Size grip cannot be controlled on Mac

There is currently no way to remove the sizing grip from the QMainWindow on Mac.
There is no Window flag to set the window to 'non-resizable', even when the QMainWindow has Fixed size.

Currently I am using the following hack to remove the status bar area with size grip, and then reduce window height accordingly.

void setupWindowWithoutStatus(QWidget* w){
NSView* view = (NSView*) w->winId();
NSWindow* win = [view window ];
NSRect fr = win.frame;
fr.size.height -= 22;
[win setFrame:fr display:YES];

NSUInteger mask = [win styleMask];
[win setStyleMask:(mask & ~NSResizableWindowMask)];

}