And port the graph example to QSGMaterial and the RHI. We will not anymore add a
direct OpenGL path (that would mean using QSGMaterialShader) for the example because
the upcoming purge renders that useless anyway.
Task-number: QTBUG-82988
Change-Id: I137575ed5df45b6bfc34a11d73dc5100945081c5
Reviewed-by: Andy Nichols <andy.nichols@qt.io>
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