Mouse events use rounded float local pos

QMouseEvent::localPos returns a PointF, however, in  the {{QWidgetWindow::}}handleMouseEvent function it has been rounded.

In Qt 5.15.2, this is the line QPoint mapped = event->pos();

Looking at the code of the latest Qt version, that still seems to be the case, though more explicit:

qwidgetwindow.cpp\kernel\widgets\src - qt/qtbase.git - Qt Base (Core, Gui, Widgets, Network, ...)

QPoint mapped = event->position().toPoint();

This rounding means that for example with 200% DPI scaling, when clicking a widget, the selected pixel can't be properly calculated - only even pixels can be selected.