[Interest] QDatastream, QMap, QImage serialization

[Christian Gagneraud]

On 21 May 2018 at 20:12, Jean-Michaël Celerier
<jeanmichael.celerier at gmail.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.
>
> +1 (and also QColor ! plenty of command-line apps that work with colors :p)

+1 (and also QPen and QBrush, they are (should be) just bundled properties)

Once i wrote a graphical document format library (load, store and
models), that could have not depend on GUI at all if it didn't use
QColor, QPen, QBrush.

Chris

>
>
> -------
> 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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