From 79b7e1641d87d3fa92837b1478985ab57cb89d48 Mon Sep 17 00:00:00 2001
From: Zoltan Bettenbuk <zoltan.bettenbuk@gmail.com>
Date: Sat, 7 Apr 2018 02:52:38 -0500
Subject: [PATCH] Add pinch zoom functionality

---
 react/features/base/media/actionTypes.js      |  12 +
 react/features/base/media/actions.js          |  27 +-
 .../media/components/AbstractVideoTrack.js    |  21 +-
 .../base/media/components/native/Video.js     |  32 +-
 .../media/components/native/VideoTransform.js | 714 ++++++++++++++++++
 .../base/media/components/native/styles.js    |  17 +
 react/features/base/media/reducer.js          |  83 +-
 .../components/ParticipantView.native.js      |  11 +-
 .../components/LargeVideo.native.js           |   3 +-
 9 files changed, 895 insertions(+), 25 deletions(-)
 create mode 100644 react/features/base/media/components/native/VideoTransform.js

diff --git a/react/features/base/media/actionTypes.js b/react/features/base/media/actionTypes.js
index 592644e7e..8b9866c50 100644
--- a/react/features/base/media/actionTypes.js
+++ b/react/features/base/media/actionTypes.js
@@ -49,6 +49,18 @@ export const SET_VIDEO_AVAILABLE = Symbol('SET_VIDEO_AVAILABLE');
  */
 export const SET_VIDEO_MUTED = Symbol('SET_VIDEO_MUTED');
 
+/**
+ * The type of (redux) action to store the last video {@link Transform} applied
+ * to a stream.
+ *
+ * {
+ *     type: STORE_VIDEO_TRANSFORM,
+ *     streamId: string,
+ *     transform: Transform
+ * }
+ */
+export const STORE_VIDEO_TRANSFORM = Symbol('STORE_VIDEO_TRANSFORM');
+
 /**
  * The type of (redux) action to toggle the local video camera facing mode. In
  * contrast to SET_CAMERA_FACING_MODE, allows the toggling to be optimally
diff --git a/react/features/base/media/actions.js b/react/features/base/media/actions.js
index 79a203b19..7eab0977f 100644
--- a/react/features/base/media/actions.js
+++ b/react/features/base/media/actions.js
@@ -8,6 +8,7 @@ import {
     SET_CAMERA_FACING_MODE,
     SET_VIDEO_AVAILABLE,
     SET_VIDEO_MUTED,
+    STORE_VIDEO_TRANSFORM,
     TOGGLE_CAMERA_FACING_MODE
 } from './actionTypes';
 import { CAMERA_FACING_MODE, VIDEO_MUTISM_AUTHORITY } from './constants';
@@ -18,9 +19,9 @@ import { CAMERA_FACING_MODE, VIDEO_MUTISM_AUTHORITY } from './constants';
  * @param {boolean} available - True if the local audio is to be marked as
  * available or false if the local audio is not available.
  * @returns {{
- *      type: SET_AUDIO_AVAILABLE,
- *      available: boolean
- *  }}
+ *     type: SET_AUDIO_AVAILABLE,
+ *     available: boolean
+ * }}
  */
 export function setAudioAvailable(available: boolean) {
     return {
@@ -112,6 +113,26 @@ export function setVideoMuted(
     };
 }
 
+/**
+ * Creates an action to store the last video {@link Transform} applied to a
+ * stream.
+ *
+ * @param {string} streamId - The ID of the stream.
+ * @param {Object} transform - The {@code Transform} to store.
+ * @returns {{
+ *     type: STORE_VIDEO_TRANSFORM,
+ *     streamId: string,
+ *     transform: Object
+ * }}
+ */
+export function storeVideoTransform(streamId: string, transform: Object) {
+    return {
+        type: STORE_VIDEO_TRANSFORM,
+        streamId,
+        transform
+    };
+}
+
 /**
  * Toggles the camera facing mode. Most commonly, for example, mobile devices
  * such as phones have a front/user-facing and a back/environment-facing
diff --git a/react/features/base/media/components/AbstractVideoTrack.js b/react/features/base/media/components/AbstractVideoTrack.js
index 721a531f6..5a2321965 100644
--- a/react/features/base/media/components/AbstractVideoTrack.js
+++ b/react/features/base/media/components/AbstractVideoTrack.js
@@ -36,7 +36,12 @@ export default class AbstractVideoTrack extends Component {
          * of all Videos. For more details, refer to the zOrder property of the
          * Video class for React Native.
          */
-        zOrder: PropTypes.number
+        zOrder: PropTypes.number,
+
+        /**
+         * Indicates whether zooming (pinch to zoom and/or drag) is enabled.
+         */
+        zoomEnabled: PropTypes.bool
     };
 
