MediaTrackConstraints.logicalSurface - Web APIs 编辑

The MediaTrackConstraints dictionary's logicalSurface property is a ConstrainDOMString describing the requested or mandatory constraints placed upon the value of the logicalSurface constrainable property. This is used to specify whether or not getDisplayMedia() should allow the user to choose display surfaces which are not necessarily fully visible on the screen, such as occluded windows or the complete content of windows which are large enough to require scrolling to see their entire contents.

If needed, you can determine whether or not this constraint is supported by checking the value of MediaTrackSupportedConstraints.logicalSurface as returned by a call to MediaDevices.getSupportedConstraints(). However, typically this is unnecessary since browsers will ignore any constraints they're unfamiliar with.

Syntax

var constraintsObject = { logicalSurface: constraint };

constraintsObject.logicalSurface = constraint;

Value

A ConstrainBoolean which is true if logical surfaces should be permitted among the selections available to the user.

See How constraints are defined in Capabilities, constraints, and settings for an explanation of how to define constraints.

Usage notes

You can check the setting selected by the user agent after the display media has been created by getDisplayMedia() by calling getSettings() on the display media's video MediaStreamTrack, then checking the value of  the returned MediaTrackSettings object's logicalSurface object.

For example, if your app needs to know if the selected display surface is a logical one:

let isLogicalSurface = displayStream.getVideoTracks()[0].getSettings().logicalSurface;

Following this code, isLogicalSurface  is true if the display surface contained in the stream is a logical surface; that is, one which may not be entirely onscreen, or may even be entirely offscreen.

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• Screen Capture API
• Using the Screen Capture API
• Capabilities, constraints, and settings
• MediaTrackConstraints
• MediaDevices.getSupportedConstraints()
• MediaTrackSupportedConstraints