5eebb559_nd_for_the_PostScript_language__Purpose
[Key] BareLine [Purpose] 
Procedure to be executed when readline has returned true, meaning a newline was encountered, and the line read was of zero length. This can happen for an actual bare line in the input, or for the final readline of a line that ends with a self-delimiting PostScript token. For consistency with FullLine and PartLine, the stack contains (a) whatever was on it when \markup was invoked (except for the parameter dictionary), (b) as modified by any embedded PostScript tokens since, and not consumed by HandleToken or HandleResult, and (c) on top, the string just read, though in this case it is known to be empty; in some uses (simple line-by-line setting), it can make sense for BareLine and FullLine to be the same procedure. When used with paragraph-at-a-time systems, BareLine will usually be defined to invoke the library procedure for filling and setting the completed paragraph. \markup fetches this value only once, so changing it from embedded PostScript code has no effect, but nothing stops the supplied procedure looking at other keys and having changeable behavior.
Markup: a minimalist markup frontend for the PostScript language
Purpose