How to remove margins of QLayout completely (Mac OS specific)

Question

Let me explain a simplified situation. In Qt Creator, create a QHBoxLayout containing a QPushButton and another QHBoxLayout which cont

Answer 1

This issue is only visible for several certain widgets (e.g QPushButton, QComboBox etc) on Mac OS.

Setting Qt::WA_LayoutUsesWidgetRectattribute on those widgets would solve it:

button->setAttribute(Qt::WA_LayoutUsesWidgetRect);

Reference: QMacStyle: QPushButtons always have space below when in a QLayout

A related issue with the same solution could be found here: Why is QHBoxLayout causing widgets to overlap?