Add missing functionality for screensaver. WIP

[ebrasca]

Can you read over the code and finish "screen-saver-select-input"?

[PuercoPop]

@ebrasca, as requested on #lisp I'm writing some feedback on the PR. If you wrote some questions on the PR (or by mail) it would be easier for me to understand what problems you are facing. From our exchange on irc I remember you mentioned that you didn't know how to implement that line. But I don't know what exactly are you having trouble with.

So as a general note, first we need to understand what screen-saver-select input does[1]. is the way the client asks to by notified of Screen Saver events. There are two types of Events that one may ask to be notified of:

• ScreenSaverNotify: When the screen saver is activated or deactivated.
• ScreenSaverCycle: When the cycle interval passes

And the Specification describes those events as

SETofSCREENSAVEREVENT

#x00000001 ScreenSaverNotifyMask
#x00000002 ScreenSaverCycleMask

which translates into

(defconstant +screen-saver-notify-mask+  #x01)
(defconstant +screen-saver-cycle-mask+ #x02)

For this we can see that screen-saver-select-input is missing a parameter, the event mask the client is interest in. For the API it would be more convenient to take a list of keywords and build the event mask inside the function. For that ideally we could use xlib:make-event-mask. However define-event is internal to the xlib package and it doesn't seem to be taylored for extension so I have to read CLX source code some more. I hope this is of some help.

On a more general note:

• It would be a good idea to update the document reference to point to https://www.x.org/docs/saver/saver.pdf
• It would be better to implement the extension in its own package and export to xlib the relevant API, similar to xtest.lisp (except that it doesn't export symbols to xlib).
• It small change would be to use a 'constant' to mark the major and minor version instead of hardcoding them in the functions. If the code is still in the xlib package one would have to 'namespace' it similar to how dbe.lisp does, ej (defconstant +screensaver-major+ 1)

[1]: See man 3 XScreenSaverSelectInput

[ebrasca]

I stoped working on clx. Thanks you.