Uninitialized canvas display

vweb/src/emulator_display.jsx

@@ -0,0 +1,17 @@
+import React, { useState, useCallback, useEffect, useRef } from 'react'
+import { WasmCPU } from '../pkg/vweb.js'
+
+export default function({}) {
+    const canvas = useRef(null)
+    const [ctx, setCtx] = useState(null)
+    const [cpu, _setCpu] = useState(new WasmCPU())
+
+    useEffect(() => {
+        const c = canvas.current.getContext('2d')
+        setCtx(c)
+        cpu.draw_frame(c)
+    }, [canvas.current])
+    return (
+        <canvas ref={canvas} width={640} height={480}></canvas>
+    )
+}