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(ediff)Refinement of Difference Regions

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Refinement of Difference Regions
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   Ediff has variables to control the way fine differences are
highlighted.  This feature gives you control over the process of
refinement.  Note that refinement ignores spaces, tabs, and newlines.

`ediff-auto-refine'
     This variable controls whether fine differences within regions are
     highlighted automatically ("auto-refining").  The default is yes
     (`on').

     On a slow machine, automatic refinement may be painful.  In that
     case, you can turn auto-refining on or off interactively by typing
     `@'.  You can also turn off display of refining that has already
     been done.

     When auto-refining is off, fine differences are shown only for
     regions for which these differences have been computed and saved
     before.  If auto-refining and display of refining are both turned
     off, fine differences are not shown at all.

     Typing `*' computes and displays fine differences for the current
     difference region, regardless of whether auto-refining is turned
     on.

`ediff-auto-refine-limit'
     If auto-refining is on, this variable limits the size of the
     regions to be auto-refined.  This guards against the possible
     slowdown that may be caused by extraordinary large difference
     regions.

     You can always refine the current region by typing `*'.

`ediff-forward-word-function'
     This variable controls how fine differences are computed.  The
     value must be a Lisp function that determines how the current
     difference region should be split into words.

     Fine differences are computed by first splitting the current
     difference region into words and then passing the result to
     `ediff-diff-program'.  For the default forward word function
     (which is `ediff-forward-word'), a word is a string consisting of
     letters, `-', or `_'; a string of punctuation symbols; a string of
     digits, or a string consisting of symbols that are neither space,
     nor a letter.

     This default behavior is controlled by four variables:
     `ediff-word-1', ..., `ediff-word-4'.  See the on-line
     documentation for these variables and for the function
     `ediff-forward-word' for an explanation of how to modify these
     variables.

   Sometimes, when a region has too many differences between the
variants, highlighting of fine differences is inconvenient, especially
on color displays.  If that is the case, type `*' with a negative
prefix argument.  This unhighlights fine differences for the current
region.

   To unhighlight fine differences in all difference regions, use the
command `@'.  Repeated typing of this key cycles through three
different states: auto-refining, no-auto-refining, and no-highlighting
of fine differences.