[amp-list-load-more] documentation, demo, bugfix, and ui tweaks

build-system/app.js

@@ -1164,6 +1164,33 @@ app.get('/dist/ww(.max)?.js', (req, res) => {
   });
 });
 
+app.get('/infinite-scroll', function(req, res) {
+  const query = {req};
+  const results = [];
+  const numberOfItems = query['items'] ? query['items'] : 10;
+  const pagesLeft = query['left'] ? query['left'] : 1;
+
+  if (pagesLeft == 0) {
+    res.json({items: []});
+  }
+
+  for (let i = 0; i < numberOfItems; i++) {
+    const imageUrl = 'http://picsum.photos/200?' +
+        Math.floor(Math.random() * Math.floor(50));
+    const r = {
+      'title': 'Item ' + i,
+      imageUrl,
+      'price': i + 0.99,
+    };
+    results.push(r);
+  }
+
+  const nextUrl = '/infinite-scroll?items=' +
+    numberOfItems + '&left=' + JSON.stringify(pagesLeft - 1);
+  res.json({'items': results, 'next': nextUrl});
+});
+
+
 /**
  * Autosuggest endpoint
  */

extensions/amp-list/0.1/amp-list.js

@@ -119,8 +119,6 @@ export class AmpList extends AMP.BaseElement {
     this.loadMoreLoadingElement_ = null;
     /** @private {?Element} */
     this.loadMoreFailedElement_ = null;
-    /** @private {?Element} */
-    this.loadMoreOverflowElement_ = null;
     /** @private {?../../../src/service/position-observer/position-observer-impl.PositionObserver} */
     this.positionObserver_ = null;
 
@@ -184,9 +182,9 @@ export class AmpList extends AMP.BaseElement {
     });
 
     if (this.loadMoreEnabled_) {
-      this.getLoadMoreOverflowElement_();
+      this.getLoadMoreOverflow_();
       this.getLoadMoreLoadingElement_();
-      if (!this.loadMoreLoadingElement_) {
+      if (!this.loadMoreLoadingOverlay_) {
         this.getLoadMoreLoadingOverlay_();
       }
       this.getLoadMoreFailedElement_();
@@ -197,12 +195,12 @@ export class AmpList extends AMP.BaseElement {
    * @private
    * @return {!Element|null}
    */
-  getLoadMoreOverflowElement_() {
+  getLoadMoreOverflow_() {
     if (!this.loadMoreOverflow_) {
       this.loadMoreOverflow_ = childElementByAttr(
           this.element, 'load-more-button');
     }
-    return this.loadMoreOverflowElement_;
+    return this.loadMoreOverflow_;
   }
 
   /** @override */
@@ -373,13 +371,32 @@ export class AmpList extends AMP.BaseElement {
           items = items.slice(0, maxLen);
         }
         return this.scheduleRender_(/** @type {!Array} */(items), !!opt_append);
-      }, error => {
-        throw user().createError('Error fetching amp-list', error);
       });
     }
-    return fetch.catch(error => this.showFallback_(error));
+
+    return fetch.catch(error => {
+      if (opt_append) {
+        this.handleLoadMoreFailed_();
+      } else {
+        this.showFallback_(error);
+      }
+    });
   }
 
+  /**
+   * When the fetch fails, we should show the "load-failed" element if
+   * one exists, otherwise show the overflow element that triggers a new
+   * fetch on click.
+   * @private
+   */
+  handleLoadMoreFailed_() {
+    if (this.loadMoreFailedElement_) {
+      this.setLoadMoreFailed_();
+    } else {
+      // TODO (#14060): implement reload for append after failed load
+      this.setLoadMoreReload_();
+    }
+  }
   /**
    * Proxies the template rendering to the viewer.
    * @param {boolean} refresh
@@ -692,6 +709,29 @@ export class AmpList extends AMP.BaseElement {
     }
   }
 
+  /**
+   * @private
+   */
+  setLoadMoreReload_() {
+    if (this.loadMoreOverflow_) {
+      this.mutateElement(() => {
+        this.loadMoreOverflow_.classList.toggle('amp-visible', true);
+        listen(this.loadMoreOverflow_, 'click',
+            () => this.loadMoreReloadCallback_());
+      });
+    }
+  }
+
+  /**
+   * @return {!Promise}
+   * @private
+   */
+  loadMoreReloadCallback_() {
+    this.toggleLoadMoreLoading_(true);
+    return this.fetchList_(/* opt_append */ true)
+        .then(() => this.toggleLoadMoreLoading_(false));
+  }
+
   /**
    * @private
    */
@@ -706,7 +746,6 @@ export class AmpList extends AMP.BaseElement {
     this.loadMoreSrc_ = null;
     this.toggleLoadMoreLoading_(true);
     return this.fetchList_(/* opt_append */ true)
-        .catch(() => this.setLoadMoreFailed_())
         .then(() => this.toggleLoadMoreLoading_(false));
   }
 
