[ADF-2032] viewer reopening fixes (#2739)

* viewer reopening fixes

* docs update

demo-shell/src/app/components/overlay-viewer/overlay-viewer.component.html

@@ -0,0 +1,12 @@
+<h1>Overlay Viewer</h1>
+
+<adf-document-list
+    currentFolderId="-my-"
+    (preview)="showPreview($event)">
+</adf-document-list>
+
+<adf-viewer
+    [(showViewer)]="showViewer"
+    [overlayMode]="true"
+    [fileNodeId]="nodeId">
+</adf-viewer>

demo-shell/src/app/components/overlay-viewer/overlay-viewer.component.ts

@@ -0,0 +1,36 @@
+/*!
+ * @license
+ * Copyright 2016 Alfresco Software, Ltd.
+ *
+ * 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.
+ */
+
+import { Component, Input } from '@angular/core';
+
+@Component({
+    templateUrl: 'overlay-viewer.component.html'
+})
+export class OverlayViewerComponent {
+
+    @Input()
+    showViewer: boolean = false;
+
+    nodeId: string;
+
+    showPreview(event) {
+        if (event.value.entry.isFile) {
+            this.nodeId = event.value.entry.id;
+            this.showViewer = true;
+        }
+    }
+}