feat: add special platform event

There are many different events in different platform, so they should
not included in any of the events, like touch, window or etc. This maybe
will make the production platform plugin more flexible

core/src/event.rs

@@ -23,6 +23,32 @@ pub enum Event {
 
     /// A touch event
     Touch(touch::Event),
+
+    /// Special platform event
+    Special(Box<dyn SpecialEvent + Send>),
+}
+
+/// Define the trait without Clone and PartialEq
+pub trait SpecialEvent: std::fmt::Debug {
+    /// check if it is equal
+    fn equal(&self, other: &dyn SpecialEvent) -> bool;
+
+    /// We add a `clone_box` method for cloning trait objects
+    fn clone_box(&self) -> Box<dyn SpecialEvent + Send>;
+}
+
+// Implement `CustomInner` for `Clone`
+impl Clone for Box<dyn SpecialEvent + Send> {
+    fn clone(&self) -> Box<dyn SpecialEvent + Send> {
+        self.clone_box()
+    }
+}
+
+// Example implementation for PartialEq
+impl PartialEq for Box<dyn SpecialEvent + Send> {
+    fn eq(&self, other: &Self) -> bool {
+        self.equal(&(**other)) // Customize this equality check as needed
+    }
 }
 
 /// The status of an [`Event`] after being processed.

widget/src/canvas.rs

@@ -233,6 +233,7 @@ where
                 Some(Event::Keyboard(keyboard_event))
             }
             core::Event::Window(_) => None,
+            core::Event::Special(_) => None,
         };
 
         if let Some(canvas_event) = canvas_event {

widget/src/shader.rs

@@ -110,6 +110,7 @@ where
                 Some(Event::RedrawRequested(instant))
             }
             core::Event::Window(_) => None,
+            core::Event::Special(_) => None,
         };
 
         if let Some(custom_shader_event) = custom_shader_event {