@@ -805,7 +844,7 @@ export class AmpList extends AMP.BaseElement {
       this.positionObserver_.observe(this.container_,
           PositionObserverFidelity.LOW,
           ({positionRect, viewportRect}) => {
-            const ratio = 1.5;
+            const ratio = 3;
             if (this.loadMoreSrc_ &&
                 positionRect.bottom < ratio * viewportRect.bottom) {
               this.loadMoreCallback_();

extensions/amp-list/amp-list.md

@@ -99,9 +99,9 @@ Here is how we styled the content fetched:
     amp-list div[role="list"] {
       display: grid;
       grid-gap: 0.5em;
-    } 
+    }
 ```
-    
+
 ## Behavior
 
 The request is always made from the client, even if the document was served from the AMP Cache. Loading is triggered using normal AMP rules depending on how far the element is from
@@ -261,6 +261,35 @@ We recommend using `binding="no"` or `binding="refresh"` for faster performance.
 
 If `binding` attribute is not provided, default is `always`.
 
+## Experimental: Infinite Scroll (amp-list-load-more)
+We've introduced an experiment called `amp-list-load-more` as an implementation for pagination and infinite scroll in amp-list. This is an experimental feature, and final APIs may change.
+
+### Attributes
+#### load-more (mandatory)
+Adding this attribute will allow amp-list (with no value) to show a “load-more” button at the end of the amp-list. The value of this attribute can be set to “auto” to trigger automatic loading more elements three viewports down for an infinite scroll effect.
+
+#### load-more-bookmark (mandatory)
+This attribute specifies an attribute in the returned data that will give the url of the next items to load. E.g. In the following sample payload, we would specify `load-more-bookmark=”next”`.
+
+```
+{ “items”: [], “next”: “https://url.to.load” }
+```
+
+### Additional children of `<amp-list>`
+`<amp-list>` with the `load-more` attribute expects the following additional child elements:
+
+#### load-more-button (mandatory)
+An element containing the `load-more-button` attribute. Clicking on this button will trigger a fetch to load more elements from the url contained in the field of the data returned corresponding to the `load-more-bookmark` attribute.
+
+In the case of `load-more=”auto”`, or infinite scroll, this button will show up if the user has reached the end of the list but the contents are still loading.
+
+#### load-more-failed (optional)
+An element containing the `load-more-failed` attribute. This element will be displayed at the bottom of the `<amp-list>` if loading failed. If this element is not provided, the `load-more-button` element will be displayed and clicking on it will result in an attempt to re-fetch data from the last (failed) url.
+
+#### .amp-load-more-loading (css class)
+This class is applied to the element with the `load-more-button` attribute while the data is loading. This can be used to tweak the visual appearance of the load-more-button (e.g. show a loader) when the `<amp-list>` is in the middle of loading data.
+
+
 ##### common attributes
 
 This element includes [common attributes](https://www.ampproject.org/docs/reference/common_attributes) extended to AMP components.

test/manual/amp-list/infinite-scroll-1.amp.html

@@ -0,0 +1,89 @@
+<!doctype html>
+<html ⚡>
+<head>
+  <meta charset="utf-8">
+  <title>AMP #0</title>
+  <link rel="canonical" href="amps.html" >
+  <meta name="viewport" content="width=device-width,minimum-scale=1,initial-scale=1">
+  <link href='https://fonts.googleapis.com/css?family=Questrial' rel='stylesheet' type='text/css'>
+  <style amp-custom>
+    body {
+      font-family: 'Questrial', Arial;
+    }
+    article {
+      display: block;
+      margin: 8px;
+    }
+    amp-list {
+      border: 1px solid green;
+    }
+    [load-more-button], [load-more-failed], [load-more-loading] {
+      background: gray;
+      color: #fff;
+      cursor: pointer;
+      position: absolute;
+      bottom: 0;
+      left: 0;
+      right: 0;
+      z-index: 2;
+      padding: 16px;
+    }
+
+    .amp-load-more-loading {
+      background: red;
+    }
+    .story-entry {
+      padding: 40px;
+      border: 1px solid gray;
+      text-align: center;
+      border-radius: 8px;
+
+    }
+
+    div[role="list"] {
+      display: flex;
+      flex-wrap: wrap;
+      flex-direction: row;
+      align-items: flex-start;
+      justify-content: center;
+    }
+
+  </style>
