syntax, TUI: support "strikethrough"

fix #3436

Includes:
vim-patch:8.0.1038: strike-through text not supported

6 files changed, 34 insertions, 13 deletions

diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index f9d346ea68..fbfc5a5f76 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -17584,6 +17584,9 @@ static void f_synIDattr(typval_T *argvars, typval_T *rettv, FunPtr fptr)
     case 's': {
       if (TOLOWER_ASC(what[1]) == 'p') {  // sp[#]
         p = highlight_color(id, what, modec);
+      } else if (TOLOWER_ASC(what[1]) == 't'
+                 && TOLOWER_ASC(what[2]) == 'r') {  // strikethrough
+        p = highlight_has_attr(id, HL_STRIKETHROUGH, modec);
       } else {  // standout
         p = highlight_has_attr(id, HL_STANDOUT, modec);
       }
diff --git a/src/nvim/highlight.c b/src/nvim/highlight.c
index f44cd5cdab..093cc4923b 100644
--- a/src/nvim/highlight.c
+++ b/src/nvim/highlight.c
@@ -598,6 +598,10 @@ Dictionary hlattrs2dict(HlAttrs ae, bool use_rgb)
     PUT(hl, "reverse", BOOLEAN_OBJ(true));
   }
 
+  if (mask & HL_STRIKETHROUGH) {
+    PUT(hl, "strikethrough", BOOLEAN_OBJ(true));
+  }
+
   if (use_rgb) {
     if (ae.rgb_fg_color != -1) {
       PUT(hl, "foreground", INTEGER_OBJ(ae.rgb_fg_color));
diff --git a/src/nvim/highlight_defs.h b/src/nvim/highlight_defs.h
index 512d87fa34..f9c2c03fc6 100644
--- a/src/nvim/highlight_defs.h
+++ b/src/nvim/highlight_defs.h
@@ -11,12 +11,13 @@ typedef int32_t RgbValue;
 ///
 /// sign bit should not be used here, as it identifies invalid highlight
 typedef enum {
-  HL_INVERSE     = 0x01,
-  HL_BOLD        = 0x02,
-  HL_ITALIC      = 0x04,
-  HL_UNDERLINE   = 0x08,
-  HL_UNDERCURL   = 0x10,
-  HL_STANDOUT    = 0x20,
+  HL_INVERSE         = 0x01,
+  HL_BOLD            = 0x02,
+  HL_ITALIC          = 0x04,
+  HL_UNDERLINE       = 0x08,
+  HL_UNDERCURL       = 0x10,
+  HL_STANDOUT        = 0x20,
+  HL_STRIKETHROUGH   = 0x40,
 } HlAttrFlags;
 
 /// Stores a complete highlighting entry, including colors and attributes
diff --git a/src/nvim/syntax.c b/src/nvim/syntax.c
index 613c9e6d63..c811fae916 100644
--- a/src/nvim/syntax.c
+++ b/src/nvim/syntax.c
@@ -115,11 +115,11 @@ static int include_link = 0;    /* when 2 include "nvim/link" and "clear" */
 /// The "term", "cterm" and "gui" arguments can be any combination of the
 /// following names, separated by commas (but no spaces!).
 static char *(hl_name_table[]) =
-{"bold", "standout", "underline", "undercurl",
- "italic", "reverse", "inverse", "NONE"};
+{ "bold", "standout", "underline", "undercurl",
+  "italic", "reverse", "inverse", "strikethrough", "NONE" };
 static int hl_attr_table[] =
-{HL_BOLD, HL_STANDOUT, HL_UNDERLINE, HL_UNDERCURL, HL_ITALIC, HL_INVERSE,
- HL_INVERSE, 0};
+{ HL_BOLD, HL_STANDOUT, HL_UNDERLINE, HL_UNDERCURL, HL_ITALIC, HL_INVERSE,
+  HL_INVERSE, HL_STRIKETHROUGH, 0 };
 
