I’m trying to make a offscreen renderer for a quick scene and then display it’s 
output in the main and visible QQuickWindow scene.

The reason I’m trying to achieve this is because I need to intercept the frames 
to be able to send them to other programs or encode as a video file.

I’ve based myself on the rendercontrol example and I have a working offscreen 
renderer. Now, what I’m trying to do is to paint the result of the offscreen 
renderer into the main QQuickWindow.

What I’m doing is creating a new QQuickItem that paints a texture. When I 
declare this item in qml, I register it on the render control. Render control 
has it’s own render timing. Whenever render control paints, I tell the 
registered quick item to paint with the fbo texture.

The problem is that the only thing that is painted is black. I’m pretty sure 
the quick item is paint texture correctly because it works with images:

// render method


if (_renderView)
    _renderView->setImage(_fbo->toImage()); // this works
_size)); // this doesn’t work - only black is painted


I wonder if I’m stumbling on synchronisation issues. Maybe when its time for 
the main window to paint again, that texture is not valid anymore. 

Performance is a key factor in this architecture. I need the fastest solution 
possible and it doesn’t seem that creating a QImage from a texture and then 
convert it to QSGTexture is the most performant solution possible.

Has anyone been here before? 

Any advise on how to overcome this problem?


Best regards,

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