[Interest] QDatastream, QMap, QImage serialization

[Michael Jackson]

-----Original Message-----
From: Interest <interest-bounces+mike.jackson=bluequartz.net at qt-project.org> on behalf of Jason H <jhihn at gmx.com>
Date: Tuesday, May 22, 2018 at 10:16 AM
To: Thiago Macieira <thiago.macieira at intel.com>
Cc: <interest at qt-project.org>
Subject: Re: [Interest] QDatastream, QMap, QImage serialization
    
    > >  There is a difference. As you already stated, a QPixmap requires more than
    > >  a QImage, so what should be provided is a QImage,
    > 
    > Now think about how it's constructed internally.
    > 
    > QBrush only exists to paint, which means GUI (QPaintDevice is the basis of all 
    > GUI). It is meant to paint efficiently. If QPixmap can do that more 
    > efficiently, why should it store a QImage instead?
    
    Admittedly I don't understand the nuances of QPixmap. But I know working with a QImage should not require a windowing server. 

THIS. I had to refactor a bunch of our code because our application needs to create an "image" of some data. I was using QPainter/QImage to do this, but then the use case came up of having to run the code on a headless server or through command line Python. I would get failures because there was no windowing system to use for QImage. I ended finding "libHaru" which allows one to "Draw" a PDF without the need for a windowing system. The API is similar to QPainter, one can draw basic polygons, fills, brushes, pens, lines. All _without_ the need for a windowing system. I didn't really want to bring in another dependency but I didn't really have a choice: QImage simply will not work in this situation.

For Qt6 what I would like to see is QPainter abstracted out to just an interface and have the normal accelerated implementation that we have now in QtGui but also have a non-accelerated version living in QtCore or a library that does NOT depend on a windowing system. All the other classes that have been discussed as having to be moved like the Polygon/Matrix classes should also be moved. There are a lot of science type of apps that could instantly make use of these kinds of things. Instead I have to bring in something huge like ITK just to read/write some images.

My point is that for me, I am ok with a non-accelerated 2D drawing system if it does not depend on a windowing system. Qt is a wonderful overall toolkit. It isn't *just* a GUI toolkit as another poster has suggested. It is a unifying toolkit that is well written and documented that is cross platform.

Just my nickel's worth.
--
Mike Jackson