Rendering bug discovered with the usage of enviroment variable QT_XCB_NATIVE_PAINTING using QT5.11.1

Recently we discovered that with the Qt5 there is performance degradation when
Qt5 application is being used over the NoMachine that us caused by the fact
that Qt5 removed the support for the native renderer and switched to something
similar to the 'raster' rendered from the Qt4. After some research we found
out that starting from the Qt 5.10 (we actually tried 5.11.1) the native
rendered can be re-enabled with the environment variable
(QT_XCB_NATIVE_PAINTING). Doing that speeds up the rendering of all our
widgets over the NoMachine, but it causes issues with the rendered view .
Basically what happens is that there is a part of the canvas that is not being
rendered. See sample view attached.
By default , without this environmental variable QT_XCB_NATIVE_PAINTING),
rendering using same codebase works fine but slow on nomachine.

Please look into this issue on priority.
Regards

Amarpal Singh
Mentor graphics