The Trolls got back to me with their usual speed. Turns out you can reactivate autoraise by modifying the QWidget "polish()" function. But this is sub-optimal, and there are other issues. Here is the message from qt-bugs followed by my reply...
We turn this off in qmacstyle_mac.cpp, in the polish() function for
widgets. This is done to be more native. You can comment this out if
Trolltech AS, Waldemar Thranes gate 98, NO-0175 Oslo, Norway
Thanks for your quick reply. I see the line where autoraise is turned off.
I've given this some more thought, and autoraise is only part of the story. These days, Apple developers tend to use flat toobar buttons that don't autoraise (see below). But there is no "setFlat( bool )" function for QToolButton (only for QPushButton).
Could you please pass the following comment on to the appropriate developer(s)...
My comment relates to Qt-Mac 3.3.4, but may also be relevant for Qt 4.0. I disagree with Trolltech's decision to disable the QToolbutton autoraise feature under OS X. This forces all QToolButtons to be drawn with a 3D border. In my opinion, it would have been better to make this the default behavior for toolbuttons, but to leave the developer the option of setting autoraise manually.
Many mainstream OS X applications employ tool button autoraise - Microsoft Word, Excel, Adobe Photoshop, etc. So most Mac users are familiar with this behavior. A developer may want their application to behave identically on all platforms - even if autoraise is not recommended by Apple's UI guidelines.
A more important issue is that Apple's own applications have moved away from using 3D toolbuttons and are now employing well-spaced flat tool buttons (no autoraise). I have attached screenshots of the toolbars from the two new "iWork" applications, the Pages word processor and the Keynote presentation app. It is difficult achieve this appearance with Qt in a cross-platform friendly way. The addition of a 'flat' property and a 'setFlat( bool )' function to QToolButton would be helpful.