feat(1-on-1): Initial implementation

- Expose an api on Filmstrip to hide the remote videos container, which does so
  by adding a class
- Modify listeners for user join, leave, share video to call the api
- Hide the container when there is 1 or fewer remote participants
- Always show the container if self view is in focus
- Show the container if the number of remote thumbnails does not match the count
  of remote participants, such as the case of sharing a video

conference.js

 
             // check the roles for the new user and reflect them
             APP.UI.updateUserRole(user);
+
+            updateRemoteThumbnailsVisibility();
         });
         room.on(ConferenceEvents.USER_LEFT, (id, user) => {
             APP.store.dispatch(participantLeft(id, user));
             APP.API.notifyUserLeft(id);
             APP.UI.removeUser(id, user.getDisplayName());
             APP.UI.onSharedVideoStop(id);
+
+            updateRemoteThumbnailsVisibility();
         });
 
         room.on(ConferenceEvents.USER_STATUS_CHANGED, (id, status) => {
                         reportError(e);
                     }
                 }
+
+                updateRemoteThumbnailsVisibility();
             });
         }
 
                     }
                 });
             }
+
+            updateRemoteThumbnailsVisibility();
         });
         room.addCommandListener(
             this.commands.defaults.SHARED_VIDEO, ({value, attributes}, id) => {
                     APP.UI.onSharedVideoUpdate(id, value, attributes);
                 }
             });
+
+        function updateRemoteThumbnailsVisibility() {
+            const localUserId = APP.conference.getMyUserId();
+            const remoteParticipantsCount = room.getParticipantCount() - 1;
+
+            // Get the remote thumbnail count for cases where there are
+            // non-participants displaying video, such as with video sharing.
+            const remoteVideosCount = APP.UI.getRemoteVideosCount();
+
+            const shouldShowRemoteThumbnails = APP.UI.isPinned(localUserId)
+                || remoteVideosCount > 1
+                || remoteParticipantsCount !== remoteVideosCount;
+
+            APP.UI.setRemoteThumbnailsVisibility(shouldShowRemoteThumbnails);
+        }
     },
     /**
     * Adds any room listener.

config.js

     webrtcIceTcpDisable: false,
 
     openSctp: true, // Toggle to enable/disable SCTP channels
+
+    // Disable hiding of remote thumbnails when in a 1-on-1 conference call.
+    disable1On1Mode: false,
     disableStats: false,
     disableAudioLevels: false,
     channelLastN: -1, // The default value of the channel attribute last-n.

css/_filmstrip.scss

         margin-bottom: auto;
         padding-right: $defaultToolbarSize;
     }
+
+    .remote-videos-container {
+        transition: opacity 1s;
+
+        &.hide-videos {
+            opacity: 0;
+            pointer-events: none;
+        }
+    }
 }

modules/UI/UI.js

     SideContainerToggler.init(eventEmitter);
     Filmstrip.init(eventEmitter);
 
+    // By default start with remote videos hidden and rely on other logic to
+    // make them visible.
+    UI.setRemoteThumbnailsVisibility(false);
+
     VideoLayout.init(eventEmitter);
     if (!interfaceConfig.filmStripOnly) {
         VideoLayout.initLargeVideo();
     return VideoLayout.getLargeVideo();
 };
 
+/**
+ * Returns whether or not the passed in user id is currently pinned to the large
+ * video.
+ *
+ * @param {string} userId - The id of the user to check is pinned or not.
+ * @returns {boolean} True if the user is currently pinned to the large video.
+ */
+UI.isPinned = userId => VideoLayout.getPinnedId() === userId;
+
 /**
  * Shows dialog with a link to FF extension.
  */
  */
 UI.onUserFeaturesChanged = user => VideoLayout.onUserFeaturesChanged(user);
 
+/**
+ * Returns the number of known remote videos.
+ *
+ * @returns {number} The number of remote videos.
+ */
+UI.getRemoteVideosCount = () => VideoLayout.getRemoteVideosCount();
+
+/**
+ * Makes remote thumbnail videos visible or not visible.
+ *
+ * @param {boolean} shouldHide - True if remote thumbnails should be hidden,
+ * false f they should be visible.
+ * @returns {void}
+ */
+UI.setRemoteThumbnailsVisibility
+    = shouldHide => Filmstrip.setRemoteVideoVisibility(shouldHide);
+
 const UIListeners = new Map([
     [
         UIEvents.ETHERPAD_CLICKED,

modules/UI/shared_video/SharedVideo.js

                 // revert to original behavior (prevents pausing
                 // for participants not sharing the video to pause it)
                 $("#sharedVideo").css("pointer-events","auto");
+
+                this.emitter.emit(
+                    UIEvents.UPDATE_SHARED_VIDEO, null, 'removed');
         });
 
         this.url = null;

modules/UI/videolayout/Filmstrip.js

-/* global $, APP, JitsiMeetJS, interfaceConfig */
+/* global $, APP, config, JitsiMeetJS, interfaceConfig */
 
 import UIEvents from "../../../service/UI/UIEvents";
 import UIUtil from "../util/UIUtil";
         }
     },
 
+    /**
+     * Sets a class on the remote videos container for CSS to adjust visibility
+     * of the remote videos. Will no-op if config.debug is truthy, as should be
+     * the case with torture tests.
+     *
+     * @param {boolean} shouldHide - True if remote videos should be hidden,
+     * false if they should be visible.
+     * @returns {void}
+     */
+    setRemoteVideoVisibility(shouldShow) {
+        // FIXME Checking config.debug is a grand hack to avoid fixing the
+        // torture tests after the 1-on-1 UI was implemented, which hides remote
+        // videos on 1-on-1 calls. If this check is to be kept, at least create
+        // new torture tests to verify 1-on-1 mode.
+        if (config.debug || config.disable1On1Mode) {
+            return;
+        }
+
+        this.filmstripRemoteVideos.toggleClass('hide-videos', !shouldShow);
+    },
+
     /**
      * Initializes the filmstrip toolbar.
      */

modules/UI/videolayout/VideoLayout.js

      */
     getLargeVideoWrapper() {
         return this.getCurrentlyOnLargeContainer().$wrapper;
+    },
+
+    /**
+     * Returns the number of remove video ids.
+     *
+     * @returns {number} The number of remote videos.
+     */
+    getRemoteVideosCount() {
+        return Object.keys(remoteVideos).length;
     }
 };