fix(windows): preserve dead-key composition in kitty panes (#3548)

refs #3546

Co-authored-by: akbash-bot <300245827+akbash-bot@users.noreply.github.com>
Co-authored-by: JJ Liebig <jonathan.liebig@gmail.com>

2 files changed, 24 insertions, 0 deletions

diff --git a/src/input/encode.rs b/src/input/encode.rs
index 774ab1a6..6dfff4ce 100644
--- a/src/input/encode.rs
+++ b/src/input/encode.rs
@@ -16,6 +16,13 @@ pub fn encode_key(key: KeyEvent, protocol: KeyboardProtocol) -> Vec<u8> {
 }
 
 pub fn encode_terminal_key(key: TerminalKey, protocol: KeyboardProtocol) -> Vec<u8> {
+    // A zero Unicode value on this Windows character event means the host layout is
+    // still composing a dead key. Kitty panes must not receive its physical fallback.
+    // Legacy Windows panes take the native ConPTY fallback before reaching this encoder.
+    if matches!(protocol, KeyboardProtocol::Kitty { .. }) && key.is_windows_shift_dead_key() {
+        return Vec::new();
+    }
+
     // REPORT_ALL_KEYS must retain physical press/repeat/release semantics instead of
     // reducing a native key to its layout-generated text.
     let preserve_physical_key = key.has_physical_identity() && protocol.reports_all_keys();
diff --git a/src/input/model.rs b/src/input/model.rs
index 304c4f20..50cd7e42 100644
--- a/src/input/model.rs
+++ b/src/input/model.rs
@@ -78,6 +78,7 @@ pub struct TerminalKey {
     pub shifted_codepoint: Option<u32>,
     pub generated_text: Option<String>,
     physical_identity_hint: bool,
+    windows_shift_dead_key: bool,
     source: KeySource,
 }
 
@@ -91,6 +92,7 @@ impl TerminalKey {
             shifted_codepoint: None,
             generated_text: None,
             physical_identity_hint: false,
+            windows_shift_dead_key: false,
             source: KeySource::Synthesized,
         }
     }
@@ -139,6 +141,7 @@ impl TerminalKey {
 
     #[cfg(any(windows, test))]
     pub fn with_windows_record(mut self, record: WindowsKeyRecord) -> Self {
+        self = self.with_windows_composition_hint(Some(record));
         self.repeat_count = if self.kind == crossterm::event::KeyEventKind::Release {
             1
         } else {
@@ -153,6 +156,16 @@ impl TerminalKey {
         self
     }
 
+    pub(crate) fn with_windows_composition_hint(
+        mut self,
+        record: Option<WindowsKeyRecord>,
+    ) -> Self {
+        self.windows_shift_dead_key = matches!(self.code, KeyCode::Char(_))
+            && self.modifiers == KeyModifiers::SHIFT
+            && record.is_some_and(|record| record.unicode == 0);
+        self
+    }
+
     pub(crate) fn with_physical_identity_hint(mut self, physical: bool) -> Self {
         self.physical_identity_hint = physical;
         self
@@ -176,6 +189,10 @@ impl TerminalKey {
         None
     }
 
+    pub(crate) fn is_windows_shift_dead_key(&self) -> bool {
+        self.windows_shift_dead_key
+    }
+
     pub(crate) fn identity(&self) -> KeyIdentity {
         match self.source {
             #[cfg(any(windows, test))]