(internal_self_insert): Only set TARGET_CLM when C2 is tab.

When multibyte characters are disabled,
use 1 as the width of the inserted character.

1 files changed, 12 insertions, 11 deletions

diff --git a/src/cmds.c b/src/cmds.c
index fac3791794f..70dfbceb7f0 100644
--- a/src/cmds.c
+++ b/src/cmds.c
@@ -396,20 +396,21 @@ internal_self_insert (c, noautofill)
          The correct value should be calculated only when necessary.  */
       int target_clm = 0;
 
-      /* Overwriting in binary-mode always substitute C2 by C.  But,
-         overwriting in textual-mode does this substitution in the
-         case that C is not NEWLINE and C2 is not NEWLINE nor TAB.  If
-         C2 is TAB, the substitution is done only when C2 is currently
-         expanded to 0 column, or more than 20 columns, or more than
-         the width of C.  */
+      /* Overwriting in binary-mode always replaces C2 by C.
+         Overwriting in textual-mode doesn't always do that.
+         It inserts newlines in the usual way,
+         and inserts any character at end of line
+         or before a tab if it doesn't use the whole width of the tab.  */
       if (EQ (overwrite, Qoverwrite_mode_binary)
           || (c != '\n'
               && c2 != '\n'
-              && (target_clm = current_column() + WIDTH_BY_CHAR_HEAD (str[0]),
-                  (c2 != '\t'
-                   || XINT (current_buffer->tab_width) <= 0
-                   || XFASTINT (current_buffer->tab_width) > 20
-                   || !(target_clm % XFASTINT (current_buffer->tab_width))))))
+              && ! (c2 == '\t'
+                    && XINT (current_buffer->tab_width) > 0
+                    && XFASTINT (current_buffer->tab_width) < 20
+                    && ((NILP (current_buffer->enable_multibyte_characters)
+                         ? (target_clm = current_column () + 1)
+                         : (target_clm = current_column () + WIDTH_BY_CHAR_HEAD (str[0]))),
+                        target_clm % XFASTINT (current_buffer->tab_width)))))
         {
           int pos = PT;