Manual pages, in précis and largely ignoring the preprocessing stages, work like this:
- troff source, with one of a number of macro sets, is turned into ditroff ("device-independent troff") output format, also known in the GNU world as intermediate output format
- ditroff output is rendered into a final output format for a specific device (or device family) by a postprocessor such as (from the GNU toolset)
grohtml, and so forth. The actual Unix postprocessors for the original ditroff were called things like
devlp and there were third-party ones such as TextWare's
- The output of the post-processor for a terminal device (
grotty in the GNU toolset) is fed into one's chosen pager.
It isn't known well enough as it should be, but the input to a Unix pager is what one would feed to a Teletype Model 37 paper terminal in 1968, complete with overstriking for underscore, boldface, and fancy bullets in bulleted lists. The pager then turns this into the control sequences appropriate to the actual terminal type. (Most Unix pagers cannot handle the fancy overstruck bullets, and they don't come out as the crossed circles, a
+ overstruck by an
o, that they actually are in 7-bit mode.)
Some pagers, such as
less can sort of handle the "new" terminal encoding from ECMA-48, first published in 1976 and used on video terminals, but they aren't particularly smart about it and can go wrong if one uses anything but the most basic ECMA-48 functionality.
grotty can output either of these. Sad to say, it is usually forced by some local configuration file to use the old 1968 paper terminal output format.
By the time that things reach the pager, the document has already been formatted to a particular device width, by the post-processor (which converts "device-independent" into "device-specific" remember).
most aren't responsible for the wrapping, and don't re-wrap. The best that you will get is, as you have discovered, sideways scrolling from these pagers if the terminal width is reduced below what width was used to format the document.
You can possibly get closer to a reflowing manual page by using one of the other output formats, but this will obviously not involve a Unix pager as the final document viewer.