Problem is, though, where exactly to break a line.

That's the problem I was referring to.  Algorithmically speaking, it's simple enough to just split a line exceeding the length limit in an acceptable (from a strict standards point of view) position.  The problem actually becomes where to do it that it makes sense from a human perspective.  You could probably set some arbitrary rules, but there are so many edge cases. 

For example, what if a continuation already exists, and 4 characters exist on the continued line.  When Smart Indent runs, it finds that the first line is now too long again and continues it on a second line, but there's already a third line.  Something along the lines of (and this is purely an example):

         WRITE (1000, 1200) "Here's a string with some output variables", X, Y, Z,
     .                      A, B ,C

Smart Indent with automatic wrapping, however, might do something like:

                 WRITE (1000, 1200) "Here's a string with some output variables", 
     &           X, Y, Z,
     .                      A, B ,C

The above is just an example (I probably got the columns wrong), but it shows why automatically wrapping is probably a bad idea.

..strictly restricted to .for and .f90/.f95 code, or are they interchangeable?

I've neither experimented with thjs nor even ever used the '&' continuation method - though I really should start doing so.
If that can be used in all flavours of FORTRAN then my suggestion would be to adopt it for linewraps in auto-indenting.

Problem is, though, where exactly to break a line. 
I'm sure most of us do this just before or just after = signs or + - * / arithmetic operators, or // concatenation symbols, and try always to do it outside not inside quoted strings, etc, but there must be a lot of rules that need to be thought up to make this automatic.

Another way might be deliberately to trigger an error, eg by wrapping the line without a line-wrap instructio, or perhaps better by not doing so but inserting instead an extra line with an illegal character, to force a compile error that will bring the user straight to each place where line-wrap is needed.  This might me made optional.
---
J.

Any thoughts from users?

I agree, though.  A "beautifier" feature would certainly be nice to have.  I'll have a look at how it can be done.

Feature request - add "indent whole file" menu.
Or even better like in slickedit http://www.slickedit.com/products/slick … s/#xmlhtml

Thank you