Is there a way I can see the QML widget to influence the content below it using the GLSL shader?

Question

I am trying to create a QML widget with a glazed transparent appearance; the idea is that I want to blur and discolor everything that the widget will be drawn on top of, which should be easy with the GLSL shader. Unfortunately, it would seem that QML widgets are seen from top to bottom, so at the time when I was drawing a specific widget, the material below it was not drawn. If I refer to the contents of the parent widget, it first draws all the child widgets, which in turn refers to the contents of the parent widget, causing it to draw again, etc.

It seems that there must be some simple way to achieve this effect. Does anyone know how to do this?