Fix 'current-column' in presence of :relative-width

* src/indent.c (check_display_width): Support ':relative-width'
in a display spec that specifies a stretch glyph.  (Bug#21533)

1 files changed, 15 insertions, 1 deletions

diff --git a/src/indent.c b/src/indent.c
index ded18439fd9..584f2179bc5 100644
--- a/src/indent.c
+++ b/src/indent.c
@@ -485,7 +485,9 @@ check_display_width (ptrdiff_t pos, ptrdiff_t col, ptrdiff_t *endpos)
          : MOST_POSITIVE_FIXNUM);
 
       if ((prop = Fplist_get (plist, QCwidth),
-           RANGED_INTEGERP (0, prop, INT_MAX)))
+           RANGED_INTEGERP (0, prop, INT_MAX))
+          || (prop = Fplist_get (plist, QCrelative_width),
+              RANGED_INTEGERP (0, prop, INT_MAX)))
         width = XINT (prop);
       else if (FLOATP (prop) && 0 <= XFLOAT_DATA (prop)
                && XFLOAT_DATA (prop) <= INT_MAX)
@@ -504,6 +506,18 @@ check_display_width (ptrdiff_t pos, ptrdiff_t col, ptrdiff_t *endpos)
             *endpos = OVERLAY_POSITION (OVERLAY_END (overlay));
           else
             get_property_and_range (pos, Qdisplay, &val, &start, endpos, Qnil);
+
+          /* For :relative-width, we need to multiply by the column
+             width of the character at POS, if it is greater than 1.  */
+          if (!NILP (Fplist_get (plist, QCrelative_width))
+              && !NILP (BVAR (current_buffer, enable_multibyte_characters)))
+            {
+              int b, wd;
+              unsigned char *p = BYTE_POS_ADDR (CHAR_TO_BYTE (pos));
+
+              MULTIBYTE_BYTES_WIDTH (p, buffer_display_table (), b, wd);
+              width *= wd;
+            }
           return width;
         }
     }