     /**
@@ -80,7 +85,7 @@ export default class AbstractVideoTrack extends Component {
      * @returns {ReactElement}
      */
     render() {
-        const videoTrack = this.state.videoTrack;
+        const { videoTrack } = this.state;
         let render;
 
         if (this.props.waitForVideoStarted) {
@@ -108,13 +113,21 @@ export default class AbstractVideoTrack extends Component {
         const stream
             = render ? videoTrack.jitsiTrack.getOriginalStream() : null;
 
+        // Actual zoom is currently only enabled if the stream is a desktop
+        // stream.
+        const zoomEnabled
+            = this.props.zoomEnabled
+                && stream
+                && videoTrack.videoType === 'desktop';
+
         return (
             <Video
                 mirror = { videoTrack && videoTrack.mirror }
                 onPlaying = { this._onVideoPlaying }
                 onPress = { this.props.onPress }
                 stream = { stream }
-                zOrder = { this.props.zOrder } />
+                zOrder = { this.props.zOrder }
+                zoomEnabled = { zoomEnabled } />
         );
     }
 
@@ -125,7 +138,7 @@ export default class AbstractVideoTrack extends Component {
      * @returns {void}
      */
     _onVideoPlaying() {
-        const videoTrack = this.props.videoTrack;
+        const { videoTrack } = this.props;
 
         if (videoTrack && !videoTrack.videoStarted) {
             this.props.dispatch(trackVideoStarted(videoTrack.jitsiTrack));
diff --git a/react/features/base/media/components/native/Video.js b/react/features/base/media/components/native/Video.js
index f3dd668cf..b1215cd50 100644
--- a/react/features/base/media/components/native/Video.js
+++ b/react/features/base/media/components/native/Video.js
@@ -4,9 +4,8 @@ import PropTypes from 'prop-types';
 import React, { Component } from 'react';
 import { RTCView } from 'react-native-webrtc';
 
-import { Pressable } from '../../../react';
-
 import styles from './styles';
+import VideoTransform from './VideoTransform';
 
 /**
  * The React Native {@link Component} which is similar to Web's
@@ -54,7 +53,12 @@ export default class Video extends Component<*> {
          * values: 0 for the remote video(s) which appear in the background, and
          * 1 for the local video(s) which appear above the remote video(s).
          */
-        zOrder: PropTypes.number
+        zOrder: PropTypes.number,
+
+        /**
+         * Indicates whether zooming (pinch to zoom and/or drag) is enabled.
+         */
+        zoomEnabled: PropTypes.bool
     };
 
     /**
@@ -77,29 +81,29 @@ export default class Video extends Component<*> {
      * @returns {ReactElement|null}
      */
     render() {
-        const { stream } = this.props;
+        const { stream, zoomEnabled } = this.props;
 
         if (stream) {
             const streamURL = stream.toURL();
-
-            // XXX The CSS style object-fit that we utilize on Web is not
-            // supported on React Native. Adding objectFit to React Native's
-            // StyleSheet appears to be impossible without hacking and an
-            // unjustified amount of effort. Consequently, I've chosen to define
-            // objectFit on RTCView itself. Anyway, prepare to accommodate a
-            // future definition of objectFit in React Native's StyleSheet.
             const style = styles.video;
-            const objectFit = (style && style.objectFit) || 'cover';
+            const objectFit
+                = zoomEnabled
+                    ? 'contain'
+                    : (style && style.objectFit) || 'cover';
 
             return (
-                <Pressable onPress = { this.props.onPress }>
+                <VideoTransform
+                    enabled = { zoomEnabled }
+                    onPress = { this.props.onPress }
+                    streamId = { stream.id }
+                    style = { style }>
                     <RTCView
                         mirror = { this.props.mirror }
                         objectFit = { objectFit }
                         streamURL = { streamURL }
                         style = { style }
                         zOrder = { this.props.zOrder } />
-                </Pressable>
+                </VideoTransform>
             );
         }
 