+  <style amp-boilerplate>body{-webkit-animation:-amp-start 8s steps(1,end) 0s 1 normal both;-moz-animation:-amp-start 8s steps(1,end) 0s 1 normal both;-ms-animation:-amp-start 8s steps(1,end) 0s 1 normal both;animation:-amp-start 8s steps(1,end) 0s 1 normal both}@-webkit-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-moz-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-ms-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-o-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}</style><noscript><style amp-boilerplate>body{-webkit-animation:none;-moz-animation:none;-ms-animation:none;animation:none}</style></noscript>
+  <script async src="https://cdn.ampproject.org/v0.js"></script>
+  <script async custom-element="amp-list" src="https://cdn.ampproject.org/v0/amp-list-0.1.js"></script>
+  <script async custom-template="amp-mustache" src="https://cdn.ampproject.org/v0/amp-mustache-latest.js"></script>
+</head>
+<body>
+<article>
+  <h1>AMP List</h1>
+  <p>This is a flexbox amp-list with tiles, something like an infinite image gallery.</p>
+
+  <amp-list width="auto" height="200"
+    layout="fixed-height"
+    src="/infinite-scroll?items=5&left=3"
+    load-more="auto"
+    load-more-bookmark="next">
+    <template type="amp-mustache">
+      <div class="story-entry">
+        <amp-img src="{{imageUrl}}" width="160" height="160"></amp-img>
+        <div><a href="/link.html">{{title}}</a></div>
+      </div>
+    </template>
+    <div load-more-button>
+      SEE MORE
+    </div>
+    <div load-more-failed>
+      LOAD FAILED
+    </div>
+    <div fallback>
+      FALLBACK
+    </div>
+    <div load-more-loading>
+      LOADING
+    </div>
+  </amp-list>
+
+</article>
+</body>
+</html>

test/manual/amp-list/infinite-scroll-2.amp.html

@@ -0,0 +1,86 @@
+<!doctype html>
+<html ⚡>
+<head>
+  <meta charset="utf-8">
+  <title>AMP #0</title>
+  <link rel="canonical" href="amps.html" >
+  <meta name="viewport" content="width=device-width,minimum-scale=1,initial-scale=1">
+  <link href='https://fonts.googleapis.com/css?family=Questrial' rel='stylesheet' type='text/css'>
+  <style amp-custom>
+    body {
+      font-family: 'Questrial', Arial;
+    }
+    article {
+      display: block;
+      margin: 8px;
+    }
+    amp-list {
+      border: 1px solid green;
+    }
+    [load-more-button], [load-more-failed] {
+      background: gray;
+      color: #fff;
+      cursor: pointer;
+      position: absolute;
+      bottom: 0;
+      left: 0;
+      right: 0;
+      z-index: 2;
+      padding: 16px;
+    }
+
+    .amp-load-more-loading {
+      background: red;
+    }
+    .story-entry {
+      padding: 40px;
+      border: 1px solid gray;
+      text-align: center;
+      border-radius: 8px;
+
+    }
+
+    div[role="list"] {
+      display: flex;
+      flex-wrap: wrap;
+      flex-direction: row;
+      align-items: flex-start;
+      justify-content: center;
+    }
+
+  </style>
+  <style amp-boilerplate>body{-webkit-animation:-amp-start 8s steps(1,end) 0s 1 normal both;-moz-animation:-amp-start 8s steps(1,end) 0s 1 normal both;-ms-animation:-amp-start 8s steps(1,end) 0s 1 normal both;animation:-amp-start 8s steps(1,end) 0s 1 normal both}@-webkit-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-moz-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-ms-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-o-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}</style><noscript><style amp-boilerplate>body{-webkit-animation:none;-moz-animation:none;-ms-animation:none;animation:none}</style></noscript>
+  <script async src="https://cdn.ampproject.org/v0.js"></script>
+  <script async custom-element="amp-list" src="https://cdn.ampproject.org/v0/amp-list-0.1.js"></script>
+  <script async custom-template="amp-mustache" src="https://cdn.ampproject.org/v0/amp-mustache-latest.js"></script>
+</head>
+<body>
+<article>
+  <h1>AMP List</h1>
+  <p>This is a flexbox amp-list with tiles, something like an infinite image gallery.</p>
+
+  <amp-list width="auto" height="200"
+    layout="fixed-height"
+    src="/infinite-scroll?items=5&left=3"
+    load-more="auto"
+    load-more-bookmark="next">
+    <template type="amp-mustache">
+      <div class="story-entry">
+        <amp-img src="{{imageUrl}}" width="160" height="160"></amp-img>
+        <div><a href="/link.html">{{title}}</a></div>
+      </div>
+    </template>
+    <div overflow>
+      OVERFLOW
+    </div>
+    <div load-more-button>
+      SEE MORE
+    </div>
+    <div fallback>
+      FALLBACK
+    </div>
+  </amp-list>
+
+</article>
+</body>
+</html>