[Interest] QDatastream, QMap, QImage serialization

[Christian Gagneraud]

On 22 May 2018 at 02:03, Jason H <jhihn at gmx.com> wrote:
> Going through the list of Qt GUI classes, there are several that I think should be moved:
> QImage
> QStandardItem*

It's GUI stuff, what's wrong with that?

> Matrix and Vector classes

Definitely, I should be able to do 2D/3D/4D transforms without Qt GUI.
But aren't they part of QtCore already?

> QPdfWriter

If only Qt could deal with modern PDF to start with, gui or  not...

> QPen, QBrush, etc.

Yep!

> QText* QTextDocument et al.
> QValidator et al.

That's GUI stuff, definitely. These things don't make sense out of GUI
context. It's pushing a bit far, but as i get pushed a bit far i start
to get where you're coming from ....

> QFont* (where applicable. QFontDatabase, QRawFont)

How fonts can be separated from GUI? Good luck with that!
Honestly, try to build Qt on a Linux headless server without
installing an X server.... Unix epic fail!

> Various geometrics (QPolygon, QRegion)

Unfortunately, look at all the "qt private" stuff behind these, it's quite ugly.
May I add the mighty QPainterPath? A very promising piece of code,
unless you realised it's tailored to graphical/painting operation.
Contains hard coded CPU calculation precision limit, approximation of
all sort, circles as polygon, dirty bezier approximation/optimisation,
....
QGraphicsScene/View attempted to introduced qreal instead of int, what
did go wrong? ....
Premature optimisation that wasn't actually premature back at that
time... Who to blame?
Anyone running on a processor w/o floating point registers nowaday?

But again, how dare do we ask for more?
Qt is a graphical toolkit, not a scientific spline/polygon/geometry library.
Maybe look at boost::geometry instead....
Well, watch your CPU burning templates and meta-programming....
And failing like shit! Understandable compiler errors are utopia,
opaque meta-programming logic brings opaque meta-programming errors.
I once tried to contribute to https://www.cgal.org/ but gave up b/c
filling a bug report wasn't even human friendly.
(PS: I had fun with their stuff, try it!)

To summarise:
- Qt is a graphical toolkit
- Some Qt classes shouldn't be part of QtGui
- We have to accept that Qt doesn't give a bullock about mathematical
exactness (Graphical rendering is key)

My 2 cents.