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font: specifying OpenType font language with .ffsc

Now .ffsc can take three arguments:

  .ffsc FN SCRP LANG

This enables the substitution and positioning rules specific to
language LANG.  If LANG is missing, the rules specified for the
default language of the script are enabled.

Suggested and tested by aksr <aksr@t-com.me>.

--- a/font.c

+++ b/font.c

@@ -21,7 +21,7 @@

 		short x, y, xadv, yadv;	/* gpos data */

 	} *pats;			/* rule pattern */

 	short len;			/* pats[] length */

-	short feat, scrp;		/* rule's feature and script */

+	short feat, scrp, lang;		/* rule's feature and script */

 };

 struct font {

@@ -41,6 +41,8 @@

 	int feat_set[NFEATS];		/* feature enabled */

 	char scrp_name[NSCRPS][8];	/* script names */

 	int scrp;			/* current script */

+	char lang_name[NLANGS][8];	/* language names */

+	int lang;			/* current language */

 	/* glyph substitution and positioning */

 	struct grule *gsub;		/* glyph substitution rules */

 	int gsub_n, gsub_sz;

@@ -141,8 +143,12 @@

 	int ncon = 0;		/* number of initial context glyphs */

 	struct gpat *pats = rule->pats;

 	int j;

+	/* enable only the active script if set */

 	if (fn->scrp >= 0 && fn->scrp != rule->scrp)

 		return 0;

+	/* enable common script features and those in the active language */

+	if (rule->lang >= 0 && fn->lang != rule->lang)

+		return 0;

 	if (!fn->feat_set[rule->feat])

 		return 0;

 	/* the number of initial context glyphs */

@@ -360,13 +366,24 @@

 	for (i = 0; i < LEN(fn->scrp_name) && fn->scrp_name[i][0]; i++)

 		if (!strcmp(scrp, fn->scrp_name[i]))

 			return i;

-	if (i < LEN(fn->scrp_name)) {

-		snprintf(fn->scrp_name[i], sizeof(fn->scrp_name[i]), "%s", scrp);

-		return i;

-	}

-	return -1;

+	if (i == LEN(fn->scrp_name))

+		return -1;

+	snprintf(fn->scrp_name[i], sizeof(fn->scrp_name[i]), "%s", scrp);

+	return i;

 }

+static int font_findlang(struct font *fn, char *lang)

+{

+	int i;

+	for (i = 0; i < LEN(fn->lang_name) && fn->lang_name[i][0]; i++)

+		if (!strcmp(lang, fn->lang_name[i]))

+			return i;

+	if (i == LEN(fn->lang_name))

+		return -1;

+	snprintf(fn->lang_name[i], sizeof(fn->lang_name[i]), "%s", lang);

+	return i;

+}

+

 static struct gpat *font_gpat(struct font *fn, int len)

 {

 	struct gpat *pats = xmalloc(len * sizeof(pats[0]));

@@ -374,7 +391,7 @@

 	return pats;

 }

-static struct grule *font_gsub(struct font *fn, int len, int feat, int scrp)

+static struct grule *font_gsub(struct font *fn, int len, int feat, int scrp, int lang)

 {

 	struct grule *rule;

 	struct gpat *pats = font_gpat(fn, len);

@@ -388,10 +405,11 @@

 	rule->len = len;

 	rule->feat = feat;

 	rule->scrp = scrp;

+	rule->lang = lang;

 	return rule;

 }

-static struct grule *font_gpos(struct font *fn, int len, int feat, int scrp)

+static struct grule *font_gpos(struct font *fn, int len, int feat, int scrp, int lang)

 {

 	struct grule *rule;

 	struct gpat *pats = font_gpat(fn, len);

@@ -405,6 +423,7 @@

 	rule->len = len;

 	rule->feat = feat;

 	rule->scrp = scrp;

+	rule->lang = lang;

 	return rule;

 }

@@ -422,13 +441,25 @@

 	return p->g < 0;

 }

-static void font_readfeat(struct font *fn, char *tok, int *feat, int *scrp)

+static void font_readfeat(struct font *fn, char *tok, int *feat, int *scrp, int *lang)

 {

+	char *ftag = tok;

+	char *stag = NULL;

+	char *ltag = NULL;

 	*scrp = -1;

-	if (strchr(tok, ':')) {		/* "feature:script" */

-		*scrp = font_findscrp(fn, strchr(tok, ':') + 1);

-		strchr(tok, ':')[0] = '\0';

+	*lang = -1;

+	if (strchr(ftag, ':')) {

+		stag = strchr(ftag, ':') + 1;

+		stag[-1] = '\0';

 	}

+	if (strchr(stag, ':')) {

+		ltag = strchr(stag, ':') + 1;

