When using a QPushButton having a customized border (stylesheet contains “border: 1 px solid #a8a8a8”), we need to set the attribute Qt::WA_MacShowFocusRect in order to show the focusRing.
This worked in Qt 5.6.0, but after upgrading to Qt 5.12.6 this no longer works. (minimal example in attachment)

This is because QMacStylePrivate::drawFocusRing is drawing the focusRing outside the bounds of the QPixmap used by the QPainter in this function. (This drawing code was introduced by https://code.qt.io/cgit/qt/qtbase.git/commit/src/plugins/styles/mac/qmacstyle_mac.mm?h=5.11&id=4b9e6b65c9036085b99ab9ef97c8136fb684ee89)