feat(tui): handle kitty key events in libtermkey (#31727)

Enable key event reporting in the kitty keyboard protocol. This causes
supporting terminals to send key events for presses, repeats, and key
releases. For now we ignore release events, but eventually we will
support users mapping those.

src/nvim/tui/input.c

@@ -431,6 +431,15 @@ static void tk_getkeys(TermInput *input, bool force)
   TermKeyResult result;
 
   while ((result = tk_getkey(input->tk, &key, force)) == TERMKEY_RES_KEY) {
+    // Only press and repeat events are handled for now
+    switch (key.event) {
+    case TERMKEY_EVENT_PRESS:
+    case TERMKEY_EVENT_REPEAT:
+      break;
+    default:
+      continue;
+    }
+
     if (key.type == TERMKEY_TYPE_UNICODE && !key.modifiers) {
       forward_simple_utf8(input, &key);
     } else if (key.type == TERMKEY_TYPE_UNICODE

src/nvim/tui/termkey/driver-csi.c

@@ -177,9 +177,21 @@ static TermKeyResult handle_csi_u(TermKey *tk, TermKeyKey *key, int cmd, TermKey
         return TERMKEY_RES_ERROR;
       }
 
-      if (nsubparams > 0 && subparam != 1) {
-        // Not a press event. Ignore for now
-        return TERMKEY_RES_NONE;
+      if (nsubparams > 0) {
+        switch (subparam) {
+        case 1:
+          key->event = TERMKEY_EVENT_PRESS;
+          break;
+        case 2:
+          key->event = TERMKEY_EVENT_REPEAT;
+          break;
+        case 3:
+          key->event = TERMKEY_EVENT_RELEASE;
+          break;
+        default:
+          // Invalid event
+          return TERMKEY_RES_NONE;
+        }
       }
 
       key->modifiers = args[1] - 1;

src/nvim/tui/termkey/termkey.c

@@ -834,6 +834,9 @@ static TermKeyResult peekkey(TermKey *tk, TermKeyKey *key, int force, size_t *nb
     return TERMKEY_RES_ERROR;
   }
 
+  // Press is the default event type.
+  key->event = TERMKEY_EVENT_PRESS;
+
 #ifdef DEBUG
   fprintf(stderr, "getkey(force=%d): buffer ", force);
   print_buffer(tk);

src/nvim/tui/termkey/termkey_defs.h

@@ -123,6 +123,12 @@ typedef enum {
   TERMKEY_MOUSE_RELEASE,
 } TermKeyMouseEvent;
 
+typedef enum {
+  TERMKEY_EVENT_PRESS,
+  TERMKEY_EVENT_REPEAT,
+  TERMKEY_EVENT_RELEASE,
+} TermKeyEvent;
+
 enum {
   TERMKEY_KEYMOD_SHIFT = 1 << 0,
   TERMKEY_KEYMOD_ALT   = 1 << 1,
@@ -163,6 +169,8 @@ typedef struct {
 
   int modifiers;
 
+  TermKeyEvent event;
+
   // Any Unicode character can be UTF-8 encoded in no more than 6 bytes, plus
   // terminating NUL
   char utf8[7];

src/nvim/tui/tui.c

@@ -296,7 +296,10 @@ void tui_set_key_encoding(TUIData *tui)
 {
   switch (tui->input.key_encoding) {
   case kKeyEncodingKitty:
-    out(tui, S_LEN("\x1b[>1u"));
+    // Progressive enhancement flags:
+    //   0b01   (1) Disambiguate escape codes
+    //   0b10   (2) Report event types
+    out(tui, S_LEN("\x1b[>3u"));
     break;
   case kKeyEncodingXterm:
     out(tui, S_LEN("\x1b[>4;2m"));
@@ -311,7 +314,7 @@ static void tui_reset_key_encoding(TUIData *tui)
 {
   switch (tui->input.key_encoding) {
   case kKeyEncodingKitty:
-    out(tui, S_LEN("\x1b[<1u"));
+    out(tui, S_LEN("\x1b[<u"));
     break;
   case kKeyEncodingXterm:
     out(tui, S_LEN("\x1b[>4;0m"));