modify Shell::merge to take FnMut(B) -> Option<Message>

Author: edwloef

core/src/element.rs

@@ -333,7 +333,7 @@ where
             viewport,
         );
 
-        shell.merge(local_shell, &self.mapper);
+        shell.merge(local_shell, |m| Some((self.mapper)(m)));
     }
 
     fn draw(

core/src/overlay/element.rs

@@ -89,7 +89,7 @@ where
         self.content
             .update(event, layout, cursor, renderer, &mut local_shell);
 
-        shell.merge(local_shell, self.mapper);
+        shell.merge(local_shell, |m| Some((self.mapper)(m)));
     }
 
     fn mouse_interaction(

core/src/shell.rs

@@ -201,8 +201,8 @@ impl<'a, Message> Shell<'a, Message> {
     /// function to the messages of the latter.
     ///
     /// This method is useful for composition.
-    pub fn merge<B>(&mut self, mut other: Shell<'_, B>, f: impl Fn(B) -> Message) {
-        self.messages.extend(other.messages.drain(..).map(f));
+    pub fn merge<B>(&mut self, mut other: Shell<'_, B>, f: impl FnMut(B) -> Option<Message>) {
+        self.messages.extend(other.messages.drain(..).filter_map(f));
 
         self.is_layout_invalid = match (self.is_layout_invalid, other.is_layout_invalid) {
             (Some(a), Some(b)) => Some(a.max(b)),

examples/toast/src/main.rs

@@ -522,7 +522,7 @@ mod toast {
                     instant.take();
                 }
 
-                shell.merge(local_shell, std::convert::identity);
+                shell.merge(local_shell, |m| Some(m));
             }
         }