hl

General purpose highlighter.

// it would be lovely to have a different name the "library" part and the cli

Usage

hl will read from stdin and write to stdout. hl < source/main.c

Cli Options

-h          : display help message
-F <dir>    : syntax file look up directory
-s <syntax> : specify syntax to load

Environment variables

HL_HOME	: default directory to load syntax files from

API

void render_string(const char * const string, const char * const mode);

This function matches string against all known highlighting rules and dispatches the appropriate callback defending on mode.

typedef void (*attribute_callback_t)(const char * const string, const int length, void * const attributes);

The type used for defining appropriate callbacks for render_string(). string - string to be outputed length - number of characters that matched a highlighting rule; 0 if rule passed, in such a case the user is expected still want 1 character outputed attributes - arbitrary data associated with the matched rule; intended to hold color/font information for example

typedef struct {
    char * key;
    attribute_callback_t callback;
} display_t;

The type for defining display modes.

void new_display_mode(display_t * mode);

This is how you append a display mode that render_string() will search based on .key.

typedef enum {
    KEYSYMBOL,
    KEYWORD,
    MATCH,
    REGION
} token_type_t;

These are the valid type of distinct token types.

KEYSYMBOL - a string which is contextless, the surounding text is ignored
             "mysymbol" will match inside all of these:
                 "something mysymbol something"
                 "somethingmysymbolsomething"
            it is intended to match such thing as programming language operators,
             so both "var a = 'a'" and "var a='a'" are recognized
KEYWORD   - a string which is recognized when surounded by word bundaries such as ' ' or '\t'
MATCH     - a Vim style regular expression to be recognized
REGION    - a Vim style regular expression where the starting and ending patters are to be distinguished from the contents

The universal way to add a new pattern to be recognized is with:

token * new_token(const char * const syntax, const token_type_t t, const hl_group_t * const g);

This wraps one of the following:

// ?!

There are also convinience functions:

// NOTE: the return value is the number tokens successfully inserted
int new_keyword_tokens(const char * const * words, hl_group_t * const g);
int new_syntax_character_tokens(const char * const chars, hl_group_t * const g);

Scripting

hl can parse a small subset of VimScript: the few instructions related to highlighing, and it ignores everything else. All Vim highlighing scripts should be valid hl scripts. The instrunctions in particular are:

sy[ntax] keyword <hl_group> <word>+
sy[ntax] match   <hl_group> <regex>
sy[ntax] region  <hl_group> start=<string|match> end=<string|match>
hi[ghtlight] link <from_group> <to_group>
hi[ghtlight] def  <group> <display_t>=<data>+

Additionally hl recognizes:

syn[ntax] keysymbol <char>+