When a QTreeview is put in GraphicsView using QGraphicsProxyWidget, and ItemIgnoresTransformations is set on its proxyWidget and scaling is done, It seems that The item itself (in this case, the QTreeView inside the QGraphicsProxyWidget) ignores scaling and transformation , but the scene and the other items such as tooltip/context menu poups etc are still transformed by the QGraphicsView

Attached little code and screen recording shows this.