The documentation for QFontMetrics::boundingRect and QFontMetrics::tightBoundingRect include this sentence:

If you want to know the advance width of the string (to layout a set of strings next to each other), use width() instead.

It uses the word "layout" as if it is a verb. It should instead say "to lay out".

See also http://grammarist.com/spelling/lay-out-layout/