Info Catalog ccmode: c-offsets-alist ccmode: Customizing Indentation ccmode: Line-Up Functions

ccmode: Interactive Customization

 
 11.2 Interactive Customization
 ==============================
 
 As an example of how to customize indentation, let’s change the style of
 this example(1):
 
       1: int add( int val, int incr, int doit )
       2: {
       3:   if( doit )
       4:     {
       5:       return( val + incr );
       6:     }
       7:   return( val );
       8: }
 
 to:
 
       1: int add( int val, int incr, int doit )
       2: {
       3:   if( doit )
       4:   {
       5:     return( val + incr );
       6:   }
       7:   return( val );
       8: }
 
    In other words, we want to change the indentation of braces that open
 a block following a condition so that the braces line up under the
 conditional, instead of being indented.  Notice that the construct we
 want to change starts on line 4.  To change the indentation of a line,
 we need to see which syntactic symbols affect the offset calculations
 for that line.  Hitting ‘C-c C-s’ on line 4 yields:
 
      ((substatement-open 44))
 
 so we know that to change the offset of the open brace, we need to
 change the indentation for the ‘substatement-open’ syntactic symbol.
 
    To do this interactively, just hit ‘C-c C-o’.  This prompts you for
 the syntactic symbol to change, providing a reasonable default.  In this
 case, the default is ‘substatement-open’, which is just the syntactic
 symbol we want to change!
 
    After you hit return, CC Mode will then prompt you for the new offset
 value, with the old value as the default.  The default in this case is
 ‘+’, but we want no extra indentation so enter ‘0’ and ‘RET’.  This will
 associate the offset 0 with the syntactic symbol ‘substatement-open’.
 
    To check your changes quickly, just hit ‘C-c C-q’ (‘c-indent-defun’)
 to reindent the entire function.  The example should now look like:
 
       1: int add( int val, int incr, int doit )
       2: {
       3:   if( doit )
       4:   {
       5:     return( val + incr );
       6:   }
       7:   return( val );
       8: }
 
    Notice how just changing the open brace offset on line 4 is all we
 needed to do.  Since the other affected lines are indented relative to
 line 4, they are automatically indented the way you’d expect.  For more
 complicated examples, this might not always work.  The general approach
 to take is to always start adjusting offsets for lines higher up in the
 file, then reindent and see if any following lines need further
 adjustments.
 
  -- Command: c-set-offset symbol offset
      This is the command bound to ‘C-c C-o’.  It provides a convenient
      way to set offsets on ‘c-offsets-alist’ both interactively (see the
      example above) and from your mode hook.
 
      It takes two arguments when used programmatically: SYMBOL is the
      syntactic element symbol to change and OFFSET is the new offset for
      that syntactic element.
 
    ---------- Footnotes ----------
 
    (1) In this and subsequent examples, the original code is formatted
 using the ‘gnu’ style unless otherwise indicated.  Styles.
 

Info Catalog ccmode: c-offsets-alist ccmode: Customizing Indentation ccmode: Line-Up Functions