On Sat, 02 Nov 2013 15:29:05 -0300 Lisandro Damián Nicanor Pérez Meyer <perezmeyer@gmail.com> wrote: > Hi! Starting from Qt 5.2.0 (most probably from rc1 and definitely not > from beta1 currently in experimental) Qt5 will switch qreal from > float to double on arm*. > > We have the option to keep some archs in float by passing a > compilation parameter. I've done so for armel and sh4, so only armhf > will switch to double. > > Of course we are still on time to discuss this, and this is the > reason of this mail. What do you think WRT the above changes? FWIW, I was a bit sceptical about switching qreal to double. True this would minimise the patches some packages would need on armhf, but OTOH, I don't know what would happen to packages that use both GL graphics and Qt at the same time. All armhf platforms support only OpenGLES and not full OpenGL stack which supports *only* 32-bit floats. However Lissandro just told me on IRC that GL-stuff on Qt5 switched to float for exactly that reason). So apart from speed I don't see a reason for not going that route. If anything, FPU in recent armv7-a systems has become increasingly better so this will be better in a couple of years (it will still suck on a Cortex-A8, but will be less apparent on a Cortex-A15 or better). FTR, I don't think many apps would mind that much. Most apps that would actually care for speed/accuracy would use float/double directly and not qreal, for most it would save us the burden of patching (eg. scribus, qgis). So unless, we find some particular strong cases for *not* switching to double, I'd vote in favour of that. Regards Konstantinos
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