Overlay windows and backwards compatibility

[Deron Johnson]

The main reason why these extensions were added was to support composite
managers. Typically one usually always runs a composite manager for a
display locally.

But if an arbitrary application wishes to use the extensions on
an arbitrary display, it should check the version numbers of the
composite and/or xfixes extension to make sure that the version number
is big enough so that the desired requests will be supported. This is
standard X client practice. This type of version checking is often
done by the protocol extension library itself.

However, I notice that the Xfixes client library performs this
sort of version checking, converting unsupported routines into
no-ops. But I notice that the Composite client library doesn't
do any checking at all. When I added the new functions to the
Xfixes client library I made sure that XFixesHide/ShowCursor checked
the version number and simply returned if it wasn't 4.0 or greater.
But I didn't do this in the Composite client library because
version checking wasn't being done in any of the other functions.

Donnie Berkholz wrote On 03/23/06 13:40,:
> Hi all,
> 
> I've run into an issue today with how the overlay windows patches etc
> work. Picture a situation where the client box has the new composite 0.3
> and fixes 4.0, and its libXcomposite/libXfixes etc support the new
> features. Now try running an application across the network on an X
> server that doesn't support overlay windows.
> 
> Should this work, or should it be broken? I feel like there should be
> some sort of check for whether overlay windows etc work, but currently
> what happens is that GTK2 applications just crash with BadRequest
> errors. The same would hold true for a local X server not supporting
> overlay windows, which is where I actually ran into the problem, but the
> above scenario seems more likely.
> 
> Thanks,
> Donnie
> 
> 
> 
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