Keep Initializr loader visible until CN1 UI ready

docs/website/layouts/_default/initializr.html

@@ -212,8 +212,26 @@
   }
 
   if (frame && loader) {
-    frame.addEventListener("load", function () {
+    var loaderHidden = false;
+    var hideLoader = function () {
+      if (loaderHidden) {
+        return;
+      }
+      loaderHidden = true;
       loader.classList.add("done");
+    };
+
+    frame.addEventListener("load", function () {
+      window.setTimeout(hideLoader, 8000);
+    });
+
+    window.addEventListener("message", function (evt) {
+      if (evt.source !== frame.contentWindow || !evt.data || evt.data.type !== "cn1-initializr-ui-ready") {
+        return;
+      }
+      window.requestAnimationFrame(function () {
+        hideLoader();
+      });
     });
   }
 })();

scripts/initializr/common/src/main/java/com/codename1/initializr/Initializr.java

@@ -150,6 +150,14 @@ public void run() {
         refresh.run();
         initWebsiteThemeSync(form);
         form.show();
+        notifyWebsiteUiReady();
+    }
+
+    private void notifyWebsiteUiReady() {
+        WebsiteThemeNative nativeBridge = NativeLookup.create(WebsiteThemeNative.class);
+        if (nativeBridge != null && nativeBridge.isSupported()) {
+            nativeBridge.notifyUiReady();
+        }
     }
 
     private Container createLocalizationPanel(boolean[] includeLocalizationBundles,

scripts/initializr/common/src/main/java/com/codename1/initializr/WebsiteThemeNative.java

@@ -4,4 +4,5 @@
 
 public interface WebsiteThemeNative extends NativeInterface {
     boolean isDarkMode();
+    void notifyUiReady();
 }

scripts/initializr/javascript/src/main/javascript/com_codename1_initializr_WebsiteThemeNative.js

@@ -29,6 +29,28 @@ var o = {};
         callback.complete(!!dark);
     };
 
+
+    o.notifyUiReady_ = function(callback) {
+        var sendReady = function() {
+            try {
+                if (window.parent && window.parent !== window && window.parent.postMessage) {
+                    window.parent.postMessage({ type: "cn1-initializr-ui-ready" }, "*");
+                }
+            } catch (ignored) {
+                // Ignore cross-origin or sandbox restrictions.
+            }
+            callback.complete();
+        };
+
+        if (window.requestAnimationFrame) {
+            window.requestAnimationFrame(function() {
+                window.requestAnimationFrame(sendReady);
+            });
+        } else {
+            window.setTimeout(sendReady, 48);
+        }
+    };
+
     o.isSupported_ = function(callback) {
         callback.complete(true);
     };