[PATCH] console utf-8 mode fixes

Fix utf-8 mode so alternate charset modes always work according to control
sequences interpreted in do_con_trol function preserving backward US-ASCII
and VT100 semigraphics compatibility.

Malformed utf-8 sequences are represented as sequences of replacement
glyphs,original codes or '?' as a last resort.

unicode-xterm, gnome-terminal, kconsole and other terminal emulators in
utf-8 mode respect acsc, enacs, rmacs sequences.  Also I found that some
important system programs (from Debian distro) uses acsc in utf-8 mode -
dselect, aptitude, w3m for example.

Signed-off-by: Adam Tlalka <atlka@pg.gda.pl>
Acked-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 52 insertions, 27 deletions

diff --git a/drivers/char/vt.c b/drivers/char/vt.c
index d7d880f8147b..0fca83ededff 100644
--- a/drivers/char/vt.c
+++ b/drivers/char/vt.c
@@ -63,6 +63,13 @@
  *
  * Removed console_lock, enabled interrupts across all console operations
  * 13 March 2001, Andrew Morton
+ *
+ * Fixed UTF-8 mode so alternate charset modes always work according
+ * to control sequences interpreted in do_con_trol function
+ * preserving backward VT100 semigraphics compatibility,
+ * malformed UTF sequences represented as sequences of replacement glyphs,
+ * original codes or '?' as a last resort if replacement glyph is undefined
+ * by Adam Tla/lka <atlka@pg.gda.pl>, Aug 2006
  */
 
 #include <linux/module.h>
@@ -2005,17 +2012,23 @@ static int do_con_write(struct tty_struct *tty, const unsigned char *buf, int co
                 /* Do no translation at all in control states */
                 if (vc->vc_state != ESnormal) {
                         tc = c;
-                } else if (vc->vc_utf) {
+                } else if (vc->vc_utf && !vc->vc_disp_ctrl) {
                     /* Combine UTF-8 into Unicode */
-                    /* Incomplete characters silently ignored */
+                    /* Malformed sequences as sequences of replacement glyphs */
+rescan_last_byte:
                     if(c > 0x7f) {
-                        if (vc->vc_utf_count > 0 && (c & 0xc0) == 0x80) {
-                                vc->vc_utf_char = (vc->vc_utf_char << 6) | (c & 0x3f);
-                                vc->vc_utf_count--;
-                                if (vc->vc_utf_count == 0)
-                                    tc = c = vc->vc_utf_char;
-                                else continue;
+                        if (vc->vc_utf_count) {
+                               if ((c & 0xc0) == 0x80) {
+                                       vc->vc_utf_char = (vc->vc_utf_char << 6) | (c & 0x3f);
+                                       if (--vc->vc_utf_count) {
+                                               vc->vc_npar++;
+                                               continue;
+                                       }
+                                       tc = c = vc->vc_utf_char;
+                               } else
+                                       goto replacement_glyph;
                         } else {
+                                vc->vc_npar = 0;
                                 if ((c & 0xe0) == 0xc0) {
                                     vc->vc_utf_count = 1;
                                     vc->vc_utf_char = (c & 0x1f);
@@ -2032,14 +2045,15 @@ static int do_con_write(struct tty_struct *tty, const unsigned char *buf, int co
                                     vc->vc_utf_count = 5;
                                     vc->vc_utf_char = (c & 0x01);
                                 } else
-                                    vc->vc_utf_count = 0;
+                                    goto replacement_glyph;
                                 continue;
                               }
                     } else {
+                      if (vc->vc_utf_count)
+                              goto replacement_glyph;
                       tc = c;
-                      vc->vc_utf_count = 0;
                     }
-                } else {        /* no utf */
+                } else {        /* no utf or alternate charset mode */
                   tc = vc->vc_translate[vc->vc_toggle_meta ? (c | 0x80) : c];
                 }
 
@@ -2054,31 +2068,33 @@ static int do_con_write(struct tty_struct *tty, const unsigned char *buf, int co
                  * direct-to-font zone in UTF-8 mode.
                  */
                 ok = tc && (c >= 32 ||
-                            (!vc->vc_utf && !(((vc->vc_disp_ctrl ? CTRL_ALWAYS
-                                                : CTRL_ACTION) >> c) & 1)))
+                            !(vc->vc_disp_ctrl ? (CTRL_ALWAYS >> c) & 1 :
+                                  vc->vc_utf || ((CTRL_ACTION >> c) & 1)))
                         && (c != 127 || vc->vc_disp_ctrl)
                         && (c != 128+27);
 
                 if (vc->vc_state == ESnormal && ok) {
                         /* Now try to find out how to display it */
                         tc = conv_uni_to_pc(vc, tc);
-                        if ( tc == -4 ) {
+                        if (tc & ~charmask) {
+                                if ( tc == -4 ) {
                                 /* If we got -4 (not found) then see if we have
                                    defined a replacement character (U+FFFD) */
-                                tc = conv_uni_to_pc(vc, 0xfffd);
-
-                                /* One reason for the -4 can be that we just
-                                   did a clear_unimap();
-                                   try at least to show something. */
-                                if (tc == -4)
-                                     tc = c;
-                        } else if ( tc == -3 ) {
-                                /* Bad hash table -- hope for the best */
-                                tc = c;
-                        }
-                        if (tc & ~charmask)
-                                continue; /* Conversion failed */
+replacement_glyph:
+                                        tc = conv_uni_to_pc(vc, 0xfffd);
+                                        if (!(tc & ~charmask))
+                                                goto display_glyph;
+                                } else if ( tc != -3 )
+                                        continue; /* nothing to display */
+                                /* no hash table or no replacement --
+                                 * hope for the best */
+                                if ( c & ~charmask )
+                                        tc = '?';
+                                else
+                                        tc = c;
+                        }
 
+display_glyph:
                         if (vc->vc_need_wrap || vc->vc_decim)
                                 FLUSH
                         if (vc->vc_need_wrap) {
@@ -2102,6 +2118,15 @@ static int do_con_write(struct tty_struct *tty, const unsigned char *buf, int co
                                 vc->vc_x++;
                                 draw_to = (vc->vc_pos += 2);
                         }
+                        if (vc->vc_utf_count) {
+                                if (vc->vc_npar) {
+                                        vc->vc_npar--;
+                                        goto display_glyph;
+                                }
+                                vc->vc_utf_count = 0;
+                                c = orig;
+                                goto rescan_last_byte;
+                        }
                         continue;
                 }
                 FLUSH