csi: add support for DECNKM private mode

This is equivalent to DECKPAM/DECKPNM when enabled/disabled, but can
also be saved/restored/queried with XTSAVE/XTRESTORE/DECRQM.

See also:

* https://vt100.net/docs/vt510-rm/DECNKM.html
* https://vt100.net/docs/vt510-rm/DECKPAM.html
* https://invisible-island.net/xterm/ctlseqs/ctlseqs.html#h3-PC-Style-Function-Keys

CHANGELOG.md

@@ -45,6 +45,8 @@
 * Add "xterm" as fallback cursor where "text" is not available.
 * `[key-bindings].scrollback-home|end` options.
 * Socket activation for `foot --server` and accompanying systemd unit files
+* Support for [DECNKM](https://vt100.net/docs/vt510-rm/DECNKM.html), which
+  allows setting/saving/restoring/querying the keypad mode.
 
 
 ### Changed
@@ -88,8 +90,11 @@
 
 
 ### Security
+
 ### Contributors
 
+* Craig Barnes
+
 
 ## 1.11.0
 

csi.c

@@ -393,6 +393,11 @@ decset_decrst(struct terminal *term, unsigned param, bool enable)
         term->reverse_wrap = enable;
         break;
 
+    case 66:
+        /* DECNKM */
+        term->keypad_keys_mode = enable ? KEYPAD_APPLICATION : KEYPAD_NUMERICAL;
+        break;
+
     case 80:
         term->sixel.scrolling = !enable;
         break;
@@ -603,6 +608,7 @@ decrqm(const struct terminal *term, unsigned param, bool *enabled)
     case 12: *enabled = term->cursor_blink.decset; return true;
     case 25: *enabled = !term->hide_cursor; return true;
     case 45: *enabled = term->reverse_wrap; return true;
+    case 66: *enabled = term->keypad_keys_mode == KEYPAD_APPLICATION; return true;
     case 80: *enabled = !term->sixel.scrolling; return true;
     case 1000: *enabled = term->mouse_tracking == MOUSE_CLICK; return true;
     case 1001: *enabled = false; return true;
@@ -646,6 +652,7 @@ xtsave(struct terminal *term, unsigned param)
     case 25: term->xtsave.show_cursor = !term->hide_cursor; break;
     case 45: term->xtsave.reverse_wrap = term->reverse_wrap; break;
     case 47: term->xtsave.alt_screen = term->grid == &term->alt; break;
+    case 66: term->xtsave.application_keypad_keys = term->keypad_keys_mode == KEYPAD_APPLICATION; break;
     case 80: term->xtsave.sixel_display_mode = !term->sixel.scrolling; break;
     case 1000: term->xtsave.mouse_click = term->mouse_tracking == MOUSE_CLICK; break;
     case 1001: break;
@@ -688,6 +695,7 @@ xtrestore(struct terminal *term, unsigned param)
     case 25: enable = term->xtsave.show_cursor; break;
     case 45: enable = term->xtsave.reverse_wrap; break;
     case 47: enable = term->xtsave.alt_screen; break;
+    case 66: enable = term->xtsave.application_keypad_keys; break;
     case 80: enable = term->xtsave.sixel_display_mode; break;
     case 1000: enable = term->xtsave.mouse_click; break;
     case 1001: return;

doc/foot-ctlseqs.7.scd

@@ -268,6 +268,9 @@ that corresponds to one of the following modes:
 |  47
 :  xterm
 :  Same as 1047 (see below)
+|  66
+:  VT320
+:  Numeric keypad mode (DECNKM); same as DECKPAM/DECKPNM when enabled/disabled
 |  1000
 :  xterm
 :  Send mouse x/y on button press/release

terminal.h

@@ -393,6 +393,7 @@ struct terminal {
     struct {
         bool origin:1;
         bool application_cursor_keys:1;
+        bool application_keypad_keys:1;
         bool reverse:1;
         bool show_cursor:1;
         bool reverse_wrap:1;