Handling X errors using exception handlers

[Lionel Ulmer]

> The main problem with that is that I don't think you can jump out of
> Xlib without corrupting its state. Also you'd need to properly unlock
> the tsx11 lock in case of exception, which will probably require an
> finally handler around each X call.

Well, seems you are right about X not liking the 'longjmp' stuff (I asked on
the XPert mailing list to confirm :-) ).

> My idea was to have the following two functions:
> 
> void X11DRV_expect_error( unsigned char request, unsigned char error, XID id );
> int X11DRV_check_error(void);
> 
> You'd call X11DRV_expect_error before doing an X call that can fail;
> then if an X error happens that matches what you expect, the X error
> handler will simply set a flag and ignore the error (if it doesn't
> match you get the standard error handling). Then after the call you
> use X11DRV_check_error to see if your error happened or not. Would
> this work for what you need?

Yeah, this would work (and is about what I already did in the XShm and WGL
code to detect X errors, except that I just set a global variable in case of
error :-) ).

The only problems I could see with this approach is that :

 - it cannot 'expect' more than one kind of error at the same time
 
 - I am not sure that the parameters thing are really a good idea. Are we
   sure that the error code are the same on all X servers ? Are they
   standardized ?

                                  Lionel

-- 
		 Lionel Ulmer - http://www.bbrox.org/