Using webRTC you can transmit an image of your screen instead of the camera image. You can transmit the image of your entire screen or select a specific window to transmit only that window's contents. webRTC treats the user's screen as a virtual camera, transmitting a video screen. Thus receiving end can see what's on the screen but cannot alter it, eg moving the mouse or typing anything.
When screen sharing is started by calling wrtc.getScreen(true). User is then presented with a list of choices to share the entire screen or just one specific window.
To stop screen sharing and transmit local camera image again call wrtc.getScreen(false).