[OS X] Modal dialog can appear active when another modal dialog is active

When a modal dialog is active, and another sub-dialog becomes active, if you click in the first dialog it is painted in active colors and the sub-dialog is painted inactive. This is in spite of the fact that the active-looking dialog is not responsive and is not layered on top.

The attached application shows the problem. Run the application; it puts up a QMainWindow with a button "Put up a dialog". Click the button and a dialog is displayed, with a button "Another dialog". Click that and you now have two modal dialogs.

Click in the first dialog, and you will see that the window title buttons become colored, but it isn't raised. It looks active, but it isn't.

I show the environment as 10.10.3. I haven't tested other OS X versions.