diff --git a/react/features/base/media/components/native/VideoTransform.js b/react/features/base/media/components/native/VideoTransform.js
new file mode 100644
index 000000000..6e1cdff8c
--- /dev/null
+++ b/react/features/base/media/components/native/VideoTransform.js
@@ -0,0 +1,714 @@
+// @flow
+
+import React, { Component } from 'react';
+import { PanResponder, View } from 'react-native';
+import { connect } from 'react-redux';
+
+import { storeVideoTransform } from '../../actions';
+import styles from './styles';
+
+/**
+ * The default/initial transform (= no transform).
+ */
+const DEFAULT_TRANSFORM = {
+    scale: 1,
+    translateX: 0,
+    translateY: 0
+};
+
+/**
+ * The minimum scale (magnification) multiplier. 1 is equal to objectFit
+ * = 'contain'.
+ */
+const MIN_SCALE = 1;
+
+/*
+ * The max distance from the edge of the screen where we let the user move the
+ * view to. This is large enough now to let the user drag the view to a position
+ * where no other displayed components cover it (such as filmstrip). If a
+ * ViewPort (hint) support is added to the LargeVideo component then this
+ * contant will not be necessary anymore.
+ */
+const MAX_OFFSET = 100;
+
+/**
+ * The max allowed scale (magnification) multiplier.
+ */
+const MAX_SCALE = 5;
+
+/**
+ * The length of a minimum movement after which we consider a gesture a move
+ * instead of a tap/long tap.
+ */
+const MOVE_THRESHOLD_DISMISSES_TOUCH = 2;
+
+/**
+ * A tap timeout after which we consider a gesture a long tap and will not
+ * trigger onPress (unless long tap gesture support is added in the future).
+ */
+const TAP_TIMEOUT_MS = 400;
+
+/**
+ * Type of a transform object this component is capable of handling.
+ */
+type Transform = {
+    scale: number,
+    translateX: number,
+    translateY: number
+};
+
+type Props = {
+
+    /**
+     * The children components of this view.
+     */
+    children: Object,
+
+    /**
+     * Transformation is only enabled when this flag is true.
+     */
+    enabled: boolean,
+
+    /**
+     * Function to invoke when a press event is detected.
+     */
+    onPress?: Function,
+
+    /**
+     * The id of the current stream that is displayed.
+     */
+    streamId: string,
+
+    /**
+     * Style of the top level transformable view.
+     */
+    style: Object,
+
+    /**
+     * The stored transforms retreived from Redux to be initially applied
+     * to different streams.
+     */
+    _transforms: Object,
+
+    /**
+     * Action to dispatch when the component is unmounted.
+     */
+    _onUnmount: Function
+};
+
+type State = {
+
+    /**
+     * The current (non-transformed) layout of the View.
+     */
+    layout: ?Object,
+
+    /**
+     * The current transform that is applied.
+     */
+    transform: Transform
+};
+
+/**
+ * An container that captures gestures such as pinch&zoom, touch or move.
+ */
+class VideoTransform extends Component<Props, State> {
+    /**
+     * The gesture handler object.
+     */
+    gestureHandlers: PanResponder;
+
+    /**
+     * The initial distance of the fingers on pinch start.
+     */
+    initialDistance: number;
+
+    /**
+     * The initial position of the finger on touch start.
+     */
+    initialPosition: {
+        x: number,
+        y: number
+    };
+
+    /**
+     * Time of the last tap.
+     */
+    lastTap: number;
+
+    /**
+     * Constructor of the component.
+     *
+     * @inheritdoc
+     */
+    constructor(props: Props) {
+        super(props);
+
+        this.state = {
+            layout: null,
+            transform: DEFAULT_TRANSFORM
+        };
+
+        this._getTransformStyle = this._getTransformStyle.bind(this);
+        this._onGesture = this._onGesture.bind(this);
+        this._onLayout = this._onLayout.bind(this);
+        this._onMoveShouldSetPanResponder
+            = this._onMoveShouldSetPanResponder.bind(this);
+        this._onPanResponderGrant = this._onPanResponderGrant.bind(this);
+        this._onPanResponderMove = this._onPanResponderMove.bind(this);
+        this._onPanResponderRelease = this._onPanResponderRelease.bind(this);
+        this._onStartShouldSetPanResponder
+            = this._onStartShouldSetPanResponder.bind(this);
+    }
+
+    /**
+     * Implements React Component's componentWillMount.
+     *
+     * @inheritdoc
+     */
+    componentWillMount() {
+        this.gestureHandlers = PanResponder.create({
+            onPanResponderGrant: this._onPanResponderGrant,
+            onPanResponderMove: this._onPanResponderMove,
+            onPanResponderRelease: this._onPanResponderRelease,
+            onPanResponderTerminationRequest: () => true,
+            onMoveShouldSetPanResponder: this._onMoveShouldSetPanResponder,
+            onShouldBlockNativeResponder: () => false,
+            onStartShouldSetPanResponder: this._onStartShouldSetPanResponder
+        });
+
+        const { streamId } = this.props;
+
+        this._restoreTransform(streamId);
+    }
+
+    /**
+     * Implements React Component's componentWillReceiveProps.
+     *
+     * @inheritdoc
+     */
+    componentWillReceiveProps({ streamId: newStreamId }) {
+        if (this.props.streamId !== newStreamId) {
+            this._storeTransform();
+            this._restoreTransform(newStreamId);
+        }
+    }
+
+    /**
+     * Implements React Component's componentWillUnmount.
+     *
+     * @inheritdoc
+     */
+    componentWillUnmount() {
+        this._storeTransform();
+    }
+
+    /**
