From 74cce164a329cc110d8eb2a959391d7b3bbba2ab Mon Sep 17 00:00:00 2001
From: "Manu Mtz.-Almeida" <manu.mtza@gmail.com>
Date: Thu, 8 Feb 2018 17:05:16 +0100
Subject: [PATCH] feat(tabs): adds lazy loading

---
 packages/core/src/components.d.ts             |  5 +++
 .../core/src/components/content/content.tsx   |  2 +-
 .../components/nav/test/routing/index.html    |  3 +-
 .../core/src/components/router/router.tsx     |  4 ++
 packages/core/src/components/tab/readme.md    | 24 +++++++++++
 packages/core/src/components/tab/tab.tsx      | 40 ++++++++++++++++++-
 .../src/components/tabs/test/basic/index.html | 20 +++-------
 7 files changed, 80 insertions(+), 18 deletions(-)

diff --git a/packages/core/src/components.d.ts b/packages/core/src/components.d.ts
index 040d8f7ca5..3ab8c6e870 100644
--- a/packages/core/src/components.d.ts
+++ b/packages/core/src/components.d.ts
@@ -40,6 +40,9 @@ import {
 import {
   SelectPopoverOption,
 } from './components/select-popover/select-popover';
+import {
+  FrameworkDelegate as FrameworkDelegate2,
+} from '.';
 import {
   DomRenderFn,
   HeaderFn,
@@ -2995,6 +2998,8 @@ declare global {
       badge?: string;
       badgeStyle?: string;
       btnId?: string;
+      component?: any;
+      delegate?: FrameworkDelegate;
       disabled?: boolean;
       icon?: string;
       path?: string;
diff --git a/packages/core/src/components/content/content.tsx b/packages/core/src/components/content/content.tsx
index 29a48415f2..58914fd51b 100644
--- a/packages/core/src/components/content/content.tsx
+++ b/packages/core/src/components/content/content.tsx
@@ -102,7 +102,7 @@ export class Content {
       });
     } else {
       this.cTop = this.cBottom = null;
-      this.dom.write(() => this.scrollEl.removeAttribute('style'));
+      this.dom.write(() => this.scrollEl && this.scrollEl.removeAttribute('style'));
     }
   }
 
diff --git a/packages/core/src/components/nav/test/routing/index.html b/packages/core/src/components/nav/test/routing/index.html
index e1017d1a46..38160b8371 100644
--- a/packages/core/src/components/nav/test/routing/index.html
+++ b/packages/core/src/components/nav/test/routing/index.html
@@ -13,11 +13,12 @@
   <ion-app>
 
     <ion-router>
+
       <ion-route path="/" component="page-one">
         <ion-route path="/nested" component="page-nested-one"></ion-route>
         <ion-route path="/nestes2" component="page-nested-two"></ion-route>
       </ion-route>
-      
+
       <ion-route path="/two" component="page-two"></ion-route>
     </ion-router>
 
diff --git a/packages/core/src/components/router/router.tsx b/packages/core/src/components/router/router.tsx
index 1c2db9f5f8..5e1076a0b4 100644
--- a/packages/core/src/components/router/router.tsx
+++ b/packages/core/src/components/router/router.tsx
@@ -88,4 +88,8 @@ export class Router {
   private readPath(): string[] | null {
     return readPath(window.location, this.base, this.useHash);
   }
+
+  render() {
+    return <slot/>;
+  }
 }
diff --git a/packages/core/src/components/tab/readme.md b/packages/core/src/components/tab/readme.md
index 83a70114fd..f4679940bd 100644
--- a/packages/core/src/components/tab/readme.md
+++ b/packages/core/src/components/tab/readme.md
@@ -71,6 +71,18 @@ string
 Set the root page for this tab.
 
 
+#### component
+
+any
+
+The badge for the tab button.
+
+
+#### delegate
+
+
+
+
 #### disabled
 
 boolean
@@ -142,6 +154,18 @@ string
 Set the root page for this tab.
 
