Fix non tokio builds for desktop

packages/desktop/src/event_handlers.rs

@@ -0,0 +1,65 @@
+use crate::{ipc::UserWindowEvent, window};
+use slab::Slab;
+use std::cell::RefCell;
+use tao::{event::Event, event_loop::EventLoopWindowTarget, window::WindowId};
+
+/// The unique identifier of a window event handler. This can be used to later remove the handler.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct WryEventHandler(pub(crate) usize);
+
+impl WryEventHandler {
+    /// Unregister this event handler from the window
+    pub fn remove(&self) {
+        window().shared.event_handlers.remove(*self)
+    }
+}
+
+#[derive(Default)]
+pub struct WindowEventHandlers {
+    handlers: RefCell<Slab<WryWindowEventHandlerInner>>,
+}
+
+struct WryWindowEventHandlerInner {
+    window_id: WindowId,
+
+    #[allow(clippy::type_complexity)]
+    handler:
+        Box<dyn FnMut(&Event<UserWindowEvent>, &EventLoopWindowTarget<UserWindowEvent>) + 'static>,
+}
+
+impl WindowEventHandlers {
+    pub(crate) fn add(
+        &self,
+        window_id: WindowId,
+        handler: impl FnMut(&Event<UserWindowEvent>, &EventLoopWindowTarget<UserWindowEvent>) + 'static,
+    ) -> WryEventHandler {
+        WryEventHandler(
+            self.handlers
+                .borrow_mut()
+                .insert(WryWindowEventHandlerInner {
+                    window_id,
+                    handler: Box::new(handler),
+                }),
+        )
+    }
+
+    pub(crate) fn remove(&self, id: WryEventHandler) {
+        self.handlers.borrow_mut().try_remove(id.0);
+    }
+
+    pub fn apply_event(
+        &self,
+        event: &Event<UserWindowEvent>,
+        target: &EventLoopWindowTarget<UserWindowEvent>,
+    ) {
+        for (_, handler) in self.handlers.borrow_mut().iter_mut() {
+            // if this event does not apply to the window this listener cares about, return
+            if let Event::WindowEvent { window_id, .. } = event {
+                if *window_id != handler.window_id {
+                    return;
+                }
+            }
+            (handler.handler)(event, target)
+        }
+    }
+}