+		ltag[-1] = '\0';

+	}

+	if (stag)

+		*scrp = font_findscrp(fn, stag);

+	if (ltag)

+		*lang = font_findlang(fn, ltag);

 	*feat = font_findfeat(fn, tok);

 }

@@ -436,12 +467,12 @@

 {

 	char tok[128];

 	struct grule *rule;

-	int feat, scrp;

+	int feat, scrp, lang;

 	int i, n;

 	if (fscanf(fin, "%s %d", tok, &n) != 2)

 		return 1;

-	font_readfeat(fn, tok, &feat, &scrp);

-	rule = font_gsub(fn, n, feat, scrp);

+	font_readfeat(fn, tok, &feat, &scrp, &lang);

+	rule = font_gsub(fn, n, feat, scrp, lang);

 	for (i = 0; i < n; i++) {

 		if (fscanf(fin, "%s", tok) != 1)

 			return 1;

@@ -462,12 +493,12 @@

 	char tok[128];

 	char *col;

 	struct grule *rule;

-	int feat, scrp;

+	int feat, scrp, lang;

 	int i, n;

 	if (fscanf(fin, "%s %d", tok, &n) != 2)

 		return 1;

-	font_readfeat(fn, tok, &feat, &scrp);

-	rule = font_gpos(fn, n, feat, scrp);

+	font_readfeat(fn, tok, &feat, &scrp, &lang);

+	rule = font_gpos(fn, n, feat, scrp, lang);

 	for (i = 0; i < n; i++) {

 		if (fscanf(fin, "%s", tok) != 1)

 			return 1;

@@ -508,7 +539,7 @@

 	int val;

 	if (fscanf(fin, "%s %s %d", c1, c2, &val) != 3)

 		return 1;

-	rule = font_gpos(fn, 2, font_findfeat(fn, "kern"), -1);

+	rule = font_gpos(fn, 2, font_findfeat(fn, "kern"), -1, -1);

 	rule->pats[0].g = font_idx(fn, font_glyph(fn, c1));

 	rule->pats[1].g = font_idx(fn, font_glyph(fn, c2));

 	rule->pats[0].xadv = val;

@@ -526,7 +557,7 @@

 	int j, n = 0;

 	while (utf8read(&s, c) > 0)

 		g[n++] = font_idx(fn, font_find(fn, c));

-	rule = font_gsub(fn, n + 1, font_findfeat(fn, "liga"), -1);

+	rule = font_gsub(fn, n + 1, font_findfeat(fn, "liga"), -1, -1);

 	for (j = 0; j < n; j++) {

 		rule->pats[j].g = g[j];

 		rule->pats[j].flg = GF_PAT;

@@ -632,6 +663,7 @@

 		font_isetinsert(fn, fn->gpos0, i,

 			font_rulefirstpat(fn, &fn->gpos[i]));

 	fn->scrp = -1;

+	fn->lang = -1;

 	return fn;

 }

@@ -749,4 +781,10 @@

 void font_scrp(struct font *fn, char *name)

 {

 	fn->scrp = name ? font_findscrp(fn, name) : -1;

+}

+

+/* set font language */

+void font_lang(struct font *fn, char *name)

+{

+	fn->lang = name ? font_findlang(fn, name) : -1;

 }

--- a/roff.h

+++ b/roff.h

@@ -48,7 +48,8 @@

 #define NHCODES		512	/* number of .hcode characters */

 #define WORDLEN		256	/* word length (for hyph.c) */

 #define NFEATS		128	/* number of features per font */

-#define NSCRPS		128	/* number of scripts per font */

+#define NSCRPS		64	/* number of scripts per font */

+#define NLANGS		64	/* number of languages per font */

 /* converting scales */

 #define SC_IN		(dev_res)	/* inch in units */

@@ -175,6 +176,7 @@

 int font_zoom(struct font *fn, int sz);

 int font_feat(struct font *fn, char *name, int val);

 void font_scrp(struct font *fn, char *name);

+void font_lang(struct font *fn, char *name);

 int font_layout(struct font *fn, struct glyph **src, int nsrc, int sz,

 		struct glyph **dst, int *dmap,

 		int *x, int *y, int *xadv, int *yadv, int lg, int kn);

--- a/tr.c

+++ b/tr.c

@@ -630,6 +630,8 @@

 	struct font *fn = args[1] ? dev_font(dev_pos(args[1])) : NULL;

 	if (fn && args[2])

 		font_scrp(fn, args[2] ? args[2] : NULL);

+	if (fn && args[3])

+		font_lang(fn, args[3] ? args[3] : NULL);

 }

 static void tr_nm(char **args)