 
+#### component
+
+any
+
+The badge for the tab button.
+
+
+#### delegate
+
+
+
+
 #### disabled
 
 boolean
diff --git a/packages/core/src/components/tab/tab.tsx b/packages/core/src/components/tab/tab.tsx
index 6c80c4a17f..6fe90e2d13 100644
--- a/packages/core/src/components/tab/tab.tsx
+++ b/packages/core/src/components/tab/tab.tsx
@@ -1,12 +1,14 @@
 import { Component, Element, Event, EventEmitter, Method, Prop, State, Watch } from '@stencil/core';
 
 import { getNavAsChildIfExists } from '../../utils/helpers';
+import { FrameworkDelegate } from '../..';
 
 @Component({
   tag: 'ion-tab',
 })
 export class Tab {
 
+  private loaded = false;
   @Element() el: HTMLElement;
 
   @State() init = false;
@@ -37,6 +39,11 @@ export class Tab {
    */
   @Prop() badge: string;
 
+  /**
+   * The badge for the tab button.
+   */
+  @Prop() component: any;
+
   /**
    * The badge color for the tab button.
    */
@@ -58,6 +65,7 @@ export class Tab {
    */
   @Prop() tabsHideOnSubPages = false;
 
+  @Prop() delegate: FrameworkDelegate;
 
   @Prop({ mutable: true }) selected = false;
 
@@ -76,6 +84,25 @@ export class Tab {
   @Method()
   setActive(active: boolean): Promise<any> {
     this.active = active;
+    if (this.loaded || !active) {
+      return Promise.resolve();
+    }
+
+    this.loaded = true;
+
+    let promise: Promise<any>;
+    if (this.component) {
+      promise = (this.delegate)
+       ? this.delegate.attachViewToDom(this.el, this.component)
+       : attachViewToDom(this.el, this.component);
+
+    } else {
+      promise = Promise.resolve();
+    }
+    return promise.then(() => this.fireChildren());
+  }
+
+  fireChildren() {
     const nav = getNavAsChildIfExists(this.el);
     if (nav && nav.getViews().length === 0 && nav.root) {
       // we need to initialize
@@ -99,7 +126,7 @@ export class Tab {
   hostData() {
     const visible = this.active && this.selected;
     return {
-      'aria-hidden': !visible ? 'true' : null,
+      'aria-hidden': !visible,
       'aria-labelledby': this.btnId,
       'role': 'tabpanel',
       class: {
@@ -109,10 +136,19 @@ export class Tab {
   }
 
   render() {
-    return <slot></slot>;
+    return <slot/>;
   }
 }
 
+function attachViewToDom(container: HTMLElement, cmp: string): Promise<any> {
+  const el = document.createElement(cmp) as HTMLStencilElement;
+  container.appendChild(el);
+  if (el.componentOnReady ) {
+    return el.componentOnReady();
+  }
+  return Promise.resolve();
+}
+
 export interface TabEvent extends CustomEvent {
   detail: TabEventDetail;
 }
diff --git a/packages/core/src/components/tabs/test/basic/index.html b/packages/core/src/components/tabs/test/basic/index.html
index e53daae581..f800a74591 100644
--- a/packages/core/src/components/tabs/test/basic/index.html
+++ b/packages/core/src/components/tabs/test/basic/index.html
@@ -5,9 +5,7 @@
   <title>Tab - Basic</title>
   <meta name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=1.0, maximum-scale=1.0, user-scalable=no, viewport-fit=cover">
   <script src="/dist/ionic.js"></script>
-  <script type="text/javascript">
-    window.Ionic.config = {useRouter: true};
-  </script>
+  <script src="/test-components/build/app.js"></script>
 </head>
 <body>
 
@@ -52,17 +50,11 @@
         </ion-page>
       </ion-tab>
 
-      <ion-tab title="Messages" icon="chatboxes" path="tab4">
-        <ion-page>
-          <ion-header>
-            <ion-toolbar>
-              <ion-title>Tab Four</ion-title>
-            </ion-toolbar>
-          </ion-header>
-          <ion-content padding>
-            Tab Four
-          </ion-content>
-        </ion-page>
+      <ion-tab
+        title="Messages"
+        icon="chatboxes"
+        component="page-one"
+        path="tab4">
       </ion-tab>
     </ion-tabs>
   </ion-app>