refactor: tabs rewrite to clean up API

Tabs relied heavily on `ViewExt`'s `title()` function, while also
requiring a separate `id`. The `id`, if used, should be an internal part
of the struct and not part of its API. This also removes the hashmap as
it will never be faster than sequentially looking up all the names,
since there will most likely never be that many tabs in a `TabbedView`.

src/traits.rs

@@ -104,3 +104,79 @@ impl<V: ViewExt> IntoBoxedViewExt for V {
         Box::new(self)
     }
 }
+
+pub struct BoxedViewExt {
+    boxed_view: Box<dyn ViewExt>,
+}
+
+impl BoxedViewExt {
+    pub fn new(view: Box<dyn ViewExt>) -> Self {
+        Self { boxed_view: view }
+    }
+}
+
+impl View for BoxedViewExt {
+    fn draw(&self, printer: &cursive::Printer) {
+        self.boxed_view.draw(printer);
+    }
+
+    fn layout(&mut self, xy: cursive::Vec2) {
+        self.boxed_view.layout(xy);
+    }
+
+    fn needs_relayout(&self) -> bool {
+        self.boxed_view.needs_relayout()
+    }
+
+    fn required_size(&mut self, constraint: cursive::Vec2) -> cursive::Vec2 {
+        self.boxed_view.required_size(constraint)
+    }
+
+    fn on_event(&mut self, event: cursive::event::Event) -> cursive::event::EventResult {
+        self.boxed_view.on_event(event)
+    }
+
+    fn call_on_any(&mut self, selector: &cursive::view::Selector, callback: cursive::event::AnyCb) {
+        self.boxed_view.call_on_any(selector, callback);
+    }
+
+    fn focus_view(
+        &mut self,
+        selector: &cursive::view::Selector,
+    ) -> Result<cursive::event::EventResult, cursive::view::ViewNotFound> {
+        self.boxed_view.focus_view(selector)
+    }
+
+    fn take_focus(
+        &mut self,
+        source: cursive::direction::Direction,
+    ) -> Result<cursive::event::EventResult, cursive::view::CannotFocus> {
+        self.boxed_view.take_focus(source)
+    }
+
+    fn important_area(&self, view_size: cursive::Vec2) -> cursive::Rect {
+        self.boxed_view.important_area(view_size)
+    }
+
+    fn type_name(&self) -> &'static str {
+        std::any::type_name::<Self>()
+    }
+}
+
+impl ViewExt for BoxedViewExt {
+    fn title(&self) -> String {
+        self.boxed_view.title()
+    }
+
+    fn title_sub(&self) -> String {
+        self.boxed_view.title_sub()
+    }
+
+    fn on_leave(&self) {
+        self.boxed_view.on_leave();
+    }
+
+    fn on_command(&mut self, s: &mut Cursive, cmd: &Command) -> Result<CommandResult, String> {
+        self.boxed_view.on_command(s, cmd)
+    }
+}