keymap: Support <D-...> (super/command key).

Adds support for:
  - api:vim_input("<D-a>")
  - ":nnoremap <C-D-S-...>" and permutations thereof

UIs must capture the modifier and send it as "<D-...>" to vim_input().

Note: Before this commit, any arbitrary ":nnoremap <{foo}-{bar}>"
mapping could already be invoked with feedkeys("\<{foo}-{bar}>"). This
commit supports "D-" as a modifier that can be combined with "C-", "A-",
"S-" in any order.

For non-GUI (terminal) support, user must:
  :set <D-a>={CSI sequence}
then send the {CSI sequence} from their terminal. But this does not work
yet (regression #2204).

Closes #2190

1 files changed, 7 insertions, 9 deletions

diff --git a/src/nvim/keymap.c b/src/nvim/keymap.c
index 65c808eb06..6c75d8bdf4 100644
--- a/src/nvim/keymap.c
+++ b/src/nvim/keymap.c
@@ -1,8 +1,3 @@
-/*
- * functions that use lookup tables for various things, generally to do with
- * special key codes.
- */
-
 #include <assert.h>
 #include <inttypes.h>
 #include <limits.h>
@@ -39,7 +34,8 @@ static struct modmasktable {
   {MOD_MASK_MULTI_CLICK,      MOD_MASK_2CLICK,        (char_u)'2'},
   {MOD_MASK_MULTI_CLICK,      MOD_MASK_3CLICK,        (char_u)'3'},
   {MOD_MASK_MULTI_CLICK,      MOD_MASK_4CLICK,        (char_u)'4'},
-  /* 'A' must be the last one */
+  {MOD_MASK_CMD,              MOD_MASK_CMD,           (char_u)'D'},
+  // 'A' must be the last one
   {MOD_MASK_ALT,              MOD_MASK_ALT,           (char_u)'A'},
   {0, 0, NUL}
 };
@@ -658,9 +654,11 @@ static int extract_modifiers(int key, int *modp)
 {
   int modifiers = *modp;
 
-  if ((modifiers & MOD_MASK_SHIFT) && ASCII_ISALPHA(key)) {
-    key = TOUPPER_ASC(key);
-    modifiers &= ~MOD_MASK_SHIFT;
+  if (!(modifiers & MOD_MASK_CMD)) {  // Command-key is special
+    if ((modifiers & MOD_MASK_SHIFT) && ASCII_ISALPHA(key)) {
+      key = TOUPPER_ASC(key);
+      modifiers &= ~MOD_MASK_SHIFT;
+    }
   }
   if ((modifiers & MOD_MASK_CTRL)
       && ((key >= '?' && key <= '_') || ASCII_ISALPHA(key))) {