+     * Renders the empty component that captures the gestures.
+     *
+     * @inheritdoc
+     */
+    render() {
+        const { children, style } = this.props;
+
+        return (
+            <View
+                onLayout = { this._onLayout }
+                pointerEvents = 'box-only'
+                style = { [
+                    styles.videoTransformedViewContaier,
+                    style
+                ] }
+                { ...this.gestureHandlers.panHandlers }>
+                <View
+                    style = { [
+                        styles.videoTranformedView,
+                        this._getTransformStyle()
+                    ] }>
+                    { children }
+                </View>
+            </View>
+        );
+    }
+
+    /**
+     * Calculates the new transformation to be applied by merging the current
+     * transform values with the newly received incremental values.
+     *
+     * @param {Transform} transform - The new transform object.
+     * @private
+     * @returns {Transform}
+     */
+    _calculateTransformIncrement(transform: Transform) {
+        let {
+            scale,
+            translateX,
+            translateY
+        } = this.state.transform;
+        const {
+            scale: newScale,
+            translateX: newTranslateX,
+            translateY: newTranslateY
+        } = transform;
+
+        // Note: We don't limit MIN_SCALE here yet, as we need to detect a scale
+        // down gesture even if the scale is already at MIN_SCALE to let the
+        // user return the screen to center with that gesture. Scale is limited
+        // to MIN_SCALE right before it gets applied.
+        scale = Math.min(scale * (newScale || 1), MAX_SCALE);
+
+        translateX = translateX + ((newTranslateX || 0) / scale);
+        translateY = translateY + ((newTranslateY || 0) / scale);
+
+        return {
+            scale,
+            translateX,
+            translateY
+        };
+    }
+
+    _didMove: Object => boolean
+
+    /**
+     * Determines if there was large enough movement to be handled.
+     *
+     * @param {Object} gestureState - The gesture state.
+     * @returns {boolean}
+     */
+    _didMove({ dx, dy }) {
+        return Math.abs(dx) > MOVE_THRESHOLD_DISMISSES_TOUCH
+                || Math.abs(dy) > MOVE_THRESHOLD_DISMISSES_TOUCH;
+    }
+
+    _getTouchDistance: Object => number;
+
+    /**
+     * Calculates the touch distance on a pinch event.
+     *
+     * @param {Object} evt - The touch event.
+     * @private
+     * @returns {number}
+     */
+    _getTouchDistance({ nativeEvent: { touches } }) {
+        const dx = Math.abs(touches[0].pageX - touches[1].pageX);
+        const dy = Math.abs(touches[0].pageY - touches[1].pageY);
+
+        return Math.sqrt(Math.pow(dx, 2) + Math.pow(dy, 2));
+    }
+
+    _getTouchPosition: Object => Object
+
+    /**
+     * Calculates the position of the touch event.
+     *
+     * @param {Object} evt - The touch event.
+     * @private
+     * @returns {Object}
+     */
+    _getTouchPosition({ nativeEvent: { touches } }) {
+        return {
+            x: touches[0].pageX,
+            y: touches[0].pageY
+        };
+    }
+
+    _getTransformStyle: () => Object
+
+    /**
+     * Generates a transform style object to be used on the component.
+     *
+     * @returns {{string: Array<{string: number}>}}
+     */
+    _getTransformStyle() {
+        const { enabled } = this.props;
+
+        if (!enabled) {
+            return null;
+        }
+
+        const {
+            scale,
+            translateX,
+            translateY
+        } = this.state.transform;
+
+        return {
+            transform: [
+                { scale },
+                { translateX },
+                { translateY }
+            ]
+        };
+    }
+
+    /**
+     * Limits the move matrix and then applies the transformation to the
+     * component (updates state).
+     *
+     * Note: Points A (top-left) and D (bottom-right) are opposite points of
+     * the View rectangle.
+     *
+     * @param {Transform} transform - The transformation object.
+     * @private
+     * @returns {void}
+     */
+    _limitAndApplyTransformation(transform: Transform) {
+        const { layout } = this.state;
+
+        if (layout) {
+            const { scale } = this.state.transform;
+            const { scale: newScaleUnlimited } = transform;
+            let {
+                translateX: newTranslateX,
+                translateY: newTranslateY
+            } = transform;
+
+            // Scale is only limited to MIN_SCALE here to detect downscale
+            // gesture later.
+            const newScale = Math.max(newScaleUnlimited, MIN_SCALE);
+
+            // The A and D points of the original View (before transform).
+            const originalLayout = {
+                a: {
+                    x: layout.x,
+                    y: layout.y
+                },
+                d: {
+                    x: layout.x + layout.width,
+                    y: layout.y + layout.height
+                }
+            };
+
+            // The center point (midpoint) of the transformed View.
+            const transformedCenterPoint = {
+                x: ((layout.x + layout.width) / 2) + (newTranslateX * newScale),
+                y: ((layout.y + layout.height) / 2) + (newTranslateY * newScale)
+            };
+
+            // The size of the transformed View.
+            const transformedSize = {
+                height: layout.height * newScale,
