gpui: Introduce PlatformKeyboardLayout trait for human-friendly keyboard layout names (#29049)

This PR adds a new `PlatformKeyboardLayout` trait with two methods:
`id(&self) -> &str` and `name(&self) -> &str`. The `id()` method returns
a unique identifier for the keyboard layout, while `name()` provides a
human-readable name. This distinction is especially important on
Windows, where the `id` and `name` can be quite different. For example,
the French layout has an `id` of `0000040C`, which is not
human-readable, whereas the `name` would simply be `French`. Currently,
the existing `keyboard_layout()` method returns what's essentially the
same as `id()` in this new design.

This PR implements the `name()` method for both Windows and macOS. On
Linux, for now, `name()` still returns the same value as `id()`.

Release Notes:

- N/A

crates/gpui/src/platform/windows/platform.rs

@@ -297,8 +297,12 @@ impl Platform for WindowsPlatform {
         self.text_system.clone()
     }
 
-    fn keyboard_layout(&self) -> String {
-        "unknown".into()
+    fn keyboard_layout(&self) -> Box<dyn PlatformKeyboardLayout> {
+        Box::new(
+            KeyboardLayout::new()
+                .log_err()
+                .unwrap_or(KeyboardLayout::unknown()),
+        )
     }
 
     fn on_keyboard_layout_change(&self, _callback: Box<dyn FnMut()>) {
@@ -836,6 +840,42 @@ fn should_auto_hide_scrollbars() -> Result<bool> {
     Ok(ui_settings.AutoHideScrollBars()?)
 }
 
+struct KeyboardLayout {
+    id: String,
+    name: String,
+}
+
+impl PlatformKeyboardLayout for KeyboardLayout {
+    fn id(&self) -> &str {
+        &self.id
+    }
+
+    fn name(&self) -> &str {
+        &self.name
+    }
+}
+
+impl KeyboardLayout {
+    fn new() -> Result<Self> {
+        let mut buffer = [0u16; KL_NAMELENGTH as usize];
+        unsafe { GetKeyboardLayoutNameW(&mut buffer)? };
+        let id = HSTRING::from_wide(&buffer).to_string();
+        let entry = windows_registry::LOCAL_MACHINE.open(format!(
+            "System\\CurrentControlSet\\Control\\Keyboard Layouts\\{}",
+            id
+        ))?;
+        let name = entry.get_hstring("Layout Text")?.to_string();
+        Ok(Self { id, name })
+    }
+
+    fn unknown() -> Self {
+        Self {
+            id: "unknown".to_string(),
+            name: "unknown".to_string(),
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use crate::{ClipboardItem, read_from_clipboard, write_to_clipboard};