add state to counter example

examples/counter.rs

@@ -1,19 +1,68 @@
+use std::cell::Cell;
+use std::rc::Rc;
+
 use reflector::build::{Build, Button, Row, Text};
-use reflector::elem::Elem;
-use reflector::graphics::Font;
-use reflector::{App, Size, WindowOptions};
-
-fn build() -> impl Elem {
-    let font = Font::from_bytes(
-        include_bytes!("../reflector-graphics/examples/res/SourceSansPro-Regular.otf"),
-        0,
-    )
-    .unwrap();
-
-    Row::new(5.0)
-        .child(Text::new("text", font.clone(), 16.0))
-        .child(Button::new(Text::new("button", font.clone(), 16.0)).action(|| println!("click")))
-        .build()
+use reflector::elem::{Context, Elem, Event, Response};
+use reflector::graphics::{Canvas, Font};
+use reflector::{App, Point, ProposedSize, Size, WindowOptions};
+
+struct Counter {
+    counter: Rc<Cell<usize>>,
+    inner: Box<dyn Elem>,
+}
+
+impl Counter {
+    fn new() -> Counter {
+        let counter = Rc::new(Cell::new(0));
+        let inner = Box::new(Self::build(&counter).build());
+
+        Counter { counter, inner }
+    }
+
+    fn build(counter: &Rc<Cell<usize>>) -> impl Build {
+        let font = Font::from_bytes(
+            include_bytes!("../reflector-graphics/examples/res/SourceSansPro-Regular.otf"),
+            0,
+        )
+        .unwrap();
+
+        let counter = counter.clone();
+
+        Row::new(5.0)
+            .child(Text::new(format!("{}", counter.get()), font.clone(), 16.0))
+            .child(
+                Button::new(Text::new("button", font.clone(), 16.0))
+                    .action(move || counter.set(counter.get() + 1)),
+            )
+    }
+}
+
+impl Elem for Counter {
+    fn update(&mut self, cx: &mut Context) {
+        Self::build(&self.counter).rebuild(self.inner.downcast_mut().unwrap());
+
+        self.inner.update(cx);
+    }
+
+    fn hit_test(&mut self, cx: &mut Context, point: Point) -> bool {
+        self.inner.hit_test(cx, point)
+    }
+
+    fn handle(&mut self, cx: &mut Context, event: &Event) -> Response {
+        self.inner.handle(cx, event)
+    }
+
+    fn measure(&mut self, cx: &mut Context, proposal: ProposedSize) -> Size {
+        self.inner.measure(cx, proposal)
+    }
+
+    fn place(&mut self, cx: &mut Context, size: Size) {
+        self.inner.place(cx, size);
+    }
+
+    fn render(&mut self, cx: &mut Context, canvas: &mut Canvas) {
+        self.inner.render(cx, canvas);
+    }
 }
 
 fn main() {
@@ -22,7 +71,7 @@ fn main() {
     WindowOptions::new()
         .title("window")
         .size(Size::new(512.0, 512.0))
-        .open(&app, build())
+        .open(&app, Counter::new())
         .unwrap();
 
     app.run().unwrap();