 // The patterns that are being searched for are stored in a syn_pattern.
 // A match item consists of one pattern.
diff --git a/src/nvim/terminal.c b/src/nvim/terminal.c
index dfee11c468..b1ce0e6592 100644
--- a/src/nvim/terminal.c
+++ b/src/nvim/terminal.c
@@ -605,7 +605,8 @@ void terminal_get_line_attributes(Terminal *term, win_T *wp, int linenr,
     int hl_attrs = (cell.attrs.bold ? HL_BOLD : 0)
                  | (cell.attrs.italic ? HL_ITALIC : 0)
                  | (cell.attrs.reverse ? HL_INVERSE : 0)
-                 | (cell.attrs.underline ? HL_UNDERLINE : 0);
+                 | (cell.attrs.underline ? HL_UNDERLINE : 0)
+                 | (cell.attrs.strike ? HL_STRIKETHROUGH: 0);
 
     int attr_id = 0;
 
diff --git a/src/nvim/tui/tui.c b/src/nvim/tui/tui.c
index 6e1b7ef2db..791756e5c5 100644
--- a/src/nvim/tui/tui.c
+++ b/src/nvim/tui/tui.c
@@ -115,6 +115,7 @@ typedef struct {
     int enable_mouse, disable_mouse;
     int enable_bracketed_paste, disable_bracketed_paste;
     int enable_lr_margin, disable_lr_margin;
+    int enter_strikethrough_mode;
     int set_rgb_foreground, set_rgb_background;
     int set_cursor_color;
     int reset_cursor_color;
@@ -208,6 +209,7 @@ static void terminfo_start(UI *ui)
   data->unibi_ext.reset_cursor_color = -1;
   data->unibi_ext.enable_bracketed_paste = -1;
   data->unibi_ext.disable_bracketed_paste = -1;
+  data->unibi_ext.enter_strikethrough_mode = -1;
   data->unibi_ext.enable_lr_margin = -1;
   data->unibi_ext.disable_lr_margin = -1;
   data->unibi_ext.enable_focus_reporting = -1;
@@ -529,6 +531,7 @@ static void update_attrs(UI *ui, int attr_id)
   bool italic = attr & HL_ITALIC;
   bool reverse = attr & HL_INVERSE;
   bool standout = attr & HL_STANDOUT;
+  bool strikethrough = attr & HL_STRIKETHROUGH;
 
   bool underline;
   bool undercurl;
@@ -575,6 +578,9 @@ static void update_attrs(UI *ui, int attr_id)
   if (italic) {
     unibi_out(ui, unibi_enter_italics_mode);
   }
+  if (strikethrough && data->unibi_ext.enter_strikethrough_mode != -1) {
+    unibi_out_ext(ui, data->unibi_ext.enter_strikethrough_mode);
+  }
   if (undercurl && data->unibi_ext.set_underline_style != -1) {
     UNIBI_SET_NUM_VAR(data->params[0], 3);
     unibi_out_ext(ui, data->unibi_ext.set_underline_style);
@@ -615,13 +621,14 @@ static void update_attrs(UI *ui, int attr_id)
   }
 
   data->default_attr = fg == -1 && bg == -1
-    && !bold && !italic && !underline && !undercurl && !reverse && !standout;
+    && !bold && !italic && !underline && !undercurl && !reverse && !standout
+    && !strikethrough;
 
   // Non-BCE terminals can't clear with non-default background color. Some BCE
   // terminals don't support attributes either, so don't rely on it. But assume
   // italic and bold has no effect if there is no text.
   data->can_clear_attr = !reverse && !standout && !underline && !undercurl
-    && (data->bce || bg == -1);
+    && !strikethrough && (data->bce || bg == -1);
 }
 
 static void final_column_wrap(UI *ui)
@@ -1826,6 +1833,11 @@ static void augment_terminfo(TUIData *data, const char *term,
       "\x1b[r");
   }
 
+  // terminfo describes strikethrough modes as rmxx/smxx with respect
+  // to the ECMA-48 strikeout/crossed-out attributes.
+  data->unibi_ext.enter_strikethrough_mode = (int)unibi_find_ext_str(
+      ut, "smxx");
+
   // Dickey ncurses terminfo does not include the setrgbf and setrgbb
   // capabilities, proposed by Rüdiger Sonderfeld on 2013-10-15.  Adding
   // them here when terminfo lacks them is an augmentation, not a fixup.