[Interest] What for does qt5gui need OpenGL?

André Pönitz andre.poenitz at mathematik.tu-chemnitz.de
Thu Nov 7 20:33:49 CET 2013

On Thu, Nov 07, 2013 at 07:51:16AM +0100, Tomasz Olszak wrote:
> 2013/11/7 Uwe Rathmann <Uwe.Rathmann at tigertal.de>
>     On Wed, 06 Nov 2013 08:03:47 -0800, Thiago Macieira wrote:
>     >> Shouldn't they be in Qt5OpenGL.dll?
>     >
>     > No, they are where they were supposed to be. That's by design.
>     With some nasty consequences for us users:
>     Our applications run on several pieces of embedded hardware, where one of
>     them had been designed 7 years ago with a graphic chip, where only OpenGL
>     ES 1.1 is supported. This board needs to be supported and updated for
>     many, many years - no way to exchange it by something more recent.
>     Even if we don't need OpenGL ( using widgets only ) we are stuck with Qt
>     4 forever, because Qt5 has this unnecessary OpenGL dependency. So far
>     this had been no big problem - Qt4 is pretty fine - and there are some
>     backports of new Qt5 features ( by the way: it would be nice to add the
>     json classes to Qt 4.9 ), but sooner or later this will become an issue.
> AFAIK you can build Qt5 with no-opengl switch and you should be able to run
> QtWidgets applications without having libQt5OpenGl dependency in libQt5Gui. 

The problem is that this won't scale. One cannot provide custom builds of
Qt for each realistic user configuration, let alone proactively package
such stuff in large quantities. Requiring the users to run one, or one out
of a few "blessed" configurations is likewise infeasible.

Runtime detection of capabilities and selecting features _then_ is
the only viable appraoch.


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