QApplication::desktop()->availableGeometry() in gnome-shell is incorrect

In CentOS 7 with Gnome-Shell as the desktop manager I'm trying to make a QWebEngineView that resizes to the dimensions of the entire screen minus the space taken up by all of the task bars (in the default Gnome-Shell this includes one at the top and one at the bottom).

availableGeometry() consistently reports a size that is too tall by roughly 38 pixels.  It seems like it's only taking into consideration one of the two desktop manager task bars.