[oden] Allow a "functional style" init/update/draw

src/script.rs

@@ -47,6 +47,8 @@ pub struct ScriptContext {
     update: Value,
     draw: Value,
 
+    state: Value,
+
     gfx: graphics::GraphicsAPI,
     gfx_receive: Receiver<graphics::GraphicsCommand>,
 
@@ -87,6 +89,8 @@ impl ScriptContext {
             .get_export(&context, "draw")
             .expect("Unable to fetch draw");
 
+        let state = context.undefined();
+
         ScriptContext {
             context,
 
@@ -94,6 +98,8 @@ impl ScriptContext {
             update,
             draw,
 
+            state,
+
             gfx,
             gfx_receive,
 
@@ -109,7 +115,8 @@ impl ScriptContext {
     pub fn init(&mut self) {
         let _span = span!("script init");
 
-        self.init
+        self.state = self
+            .init
             .call(&self.context, &[])
             .expect("Exception in init");
     }
@@ -140,8 +147,10 @@ impl ScriptContext {
         // Now run the update function.
         {
             let _span = span!("javascript update");
-            self.update
-                .call(&self.context, &[])
+            let old_state = &self.state;
+            self.state = self
+                .update
+                .call(&self.context, &[old_state])
                 .expect("Exception in update");
         }
     }
@@ -150,7 +159,7 @@ impl ScriptContext {
         let _span = span!("script render");
 
         self.draw
-            .call(&self.context, &[])
+            .call(&self.context, &[&self.state])
             .expect("Exception in draw");
         self.gfx.end_frame();