[Qt5-feedback] OpenGL ES 2.0 requirement

[gunnar.sletta at nokia.com]

On May 17, 2011, at 9:13 PM, ext Ant wrote:

> So without GL 2, it can fall back to a software implementation.  But 
> what if you have hardware OpenGL < 2 (eg. 1.5) and need hardware 
> acceleration in QGLWidgets?  Can you mix hardware and software?

This would certainly not be trivial. If UI code, through a QSGItem, uses gl function calls then that would have to use the software context because its the UI rendering context, resolved from the softwareGL.so. The QGLWidget's gl functions calls calls the hardware based context resolved from the libGL.so. The symbols need to be resolved from the same library, though. 

Maybe something could be done with some proxy GL library that forwards function calls to the actual GL library at runtime. Contributions in this area would certainly be welcome.

> Upcoming hardware may well support GL 2, but there is a lot of old 
> hardware that is perfectly good for common tasks.  Perhaps Qt4 should be 
> supported for longer?  You should still be able to run the latest 
> software and distributions on these machines, and this may be a barrier 
> to Qt5 uptake.

I don't think we have made any public statement about Qt 4's lifetime yet, but I might be mistaken on that. The fact that we start working on Qt 5 does not mean that Qt 4 suddenly becomes unusable. Just like there are developers using Qt 3 to develop their applications today, six years after Qt 4 was released and several years after all work on Qt 3 was stopped by Trolltech, I expect Qt 4 to be used for many years to come, long after Qt 5 is released. Qt 4 works pretty well for the tasks it was designed for, after all.

> 
>> We don't have such a software renderer yet, but maybe someone is willing to help us in getting it.
> Is it premature to be making this decision given there is no guarantee 
> there will be one?
> To me it seems wrong that a cross platform UI toolkit should be so 
> dependant on hardware, or that rendering core widgets is slow enough for 
> hardware acceleration to make an appreciable difference.  Accelerating 
> individual components such as 3d, graphics view and video seems more 
> appropriate and should be at the discretion of the application developer 
> not the toolkit provider.


I don't it is premature. Lars gives our reasons for choosing this path here: http://labs.qt.nokia.com/2011/05/11/responses-to-qt-5/

best regards,
Gunnar