Re: [PATCH] TTY Support for ECMA-48 strike-through graphic rendition

[Mike Hamrick <mikeh@muppetlabs.com>]

Eli Zaretskii writes:

> Thanks, a couple of really minor nits below:
>
>> @@ -1971,7 +1974,8 @@ turn_off_face (struct frame *f, int face_id)
>>        if (face->tty_bold_p
>>  	  || face->tty_italic_p
>>  	  || face->tty_reverse_p
>> -	  || face->tty_underline_p)
>> +	  || face->tty_underline_p
>> +          || face->tty_strike_through_p)
>
> Please use our style of indentation in C source files (basically, make
> sure indent-tabs-mode is non-nil).
>
> Also, please make sure the patch still applies to the current master,
> and if not, please update it.

I've fixed the indentation issue, and have updated the patch so it
applies to the current master.

Mike

* term.c: Support strike-through in capable terminals.
(no_color_bit): Replace unused NC_INVIS with NC_STRIKE_THROUGH.
(turn_on_face): Output via TS_enter_strike_through_mode if available.
(turn_off_face): Handle strike-through case.
(tty_capable_p, init_tty): Support strike-through.

* termchar.h (struct tty_display_info): Add field for strike-through.

* xfaces.c (tty_supports_face_attributes_p, realize_tty_face):
Handle strike-through case.

* dispextern.h: Add TTY_CAP_STRIKE_THROUGH definition.
(struct face): Add field tty_strike_through_p.
---
 etc/NEWS         |  7 +++++++
 src/dispextern.h |  2 ++
 src/term.c       | 34 ++++++++++++++++++++--------------
 src/termchar.h   |  1 +
 src/xfaces.c     | 12 +++++++++++-
 5 files changed, 41 insertions(+), 15 deletions(-)

diff --git a/etc/NEWS b/etc/NEWS
index 52092f2ef7..757b4c74ae 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -85,6 +85,13 @@ useful on systems such as FreeBSD which ships only with "etc/termcap".
 \f
 * Changes in Emacs 28.1

+---
+** Support for the 'strike-through' face attribute on TTY frames.
+If your terminal's termcap or terminfo database entry has the 'smxx'
+capability defined, Emacs will now emit the prescribed escape
+sequences necessary to render faces with the 'strike-through'
+attribute on TTY frames.
+
 +++
 *** Emacs now defaults to UTF-8 instead of ISO-8859-1.
 This is only for the default, where the user has set no LANG (or
diff --git a/src/dispextern.h b/src/dispextern.h
index 956ca96eb6..e20f7bb7b6 100644
--- a/src/dispextern.h
+++ b/src/dispextern.h
@@ -1744,6 +1744,7 @@ #define FONT_TOO_HIGH(ft)						\
   bool_bf tty_italic_p : 1;
   bool_bf tty_underline_p : 1;
   bool_bf tty_reverse_p : 1;
+  bool_bf tty_strike_through_p : 1;

   /* True means that colors of this face may not be freed because they
      have been copied bitwise from a base face (see
@@ -3290,6 +3291,7 @@ #define TTY_CAP_UNDERLINE	0x02
 #define TTY_CAP_BOLD		0x04
 #define TTY_CAP_DIM		0x08
 #define TTY_CAP_ITALIC  	0x10
+#define TTY_CAP_STRIKE_THROUGH	0x20

 \f
 /***********************************************************************
diff --git a/src/term.c b/src/term.c
index 5cbb092ad1..22035f4fe3 100644
--- a/src/term.c
+++ b/src/term.c
@@ -105,14 +105,14 @@ #define OUTPUT1_IF(tty, a) do { if (a) emacs_tputs ((tty), a, 1, cmputc); } whil

 enum no_color_bit
 {
-  NC_STANDOUT	 = 1 << 0,
-  NC_UNDERLINE	 = 1 << 1,
-  NC_REVERSE	 = 1 << 2,
-  NC_ITALIC	 = 1 << 3,
-  NC_DIM	 = 1 << 4,
-  NC_BOLD	 = 1 << 5,
-  NC_INVIS	 = 1 << 6,
-  NC_PROTECT	 = 1 << 7
+  NC_STANDOUT		 = 1 << 0,
+  NC_UNDERLINE		 = 1 << 1,
+  NC_REVERSE		 = 1 << 2,
+  NC_ITALIC		 = 1 << 3,
+  NC_DIM		 = 1 << 4,
+  NC_BOLD		 = 1 << 5,
+  NC_STRIKE_THROUGH	 = 1 << 6,
+  NC_PROTECT		 = 1 << 7
 };

 /* internal state */
@@ -1931,6 +1931,9 @@ turn_on_face (struct frame *f, int face_id)
   if (face->tty_underline_p && MAY_USE_WITH_COLORS_P (tty, NC_UNDERLINE))
     OUTPUT1_IF (tty, tty->TS_enter_underline_mode);

