Flesh out the editor example a bit more

core/src/renderer/null.rs

@@ -125,6 +125,10 @@ impl text::Editor for () {
         text::editor::Cursor::Caret(Point::ORIGIN)
     }
 
+    fn cursor_position(&self) -> (usize, usize) {
+        (0, 0)
+    }
+
     fn selection(&self) -> Option<String> {
         None
     }

core/src/text/editor.rs

@@ -12,6 +12,8 @@ pub trait Editor: Sized + Default {
 
     fn cursor(&self) -> Cursor;
 
+    fn cursor_position(&self) -> (usize, usize);
+
     fn selection(&self) -> Option<String>;
 
     fn line(&self, index: usize) -> Option<&str>;
@@ -52,6 +54,12 @@ pub enum Action {
     Drag(Point),
 }
 
+impl Action {
+    pub fn is_edit(&self) -> bool {
+        matches!(self, Self::Edit(_))
+    }
+}
+
 #[derive(Debug, Clone, PartialEq)]
 pub enum Edit {
     Insert(char),