gtk2/testsuite/css/parser/calc.ref.css

a {
  margin-left: calc(1em + 3px);
}

b {
  transition-duration: calc(-200ms + 1s);
}

c {
  margin-left: calc(1em + 2px);
}

d {
  background-size: calc(-10px + 100%);
}

e {
  border-left-width: 2px;
}