extensions: Add PlaceholdersExtension

dumbo-extensions/src/main/java/com/kohlschutter/dumbo/placeholders/PlaceholdersExtension.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2022,2023 Christian Kohlschütter
+ * Copyright 2014,2015 Evernote Corporation.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.kohlschutter.dumbo.placeholders;
+
+import com.kohlschutter.dumbo.annotations.CSSResource;
+import com.kohlschutter.dumbo.annotations.JavaScriptResource;
+import com.kohlschutter.dumbo.api.DumboComponent;
+
+/**
+ * Improves handling of placeholder resources
+ */
+@CSSResource(value = "css/placeholders.css", group = "dumbo")
+@JavaScriptResource(value = "js/placeholders.js", group = "dumbo", async = true)
+public interface PlaceholdersExtension extends DumboComponent {
+}

dumbo-extensions/src/main/resources/com/kohlschutter/dumbo/placeholders/webapp/css/placeholders.css

@@ -0,0 +1,7 @@
+BODY:not([class*=dumbo-ready]) .dumbo-placeholder {
+ opacity: 0;
+}
+
+BODY[class*=dumbo-ready]:not([class*=static-design-mode]) .dumbo-placeholder {
+ transition: opacity 0.33s ease-in;
+}

dumbo-extensions/src/main/resources/com/kohlschutter/dumbo/placeholders/webapp/js/placeholders.js

@@ -0,0 +1,6 @@
+Dumbo.whenReady(function() {
+ setTimeout(() => document.body.classList.add("dumbo-ready"), 0);
+});
+Dumbo.whenStatic(function() {
+ document.body.classList.add("dumbo-ready");
+});