Add support for italic text on ttys.

* src/dispextern.h: Replace unused TTY_CAP_BLINK with TTY_CAP_ITALIC.
(struct face): Remove unused fields tty_dim_p, tty_blinking_p, and
tty_alt_charset_p.  Add tty_italic_p.

* src/term.c: Support italics in capable terminals.
(no_color_bit): Replace unused NC_BLINK with NC_ITALIC.
(turn_on_face): Output using TS_enter_italic_mode if available.
Don't handle unused blinking and alt-charset cases.
(turn_off_face): Handle italic case; discard unused tty_blinking_p
and tty_alt_charset_p cases.
(tty_capable_p, init_tty): Support italics.

* src/termchar.h (struct tty_display_info): Add field for italics.
Remove unused blink field.

* src/xfaces.c (tty_supports_face_attributes_p, realize_tty_face):
Handle slant.

Fixes: debbugs:9652

1 files changed, 15 insertions, 26 deletions

diff --git a/src/term.c b/src/term.c
index 3d7a677374c..8ce2efc0929 100644
--- a/src/term.c
+++ b/src/term.c
@@ -122,12 +122,11 @@ enum no_color_bit
   NC_STANDOUT    = 1 << 0,
   NC_UNDERLINE   = 1 << 1,
   NC_REVERSE     = 1 << 2,
-  NC_BLINK       = 1 << 3,
+  NC_ITALIC      = 1 << 3,
   NC_DIM         = 1 << 4,
   NC_BOLD        = 1 << 5,
   NC_INVIS       = 1 << 6,
-  NC_PROTECT     = 1 << 7,
-  NC_ALT_CHARSET = 1 << 8
+  NC_PROTECT     = 1 << 7
 };
 
 /* internal state */
@@ -2022,17 +2021,16 @@ turn_on_face (struct frame *f, int face_id)
   if (face->tty_bold_p && MAY_USE_WITH_COLORS_P (tty, NC_BOLD))
     OUTPUT1_IF (tty, tty->TS_enter_bold_mode);
 
-  if (face->tty_dim_p && MAY_USE_WITH_COLORS_P (tty, NC_DIM))
-    OUTPUT1_IF (tty, tty->TS_enter_dim_mode);
-
-  /* Alternate charset and blinking not yet used.  */
-  if (face->tty_alt_charset_p
-      && MAY_USE_WITH_COLORS_P (tty, NC_ALT_CHARSET))
-    OUTPUT1_IF (tty, tty->TS_enter_alt_charset_mode);
-
-  if (face->tty_blinking_p
-      && MAY_USE_WITH_COLORS_P (tty, NC_BLINK))
-    OUTPUT1_IF (tty, tty->TS_enter_blink_mode);
+  if (face->tty_italic_p && MAY_USE_WITH_COLORS_P (tty, NC_ITALIC))
+    {
+      if (tty->TS_enter_italic_mode)
+        OUTPUT1 (tty, tty->TS_enter_italic_mode);
+      else
+        /* Italics mode is unavailable on many terminals.  In that
+           case, map slant to dimmed text; we want italic text to
+           appear different and dimming is not otherwise used.  */
+        OUTPUT1 (tty, tty->TS_enter_dim_mode);
+    }
 
   if (face->tty_underline_p && MAY_USE_WITH_COLORS_P (tty, NC_UNDERLINE))
     OUTPUT1_IF (tty, tty->TS_enter_underline_mode);
@@ -2077,27 +2075,19 @@ turn_off_face (struct frame *f, int face_id)
          half-bright, reverse-video, standout, underline.  It may or
          may not turn off alt-char-mode.  */
       if (face->tty_bold_p
-          || face->tty_dim_p
+          || face->tty_italic_p
           || face->tty_reverse_p
-          || face->tty_alt_charset_p
-          || face->tty_blinking_p
           || face->tty_underline_p)
         {
           OUTPUT1_IF (tty, tty->TS_exit_attribute_mode);
           if (strcmp (tty->TS_exit_attribute_mode, tty->TS_end_standout_mode) == 0)
             tty->standout_mode = 0;
         }
-
-      if (face->tty_alt_charset_p)
-        OUTPUT_IF (tty, tty->TS_exit_alt_charset_mode);
     }
   else
     {
       /* If we don't have "me" we can only have those appearances
          that have exit sequences defined.  */
-      if (face->tty_alt_charset_p)
-        OUTPUT_IF (tty, tty->TS_exit_alt_charset_mode);
-
       if (face->tty_underline_p)
         OUTPUT_IF (tty, tty->TS_exit_underline_mode);
     }
@@ -2128,8 +2118,7 @@ tty_capable_p (struct tty_display_info *tty, unsigned int caps,
   TTY_CAPABLE_P_TRY (tty, TTY_CAP_UNDERLINE,    tty->TS_enter_underline_mode,   NC_UNDERLINE);
   TTY_CAPABLE_P_TRY (tty, TTY_CAP_BOLD,         tty->TS_enter_bold_mode,        NC_BOLD);
   TTY_CAPABLE_P_TRY (tty, TTY_CAP_DIM,          tty->TS_enter_dim_mode,         NC_DIM);
-  TTY_CAPABLE_P_TRY (tty, TTY_CAP_BLINK,        tty->TS_enter_blink_mode,       NC_BLINK);
-  TTY_CAPABLE_P_TRY (tty, TTY_CAP_ALT_CHARSET,  tty->TS_enter_alt_charset_mode, NC_ALT_CHARSET);
+  TTY_CAPABLE_P_TRY (tty, TTY_CAP_ITALIC,       tty->TS_enter_italic_mode,      NC_ITALIC);
 
   /* We can do it!  */
   return 1;
@@ -3222,8 +3211,8 @@ use the Bourne shell command `TERM=... export TERM' (C-shell:\n\
   tty->TS_enter_underline_mode = tgetstr ("us", address);
   tty->TS_exit_underline_mode = tgetstr ("ue", address);
   tty->TS_enter_bold_mode = tgetstr ("md", address);
+  tty->TS_enter_italic_mode = tgetstr ("ZH", address);
   tty->TS_enter_dim_mode = tgetstr ("mh", address);
-  tty->TS_enter_blink_mode = tgetstr ("mb", address);
   tty->TS_enter_reverse_mode = tgetstr ("mr", address);
   tty->TS_enter_alt_charset_mode = tgetstr ("as", address);
   tty->TS_exit_alt_charset_mode = tgetstr ("ae", address);