+  if (face->tty_strike_through_p && MAY_USE_WITH_COLORS_P (tty, NC_STRIKE_THROUGH))
+    OUTPUT1_IF (tty, tty->TS_enter_strike_through_mode);
+
   if (tty->TN_max_colors > 0)
     {
       const char *ts;
@@ -1971,7 +1974,8 @@ turn_off_face (struct frame *f, int face_id)
       if (face->tty_bold_p
 	  || face->tty_italic_p
 	  || face->tty_reverse_p
-	  || face->tty_underline_p)
+	  || face->tty_underline_p
+	  || face->tty_strike_through_p)
 	{
 	  OUTPUT1_IF (tty, tty->TS_exit_attribute_mode);
 	  if (strcmp (tty->TS_exit_attribute_mode, tty->TS_end_standout_mode) == 0)
@@ -2006,11 +2010,12 @@ #define TTY_CAPABLE_P_TRY(tty, cap, TS, NC_bit)				\
   if ((caps & (cap)) && (!(TS) || !MAY_USE_WITH_COLORS_P(tty, NC_bit)))	\
     return 0;

-  TTY_CAPABLE_P_TRY (tty, TTY_CAP_INVERSE,	tty->TS_standout_mode, 	 	NC_REVERSE);
-  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_ITALIC, 	tty->TS_enter_italic_mode, 	NC_ITALIC);
+  TTY_CAPABLE_P_TRY (tty, TTY_CAP_INVERSE,	  tty->TS_standout_mode,		NC_REVERSE);
+  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_ITALIC,	  tty->TS_enter_italic_mode,		NC_ITALIC);
+  TTY_CAPABLE_P_TRY (tty, TTY_CAP_STRIKE_THROUGH, tty->TS_enter_strike_through_mode,	NC_STRIKE_THROUGH);

   /* We can do it!  */
   return 1;
@@ -4124,6 +4129,7 @@ init_tty (const char *name, const char *terminal_type, bool must_succeed)
   tty->TS_enter_alt_charset_mode = tgetstr ("as", address);
   tty->TS_exit_alt_charset_mode = tgetstr ("ae", address);
   tty->TS_exit_attribute_mode = tgetstr ("me", address);
+  tty->TS_enter_strike_through_mode = tgetstr ("smxx", address);

   MultiUp (tty) = tgetstr ("UP", address);
   MultiDown (tty) = tgetstr ("DO", address);
diff --git a/src/termchar.h b/src/termchar.h
index c96b81913b..a8b3051767 100644
--- a/src/termchar.h
+++ b/src/termchar.h
@@ -136,6 +136,7 @@ #define EMACS_TERMCHAR_H
   const char *TS_enter_reverse_mode; /* "mr" -- enter reverse video mode.  */
   const char *TS_exit_underline_mode; /* "us" -- start underlining.  */
   const char *TS_enter_underline_mode; /* "ue" -- end underlining.  */
+  const char *TS_enter_strike_through_mode; /* "smxx" -- turn on strike-through mode.  */

   /* "as"/"ae" -- start/end alternate character set.  Not really
      supported, yet.  */
diff --git a/src/xfaces.c b/src/xfaces.c
index 06d2f994de..73a536b19c 100644
--- a/src/xfaces.c
+++ b/src/xfaces.c
@@ -5217,7 +5217,6 @@ tty_supports_face_attributes_p (struct frame *f,
       || !UNSPECIFIEDP (attrs[LFACE_HEIGHT_INDEX])
       || !UNSPECIFIEDP (attrs[LFACE_SWIDTH_INDEX])
       || !UNSPECIFIEDP (attrs[LFACE_OVERLINE_INDEX])
-      || !UNSPECIFIEDP (attrs[LFACE_STRIKE_THROUGH_INDEX])
       || !UNSPECIFIEDP (attrs[LFACE_BOX_INDEX]))
     return false;

@@ -5282,6 +5281,15 @@ tty_supports_face_attributes_p (struct frame *f,
 	test_caps |= TTY_CAP_INVERSE;
     }

+  /* strike through */
+  val = attrs[LFACE_STRIKE_THROUGH_INDEX];
+  if (!UNSPECIFIEDP (val))
+    {
+      if (face_attr_equal_p (val, def_attrs[LFACE_STRIKE_THROUGH_INDEX]))
+	return false;		/* same as default */
+      else
+	test_caps |= TTY_CAP_STRIKE_THROUGH;
+    }

   /* Color testing.  */

@@ -6244,6 +6252,8 @@ realize_tty_face (struct face_cache *cache,
     face->tty_underline_p = true;
   if (!NILP (attrs[LFACE_INVERSE_INDEX]))
     face->tty_reverse_p = true;
+  if (!NILP (attrs[LFACE_STRIKE_THROUGH_INDEX]))
+    face->tty_strike_through_p = true;

   /* Map color names to color indices.  */
   map_tty_color (f, face, LFACE_FOREGROUND_INDEX, &face_colors_defaulted);
--
2.24.0