2 files changed, 19 insertions, 19 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 1d6d1f4..bd6395a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -18,5 +18,5 @@ features = ["js"]
 version = "2.3"
 
 [dependencies.web-sys]
-features = ["Document", "DocumentTimeline", "Element", "HtmlElement", "HtmlCanvasElement", "CanvasRenderingContext2d", "Node", "Window"]
+features = ["Document", "DocumentTimeline", "Element", "Event", "HtmlElement", "HtmlCanvasElement", "CanvasRenderingContext2d", "Node", "Window"]
 version = "0.3"
diff --git a/src/lib.rs b/src/lib.rs
index f6206da..a798872 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -6,12 +6,16 @@ use wasm_bindgen::prelude::*;
 
 use render_loop::RenderLoop;
 use state::State;
+use web_sys::Event;
 
 mod line;
 mod point;
 mod render_loop;
 mod state;
 
+type JSResult<T> = Result<T, JsValue>;
+type HandlerClosure = Closure<dyn FnMut(Event) -> JSResult<()>>;
+
 fn window() -> web_sys::Window {
     web_sys::window().expect("no window")
 }
@@ -20,30 +24,25 @@ fn document() -> web_sys::Document {
     window().document().expect("no document")
 }
 
-fn canvas() -> Result<web_sys::HtmlCanvasElement, JsValue> {
-    let x = document()
-        .query_selector("canvas")?
-        .expect("canvas element");
+fn canvas() -> JSResult<web_sys::HtmlCanvasElement> {
+    let x = document().query_selector("canvas")?.ok_or("no canvas")?;
     Ok(x.dyn_into::<web_sys::HtmlCanvasElement>()?)
 }
 
-fn fps() -> Result<web_sys::HtmlElement, JsValue> {
-    let x = document()
-        .query_selector("#fps")?
-        .expect("fps counter exists");
+fn fps() -> JSResult<web_sys::HtmlElement> {
+    let x = document().query_selector("#fps")?.ok_or("no fps counter")?;
     Ok(x.dyn_into::<web_sys::HtmlElement>()?)
 }
 
-fn go() -> Result<web_sys::HtmlElement, JsValue> {
-    let x = document()
-        .query_selector("button")?
-        .expect("go button exists");
+fn go() -> JSResult<web_sys::HtmlElement> {
+    let x = document().query_selector("button")?.ok_or("no go button")?;
     Ok(x.dyn_into::<web_sys::HtmlElement>()?)
 }
 
 #[wasm_bindgen(start)]
-pub fn init() -> Result<(), JsValue> {
-    console_log::init_with_level(Level::Debug).expect("couldn't init console log");
+pub fn init() -> JSResult<()> {
+    console_log::init_with_level(Level::Debug)
+        .map_err(|e| format!("couldn't init console: {e}"))?;
     info!("wasm init");
 
     let paused = Rc::new(Mutex::new(true));
@@ -57,17 +56,18 @@ pub fn init() -> Result<(), JsValue> {
         !*paused.lock().unwrap()
     });
 
-    let a = Closure::<dyn FnMut()>::new(move || {
+    let a: HandlerClosure = Closure::new(move |e| {
+        debug!("go clicked: {:?}", e);
         let mut p = p1.lock().unwrap();
-        debug!("go clicked: {}", *p);
         *p = !*p;
         let text = if *p {
             "go"
         } else {
-            render_loop.start().expect("start render loop");
+            render_loop.start()?;
             "pause"
         };
-        go().expect("go button works").set_text_content(Some(text));
+        go()?.set_text_content(Some(text));
+        Ok(())
     });
     go()?.set_onclick(Some(a.as_ref().unchecked_ref()));
     // otherwise it gets dropped after we're done, invalidating the