First draft of Unicode support in pterm. It's pretty complete: it

does UTF-8 copy and paste (falling back to normal strings if
necessary), it understands X font encodings and translates things
accordingly so that if you have a Unicode font you can ask for
virtually any single-byte encoding and get it (Mac-Roman pterm,
anyone?), and so on. There's work left to be done (wide fonts for
CJK spring to mind), but I reckon this is a pretty good start.

[originally from svn r2395]

charset/charset.h

@@ -0,0 +1,120 @@
+/*
+ * charset.h - header file for general character set conversion
+ * routines.
+ */
+
+#ifndef charset_charset_h
+#define charset_charset_h
+
+#include <stddef.h>
+
+/*
+ * Enumeration that lists all the multibyte or single-byte
+ * character sets known to this library.
+ */
+typedef enum {
+    CS_NONE,			       /* used for reporting errors, etc */
+    CS_ISO8859_1,
+    CS_ISO8859_1_X11,		       /* X font encoding with VT100 glyphs */
+    CS_ISO8859_2,
+    CS_ISO8859_3,
+    CS_ISO8859_4,
+    CS_ISO8859_5,
+    CS_ISO8859_6,
+    CS_ISO8859_7,
+    CS_ISO8859_8,
+    CS_ISO8859_9,
+    CS_ISO8859_10,
+    CS_ISO8859_11,
+    CS_ISO8859_13,
+    CS_ISO8859_14,
+    CS_ISO8859_15,
+    CS_ISO8859_16,
+    CS_CP437,
+    CS_CP850,
+    CS_CP1250,
+    CS_CP1251,
+    CS_CP1252,
+    CS_CP1253,
+    CS_CP1254,
+    CS_CP1255,
+    CS_CP1256,
+    CS_CP1257,
+    CS_CP1258,
+    CS_KOI8_R,
+    CS_KOI8_U,
+    CS_MAC_ROMAN,
+    CS_VISCII,
+    CS_HP_ROMAN8,
+    CS_DEC_MCS,
+    CS_UTF8
+} charset_t;
+
+typedef struct {
+    unsigned long s0;
+} charset_state;
+
+/*
+ * Routine to convert a MB/SB character set to Unicode.
+ * 
+ * This routine accepts some number of bytes, updates a state
+ * variable, and outputs some number of Unicode characters. There
+ * are no guarantees. You can't even guarantee that at most one
+ * Unicode character will be output per byte you feed in; for
+ * example, suppose you're reading UTF-8, you've seen E1 80, and
+ * then you suddenly see FE. Now you need to output _two_ error
+ * characters - one for the incomplete sequence E1 80, and one for
+ * the completely invalid UTF-8 byte FE.
+ * 
+ * Returns the number of wide characters output; will never output
+ * more than the size of the buffer (as specified on input).
+ * Advances the `input' pointer and decrements `inlen', to indicate
+ * how far along the input string it got.
+ * 
+ * The sequence of `errlen' wide characters pointed to by `errstr'
+ * will be used to indicate a conversion error. If `errstr' is
+ * NULL, `errlen' will be ignored, and the library will choose
+ * something sensible to do on its own. For Unicode, this will be
+ * U+FFFD (REPLACEMENT CHARACTER).
+ */
+
+int charset_to_unicode(char **input, int *inlen, wchar_t *output, int outlen,
+		       int charset, charset_state *state,
+		       const wchar_t *errstr, int errlen);
+
+/*
+ * Routine to convert Unicode to an MB/SB character set.
+ * 
+ * This routine accepts some number of Unicode characters, updates
+ * a state variable, and outputs some number of bytes.
+ * 
+ * Returns the number of bytes characters output; will never output
+ * more than the size of the buffer (as specified on input), and
+ * will never output a partial MB character. Advances the `input'
+ * pointer and decrements `inlen', to indicate how far along the
+ * input string it got.
+ * 
+ * The sequence of `errlen' characters pointed to by `errstr' will
+ * be used to indicate a conversion error. If `errstr' is NULL,
+ * `errlen' will be ignored, and the library will choose something
+ * sensible to do on its own (which will vary depending on the
+ * output charset).
+ */
+
+int charset_from_unicode(wchar_t **input, int *inlen, char *output, int outlen,
+			 int charset, charset_state *state,
+			 const char *errstr, int errlen);
+
+/*
+ * Convert X11 encoding names to and from our charset identifiers.
+ */
+const char *charset_to_xenc(int charset);
+int charset_from_xenc(const char *name);
+
+/*
+ * Convert MIME encoding names to and from our charset identifiers.
+ */
+const char *charset_to_mimeenc(int charset);
+int charset_from_mimeenc(const char *name);
+
+#endif /* charset_charset_h */