+                width: layout.width * newScale
+            };
+
+            // The A and D points of the transformed View.
+            const transformedLayout = {
+                a: {
+                    x: transformedCenterPoint.x - (transformedSize.width / 2),
+                    y: transformedCenterPoint.y - (transformedSize.height / 2)
+                },
+                d: {
+                    x: transformedCenterPoint.x + (transformedSize.width / 2),
+                    y: transformedCenterPoint.y + (transformedSize.height / 2)
+                }
+            };
+
+            let _MAX_OFFSET = MAX_OFFSET;
+
+            if (newScaleUnlimited < scale) {
+                // This is a negative scale event so we dynamycally reduce the
+                // MAX_OFFSET to get the screen back to the center on
+                // downscaling.
+                _MAX_OFFSET = Math.min(MAX_OFFSET, MAX_OFFSET * (newScale - 1));
+            }
+
+            // Correct move matrix if it goes out of the view
+            // too much (_MAX_OFFSET).
+            newTranslateX
+                -= Math.max(
+                    transformedLayout.a.x - originalLayout.a.x - _MAX_OFFSET,
+                    0);
+            newTranslateX
+                += Math.max(
+                    originalLayout.d.x - transformedLayout.d.x - _MAX_OFFSET,
+                    0);
+            newTranslateY
+                -= Math.max(
+                    transformedLayout.a.y - originalLayout.a.y - _MAX_OFFSET,
+                    0);
+            newTranslateY
+                += Math.max(
+                    originalLayout.d.y - transformedLayout.d.y - _MAX_OFFSET,
+                    0);
+
+            this.setState({
+                transform: {
+                    scale: newScale,
+                    translateX: Math.round(newTranslateX),
+                    translateY: Math.round(newTranslateY)
+                }
+            });
+        }
+    }
+
+    _onGesture: (string, ?Object | number) => void
+
+    /**
+     * Handles gestures and converts them to transforms.
+     *
+     * Currently supported gestures:
+     *  - scale (punch&zoom-type scale).
+     *  - move
+     *  - press.
+     *
+     * Note: This component supports onPress solely to overcome the problem of
+     * not being able to register gestures via the PanResponder due to the fact
+     * that the entire Conference component was a single touch responder
+     * component in the past (see base/react/.../Container with an onPress
+     * event) - and stock touch responder components seem to have exclusive
+     * priority in handling touches in React.
+     *
+     * @param {string} type - The type of the gesture.
+     * @param {?Object | number} value - The value of the gesture, if any.
+     * @returns {void}
+     */
+    _onGesture(type, value) {
+        let transform;
+
+        switch (type) {
+        case 'move':
+            transform = {
+                ...DEFAULT_TRANSFORM,
+                translateX: value.x,
+                translateY: value.y
+            };
+            break;
+        case 'scale':
+            transform = {
+                ...DEFAULT_TRANSFORM,
+                scale: value
+            };
+            break;
+
+        case 'press': {
+            const { onPress } = this.props;
+
+            typeof onPress === 'function' && onPress();
+            break;
+        }
+        }
+
+        if (transform) {
+            this._limitAndApplyTransformation(
+                this._calculateTransformIncrement(transform));
+        }
+
+        this.lastTap = 0;
+    }
+
+    _onLayout: Object => void
+
+    /**
+     * Callback for the onLayout of the component.
+     *
+     * @param {Object} event - The native props of the onLayout event.
+     * @private
+     * @returns {void}
+     */
+    _onLayout({ nativeEvent: { layout: { x, y, width, height } } }) {
+        this.setState({
+            layout: {
+                x,
+                y,
+                width,
+                height
+            }
+        });
+    }
+
+    _onMoveShouldSetPanResponder: (Object, Object) => boolean
+
+    /**
+     * Function to decide whether the responder should respond to a move event.
+     *
+     * @param {Object} evt - The event.
+     * @param {Object} gestureState - Gesture state.
+     * @private
+     * @returns {boolean}
+     */
+    _onMoveShouldSetPanResponder(evt, gestureState) {
+        return this.props.enabled
+            && (this._didMove(gestureState)
+                || gestureState.numberActiveTouches === 2);
+    }
+
+    _onPanResponderGrant: (Object, Object) => void
+
+    /**
+     * Calculates the initial touch distance.
+     *
+     * @param {Object} evt - Touch event.
+     * @param {Object} gestureState - Gesture state.
+     * @private
+     * @returns {void}
+     */
+    _onPanResponderGrant(evt, { numberActiveTouches }) {
+        if (numberActiveTouches === 1) {
+            this.initialPosition = this._getTouchPosition(evt);
+            this.lastTap = Date.now();
+
+        } else if (numberActiveTouches === 2) {
+            this.initialDistance = this._getTouchDistance(evt);
+        }
+    }
+
+    _onPanResponderMove: (Object, Object) => void
+
+    /**
+     * Handles the PanResponder move (touch move) event.
+     *
+     * @param {Object} evt - Touch event.
+     * @param {Object} gestureState - Gesture state.
+     * @private
+     * @returns {void}
