CaptureController: getSupportedZoomLevels() method

Syntax

getSupportedZoomLevels()

Parameters

None.

Return value

An array of numbers representing the different zoom levels that the captured display surface supports.

Exceptions

InvalidStateError DOMException

The capturing MediaStream returned by the originating MediaDevices.getDisplayMedia() call is no longer capturing, for example because the associated MediaStreamTrack objects have had stop() called on them.

NotSupportedError DOMException

The surface type being captured is not a browser tab.

Examples

Basic getSupportedZoomLevels() usage

In our live demo, shown in Using the Captured Surface Control API, we grab the supported zoom levels of the captured display surface by running getSupportedZoomLevels(), storing the resulting array in a variable called zoomLevels:

const zoomLevels = controller.getSupportedZoomLevels();

This is later used in a function called updateZoomButtonState(). The problem this solves is that, if you try to zoom out below the minimum supported zoom level, or zoom in above the maximum supported zoom level, decreaseZoomLevel()/increaseZoomLevel() will throw an InvalidStateError DOMException.

The updateZoomButtonState() function avoids this issue by first making sure both the "Zoom out" and "Zoom in" buttons are enabled. It then does two checks:

• If the current zoom level is equal to the minimum supported zoom level (stored in the first value of the zoomLevels array), we disable the "Zoom out" button so the user can't zoom out any further.
• If the current zoom level is equal to the maximum supported zoom level (stored in the last value of the zoomLevels array), we disable the "Zoom in" button so the user can't zoom in any further.

function updateZoomButtonState() {
  decBtn.disabled = false;
  incBtn.disabled = false;
  if (controller.zoomLevel === zoomLevels[0]) {
    decBtn.disabled = true;
  } else if (controller.zoomLevel === zoomLevels[zoomLevels.length - 1]) {
    incBtn.disabled = true;
  }
}

Specifications

Browser compatibility

See also

• Screen Capture API
• MediaDevices.getDisplayMedia()
• Using the Captured Surface Control API