Cutting off text so that it fits in one line in the header #4076

#let mybox = box(baseline: 20%, rect(height: 1em))

#set page(
  header: layout(size => context [
    #let boxwidth = measure(mybox).width
    #let n = 30
    #let text = "Header text: " + lorem(n)
    #let textwidth = measure(text).width // a reasonable number
    #while boxwidth + textwidth > size.width {
      n = n - 1
      text = "Header text: " + lorem(n) + "..."
      textwidth = measure(text).width
    }
    #text
    #h(1fr)
    #mybox
  ])
)