outsource async fetching

www/js/main.js

@@ -2,18 +2,31 @@ import { Smc } from "./smc/smc.js"
 
 main();
 
+async function fetchShader(uri, delegate) {
+  const res = await fetch(uri);
+  if (res.ok)
+    return await res.text();
+  this.raiseError(
+    SmcErr.FETCH_SHADER,
+    `Failed to load shader source ${url}: ${res.status} ${res.json()}`);
+  return ""
+}
+
+
 function main() {
   const canvas = document.querySelector("#gl-canvas");
   canvas.setAttribute('width', window.innerWidth);
   canvas.setAttribute('height', window.innerHeight);
 
-  new Smc(canvas)
-    .setMaxFps(30)
-    .setProgram(builder =>
-      builder
-      // .fetchVertexShader("../shaders/segfault.glsl")
-      // .fetchFragmentShader("../shaders/segfault.glsl"))
-    )
-    .run();
+
+  fetchShader("../shaders/segfault.glsl")
+    .then(frag =>
+      new Smc(canvas)
+        .setMaxFps(30)
+        .setProgram(builder =>
+          builder
+            .addFragmentShader(frag))
+        .run()
+    );
 }