KWin and Qt5

[Martin Gräßlin]

Hi all,

yes it's early, but there was something in Lars's blog post [1] which I need to 
braindump/discuss. Let me quote the important part: "Qt will require OpenGL (ES) 2.0 to work. 
QWidgets will be layered on top of the scene graph (not the scene graph on top of QWidgets 
as is currently done with Qt 4)."

This sounds to me that if we link against QtGUI we will get an OpenGL dependency whether 
we want or not. This renders some problems and opportunities we should keep in mind for 
the next two release cycles:
* We need a context managment. We can no longer rely on only KWin creating a context
* OpenGL ES backend could cause trouble if Qt pulls in desktop GL and vice versa[2]. Does 
Qt uses a plugin approach?
* If QWidgets pull in OpenGL the argument against QML that it pulls in OpenGL becomes nil
* We can consider switching completly to QtOpenGL and throwing out most of our custom 
kwinglutils
* There is no need to stabilize the effects API for 4.x
* If OpenGL (ES) 2.0 is a requirement to run KDE software, we can throw out our legacy GL 
code (maybe including XRender?)
* We should redesign the decorations API to make proper use of OpenGL
* With OpenGL becoming a requirement to run KDE software, we can go to compositing only 
(we are no longer the only ones being slow/breaking the desktop).

That's it for now. Maybe we should put it into the wiki...

Cheers
Martin

[1]: http://labs.qt.nokia.com/2011/05/09/thoughts-about-qt-5/
[2]: AFAIK no problem with mesa, don't know about the blobs
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