The constructor of QMouseEvent actually expects windowPos and/or screenPos but never globalPos.
By only supplying a localPos we have Qt figure it out correctly on its own.

• I can now drag the vertical splitter in QtCreator on my second 4k monitor, previously it would just snap to its leftmost position once I started moving, as the mapped coordinates became negative
• I still have the enlarged splitter drag area provided by Breeze compared to e.g. Fusion style