+     */
+    _onPanResponderMove(evt, gestureState) {
+        if (gestureState.numberActiveTouches === 2) {
+            // this is a zoom event
+            if (
+                this.initialDistance === undefined
+                || isNaN(this.initialDistance)
+            ) {
+                // there is no initial distance because the user started
+                // with only one finger. We calculate it now.
+                this.initialDistance = this._getTouchDistance(evt);
+            } else {
+                const distance = this._getTouchDistance(evt);
+                const scale = distance / (this.initialDistance || 1);
+
+                this.initialDistance = distance;
+
+                this._onGesture('scale', scale);
+            }
+        } else if (gestureState.numberActiveTouches === 1
+                && isNaN(this.initialDistance)
+                && this._didMove(gestureState)) {
+            // this is a move event
+            const position = this._getTouchPosition(evt);
+            const move = {
+                x: position.x - this.initialPosition.x,
+                y: position.y - this.initialPosition.y
+            };
+
+            this.initialPosition = position;
+
+            this._onGesture('move', move);
+        }
+    }
+
+    _onPanResponderRelease: () => void
+
+    /**
+     * Handles the PanResponder gesture end event.
+     *
+     * @private
+     * @returns {void}
+     */
+    _onPanResponderRelease() {
+        if (this.lastTap && Date.now() - this.lastTap < TAP_TIMEOUT_MS) {
+            this._onGesture('press');
+        }
+        delete this.initialDistance;
+        delete this.initialPosition;
+    }
+
+    _onStartShouldSetPanResponder: () => boolean
+
+    /**
+     * Function to decide whether the responder should respond to a start
+     * (thouch) event.
+     *
+     * @private
+     * @returns {boolean}
+     */
+    _onStartShouldSetPanResponder() {
+        return typeof this.props.onPress === 'function';
+    }
+
+    /**
+     * Restores the last applied transform when the component is mounted, or
+     * a new stream is about to be rendered.
+     *
+     * @param {string} streamId - The stream id to restore transform for.
+     * @private
+     * @returns {void}
+     */
+    _restoreTransform(streamId) {
+        const { enabled, _transforms } = this.props;
+
+        if (enabled) {
+            const initialTransform = _transforms[streamId];
+
+            if (initialTransform) {
+                this.setState({
+                    transform: initialTransform
+                });
+            }
+        }
+    }
+
+    /**
+     * Stores/saves the current transform when the component is destroyed, or a
+     * new stream is about to be rendered.
+     *
+     * @private
+     * @returns {void}
+     */
+    _storeTransform() {
+        const { _onUnmount, enabled, streamId } = this.props;
+
+        if (enabled) {
+            _onUnmount(streamId, this.state.transform);
+        }
+    }
+}
+
+/**
+ * Maps dispatching of some action to React component props.
+ *
+ * @param {Function} dispatch - Redux action dispatcher.
+ * @private
+ * @returns {{
+ *     _onUnmount: Function
+ * }}
+ */
+function _mapDispatchToProps(dispatch) {
+    return {
+        /**
+         * Dispatches actions to store the last applied transform to a video.
+         *
+         * @param {string} streamId - The ID of the stream.
+         * @param {Transform} transform - The last applied transform.
+         * @private
+         * @returns {void}
+         */
+        _onUnmount(streamId, transform) {
+            dispatch(storeVideoTransform(streamId, transform));
+        }
+    };
+}
+
+/**
+ * Maps (parts of) the redux state to the component's props.
+ *
+ * @param {Object} state - The redux state.
+ * @param {Object} ownProps - The component's own props.
+ * @private
+ * @returns {{
+ *     _transforms: Object
+ * }}
+ */
+function _mapStateToProps(state) {
+    return {
+        /**
+         * The stored transforms retreived from Redux to be initially applied to
+         * different streams.
+         *
+         * @private
+         * @type {Object}
+         */
+        _transforms: state['features/base/media'].video.transforms
+    };
+}
+
+export default connect(_mapStateToProps, _mapDispatchToProps)(VideoTransform);
diff --git a/react/features/base/media/components/native/styles.js b/react/features/base/media/components/native/styles.js
index c105fa069..fcf6fc83b 100644
--- a/react/features/base/media/components/native/styles.js
+++ b/react/features/base/media/components/native/styles.js
@@ -6,6 +6,23 @@ import { ColorPalette } from '../../../styles';
  * The styles of the feature base/media.
  */
 export default StyleSheet.create({
+
+    /**
+     * Base style of the transformed video view.
+     */
+    videoTranformedView: {
+        flex: 1
+    },
+
+    /**
+     * A basic style to avoid rendering a transformed view off the component,
+     * that can be visible on special occasions, such as during device rotate
+     * animation, or PiP mode.
+     */
+    videoTransformedViewContaier: {
+        overflow: 'hidden'
+    },
+
     /**
      * Make {@code Video} fill its container.
      */
diff --git a/react/features/base/media/reducer.js b/react/features/base/media/reducer.js
index b3dc17563..5157ebc87 100644
--- a/react/features/base/media/reducer.js
+++ b/react/features/base/media/reducer.js
@@ -1,6 +1,8 @@
 import { combineReducers } from 'redux';
 
