[Interest] Best way to threaded render (images) going forward?

Uwe Rathmann Uwe.Rathmann at tigertal.de
Fri Dec 6 17:54:11 CET 2019


On 11/22/19 2:14 PM, Roland Hughes wrote:

> There have been many requests over the years to allow QPainter 
> operations outside of the primary thread. In particular for running 
> graphs like heart rate monitors which are just a brick on the screen the 
> user generally cannot interact with.

With X11 it is at least possible to draw outside of the paint event - 
see Qt::WA_PaintOutsidePaintEvent. This type of operation is used in the 
Qwt plot package for exactly the use case you have mentioned.

I'm not 100% sure if it wouldn't be possible to the same in an extra thread.

With Qt3 it was even possible to draw in XOR mode, what was at that time 
the way how rubberbands were implemented. This was an operation where 
you could erase content without having to repaint from scratch. But this 
one seems to be gone forever.

Uwe




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