example.
+since they are so very simple.  For OpenGL programs, "DangerBall" is a
+good example.

 
 
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@@ -161,7 +174,7 @@ The MacOS X Port
 
   To compile on MacOS, use the XCode project included in the source
   distribution.  You shouldn't need to have X11 installed, and shouldn't
 
   To compile on MacOS, use the XCode project included in the source
   distribution.  You shouldn't need to have X11 installed, and shouldn't

-  need to run "configure" first.  MacOS 10.4.0 and XCode 2.5 or newer are
+  need to run "configure" first.  MacOS 10.4.0 and XCode 3.1 or newer are

   required.
 
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   required.
 
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