This is a regression from Qt 4.5.3.

Text with descenders have their descenders cut off when the text appears in a tab widget when the tabs are on the bottom. Specifically, the bottom few pixels are missing. This can easily be seen in the example application "dockwidgets" that ships with Qt. Simply dock two dockable windows on top of each other so that they create a tab group. One tab is called "Customers" and the other tab is called "Paragraphs". Make sure the "Customers" tab is active, and the "Paragraphs" tab is inactive. Then notice how the descenders in the letters "g" and "p" are cut off on the bottom in the "Paragraphs" tab. This has been observed on Windows and on certain Linux configurations where anti-aliasing is not available. In general it seems that the text metrics are not being calculated correctly to allow for sufficient space to paint the text descenders. This is a regression from 4.5.3, which painted correctly.