+import { CONFERENCE_FAILED, CONFERENCE_LEFT } from '../conference';
 import { ReducerRegistry } from '../redux';
+import { TRACK_REMOVED } from '../tracks';
 
 import {
     SET_AUDIO_AVAILABLE,
@@ -8,6 +10,7 @@ import {
     SET_CAMERA_FACING_MODE,
     SET_VIDEO_AVAILABLE,
     SET_VIDEO_MUTED,
+    STORE_VIDEO_TRANSFORM,
     TOGGLE_CAMERA_FACING_MODE
 } from './actionTypes';
 import { CAMERA_FACING_MODE } from './constants';
@@ -73,7 +76,13 @@ function _audio(state = AUDIO_INITIAL_MEDIA_STATE, action) {
 const VIDEO_INITIAL_MEDIA_STATE = {
     available: true,
     facingMode: CAMERA_FACING_MODE.USER,
-    muted: 0
+    muted: 0,
+
+    /**
+     * The video {@link Transform}s applied to {@code MediaStream}s by
+     * {@code id} i.e. "pinch to zoom".
+     */
+    transforms: {}
 };
 
 /**
@@ -87,6 +96,10 @@ const VIDEO_INITIAL_MEDIA_STATE = {
  */
 function _video(state = VIDEO_INITIAL_MEDIA_STATE, action) {
     switch (action.type) {
+    case CONFERENCE_FAILED:
+    case CONFERENCE_LEFT:
+        return _clearAllVideoTransforms(state);
+
     case SET_CAMERA_FACING_MODE:
         return {
             ...state,
@@ -105,6 +118,9 @@ function _video(state = VIDEO_INITIAL_MEDIA_STATE, action) {
             muted: action.muted
         };
 
