Also drop Sync requirement for editor handles

BREAKING_CHANGES.md

@@ -8,8 +8,9 @@ code then it will not be listed here.
 
 ## [2022-10-20]
 
-- `Editor` now only requires `Send` and no longer needs `Sync`. This is not a
-  breaking change, but it might be worth being aware of.
+- `Editor` and the editor handle returned by `Editor::spawn` now only require
+  `Send` and no longer need `Sync`. This is not a breaking change, but it might
+  be worth being aware of.
 - The `create_egui_editor()` function from `nih_plug_egui` now also takes a
   build closure to apply initialization logic to the egui context.
 - The `nih_plug::param` module has been renamed to `nih_plug::params`. Code that

nih_plug_egui/src/lib.rs

@@ -132,7 +132,7 @@ where
         &self,
         parent: ParentWindowHandle,
         context: Arc<dyn GuiContext>,
-    ) -> Box<dyn std::any::Any + Send + Sync> {
+    ) -> Box<dyn std::any::Any + Send> {
         let build = self.build.clone();
         let update = self.update.clone();
         let state = self.user_state.clone();
@@ -213,7 +213,6 @@ struct EguiEditorHandle {
 /// The window handle enum stored within 'WindowHandle' contains raw pointers. Is there a way around
 /// having this requirement?
 unsafe impl Send for EguiEditorHandle {}
-unsafe impl Sync for EguiEditorHandle {}
 
 impl Drop for EguiEditorHandle {
     fn drop(&mut self) {

nih_plug_iced/src/lib.rs

@@ -299,7 +299,7 @@ impl<E: IcedEditor> Editor for IcedEditorWrapper<E> {
         &self,
         parent: ParentWindowHandle,
         context: Arc<dyn GuiContext>,
-    ) -> Box<dyn std::any::Any + Send + Sync> {
+    ) -> Box<dyn std::any::Any + Send> {
         let (unscaled_width, unscaled_height) = self.iced_state.size();
         let scaling_factor = self.scaling_factor.load();
 
@@ -389,7 +389,6 @@ struct IcedEditorHandle<Message: 'static + Send> {
 /// The window handle enum stored within 'WindowHandle' contains raw pointers. Is there a way around
 /// having this requirement?
 unsafe impl<Message: Send> Send for IcedEditorHandle<Message> {}
-unsafe impl<Message: Send> Sync for IcedEditorHandle<Message> {}
 
 impl<Message: Send> Drop for IcedEditorHandle<Message> {
     fn drop(&mut self) {

nih_plug_vizia/src/lib.rs

@@ -174,7 +174,7 @@ impl Editor for ViziaEditor {
         &self,
         parent: ParentWindowHandle,
         context: Arc<dyn GuiContext>,
-    ) -> Box<dyn std::any::Any + Send + Sync> {
+    ) -> Box<dyn std::any::Any + Send> {
         let app = self.app.clone();
         let vizia_state = self.vizia_state.clone();
         let apply_theming = self.apply_theming;
@@ -258,7 +258,6 @@ struct ViziaEditorHandle {
 /// The window handle enum stored within 'WindowHandle' contains raw pointers. Is there a way around
 /// having this requirement?
 unsafe impl Send for ViziaEditorHandle {}
-unsafe impl Sync for ViziaEditorHandle {}
 
 impl Drop for ViziaEditorHandle {
     fn drop(&mut self) {

src/plugin.rs

@@ -282,7 +282,7 @@ pub trait Editor: Send {
         &self,
         parent: ParentWindowHandle,
         context: Arc<dyn GuiContext>,
-    ) -> Box<dyn Any + Send + Sync>;
+    ) -> Box<dyn Any + Send>;
 
     /// Returns the (current) size of the editor in pixels as a `(width, height)` pair. This size
     /// must be reported in _logical pixels_, i.e. the size before being multiplied by the DPI

src/wrapper/clap/wrapper.rs

@@ -115,7 +115,7 @@ pub struct Wrapper<P: ClapPlugin> {
     editor: Option<Mutex<Box<dyn Editor>>>,
     /// A handle for the currently active editor instance. The plugin should implement `Drop` on
     /// this handle for its closing behavior.
-    editor_handle: RwLock<Option<Box<dyn Any + Send + Sync>>>,
+    editor_handle: Mutex<Option<Box<dyn Any + Send>>>,
     /// The DPI scaling factor as passed to the [IPlugViewContentScaleSupport::set_scale_factor()]
     /// function. Defaults to 1.0, and will be kept there on macOS. When reporting and handling size
     /// the sizes communicated to and from the DAW should be scaled by this factor since NIH-plug's
@@ -544,7 +544,7 @@ impl<P: ClapPlugin> Wrapper<P> {
             plugin: RwLock::new(plugin),
             params,
             editor,
-            editor_handle: RwLock::new(None),
+            editor_handle: Mutex::new(None),
             editor_scaling_factor: AtomicF32::new(1.0),
 
             is_processing: AtomicBool::new(false),
@@ -2645,7 +2645,7 @@ impl<P: ClapPlugin> Wrapper<P> {
         check_null_ptr!(false, plugin);
         let wrapper = &*(plugin as *const Self);
 
-        let editor_handle = wrapper.editor_handle.read();
+        let editor_handle = wrapper.editor_handle.lock();
         if editor_handle.is_none() {
             true
         } else {
@@ -2658,7 +2658,7 @@ impl<P: ClapPlugin> Wrapper<P> {
         check_null_ptr!((), plugin);
         let wrapper = &*(plugin as *const Self);
 
-        let mut editor_handle = wrapper.editor_handle.write();
+        let mut editor_handle = wrapper.editor_handle.lock();
         if editor_handle.is_some() {
             *editor_handle = None;
         } else {
@@ -2764,7 +2764,7 @@ impl<P: ClapPlugin> Wrapper<P> {
         let window = &*window;
 
         let result = {
-            let mut editor_handle = wrapper.editor_handle.write();
+            let mut editor_handle = wrapper.editor_handle.lock();
             if editor_handle.is_none() {
                 let api = CStr::from_ptr(window.api);
                 let handle = if api == CLAP_WINDOW_API_X11 {