2 files changed, 33 insertions, 8 deletions

diff --git a/src/lib.rs b/src/lib.rs
index 8e650e5..71f0afd 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -66,6 +66,17 @@ fn results() -> JSResult<web_sys::HtmlElement> {
     Ok(x.dyn_into()?)
 }
 
+fn dots() -> JSResult<web_sys::HtmlInputElement> {
+    let x = document()
+        .query_selector("#dots")?
+        .ok_or("no dots element")?;
+    Ok(x.dyn_into()?)
+}
+
+fn dots_val() -> JSResult<usize> {
+    Ok(dots()?.value().parse().map_err(|_| "dots isn't int")?)
+}
+
 #[wasm_bindgen(start)]
 pub fn init() -> JSResult<()> {
     console_log::init_with_level(Level::Debug)
@@ -76,10 +87,12 @@ pub fn init() -> JSResult<()> {
     let p1 = paused.clone();
 
     let mut s = State::new(canvas()?, fps()?)?;
+    s.set_dot_count(dots_val()?);
     s.render_frame(0.0)?;
 
     let shared_s = Rc::new(RefCell::new(s));
     let s1 = shared_s.clone();
+    let s2 = shared_s.clone();
 
     let render_loop = RenderLoop::new(move |t| {
         let mut s = shared_s.borrow_mut();
@@ -88,6 +101,18 @@ pub fn init() -> JSResult<()> {
         Ok(!*paused.lock().unwrap())
     });
 
+    let dot_count_handler: HandlerClosure = Closure::new(move |e| {
+        debug!("dot count changed {:?} - {}", e, dots_val()?);
+        let mut s = s2.borrow_mut();
+        s.set_dot_count(dots_val()?);
+        s.render_frame(0.0)?;
+        Ok(())
+    });
+    dots()?.set_onchange(Some(dot_count_handler.as_ref().unchecked_ref()));
+    // otherwise it gets dropped after we're done, invalidating the
+    // handler.
+    dot_count_handler.forget();
+
     let go_handler: HandlerClosure = Closure::new(move |e| {
         debug!("go clicked: {:?}", e);
         let mut p = p1.lock().unwrap();
@@ -102,8 +127,7 @@ pub fn init() -> JSResult<()> {
         Ok(())
     });
     go()?.set_onclick(Some(go_handler.as_ref().unchecked_ref()));
-    // otherwise it gets dropped after we're done, invalidating the
-    // handler.
+    // ibid.
     go_handler.forget();
 
     let bench_handler: HandlerClosure = Closure::new(move |e| {
diff --git a/src/state.rs b/src/state.rs
index 592f26e..1793388 100644
--- a/src/state.rs
+++ b/src/state.rs
@@ -11,7 +11,6 @@ use crate::point::Point;
 pub const TAU: f64 = PI * 2.0;
 pub const MAX_SPEED: f64 = 0.01;
 
-const NUM_POINTS: usize = 40;
 const VELVEC_SCALE: f64 = 3.0;
 
 #[derive(Debug)]
@@ -33,15 +32,11 @@ impl State {
             .dyn_into()?;
         ctx.scale(canvas.width().into(), canvas.height().into())?;
 
-        let points = (0..NUM_POINTS)
-            .map(|_| Point::new(fastrand::f64(), fastrand::f64()))
-            .collect();
-
         Ok(Self {
             canvas,
             ctx,
             fps,
-            points,
+            points: vec![],
             last_time: None,
             inter_count: 1,
         })
@@ -104,6 +99,12 @@ impl State {
         Ok(())
     }
 
+    pub fn set_dot_count(&mut self, n: usize) {
+        self.points = (0..n)
+            .map(|_| Point::new(fastrand::f64(), fastrand::f64()))
+            .collect();
+    }
+
     fn render_points(&self) -> JSResult<()> {
         for p in &self.points {
             self.ctx.set_fill_style_str(&p.color);