Reload the live preview when the app is restarted.

frontend/components/editor/index.tsx

@@ -106,6 +106,13 @@ export default function CodeEditor({
   // Preview state
   const [previewURL, setPreviewURL] = useState<string>("");
 
+  const loadPreviewURL = (url: string) => {
+    // This will cause a reload if previewURL changed.
+    setPreviewURL(url);
+    // If the URL didn't change, still reload the preview.
+    previewWindowRef.current?.refreshIframe();
+  }
+
   const isOwner = sandboxData.userId === userData.id
   const clerk = useClerk()
 
@@ -131,6 +138,7 @@ export default function CodeEditor({
   const generateWidgetRef = useRef<HTMLDivElement>(null)
   const previewPanelRef = useRef<ImperativePanelHandle>(null)
   const editorPanelRef = useRef<ImperativePanelHandle>(null)
+  const previewWindowRef = useRef<{ refreshIframe: () => void }>(null)
 
   // Pre-mount editor keybindings
   const handleEditorWillMount: BeforeMount = (monaco) => {
@@ -467,7 +475,7 @@ export default function CodeEditor({
     socketRef.current?.on("error", onError)
     socketRef.current?.on("terminalResponse", onTerminalResponse)
     socketRef.current?.on("disableAccess", onDisableAccess)
-    socketRef.current?.on("previewURL", setPreviewURL)
+    socketRef.current?.on("previewURL", loadPreviewURL)
 
     return () => {
       socketRef.current?.off("connect", onConnect)
@@ -476,7 +484,7 @@ export default function CodeEditor({
       socketRef.current?.off("error", onError)
       socketRef.current?.off("terminalResponse", onTerminalResponse)
       socketRef.current?.off("disableAccess", onDisableAccess)
-      socketRef.current?.off("previewURL", setPreviewURL)
+      socketRef.current?.off("previewURL", loadPreviewURL)
     }
     // }, []);
   }, [terminals])
@@ -824,7 +832,7 @@ export default function CodeEditor({
                   open={() => {
                     usePreview().previewPanelRef.current?.expand()
                     setIsPreviewCollapsed(false)
-                  } } collapsed={isPreviewCollapsed} src={previewURL}/>
+                  } } collapsed={isPreviewCollapsed} src={previewURL} ref={previewWindowRef} />
               </ResizablePanel>
               <ResizableHandle />
               <ResizablePanel

frontend/components/editor/navbar/run.tsx

@@ -37,6 +37,8 @@ export default function RunButtonModal({
 
       if (terminals.length < 4) {
         createNewTerminal("yarn install && yarn start");
+        // For testing:
+        //createNewTerminal("echo http://localhost:3000");
       } else {
         toast.error("You reached the maximum # of terminals.");
         console.error('Maximum number of terminals reached.');

frontend/components/editor/preview/index.tsx

@@ -5,10 +5,10 @@ import {
   RotateCw,
   TerminalSquare,
 } from "lucide-react"
-import { useRef, useState } from "react"
+import { useEffect, useRef, useState, useImperativeHandle, forwardRef } from "react"
 import { toast } from "sonner"
 
-export default function PreviewWindow({
+export default forwardRef(function PreviewWindow({
   collapsed,
   open,
   src
@@ -16,9 +16,19 @@ export default function PreviewWindow({
   collapsed: boolean
   open: () => void
   src: string
-}) {
-  const ref = useRef<HTMLIFrameElement>(null)
+},
+ref: React.Ref<{
+  refreshIframe: () => void
+}>) {
+  const frameRef = useRef<HTMLIFrameElement>(null)
   const [iframeKey, setIframeKey] = useState(0)
+  const refreshIframe = () => {
+    setIframeKey(prev => prev + 1)
+  }
+  // Refresh the preview when the URL changes. 
+  useEffect(refreshIframe, [src])
+  // Expose refreshIframe method to the parent.
+  useImperativeHandle(ref, () => ({ refreshIframe }))
 
   return (
     <>
@@ -49,14 +59,7 @@ export default function PreviewWindow({
                 >
                   <Link className="w-4 h-4" />
                 </PreviewButton>
-                <PreviewButton
-                  onClick={() => {
-                    // if (ref.current) {
-                    //   ref.current.contentWindow?.location.reload();
-                    // }
-                    setIframeKey((prev) => prev + 1)
-                  }}
-                >
+                <PreviewButton onClick={refreshIframe}>
                   <RotateCw className="w-3 h-3" />
                 </PreviewButton>
               </>
@@ -68,7 +71,7 @@ export default function PreviewWindow({
         <div className="w-full grow rounded-md overflow-hidden bg-foreground">
           <iframe
             key={iframeKey}
-            ref={ref}
+            ref={frameRef}
             width={"100%"}
             height={"100%"}
             src={src}
@@ -77,7 +80,7 @@ export default function PreviewWindow({
       )}
     </>
   )
-}
+})
 
 function PreviewButton({
   children,