macos: fix CTRL-Backslash on German layouts

refs: https://github.com/wez/wezterm/issues/1891

docs/changelog.md

@@ -28,6 +28,7 @@ As features stabilize some brief notes about them will accumulate here.
 #### Fixed
 * Flush after replying to XTGETTCAP. [#1850](https://github.com/wez/wezterm/issues/1850)
 * macOS: CMD-. was treated as CTRL-ESC [#1867](https://github.com/wez/wezterm/issues/1867)
+* macOS: CTRL-Backslash on German layouts was incorrect [#1891](https://github.com/wez/wezterm/issues/1891)
 * `nf-mdi-contacts` nerdfont symbol treated as zero-width [#1864](https://github.com/wez/wezterm/issues/1864)
 * X11/Wayland: CTRL-i, CTRL-j, CTRL-m misinterpreted as CTRL-Tab, CTRL-Enter, CTRL-Return [#1851](https://github.com/wez/wezterm/issues/1851)
 * Scrollbar stopped working after a lot of output scrolled outside of the scrollback limit.  Thanks to [@davidrios](https://github.com/davidrios)! [#1866](https://github.com/wez/wezterm/pull/1866)

wezterm-input-types/src/lib.rs

@@ -1038,6 +1038,16 @@ fn normalize_shift(key: KeyCode, modifiers: Modifiers) -> (KeyCode, Modifiers) {
     }
 }
 
+pub fn is_ascii_control(c: char) -> Option<char> {
+    let c = c as u32;
+    if c < 0x20 {
+        let de_ctrl = ((c as u8) | 0x40) as char;
+        Some(de_ctrl.to_ascii_lowercase())
+    } else {
+        None
+    }
+}
+
 fn normalize_ctrl(key: KeyCode, modifiers: Modifiers) -> (KeyCode, Modifiers) {
     if modifiers.contains(Modifiers::CTRL) {
         if let KeyCode::Char(c) = key {

window/src/os/macos/window.rs

@@ -42,6 +42,7 @@ use std::rc::Rc;
 use std::str::FromStr;
 use std::time::Instant;
 use wezterm_font::FontConfiguration;
+use wezterm_input_types::is_ascii_control;
 
 #[allow(non_upper_case_globals)]
 const NSViewLayerContentsPlacementTopLeft: NSInteger = 11;
@@ -2159,11 +2160,6 @@ impl WindowView {
                 let array: id = msg_send![class!(NSArray), arrayWithObject: nsevent];
                 let _: () = msg_send![this, interpretKeyEvents: array];
 
-                /*
-                let input_context: id = msg_send![this, inputContext];
-                let res: BOOL = msg_send![input_context, handleEvent: nsevent];
-                if res == YES {
-                */
                 if let Some(myself) = Self::get_this(this) {
                     let mut inner = myself.inner.borrow_mut();
                     log::trace!(
@@ -2276,8 +2272,16 @@ impl WindowView {
                 let raw = key_string_to_key_code(unmod);
                 match (&key, &raw) {
                     // Avoid eg: \x01 when we can use CTRL-A.
-                    // This also helps to keep the correct sequence for backspace/delete
+                    // This also helps to keep the correct sequence for backspace/delete.
-                    (KeyCode::Char(c), Some(raw)) if c.is_ascii_control() => (raw.clone(), None),
+                    // But take care: on German layouts CTRL-Backslash has unmod="/"
+                    // but chars="\x1c"; we only want to do this transformation when
+                    // chars and unmod have that base ASCII relationship.
+                    // <https://github.com/wez/wezterm/issues/1891>
+                    (KeyCode::Char(c), Some(KeyCode::Char(raw)))
+                        if is_ascii_control(*c) == Some(raw.to_ascii_lowercase()) =>
+                    {
+                        (KeyCode::Char(*raw), None)
+                    }
                     _ => (key, raw),
                 }
             };