Now that show-paren-mode is enabled by default, I've implemented a new
customization option for Emacs 29.

When the attached patch is installed, if
show-paren-context-when-offscreen is t, when you move the point to a
closing delimiter, if the opening delimiter is offscreen, the line where
the opening line is will appear in the echo area.  This gives you
context about what a delimiter is closing without having to move the
point or reinsert it.  There is similar functionality in popular IDEs.

The feature is implemented by first extracting some code from simple.el
to reuse it from simple.el and paren.el.  The rest of the implementation
is simple.

I think it plays well with eldoc, blink-matching-paren, and the rest of
the show-paren-mode options.

I hope you find this feature useful.