No previous from tap on card on desktop

extensions/amp-story/0.1/amp-story-page.js

@@ -112,6 +112,8 @@ export class AmpStoryPage extends AMP.BaseElement {
     this.advancement_.addPreviousListener(() => this.previous());
     this.advancement_
         .addAdvanceListener(() => this.next(/* opt_isAutomaticAdvance */ true));
+    this.advancement_.addOnTapNavigationListener(
+        navigationDirection => this.navigate(navigationDirection));
     this.advancement_
         .addProgressListener(progress => this.emitProgress_(progress));
   }
@@ -404,7 +406,6 @@ export class AmpStoryPage extends AMP.BaseElement {
     return this.element.hasAttribute('active');
   }
 
-
   /**
    * Emits an event indicating that the progress of the current page has changed
    * to the specified value.
@@ -524,6 +525,17 @@ export class AmpStoryPage extends AMP.BaseElement {
     this.switchTo_(pageId);
   }
 
+  /**
+   * Delegated the navigation decision to AMP-STORY via event.
+   * @param {number} direction The direction in which navigation needs to takes place.
+   */
+  navigate(direction) {
+    const payload = {direction};
+    const eventInit = {bubbles: true};
+    dispatchCustom(this.win, this.element, EventType.TAP_NAVIGATION, payload,
+        eventInit);
+  }
+
 
   /**
    * @param {string} targetPageId

extensions/amp-story/0.1/amp-story.js

@@ -70,7 +70,7 @@ import {dict} from '../../../src/utils/object';
 import {renderSimpleTemplate} from './simple-template';
 import {MediaPool, MediaType} from './media-pool';
 import {PaginationButtons} from './pagination-buttons';
-
+import {TapNavigationDirection} from './page-advancement';
 
 
 /** @private @const {string} */
@@ -345,6 +345,21 @@ export class AmpStory extends AMP.BaseElement {
       this.ampStoryHint_.showFirstPageHintOverlay();
     });
 
+    this.element.addEventListener(EventType.TAP_NAVIGATION, e => {
+      const {direction} = e.detail;
+
+      if (this.isDesktop_()) {
+        this.next_();
+        return;
+      }
+
+      if (direction === TapNavigationDirection.NEXT) {
+        this.next_();
+      } else {
+        this.previous_();
+      }
+    });
+
     const gestures = Gestures.get(this.element,
         /* shouldNotPreventDefault */ true);
 

extensions/amp-story/0.1/events.js

@@ -46,6 +46,9 @@ export const EventType = {
   // Triggered when the story should switch to the next page
   NEXT_PAGE: 'ampstory:nextpage',
 
+  // Triggered when the story should navigate after a tap on active page.
+  TAP_NAVIGATION: 'ampstory:tapnavigation',
+
   // Triggered when a page updates its progress
   PAGE_PROGRESS: 'ampstory:pageprogress',
 

extensions/amp-story/0.1/page-advancement.js

@@ -28,6 +28,11 @@ const NEXT_SCREEN_AREA_RATIO = 0.75;
 /** @const {number} */
 const POLL_INTERVAL_MS = 250;
 
+/** @const @enum */
+export const TapNavigationDirection = {
+  'NEXT': 1,
+  'PREVIOUS': 2,
+};
 
 /**
  * Base class for the AdvancementConfig.  By default, does nothing other than
@@ -45,6 +50,9 @@ export class AdvancementConfig {
     /** @private @const {!Array<function()>} */
     this.previousListeners_ = [];
 
+    /** @private @const {!Array<function(number)>} */
+    this.tapNavigationListeners_ = [];
+
     /** @private {boolean} */
     this.isRunning_ = false;
   }
@@ -75,6 +83,14 @@ export class AdvancementConfig {
     this.previousListeners_.push(previousListener);
   }
 
+  /**
+   * @param {function(number)} onTapNavigationListener A function that handles when a
+   * navigation listener to be fired.
+   */
+  addOnTapNavigationListener(onTapNavigationListener) {
+    this.tapNavigationListeners_.push(onTapNavigationListener);
+  }
+
   /**
    * Invoked when the advancement configuration should begin taking effect.
    */
@@ -127,6 +143,16 @@ export class AdvancementConfig {
     });
   }
 
+  /**
+   * @param {number} navigationDirection Direction of navigation
+   * @protected
+   */
+  onNavigate(navigationDirection) {
+    this.tapNavigationListeners_.forEach(navigationListener => {
+      navigationListener(navigationDirection);
+    });
+  }
+
   /**
    * Provides an AdvancementConfig object for the specified amp-story-page.
    * @param {!./amp-story-page.AmpStoryPage} page
@@ -287,9 +313,9 @@ class ManualAdvancement extends AdvancementConfig {
     const nextScreenAreaMax = offsetLeft + offsetWidth;
 
     if (event.pageX >= nextScreenAreaMin && event.pageX < nextScreenAreaMax) {
-      this.onAdvance();
+      this.onNavigate(TapNavigationDirection.NEXT);
     } else if (event.pageX >= offsetLeft && event.pageX < nextScreenAreaMin) {
-      this.onPrevious();
+      this.onNavigate(TapNavigationDirection.PREVIOUS);
     }
   }
 }