remove context from ui (again) and create weird trait for it

src/testing/mod.rs

@@ -19,7 +19,7 @@ pub fn main() {
 pub struct Client {
     renderer: Renderer,
     input: Input,
-    ui: Ui<Client>,
+    ui: Ui,
     info: WidgetId<Text>,
     focus: Option<WidgetId<TextEdit>>,
 }
@@ -155,7 +155,8 @@ impl Client {
 
         let switch_button = |color, to, label| {
             let rect = rect(color)
-                .id_on(Sense::click(), move |id, ctx: &mut Client, _| {
+                .ctx::<Client>()
+                .id_on(Sense::click(), move |id, ctx, _| {
                     ctx.ui[main].inner.set_static(to);
                     ctx.ui[id].color = color.darker(0.3);
                 })
@@ -201,16 +202,18 @@ impl Client {
     }
 
     pub fn event(&mut self, event: WindowEvent, event_loop: &ActiveEventLoop) {
-        self.input.event(&event);
+        let input_changed = self.input.event(&event);
         let cursor_state = self.cursor_state().clone();
-        let window_size = self.window_size();
         if let Some(focus) = &self.focus
             && cursor_state.buttons.left.is_start()
         {
             self.ui.text(focus).deselect();
             self.focus = None;
         }
-        run_sensors(self, &cursor_state, window_size);
+        if input_changed {
+            let window_size = self.window_size();
+            run_sensors(self, &cursor_state, window_size);
+        }
         match event {
             WindowEvent::CloseRequested => event_loop.exit(),
             WindowEvent::RedrawRequested => {
@@ -249,7 +252,7 @@ impl Client {
 }
 
 impl UiCtx for Client {
-    fn ui(&mut self) -> &mut Ui<Self> {
+    fn ui(&mut self) -> &mut Ui {
         &mut self.ui
     }
 }