[Interest] Qt 5.8 and QPainter based rendering

bunjee at omega.gg bunjee at omega.gg
Fri Apr 21 13:27:48 CEST 2017

Greetings Qt community,

I'm currently working on a feasability using embedded hardware (Xilinx 
It has no dedicated GPU so I'm experimenting with:
- Qt 4.8.7 (QtQuick 1.0)
- Qt 5.8 with OpenGL (QtQuick 2.0).
- Qt 5.8 with QtQuick 2D (QtQuick 2.0).

I'm building a multitouch interface with extensive use of scaling (for 
transitions inside Row(s) or ListView(s)).
To make it clean I'm using a custom QML component that renders SVG with 
the QPainter (based on QQuickPaintedItem for Qt 5).

This is what I get with a 3.0 scale: 

- Qt 4 does a good job at scaling SVG(s) or anything QPainter based.

- I suspect that Qt 5 just caches a static texture for a given 
QQuickPaintedItem and simply scales it.
This gives a blurry output on both Qt 5 OpenGL and Software (QtQuick 

Is there a way to force Qt 5 and QQuickPaintedItem to scale without 
using its blurry texture cache ?

Note: I'm a little bit surprised about the transition to QtQuick 2.0. 
The performance are there but they come with a significant graphical 
tradeof. Having a scenegraph, shaders and particles is cool but it 
shouldn't come at the expense of basic 2d rendering.

Let me know If I'm missing something,

Thanks !

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