Double-width glyph support in terminal draw

Added unicode_to_cell detect double-width glyphs. Modified terminal draw to
correctly accept double-width glyphs.

src/intl/charsets.c

@@ -252,6 +252,38 @@ strlen_utf8(unsigned char **str)
 	return x;
 }
 
+
+/* 
+ * Find out number of standard terminal collumns needed for displaying symbol
+ * (glyph) which represents Unicode character c.
+ * TODO: Use wcwidth when it is available.
+ *
+ * @return	2 for double-width glyph, 1 for others.
+ * 		TODO: May be extended to return 0 for zero-width glyphs
+ * 		(like composing, maybe unprintable too).
+ */
+inline int
+unicode_to_cell(unicode_val_T c)
+{
+	if (c >= 0x1100
+		&& (c <= 0x115f			/* Hangul Jamo */
+		|| c == 0x2329
+		|| c == 0x232a
+		|| (c >= 0x2e80 && c <= 0xa4cf
+			&& c != 0x303f)		/* CJK ... Yi */
+		|| (c >= 0xac00 && c <= 0xd7a3)	/* Hangul Syllables */
+		|| (c >= 0xf900 && c <= 0xfaff)	/* CJK Compatibility
+								Ideographs */
+		|| (c >= 0xfe30 && c <= 0xfe6f)	/* CJK Compatibility Forms */
+		|| (c >= 0xff00 && c <= 0xff60)	/* Fullwidth Forms */
+		|| (c >= 0xffe0 && c <= 0xffe6)
+		|| (c >= 0x20000 && c <= 0x2fffd)
+		|| (c >= 0x30000 && c <= 0x3fffd)))
+		return 2;
+
+	return 1;	
+}
+
 inline unicode_val_T
 utf_8_to_unicode(unsigned char **string, unsigned char *end)
 {

src/intl/charsets.h

@@ -56,6 +56,7 @@ void free_conv_table(void);
 #ifdef CONFIG_UTF_8
 inline unsigned char *encode_utf_8(unicode_val_T);
 inline int utf8charlen(const unsigned char *);
+inline int unicode_to_cell(unicode_val_T);
 inline int strlen_utf8(unsigned char **);
 inline unicode_val_T utf_8_to_unicode(unsigned char **, unsigned char *);
 #endif /* CONFIG_UTF_8 */

src/terminal/draw.c

@@ -114,6 +114,26 @@ draw_char_data(struct terminal *term, int x, int y, unsigned char data)
 	if (!screen_char) return;
 
 	screen_char->data = data;
+	
+#ifdef CONFIG_UTF_8
+	if (unicode_to_cell(data) == 2) {
+
+#ifdef CONFIG_DEBUG
+		/* Detect attempt to draw double-width char on the last
+		 * collumn of terminal. */
+		if (x+1 > term->width) 
+			INTERNAL("Attempt to draw double-width glyph on "
+					"last collumn!!");
+#endif /* CONFIG_DEBUG */
+
+		screen_char = get_char(term, x+1, y);
+
+		if (!screen_char) return;
+
+		screen_char->data = UCS_NO_CHAR;
+	}
+#endif /* CONFIG_UTF_8 */	
+
 	set_screen_dirty(term->screen, y, y);
 }
 
@@ -315,7 +335,25 @@ draw_text_utf8(struct terminal *term, int x, int y,
 			       get_opt_int_tree(term->spec, "colors"));
 	}
 
-	for (pos = start + 1; x < term->width; x++, pos++) {
+	pos = start + 1;
+
+	if (unicode_to_cell(data) == 2) {
+
+#ifdef CONFIG_DEBUG
+		/* Detect attempt to draw double-width char on the last
+		 * collumn of terminal. */
+		if (x+1 > term->width) 
+			INTERNAL("Attempt to draw double-width character on "
+					"last collumn!!");
+#endif /* CONFIG_DEBUG */
+		
+		pos->data = UCS_NO_CHAR;
+		if (color) copy_screen_chars(pos, start, 1);
+		x++;
+		pos++;
+	}
+
+	for (; x < term->width; x++, pos++) {
 		data = utf_8_to_unicode(&text, end);
 		if (data == UCS_NO_CHAR) break;
 		if (color) copy_screen_chars(pos, start, 1);