Maybe use a scoped

const QSizeF pmSize { geom.width() * dpr, geom.height() * dpr };

instead of repeatedly recalculating width and height?

Is this change necessary? Conversion to double was already there. screenPos() would change semantic from "relative to widget" to "relative to screen". Doesn't matter because widget is probably always full screen. But otoh the whole thing is called PresentationWidget, so keeping "relative to widget" seems reasonable.

Okay!

You cannot use x() and y() because they return integer coordinates, while with fractional screen scaling the coordinates really are fractional, too. But I agree that keeping with "relative to widget" positions is better, so I changed screenPos to localPos.