add simple-host example

examples/simple-host/src/sandbox.ts

@@ -0,0 +1,41 @@
+// Double-iframe raw HTML mode (HTML sent via postMessage)
+const inner = document.createElement("iframe");
+inner.style = "width:100%; height:100%; border:none;";
+// sandbox will be set from postMessage payload; default minimal before html arrives
+inner.setAttribute("sandbox", "allow-scripts allow-same-origin allow-forms");
+document.body.appendChild(inner);
+
+// Wait for HTML content from parent
+window.addEventListener("message", async (event) => {
+  if (event.source === window.parent) {
+    if (
+      event.data &&
+      event.data.method === "ui/notifications/sandbox-resource-ready"
+    ) {
+      const { html, sandbox } = event.data.params;
+      if (typeof sandbox === "string") {
+        inner.setAttribute("sandbox", sandbox);
+      }
+      if (typeof html === "string") {
+        inner.srcdoc = html;
+      }
+    } else {
+      if (inner && inner.contentWindow) {
+        inner.contentWindow.postMessage(event.data, "*");
+      }
+    }
+  } else if (event.source === inner.contentWindow) {
+    // Relay messages from inner to parent
+    window.parent.postMessage(event.data, "*");
+  }
+});
+
+// Notify parent that proxy is ready to receive HTML (distinct event)
+window.parent.postMessage(
+  {
+    jsonrpc: "2.0",
+    method: "ui/notifications/sandbox-proxy-ready",
+    params: {},
+  },
+  "*",
+);