QCommonStyle::subElementRect uses hard-coded value to calculate the SE_HeaderArrow rect, causing the icon to be unnecessarily clipped

In QCommonStyle::subElementRect, it uses hard-coded value to calculate SE_HeaderArrow rect, and returns a small rect which causes the arrow icon to be clipped.
It happens when padding or margin or border set to 0px (then the height of the opt.rect will be smaller, then we get even much smaller height after calculation).
Test program attached.