[Interest] 2D painting toggle between raster and opengl. What is the advised method?

[Mark Gaiser]

On Sat, Nov 8, 2014 at 5:45 PM, Mark Gaiser <markg85 at gmail.com> wrote:
> On Sat, Nov 8, 2014 at 5:34 PM, Marian Beermann <public at enkore.de> wrote:
>> Depending on the platform requirements it might be possible to always
>> use OpenGL rendering in the application and back it up with a software
>> rasterizer (e.g. llvmpipe).
>>
>> (Just by the way: even old and crappy (perfomance-wise) GPUs like old
>> Intel GMAs or PowerVRs in ARM SoCs are always faster than drawing on the
>> CPU. I also think there are hardly any devices around that do not
>> support at least fixed-function OpenGL.)
>>
>> On 11/08/2014 05:28 PM, Mark Gaiser wrote:
>>> Hi,
>>>
>>> The requirement are simple: 2D painting needs to be possible and i
>>> want to toggle between raster and OpenGL. QML or _depending_ on the
>>> GPU is out of the question. Animations are also not required. Things
>>> that are required are zoomnig controls, selecting drawn objects and
>>> rendering has to be high performance. It must be capable of drawing a
>>> _lot_ of primitive objects (think about numbers between 100.000 and 1
>>> million).
>>>
>>> Given those requirements i know of two different ways to accomplish
>>> the same result.
>>>
>>> 1. QWidget and QOpenGLWidget (new in Qt 5.4). They would both use
>>> QPainter. Basically the 2dpainting example [1] that is provided with
>>> Qt.
>>>
>>> 2. Using QGraphicsView. It defaults to raster based painting and can
>>> be accelerated by calling setViewport(new QOpenGLWidget) on it. This
>>> can be done in basically all of the GraphicsView examples [2].
>>>
>>> Those are the options that i know of where it's possible to toggle
>>> between hardware and software rendering. Is this it or are there even
>>> more options out there in the Qt world?
>>>
>>> It's unclear to me which of the possible options is the advised way to
>>> go when drawing something in 2D. Therefore my question: which one
>>> would be the advised way to use given the requirements said earlier?
>>>
>>> [1] https://qt.gitorious.org/qt/qt/source/examples/opengl/2dpainting
>>> [2] https://qt.gitorious.org/qt/qt/source/examples/graphicsview
>
> Please keep the list in.
>
> Sorry for not mentioning the target platform. That would be the
> Windows desktop family, x86 and x64. It's fine if it runs on Linux,
> but that isn't the target operating system.
> OpenGL on the windows desktop is a bit of a annoyance. Besides that,
> this application also has to work well in virtual environments where
> depending on OpenGL or any GPU is really not that well supported. Thus
> software rendering is a must have. Hardware rendering where possible.
>
> Note beforehand. I know about ANGLE and it's not an option in this case.

..?? Anyone?