ccmode: Indentation Engine Basics
10 Indentation Engine Basics
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This chapter will briefly cover how CC Mode indents lines of code. It
is helpful to understand the indentation model being used so that you
will know how to customize CC Mode for your personal coding style. All
the details are in 
Customizing Indentation.
CC Mode has an indentation engine that provides a flexible and
general mechanism for customizing indentation. When CC Mode indents a
line of code, it separates its calculations into two steps:
1. It analyzes the line to determine its “syntactic symbol(s)” (the
kind of language construct it’s looking at) and its “anchor
position” (the position earlier in the file that CC Mode will
indent the line relative to). The anchor position might be the
location of an opening brace in the previous line, for example.
Syntactic Analysis.
2. It looks up the syntactic symbol(s) in the configuration to get the
corresponding “offset(s)”. The symbol ‘+’, which means “indent
this line one more level” is a typical offset. CC Mode then
applies these offset(s) to the anchor position, giving the
indentation for the line. The different sorts of offsets are
described in c-offsets-alist.
In exceptional circumstances, the syntax directed indentation
described here may be a nuisance rather than a help. You can disable it
by setting ‘c-syntactic-indentation’ to ‘nil’. (To set the variable
interactively, Minor Modes).
-- User Option: c-syntactic-indentation
When this is non-‘nil’ (which it is by default), the indentation of
code is done according to its syntactic structure. When it’s
‘nil’, every line is just indented to the same level as the
previous one, and ‘TAB’ (‘c-indent-command’) adjusts the
indentation in steps of ‘c-basic-offset’. The current style (
Config Basics) then has no effect on indentation, nor do any of
the variables associated with indentation, not even
‘c-special-indent-hook’.
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ccmode: Customizing Indentation