RULES
tags must be placed inside the
MODE
tag. Each RULES
tag defines a
ruleset. A ruleset consists of a number of
parser rules, with each parser
rule specifying how to highlight a specific syntax token. There must
be at least one ruleset in each edit mode. There can also be more
than one, with different rulesets being used to highlight different
parts of a buffer (for example, in HTML mode, one rule set
highlights HTML tags, and another highlights inline JavaScript).
For information about using more
than one ruleset, see the section called “The SPAN Tag”.
The RULES
tag supports the following attributes, all of
which are optional:
SET
- the name of this ruleset.
All rulesets other than the first must have a name.
IGNORE_CASE
- if set to
FALSE
, matches will be case sensitive. Otherwise, case
will not matter. Default is TRUE
.
NO_WORD_SEP
- any non-alphanumeric
character not in this list is treated as a word separator
for the purposes of syntax highlighting.
DEFAULT
- the token type for
text which doesn't match
any specific rule. Default is NULL
. See
the section called “Token Types” for a list of token types.
HIGHLIGHT_DIGITS
DIGIT_RE
- see below for information
about these two attributes.
Here is an example RULES
tag:
<RULES IGNORE_CASE="FALSE" HIGHLIGHT_DIGITS="TRUE">
... parser rules go here ...
</RULES>
If the HIGHLIGHT_DIGITS
attribute is set to
TRUE
, jEdit will attempt to highlight numbers in this
ruleset.
Any word consisting entirely of digits (0-9) will be highlighted with the
DIGIT
token type.
A word that contains other letters in addition to digits will be
highlighted with the
DIGIT
token type only if it matches the regular
expression specified in the DIGIT_RE
attribute.
If this attribute is not specified, it will not be highlighted.
Here is an example DIGIT_RE
regular expression that highlights
Java-style numeric literals (normal numbers, hexadecimals
prefixed with 0x
, numbers suffixed with various
type indicators, and floating point literals containing an exponent):
DIGIT_RE="(0x\p{Xdigit}+|\d+(e\d*)?)[lLdDfF]?"
Regular expression syntax is described in Appendix E, Regular Expressions.
You might encounter this very common pitfall when writing your own modes.
Since jEdit checks buffer text against parser rules in the order they appear in the ruleset, more specific rules must be placed before generalized ones, otherwise the generalized rules will catch everything.
This is best demonstrated with an example. The following is incorrect rule ordering:
<SPAN TYPE="MARKUP"> <BEGIN>[</BEGIN> <END>]</END> </SPAN> <SPAN TYPE="KEYWORD1"> <BEGIN>[!</BEGIN> <END>]</END> </SPAN>
If you write the above in a rule set, any occurrence of “[” (even things like “[!DEFINE”, etc) will be highlighted using the first rule, because it will be the first to match. This is most likely not the intended behavior.
The problem can be solved by placing the more specific rule before the general one:
<SPAN TYPE="KEYWORD1"> <BEGIN>[!</BEGIN> <END>]</END> </SPAN> <SPAN TYPE="MARKUP"> <BEGIN>[</BEGIN> <END>]</END> </SPAN>
Now, if the buffer contains the text “[!SPECIAL]”, the rules will be checked in order, and the first rule will be the first to match. However, if you write “[FOO]”, it will be highlighted using the second rule, which is exactly what you would expect.
The PROPS
tag (described in the section called “The PROPS Tag”)
can also be placed inside the RULES
tag to define
ruleset-specific properties. The following properties can
be set on a per-ruleset basis:
commentEnd
- the comment end
string.
commentStart
- the comment start
string.
lineComment
- the line comment
string.
This allows different parts of a file to have different comment strings (in the case of HTML, for example, in HTML text and inline JavaScript). For information about the commenting commands, see the section called “Commenting Out Code”.