Use QFontMetrics::boundingRect() instead. QFontMetrics::width() does
not actually calculate the width of the bounding box and is mostly
useful for knowing where to draw text after a string, taking into
account bearings. Indeed, it has been renamed to
QFontMetrics::horizontalAdvance().
For the code touched in this commit, we want to center a string.
Either method would likely be fine, but it is more easy to
understand exactly what QFontMetrics::boundingRect() does.
This commit does change functionality, although it should not be
noticeable.
In particular, the directory frontends/qt4 is renamed to frontends/qt.
Many configurations file have to be updated. All mentions of qt4 in
the source have been audited, and changed to qt if necessary.
The only part that has not been updated is the CMake build system.
