Implement IPlugView::onKeyDown with Editor::on_key_down hook

src/editor.rs

@@ -69,6 +69,20 @@ pub trait Editor: Send {
     /// loaded.
     fn param_values_changed(&self);
 
+    /// Called when the host sends a key-down event to the plugin view (VST3
+    /// `IPlugView::onKeyDown`). Return `true` if the editor consumed the key
+    /// (the wrapper will return `kResultTrue` to the host so the host skips its
+    /// own accelerator handling); return `false` to let the host process the
+    /// key normally.
+    ///
+    /// This is primarily for text-input routing in hosts like REAPER that
+    /// intercept certain keys (space, Cmd-shortcuts) before they reach the
+    /// plugin's native view. The editor should only return `true` if a text
+    /// input in the editor currently has focus and can consume the character.
+    fn on_key_down(&self, _character: Option<char>) -> bool {
+        false
+    }
+
     // TODO: Reconsider adding a tick function here for the Linux `IRunLoop`. To keep this platform
     //       and API agnostic, add a way to ask the GuiContext if the wrapper already provides a
     //       tick function. If it does not, then the Editor implementation must handle this by

src/wrapper/vst3/view.rs

@@ -338,11 +338,26 @@ impl<P: Vst3Plugin> IPlugView for WrapperView<P> {
 
     unsafe fn on_key_down(
         &self,
-        _key: vst3_sys::base::char16,
-        _key_code: i16,
+        key: vst3_sys::base::char16,
+        key_code: i16,
         _modifiers: i16,
     ) -> tresult {
-        kNotImplemented
+        // Only forward keys that carry a VST3 virtual key code. Those are
+        // keys the host (notably REAPER) may intercept as accelerators
+        // before they reach our native view — space, tab, return, arrows,
+        // etc. Plain printable characters arrive with `key_code = 0` and
+        // flow through the normal AppKit `keyDown:` path, which already
+        // handles text input via NSTextInputContext. Consuming them here
+        // would break letter input.
+        if key_code == 0 {
+            return kResultFalse;
+        }
+        let character = char::from_u32(key as u32);
+        if self.editor.lock().on_key_down(character) {
+            kResultOk
+        } else {
+            kResultFalse
+        }
     }
 
     unsafe fn on_key_up(