QMessageBox does not look native on Mac OS X

QMessageBox does not look like a native NSAlert dialog on Mac OS X.

Attached is a small app which demonstrates the two dialogs, and shows the following differences (Qt 4.6.2, Mac OS X 10.6.2):

• QMessageBox displays close/minimise/zoom widgets in the title bar, but a modal dialog should not have these widgets (not even in a disabled state).

• QMessageBox displays a grow handle in the bottom right, although the window is not resizeable

• QMessageBox packs the window contents too tightly compared to the standard NSAlert layout convention.

• QMessageBox makes the buttons too small compared to the standard NSAlert button widths.

• QMessageBox does not display the application icon