fix(virtual-background): Fix resize action and prevent mirror behavio… (#9441)

* fix(virtual-background): Fix resize action and prevent mirror behaviour on desktop share as a virtual background.
Co-authored-by: tudordan7 <tudor.pop@decagon.tech>

react/features/stream-effects/virtual-background/JitsiStreamBackgroundEffect.js

 export default class JitsiStreamBackgroundEffect {
     _model: Object;
     _options: Object;
-    _desktopShareDimensions: Object;
+    _stream: Object;
     _segmentationPixelCount: number;
     _inputVideoElement: HTMLVideoElement;
     _onMaskFrameTimer: Function;
      * @returns {void}
      */
     runPostProcessing() {
+
+        const track = this._stream.getVideoTracks()[0];
+        const { height, width } = track.getSettings() ?? track.getConstraints();
+
+        this._outputCanvasElement.height = height;
+        this._outputCanvasElement.width = width;
         this._outputCanvasCtx.globalCompositeOperation = 'copy';
 
         // Draw segmentation mask.
             );
         }
         if (this._options.virtualBackground.backgroundType === VIRTUAL_BACKGROUND_TYPE.DESKTOP_SHARE) {
+
+            // save current context before applying transformations
+            this._outputCanvasCtx.save();
+
+            // flip the canvas and prevent mirror behaviour
+            this._outputCanvasCtx.scale(-1, 1);
+            this._outputCanvasCtx.translate(-this._outputCanvasElement.width, 0);
             this._outputCanvasCtx.drawImage(
                 this._virtualVideo,
                 0,
                 0,
-                this._desktopShareDimensions.width,
-                this._desktopShareDimensions.height
+                this._outputCanvasElement.width,
+                this._outputCanvasElement.height
             );
+
+            // restore the canvas
+            this._outputCanvasCtx.restore();
         } else {
             this._outputCanvasCtx.filter = `blur(${this._options.virtualBackground.blurValue}px)`;
             this._outputCanvasCtx.drawImage(this._inputVideoElement, 0, 0);
      * @returns {void}
      */
     _renderMask() {
-        const desktopShareTrack = this._options?.virtualBackground?.virtualSource?.track;
-
-        if (desktopShareTrack) {
-            this._desktopShareDimensions = desktopShareTrack.getSettings ? desktopShareTrack.getSettings()
-                : desktopShareTrack.getConstraints();
-        }
         this.resizeSource();
         this.runInference();
         this.runPostProcessing();
      * @returns {MediaStream} - The stream with the applied effect.
      */
     startEffect(stream: MediaStream) {
+        this._stream = stream;
         this._maskFrameTimerWorker = new Worker(timerWorkerScript, { name: 'Blur effect worker' });
         this._maskFrameTimerWorker.onmessage = this._onMaskFrameTimer;
-        const firstVideoTrack = stream.getVideoTracks()[0];
+        const firstVideoTrack = this._stream.getVideoTracks()[0];
         const { height, frameRate, width }
             = firstVideoTrack.getSettings ? firstVideoTrack.getSettings() : firstVideoTrack.getConstraints();
 
         this._inputVideoElement.width = parseInt(width, 10);
         this._inputVideoElement.height = parseInt(height, 10);
         this._inputVideoElement.autoplay = true;
-        this._inputVideoElement.srcObject = stream;
+        this._inputVideoElement.srcObject = this._stream;
         this._inputVideoElement.onloadeddata = () => {
             this._maskFrameTimerWorker.postMessage({
                 id: SET_TIMEOUT,

react/features/virtual-background/components/VirtualBackgroundDialog.js

 import { createLocalTrack } from '../../base/lib-jitsi-meet/functions';
 import { VIDEO_TYPE } from '../../base/media';
 import { connect } from '../../base/redux';
+import { updateSettings } from '../../base/settings';
 import { Tooltip } from '../../base/tooltip';
 import { getLocalVideoTrack } from '../../base/tracks';
 import { showErrorNotification } from '../../notifications';
 ];
 type Props = {
 
+    /**
+     * The current local flip x status.
+     */
+    _localFlipX: boolean,
+
     /**
      * Returns the jitsi track that will have backgraund effect applied.
      */
  * @returns {{Props}}
  */
 function _mapStateToProps(state): Object {
+    const { localFlipX } = state['features/base/settings'];
+
     return {
+        _localFlipX: Boolean(localFlipX),
         _virtualBackground: state['features/virtual-background'],
         _selectedThumbnail: state['features/virtual-background'].selectedThumbnail,
         _jitsiTrack: getLocalVideoTrack(state['features/base/tracks'])?.jitsiTrack
  * @returns {ReactElement}
  */
 function VirtualBackground({
+    _localFlipX,
     _jitsiTrack,
     _selectedThumbnail,
     _virtualBackground,
         if (storedImages.length === backgroundsLimit) {
             setStoredImages(storedImages.slice(1));
         }
-    }, [ storedImages ]);
+        if (!_localFlipX) {
+            dispatch(updateSettings({
+                localFlipX: !_localFlipX
+            }));
+        }
+    }, [ storedImages, _localFlipX ]);
 
 
     const enableBlur = useCallback(async () => {

react/features/virtual-background/components/VirtualBackgroundPreview.js

 import { VIRTUAL_BACKGROUND_TYPE } from '../constants';
 import { localTrackStopped } from '../functions';
 
-const videoClassName = 'video-preview-video';
+const videoClassName = 'video-preview-video flipVideoX';
 
 /**
  * The type of the React {@code PureComponent} props of {@link VirtualBackgroundPreview}.