Thanks for the replies and apologies for the late response. I'm having a very busy period. I have in the meantime submitted a bug report: https://bugreports.qt.io/browse/QTBUG-73177

@SGaist said in Heavy flickering in QListView when appending items if VerticalScrollBarPolicy == Qt::ScrollBarAlwaysOff:

Qt 5.12.1 just got released, can you check again if you still have the same problem ?

Yes, I did check 5.12.1 and nothing has changed. I've updated my bug report accordingly.

@VRonin said in Heavy flickering in QListView when appending items if VerticalScrollBarPolicy == Qt::ScrollBarAlwaysOff:

d_cancel is a race condition, change its type to std::atomic_bool
What I suspect is happening is that this intersect check is not working correctly when you disable the scrollbars

Thanks, I just wrote that little example code quickly and indeed, d_cancel could lead to problems (though not very likely). rest assured, in the actual project where I'm seeing this problem, the equivalent bool is already a std::atomic_bool.

Thanks for the hint as to where the problem is, I will try to investigate.

I have tried to install the debug packages of qt on my machine, but the easiest way to do so, they overwrite the normal packages and make my desktop unusable (since I'm running KDE which uses qt). So I need to figure out how to install a second, separate version or try to debug on a different (virtual) machine. Either way, just getting it set up will take more time than i have had lately. To be continued.

Thanks again!

Use https://doc.qt.io/qt-6/qwindow.html#startSystemResize instead. You can call it from QML.

@SilverSurfer I don't have the time handy to do a full working example, but this is the technique in glsl:
https://www.khronos.org/opengl/wiki/Data_Type_(GLSL)#Swizzling

(The vec4 can hold "rgba" values if that's what you put in it - the example there just calls it "xyzw" because the data type generically handles any 4 floats.)

Basically, start from an example that draws an image with a simple glsl shader as a texture. Then hack on the shader until it flips around the colors like you want when it draws the texture. Then use your code that gets the image over the network to upload the image as the OpenGL texture every frame.

@D.Fahsig
I am not sure where is the error but it works for me .May be try reinstalling the Qt with necessary components may fix some times. Good luck
FYI: i also Qt 5.5 on windows 7 64 bit.