Buildsystem changes for KWin mobile

[Martin Gräßlin]

Hi,

please keep me CC-ed as I am not subscribed. Thanks

As you might know I am currently working on the OpenGL ES port of KWin and 
have some build system related questions.

First a short explanation about the general problem: you can either compile 
against OpenGL or OpenGL ES, but not both at the same time. ES is only a 
subset of OpenGL and due to the various different versions we cannot restrict 
on the subset (though I would like to do so). This means it has to be decided 
at compile time whether OpenGL or OpenGL ES has to be used.

This would be fine for mobile, but the ES port is also very important for 
desktop systems. It will give our users who are able to use ES a much more 
modern and hopefully much faster compositing system and it is a hard 
requirement for any work on Wayland[1].

So what I would like to have is: first build kwin with OpenGL, then build kwin 
again with other options set for OpenGL ES. Is something like that possible?

KWin has several build targets. There is the effects library which is linked 
against either OpenGL or ES. In the ES case symbols are removed and in future 
probably some ES specific added. Then there are the effects which link against 
this library and would need to be build twice as well, because we cannot 
support all effects in ES yet.

Last but not least there is kwin core also linking the effects library and 
using complete different code pathes for OpenGL or ES.

So what is the best way to tackle this issue? If you have further questions or 
need the current changes to the CMake files, just let me know.

Oh and we need to find OpenGL ES. I use a script from Gluon and extended it to 
also find EGL. It would be nice if someone who is competent in this area could 
do it properly and maybe add it to kdelibs  or better cmake directly. I think 
OpenGL ES support will become more of a general need for KDE development in 
future :-)

Thanks in advance for your help.
Martin

P.S. There is no code in SVN yet. I am waiting for git.

[1]: I hope Phoronix does not read this mail
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