Re: [Plib-devel] Patches for FreeBSD

[Steve B. <sjb...@ai...>]

Bert Driehuis wrote:

> One change should not be committed, which is the change that takes out 
> the call to glIsValidContext(). Not all patches in the ports tree are 
> desirable or even well thought out.

We have had continual trouble with that.

There are two conflicting aspects to this - both related to broken
OpenGL implementations.

1) Some implementations don't correctly respond to glIsValidContext -
notably one version of Mesa and one of ATI's drivers...probably both
relate to an underlying DRI issue.  In the presence of that bug, no
PLIB applications will run because the library believes there is no
valid GL context and therefore refuses to run.

2) Some implementations allow OpenGL applications to do (illegal)
OpenGL calls (glGetString(...) is a common one) without a valid
GL context.  This allows application program writers to make the
common error of trying to find out what kind of graphics card they
have BEFORE they've opened a GL context...or perhaps do some other
operation before the GL context is opened.  Then, when they move their
code to a different graphics card or driver, the formerly working
program crashes.

In order to prevent the latter problem causing a crash inside PLIB
(and typically, a complaint to our developers for something we didn't
do wrong) - I put checks for valid GL contexts in all of the PLIB
initXXX() functions.  Then, at least we know that PLIB isn't at fault.

So - the problem is that if we leave out the glIsValidContext check
then programmers make this VERY common mistake - and don't notice it
for months or years later - and blame it on us.

If we leave the glIsValidContext check in, then we sometimes fail
on broken OpenGL implementations.

I prefer to leave the check in there and try to get OpenGL fixed
wherever possible.

> By the way, I'm perfectly willing to take ownership of FreeBSD 
> portability issues if people think it'll help. My sourceforge id is 
> "driehuis".

That would be very useful.   Do you need developer access to PLIB?

---------------------------- Steve Baker -------------------------
HomeEmail: <sjb...@ai...>    WorkEmail: <sj...@li...>
HomePage : http://www.sjbaker.org
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