[Development] [QML] Avoiding graphics flicker in Quick2

Robin Burchell robin+qt at viroteck.net
Fri Jul 29 12:49:38 CEST 2016

On Thu, Jul 28, 2016, at 02:37 PM, Denis Shienkov wrote:
> So, my questions is: is there are any way to setup
> Qt::WA_OpaquePaintEvent
> and/or
> Qt::WA_NoSystemBackground in Quck2? Or, maybe is it possible to use
> another
> tricks?

Ah, the memories. Good times.

Unfortunately for you, QQ2 is a very different beast. Rendering is done
using OpenGL (unless you're using a different scenegraph backend, but
that's probably not very likely right now) and then pushed to the
windowing system of your choice using a QPA plugin via QWindow (how
exactly this is done, of course, depends on your windowing system & the
QPA plugin you are using).

If you're seeing flickering, this means you have four possibilities,
ranked in no real order:

1) OpenGL driver bug (the world is full of them..)
2) Application-side bug (make sure you don't have anything that could be
flickering in your application). Using an overlay to debug item
positions (QSG_VISUALIZE=overdraw) could be handy for trying to rule
this out, as if it is specific to the application, you'd see which part
of the application is flickering - and the overlay wouldn't be affected.
3) A problem or bug with the QPA plugin you're using (you mention
embedded, so I'm going to guess you're using eglfs or something like
4) Relatedly, a problem or bug with the windowing system (particularly
if you're doing something rather custom. If you're using e.g. OS X or
some other mainstream setup though, this is less likely)

  Robin Burchell
  robin at viroteck.net

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