MediaTrackSettings: logicalSurface property

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

The MediaTrackSettings dictionary's logicalSurface property indicates whether or not the display area being captured is a logical surface. Logical surfaces are those which are not necessarily entirely onscreen, or may even be off-screen, such as windows' backing buffers (where only part of the buffer is visible without scrolling the containing window) and offscreen rendering contexts.

Value

A Boolean value which is true if the video track in the stream of captured video is taken from a logical display surface.

The most common scenario in which a display surface may be a logical one is if the selected surface contains the entire content area of a window which is too large to display onscreen at once. Since the window that contains the surface has to be scrolled to show the rest of the contents, the surface is a logical one.

A visible display surface (that is, a surface for which logicalSurface returns false) is the portion of a logical display surface which is currently visible onscreen.

For example, a user agent may choose to allow the user to choose whether to share the entire document (a browser with logicalSurface value of true), or just the currently visible portion of the document (where the logicalSurface of the browser surface is false).