Mouse cursor handling is broken on widgets on Mac OS X

Mouse cursor is not not always switched properly when hovering widgets that should trigger non-default mouse cursors. It works sometimes, but not always. Find a test project attached.

Symptoms:
1. Launch the test program. Hover mouse over different widgets on it. Click and drag splitter, click text are etc. Cursor does not change.
2. Click the program's header or toolbar. Then hover widgets. Cursor changes properly.
3. Switch to full-screen or imply maximize main window. No matter whether you did step 2. or not, cursor doesn't change.

Possibly the same issue as https://bugreports.qt-project.org/browse/QTBUG-33479

There's no such problem on Windows or with Qt 4.8.5.