Screen sharing on macOS

1. Configure screen sharing encoding parameters

Call setScreenShareEncoderConfiguration to configure the screen sharing stream encoding: resolution, frame rate, bitrate, GOP, and rotation.

Encoding parameters:

Sample code:

/*
  config is a user-defined configuration struct
*/

AliRtcScreenShareEncoderConfiguration * encoderConfig = [[AliRtcScreenShareEncoderConfiguration alloc] init];

encoderConfig.dimensions = CGSizeMake( width_, height_);
encoderConfig.frameRate = frameRate_;   // 5/10/15...
encoderConfig.bitrate = bitrate_;	// 1200...
encoderConfig.rotation = AliRtcRotationMode_0; // 0/90/180/270
encoderConfig.keyFrameInterval = keyFrameInterval_; // 1/2/3 seconds

if (keyFrameInterval_ > 0) {
    encoderConfig.forceStrictKeyFrameInterval = TRUE;
}

encoderConfig.forceStrictKeyFrameInterval = forceStrictKeyFrameInterval_;

[self.mainEngine setScreenShareEncoderConfiguration: encoderConfig];

2. Set up screen sharing preview

Call setLocalViewConfig to set the display view for the screen sharing stream (AliEngineVideoTrackScreen).

AliVideoCanvas *canvas = [[AliVideoCanvas alloc]init];
canvas.mirrorMode = _mirrorButton.state == NSControlStateValueOn ? AliRtcRenderMirrorModeAllEnabled:AliRtcRenderMirrorModeAllDisabled;
canvas.view = renderView;
int rv = [self.mainEngine setLocalViewConfig:canvas forTrack:AliRtcVideoTrackScreen];

3. View remote screen sharing

Call setRemoteViewConfig in the onRemoteTrackAvailableNotify callback to set the display view for a remote user's screen share.

- (void)onRemoteTrackAvailableNotify:(NSString *)uid audioTrack:(AliRtcAudioTrack)audioTrack videoTrack:(AliRtcVideoTrack)videoTrack {
    
    /* Handle UI components on the main thread */
    
    dispatch_async(dispatch_get_main_queue(), ^{
      AliVideoCanvas *canvas = [[AliVideoCanvas alloc]init];
      if ( videoTrack == AliRtcVideoTrackScreen ) {
          canvas.view = self._screenshareView;
          int rv = [self.mainEngine setLocalViewConfig:canvas forTrack:AliRtcVideoTrackScreen]; 
      } else {
          /* Find the view corresponding to this user */
          canvas.view = self.findView(uid);
          int rv = [self.mainEngine setLocalViewConfig:canvas forTrack:AliRtcVideoTrackScreen]; 
      }

    });

}

4. Enumerate all shareable desktops

Call getScreenShareSourceInfoWithType to get a list of shareable windows and desktops.

A system permission prompt appears. If denied, all subsequent sharing attempts fail.

_screenInfoArray = [self.engine getScreenShareSourceInfoWithType:AliRtcScreenShareDesktop];

/* Add to list */
if (_screenInfoArray) {
    
    for (AliRtcScreenSourceInfo *info in _screenInfoArray) {
        // Name + ID
        NSString *showString = [NSString stringWithFormat:@"%@+%@",info.sourceName,info.sourceId];
        [_screenListBox addItemWithObjectValue:showString];
    }
    
}

5. Start screen sharing

Call startScreenShareWithDesktopId to start screen sharing.

Configure config.isPushStream before starting.

AliRtcScreenShareConfig *config = [[AliRtcScreenShareConfig alloc]init];

/* For region-based sharing */
if ( shareRegion ) {
    
    config.isShareByRegion = TRUE ;
    AliRtcScreenShareRegion *region = [[AliRtcScreenShareRegion alloc]init];
    region.originX = regionRect.origin.x;
    region.originY = regionRect.origin.y;
    region.width = regionRect.size.width;
    region.height = regionRect.size.height;
    
    config.shareRegion = region;
    
} else {
    config.isShareByRegion = FALSE;
}

/* Set to true to push stream immediately; otherwise, set to FALSE
   and call updateScreenShareConfig later */

if ( pushStream ) {
    config.isPushStream = TRUE ;
} else {
    config.isPushStream = FALSE ;
}

/* Set desktop ID from _screenListBox */
int idValue =  [[_screenInfoArray[_screenListBox.indexOfSelectedItem] sourceId] intValue] ;
int r = [self.engine startScreenShareWithDesktopId:idValue config:config];

NSLog(@"startScreenShareWithDesktopId:%d",r);
if ( r != 0 ) {
    // Error handling
} 

6. (Optional) Update configuration

Call updateScreenShareConfig to update the screen sharing configuration.

AliRtcScreenShareConfig *config = [[AliRtcScreenShareConfig alloc]init];

/* For region-based sharing */
if ( share_region ) {
    
    config.isShareByRegion = TRUE ;
    AliRtcScreenShareRegion *region = [[AliRtcScreenShareRegion alloc]init];
    region.originX = regionRect.origin.x;
    region.originY = regionRect.origin.y;
    region.width = regionRect.size.width;
    region.height = regionRect.size.height;
    
    config.shareRegion = region;
    
} else {
    config.isShareByRegion = FALSE;
}

/* Set to true to push stream immediately; otherwise, set to FALSE
   and call updateScreenShareConfig later */

if ( pushStream ) {
    config.isPushStream = TRUE ;
} else {
    config.isPushStream = FALSE ;
}
      
[self.engine updateScreenShareConfig:mScreenConfig];

7. Stop screen sharing

[self.engine stopScreenShare];

1. List all shareable windows

Call startScreenShareWithWindowId to share a specific window.

_windowInfoArray = [self.engine getScreenShareSourceInfoWithType:AliRtcScreenShareWindow];


/* Display in listBox */
if (_windowInfoArray) {
    for (AliRtcScreenSourceInfo *info in _windowInfoArray) {
        // Name + ID
        NSString *showString = [NSString stringWithFormat:@"%@+%@",info.sourceName,info.sourceId];
        [_windowsListBox addItemWithObjectValue:showString];
    }
}

2. Share a specific window

AliRtcScreenShareConfig *config = [[AliRtcScreenShareConfig alloc]init];

/* For region-based sharing */
if ( shareRegion ) {
    
    config.isShareByRegion = TRUE ;
    AliRtcScreenShareRegion *region = [[AliRtcScreenShareRegion alloc]init];
    region.originX = regionRect.origin.x;
    region.originY = regionRect.origin.y;
    region.width = regionRect.size.width;
    region.height = regionRect.size.height;
    
    config.shareRegion = region;
    
} else {
    config.isShareByRegion = FALSE;
}


/* Set to true to push stream immediately; otherwise, set to FALSE.
   Later, call updateScreenShareConfig to modify the push stream flag */

if ( pushStream ) {
    config.isPushStream = TRUE ;
} else {
    config.isPushStream = FALSE ;
}

/* Set window ID from _windowsListBox */

int idValue =  [[_windowInfoArray[_windowsListBox.indexOfSelectedItem] sourceId] intValue] ;
int r = [self.engine startScreenShareWithWindowId:idValue config:config];

NSLog(@"startScreenShareWithWindowId:%d",r);
if ( r != 0 ) {
    // Error handling
} 

3. Stop sharing a window or desktop

Call stopScreenShare to stop sharing.

[self.mainEngine stopScreenShare];