trait based event system

packages/html/src/events/selection.rs

@@ -1,9 +1,75 @@
 use dioxus_core::Event;
 
 pub type SelectionEvent = Event<SelectionData>;
-#[cfg_attr(feature = "serialize", derive(serde::Serialize, serde::Deserialize))]
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub struct SelectionData {}
+
+pub struct SelectionData {
+    inner: Box<dyn HasSelectionData>,
+}
+
+impl SelectionData {
+    /// Downcast this event to a concrete event type
+    pub fn downcast<T: 'static>(&self) -> Option<&T> {
+        self.inner.as_any().downcast_ref::<T>()
+    }
+}
+
+impl<E: HasSelectionData> From<E> for SelectionData {
+    fn from(e: E) -> Self {
+        Self { inner: Box::new(e) }
+    }
+}
+
+impl std::fmt::Debug for SelectionData {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("SelectionData").finish()
+    }
+}
+
+impl PartialEq for SelectionData {
+    fn eq(&self, _other: &Self) -> bool {
+        true
+    }
+}
+
+#[cfg(feature = "serialize")]
+#[derive(serde::Serialize, serde::Deserialize)]
+struct SerializedSelectionData {}
+
+#[cfg(feature = "serialize")]
+impl From<&SelectionData> for SerializedSelectionData {
+    fn from(_: &SelectionData) -> Self {
+        Self {}
+    }
+}
+
+#[cfg(feature = "serialize")]
+impl HasSelectionData for SerializedSelectionData {
+    fn as_any(&self) -> &dyn std::any::Any {
+        self
+    }
+}
+
+#[cfg(feature = "serialize")]
+impl serde::Serialize for SelectionData {
+    fn serialize<S: serde::Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
+        SerializedSelectionData::from(self).serialize(serializer)
+    }
+}
+
+#[cfg(feature = "serialize")]
+impl<'de> serde::Deserialize<'de> for SelectionData {
+    fn deserialize<D: serde::Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
+        let data = SerializedSelectionData::deserialize(deserializer)?;
+        Ok(Self {
+            inner: Box::new(data),
+        })
+    }
+}
+
+pub trait HasSelectionData: std::any::Any {
+    /// return self as Any
+    fn as_any(&self) -> &dyn std::any::Any;
+}
 
 impl_event! [
     SelectionData;