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/fromucs.c

@@ -0,0 +1,91 @@
+/*
+ * fromucs.c - convert Unicode to other character sets.
+ */
+
+#include "charset.h"
+#include "internal.h"
+
+struct charset_emit_param {
+    char *output;
+    int outlen;
+    const char *errstr;
+    int errlen;
+    int stopped;
+};
+
+static void charset_emit(void *ctx, long int output)
+{
+    struct charset_emit_param *param = (struct charset_emit_param *)ctx;
+    char outval;
+    char const *p;
+    int outlen;
+
+    if (output == ERROR) {
+	p = param->errstr;
+	outlen = param->errlen;
+    } else {
+	outval = output;
+	p = &outval;
+	outlen = 1;
+    }
+
+    if (param->outlen >= outlen) {
+	while (outlen > 0) {
+	    *param->output++ = *p++;
+	    param->outlen--;
+	    outlen--;
+	}
+    } else {
+	param->stopped = 1;
+    }
+}
+
+int charset_from_unicode(wchar_t **input, int *inlen, char *output, int outlen,
+			 int charset, charset_state *state,
+			 const char *errstr, int errlen)
+{
+    charset_spec const *spec = charset_find_spec(charset);
+    charset_state localstate;
+    struct charset_emit_param param;
+
+    param.output = output;
+    param.outlen = outlen;
+    param.stopped = 0;
+
+    /*
+     * charset_emit will expect a valid errstr.
+     */
+    if (!errstr) {
+	/* *shrug* this is good enough, and consistent across all SBCS... */
+	param.errstr = ".";
+	param.errlen = 1;
+    }
+    param.errstr = errstr;
+    param.errlen = errlen;
+
+    if (!state) {
+	localstate.s0 = 0;
+    } else {
+	localstate = *state;	       /* structure copy */
+    }
+    state = &localstate;
+
+    while (*inlen > 0) {
+	int lenbefore = param.output - output;
+	spec->write(spec, **input, &localstate, charset_emit, &param);
+	if (param.stopped) {
+	    /*
+	     * The emit function has _tried_ to output some
+	     * characters, but ran up against the end of the
+	     * buffer. Leave immediately, and return what happened
+	     * _before_ attempting to process this character.
+	     */
+	    return lenbefore;
+	}
+	if (state)
+	    *state = localstate;       /* structure copy */
+	(*input)++;
+	(*inlen)--;
+    }
+    return param.output - output;
+}