Let's have consistent and sensible 3D Quad and Cube shapes (and maybe other shapes too)

The Cube and Quad shapes are inconsistent. Cube vertices are at (0.5, 0.5, 0.5) etc, while Quad vertices are at (1,1,0) etc. They should be consistent: for my money, the Cube is more sensible; but consistency in either direction would be better than no consistency.

The texture mapping on the Cube is not sensible. You would expect that textures would naturally be oriented upwards, on the faces whose normals are in the x or z planes. But they aren't: you have to do some random rotation to get them the right way around.

Neither shape is properly documented. The size, texture orientation etc should be properly documented in each case.

The issues above probably apply to other shapes (eg Sphere and Cylinder) also. If so, they should be addressed.

This fix will break application code which uses the pre-releases of Qt. But that's no reason not to do it: the resulting shapes will be much more usable.