+static hb_bool_t
+hb_glib_unicode_compose (hb_unicode_funcs_t *ufuncs HB_UNUSED,
+ hb_codepoint_t a,
+ hb_codepoint_t b,
+ hb_codepoint_t *ab,
+ void *user_data HB_UNUSED)
+{
+#if GLIB_CHECK_VERSION(2,29,12)
+ return g_unichar_compose (a, b, ab);
+#endif
+
+ /* We don't ifdef-out the fallback code such that compiler always
+ * sees it and makes sure it's compilable. */
+
+ if (!a || !b)
+ return FALSE;
+
+ gchar utf8[12];
+ gchar *normalized;
+ gint len;
+ hb_bool_t ret;
+
+ len = g_unichar_to_utf8 (a, utf8);
+ len += g_unichar_to_utf8 (b, utf8 + len);
+ normalized = g_utf8_normalize (utf8, len, G_NORMALIZE_NFC);
+
+ len = g_utf8_strlen (normalized, -1);
+ if (len == 1) {
+ *ab = g_utf8_get_char (normalized);
+ ret = TRUE;
+ } else {
+ ret = FALSE;
+ }
+
+ g_free (normalized);
+ return ret;
+}
+
+static hb_bool_t
+hb_glib_unicode_decompose (hb_unicode_funcs_t *ufuncs HB_UNUSED,
+ hb_codepoint_t ab,
+ hb_codepoint_t *a,
+ hb_codepoint_t *b,
+ void *user_data HB_UNUSED)
+{
+#if GLIB_CHECK_VERSION(2,29,12)
+ return g_unichar_decompose (ab, a, b);
+#endif
+
+ /* We don't ifdef-out the fallback code such that compiler always
+ * sees it and makes sure it's compilable. */
+
+ gchar utf8[6];
+ gchar *normalized;
+ gint len;
+ hb_bool_t ret;
+
+ len = g_unichar_to_utf8 (ab, utf8);
+ normalized = g_utf8_normalize (utf8, len, G_NORMALIZE_NFD);
+
+ len = g_utf8_strlen (normalized, -1);
+ if (len == 1) {
+ *a = g_utf8_get_char (normalized);
+ *b = 0;
+ ret = *a != ab;
+ } else if (len == 2) {
+ *a = g_utf8_get_char (normalized);
+ *b = g_utf8_get_char (g_utf8_next_char (normalized));
+ /* Here's the ugly part: if ab decomposes to a single character and
+ * that character decomposes again, we have to detect that and undo
+ * the second part :-(. */
+ gchar *recomposed = g_utf8_normalize (normalized, -1, G_NORMALIZE_NFC);
+ hb_codepoint_t c = g_utf8_get_char (recomposed);
+ if (c != ab && c != *a) {
+ *a = c;
+ *b = 0;
+ }
+ g_free (recomposed);
+ ret = TRUE;
+ } else {
+ /* If decomposed to more than two characters, take the last one,
+ * and recompose the rest to get the first component. */
+ gchar *end = g_utf8_offset_to_pointer (normalized, len - 1);
+ gchar *recomposed;
+ *b = g_utf8_get_char (end);
+ recomposed = g_utf8_normalize (normalized, end - normalized, G_NORMALIZE_NFC);
+ /* We expect that recomposed has exactly one character now. */
+ *a = g_utf8_get_char (recomposed);
+ g_free (recomposed);
+ ret = TRUE;
+ }
+
+ g_free (normalized);
+ return ret;
+}
+
+
+extern HB_INTERNAL hb_unicode_funcs_t _hb_unicode_funcs_glib;
+hb_unicode_funcs_t _hb_glib_unicode_funcs = {
+ HB_OBJECT_HEADER_STATIC,
+