[Interest] QDatastream, QMap, QImage serialization

[Jean-Michaël Celerier]

> Why is QImage even a GUI type? 99% of what I do with QImage is not for
GUI. I can understand that QPixmap is GUI, but to me QImage is i/o and
pixel/metadata manipulation (using scanline() where appropriate) . Yes,
occasionally I use a QPainter on one, but that does not beed to be bound to
a windowing system. A non-GUI raster painter would be sufficient.

+1 (and also QColor ! plenty of command-line apps that work with colors :p)


-------
Jean-Michaël Celerier
http://www.jcelerier.name

On Mon, May 21, 2018 at 2:27 AM, Jason H <jhihn at gmx.com> wrote:

> Why is QImage even a GUI type? 99% of what I do with QImage is not for
> GUI. I can understand that QPixmap is GUI, but to me QImage is i/o and
> pixel/metadata manipulation (using scanline() where appropriate) . Yes,
> occasionally I use a QPainter on one, but that does not beed to be bound to
> a windowing system. A non-GUI raster painter would be sufficient.
>
> I (Qt?) uses QPixmap whenever it has to display an image.
>
>
> > Sent: Sunday, May 20, 2018 at 11:54 AM
> > From: "Thiago Macieira" <thiago.macieira at intel.com>
> > To: interest at qt-project.org
> > Subject: Re: [Interest] QDatastream, QMap, QImage serialization
> >
> > On Sunday, 20 May 2018 07:26:47 -03 Konstantin Shegunov wrote:
> > > On Thu, May 17, 2018 at 5:58 PM, Thiago Macieira <
> thiago.macieira at intel.com>
> > > wrote:
> > > > On Thursday, 17 May 2018 05:01:18 PDT Jean-Michaël Celerier wrote:
> > > > > Is there a reason why calling qRegisterStreamOperators<QImage>()
> would't
> > > > > work ?
> > > >
> > > > Because the vector containng the list of function pointers doesn't
> exist
> > > > for
> > > > metatypes < QMetaType::User.
> > >
> > > Is this by design, or just an unfortunate legacy?
> >
> > It's by design that the vector starts at QMetaType::User.
> >
> > > I would've expected
> > > (obviously wrongly) that the core classes provide and support all the
> > > functionalities of properly registered custom types.
> >
> > Except where it was too hard and we haven't done it. Serialisation
> appears to
> > be one such case.
> >
> > > And a follow up question: I'm not intimate with the internals, so is it
> > > feasible to actually bring this to consistency and have the stream
> > > operators registered in the meta-type system for the core classes?
> >
> > Yes. Patch accepted. See qguivariant.cpp: the two save and load
> functions are
> > currently null pointers. Replace with actual functions that save QtGui
> types
> > to a QDataStream and properly loaded back.
> >
> > --
> > Thiago Macieira - thiago.macieira (AT) intel.com
> >   Software Architect - Intel Open Source Technology Center
> >
> >
> >
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> > Interest at qt-project.org
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> >
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