+    case STORE_VIDEO_TRANSFORM:
+        return _storeVideoTransform(state, action);
+
     case TOGGLE_CAMERA_FACING_MODE: {
         let cameraFacingMode = state.facingMode;
 
@@ -119,6 +135,9 @@ function _video(state = VIDEO_INITIAL_MEDIA_STATE, action) {
         };
     }
 
+    case TRACK_REMOVED:
+        return _trackRemoved(state, action);
+
     default:
         return state;
     }
@@ -138,3 +157,65 @@ ReducerRegistry.register('features/base/media', combineReducers({
     audio: _audio,
     video: _video
 }));
+
+/**
+ * Removes all stored video {@link Transform}s.
+ *
+ * @param {Object} state - The {@code video} state of the feature base/media.
+ * @private
+ * @returns {Object}
+ */
+function _clearAllVideoTransforms(state) {
+    return {
+        ...state,
+        transforms: VIDEO_INITIAL_MEDIA_STATE.transforms
+    };
+}
+
+/**
+ * Stores the last applied transform to a stream.
+ *
+ * @param {Object} state - The {@code video} state of the feature base/media.
+ * @param {Object} action - The redux action {@link STORE_VIDEO_TRANSFORM}.
+ * @private
+ * @returns {Object}
+ */
+function _storeVideoTransform(state, { streamId, transform }) {
+    return {
+        ...state,
+        transforms: {
+            ...state.transforms,
+            [streamId]: transform
+        }
+    };
+}
+
+/**
+ * Removes the stored video {@link Transform} associated with a
+ * {@code MediaStream} when its respective track is removed.
+ *
+ * @param {Object} state - The {@code video} state of the feature base/media.
+ * @param {Object} action - The redux action {@link TRACK_REMOVED}.
+ * @private
+ * @returns {Object}
+ */
+function _trackRemoved(state, { track: { jitsiTrack } }) {
+    if (jitsiTrack) {
+        const streamId = jitsiTrack.getStreamId();
+
+        if (streamId && streamId in state.transforms) {
+            const nextTransforms = {
+                ...state.transforms
+            };
+
+            delete nextTransforms[streamId];
+
+            return {
+                ...state,
+                transforms: nextTransforms
+            };
+        }
+    }
+
+    return state;
+}
diff --git a/react/features/base/participants/components/ParticipantView.native.js b/react/features/base/participants/components/ParticipantView.native.js
index a1ef61f7b..0c9d12420 100644
--- a/react/features/base/participants/components/ParticipantView.native.js
+++ b/react/features/base/participants/components/ParticipantView.native.js
@@ -117,7 +117,12 @@ type Props = {
      * stacking space of all {@code Video}s. For more details, refer to the
      * {@code zOrder} property of the {@code Video} class for React Native.
      */
-    zOrder: number
+    zOrder: number,
+
+    /**
+     * Indicates whether zooming (pinch to zoom and/or drag) is enabled.
+     */
+    zoomEnabled: boolean
 };
 
 /**
@@ -127,6 +132,7 @@ type Props = {
  * @extends Component
  */
 class ParticipantView extends Component<Props> {
+
     /**
      * Renders the connection status label, if appropriate.
      *
@@ -235,7 +241,8 @@ class ParticipantView extends Component<Props> {
                         onPress = { renderVideo ? onPress : undefined }
                         videoTrack = { videoTrack }
                         waitForVideoStarted = { waitForVideoStarted }
-                        zOrder = { this.props.zOrder } /> }
+                        zOrder = { this.props.zOrder }
+                        zoomEnabled = { this.props.zoomEnabled } /> }
 
                 { renderAvatar
                     && <Avatar
diff --git a/react/features/large-video/components/LargeVideo.native.js b/react/features/large-video/components/LargeVideo.native.js
index b75e6437e..a86c36624 100644
--- a/react/features/large-video/components/LargeVideo.native.js
+++ b/react/features/large-video/components/LargeVideo.native.js
@@ -126,7 +126,8 @@ class LargeVideo extends Component<Props, State> {
                     participantId = { _participantId }
                     style = { styles.largeVideo }
                     useConnectivityInfoLabel = { useConnectivityInfoLabel }
-                    zOrder = { 0 } />
+                    zOrder = { 0 }
+                    zoomEnabled = { true } />
             </DimensionsDetector>
         );
     }