Add a new element to display tables controlling side-by-side

window borders.
* buffer.c (syms_of_buffer): Update doc string for
`buffer-display-table'.
* disptab.h (DISP_TABLE_SIZE): Bump to 262.
(DISP_BORDER_GLYPH): New accessor macro.
* xdisp.c (display_text_line): Consult the display table when
building side-by-side window borders.

3 files changed, 10 insertions, 4 deletions

diff --git a/src/buffer.c b/src/buffer.c
index e132f77da93..4239851b226 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -2776,7 +2776,7 @@ The display table is a vector created with `make-display-table'.\n\
 The first 256 elements control how to display each possible text character.\n\
 Each value should be a vector of characters or nil;\n\
 nil means display the character in the default fashion.\n\
-The remaining five elements control the display of\n\
+The remaining six elements control the display of\n\
   the end of a truncated screen line (element 256, a single character);\n\
   the end of a continued line (element 257, a single character);\n\
   the escape character used to display character codes in octal\n\
@@ -2784,7 +2784,9 @@ The remaining five elements control the display of\n\
   the character used as an arrow for control characters (element 259,\n\
     a single character);\n\
   the decoration indicating the presence of invisible lines (element 260,\n\
-    a vector of characters).\n\
+    a vector of characters);\n\
+  the character used to draw the border between side-by-side windows\n\
+    (element 261, a single character).;\n\
 If this variable is nil, the value of `standard-display-table' is used.\n\
 Each window can have its own, overriding display table.");
 #endif
diff --git a/src/disptab.h b/src/disptab.h
index 235f6bf24fb..d22e52034c4 100644
--- a/src/disptab.h
+++ b/src/disptab.h
@@ -19,12 +19,13 @@ the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
 
 /* Access the slots of a display-table, according to their purpose.  */
 
-#define DISP_TABLE_SIZE 261
+#define DISP_TABLE_SIZE 262
 #define DISP_TRUNC_GLYPH(dp) ((dp)->contents[256])
 #define DISP_CONTINUE_GLYPH(dp) ((dp)->contents[257])
 #define DISP_ESCAPE_GLYPH(dp) ((dp)->contents[258])
 #define DISP_CTRL_GLYPH(dp) ((dp)->contents[259])
 #define DISP_INVIS_VECTOR(dp) ((dp)->contents[260])
+#define DISP_BORDER_GLYPH(dp) ((dp)->contents[261])
 #define DISP_CHAR_VECTOR(dp, c) ((dp)->contents[c])
 
 extern struct Lisp_Vector *window_display_table ();
diff --git a/src/xdisp.c b/src/xdisp.c
index 6f22c38f4d1..1ce0c58ae0d 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -2504,7 +2504,10 @@ display_text_line (w, start, vpos, hpos, taboffset)
          them when the scroll bar windows are flickering around to be
          reconfigured.  */
       *p1++ = (FRAME_HAS_VERTICAL_SCROLL_BARS (f)
-               ? ' ' : '|');
+               ? ' '
+               : (dp && INTEGERP (DISP_BORDER_GLYPH (dp))
+                  ? DISP_BORDER_GLYPH (dp)
+                  : '|'));
     }
   desired_glyphs->used[vpos] = max (desired_glyphs->used[vpos],
                                    p1 - desired_glyphs->glyphs[vpos]);