feat: switch input source during prefix mode (#434)

On macOS, opt-in under [experimental], temporarily switch the host input
source to the current ASCII-capable layout while prefix mode is active so
prefix commands register even when a CJK IME is composing, then restore the
previous input source when prefix mode exits or is cancelled. No-op when the
current source is already ASCII-capable, on non-macOS platforms, or when any
input source call fails. Pane text input is unaffected.

Also pin next_resize_poll in next_loop_deadline_includes_selection_autoscroll_deadline
so the selection autoscroll deadline stays the earliest; the default resize
poll could otherwise beat it and flake the assertion.

refs #400

Co-authored-by: Can Celik <ogulcancelik@gmail.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/src/config/model.rs b/src/config/model.rs
index 7895341f..9fda88f4 100644
--- a/src/config/model.rs
+++ b/src/config/model.rs
@@ -477,6 +477,12 @@ pub struct ExperimentalConfig {
     /// Cursor shape rendered for the IME anchor when
     /// `reveal_hidden_cursor_for_cjk_ime` is enabled. Default: "steady_block".
     pub cjk_ime_cursor_shape: ImeCursorShape,
+    /// While prefix mode is active, temporarily switch the macOS host input
+    /// source to an ASCII-capable keyboard layout so prefix commands are read
+    /// as ASCII even when a CJK IME is active, then restore the previous input
+    /// source when prefix mode exits. macOS only; a no-op elsewhere and a
+    /// best-effort no-op if the switch fails. Default: false.
+    pub switch_ascii_input_source_in_prefix: bool,
 }
 
 impl Default for KeysConfig {
@@ -756,6 +762,23 @@ reveal_hidden_cursor_for_cjk_ime = true
     }
 
     #[test]
+    fn switch_ascii_input_source_in_prefix_default_off_and_parse() {
+        let default_config = Config::default();
+        assert!(
+            !default_config
+                .experimental
+                .switch_ascii_input_source_in_prefix
+        );
+
+        let toml = r#"
+[experimental]
+switch_ascii_input_source_in_prefix = true
+"#;
+        let config: Config = toml::from_str(toml).unwrap();
+        assert!(config.experimental.switch_ascii_input_source_in_prefix);
+    }
+
+    #[test]
     fn cjk_ime_cursor_shape_default_steady_block_and_parse() {
         let default_config = Config::default();
         assert_eq!(
@@ -1049,11 +1072,13 @@ kitty_graphics = true
 allow_nested = true
 kitty_graphics = true
 pane_history = true
+switch_ascii_input_source_in_prefix = true
 "#;
         let config: Config = toml::from_str(toml).unwrap();
         assert!(config.experimental.allow_nested);
         assert!(config.experimental.kitty_graphics);
         assert!(config.experimental.pane_history);
+        assert!(config.experimental.switch_ascii_input_source_in_prefix);
     }
 
     #[test]