[Interest] Replacement for Qt4 QMatrix4x4?

Paolo Angelelli paolo.angelelli at qt.io
Fri Feb 22 10:08:48 CET 2019

You aren't telling us much, except that you need to invert it and multiply points with it.
If QtPositioning-private is an acceptable dependency instead of pulling in eigen (or others),
you could probably get away with the private QDoubleMatrix4x4 that is in there, basically
a double QMatrix4x4.

On Thu, 21 Feb 2019 16:47:05 -0500
Matthew Woehlke <mwoehlke.floss at gmail.com> wrote:

> So... after a full day of debugging, trying to port my Qt4 app to Qt5
> and chase down a nasty case of stack clobbering, I discovered that the
> problem is that QMatrix4x4 changed from qreal to float.
> (Uh...why? I am not particularly amused by the loss of precision, nor
> the extremely subtle incompatibility.)
> Alas, there does not seem to be any feasible replacement in Qt. I can't
> use QGenericMatrix because it can't be used to transform QPointF's, nor
> can it be inverted, both of which are features I require. I *really*
> don't want to throw out the precision of double, especially as I have
> tons of other code that still uses double and would have to wade through
> mountains of conversion warnings to do so.
> Am I missing something, or do I need to drag in Eigen?

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