lack of standardization on X11

[Alan Coopersmith]

Mikhail Gusarov wrote:
> Nobody removes extensions. 

Not ones that are widely used, but we have dropped many extensions
over the years that didn't work out, never got well adopted, or just
outlived their usefulness - PEX, XIE, XPrint, EVI, AppGroup, EVI,
MIT-SUNDRY-NONSTANDARD, TOG-CUP, XTrap, XFree86-Misc, XEvIE, etc.

This is why applications should check for extensions and fall back
safely when they're not present - not just to support running on
older servers or even the rarely seen server based on someone else's
sources (much more prevalent in the past world of proprietary Unix
vendor X servers, before everyone ended up shipping the mostly
unmodified Xorg server), but to support running on future servers
once an extension passes beyond its useful life, or even on modern
X servers that someone compiled for their cell phone with tons of
--disable flags to remove extensions commonly found on desktops.

-- 
	-Alan Coopersmith-        alan.coopersmith at oracle.com
	 Oracle Solaris Platform Engineering: X Window System