VRLayerInit.leftBounds

The leftBounds property of the VRLayerInit interface (dictionary) defines the left texture bounds of the canvas whose contents will be presented by the VRDisplay.

var myVRLayerInit = { };
myVRLayerInit.leftBounds = [0.0, 0.0, 0.5, 1.0];

An array of four floating point values, which can take values from 0.0–1.0:

• The left offset of the bounds.
• The top offset of the bounds.
• The width of the bounds.
• The height of the bounds.

If leftBounds is not specified in the dictionary, the default value used is [0.0, 0.0, 0.5, 1.0].

// currently returns an empty array
var layers = vrDisplay.getLayers();

if(navigator.getVRDisplays) {
  console.log('WebVR 1.1 supported');
  // Then get the displays attached to the computer
  navigator.getVRDisplays().then(function(displays) {
    // If a display is available, use it to present the scene
    if(displays.length > 0) {
      vrDisplay = displays[0];
      console.log('Display found');
      // Starting the presentation when the button is clicked: It can only be called in response to a user gesture
      btn.addEventListener('click', function() {
        vrDisplay.requestPresent([{ source: canvas }]).then(function() {
          console.log('Presenting to WebVR display');

          // Here it returns an array of VRLayerInit objects
          var layers = vrDisplay.getLayers();

          ...
        });
      });
    }
  });
}

VRLayerInit objects look something like this:

{
  leftBounds : [ ... ],
  rightBounds: [ ... ],
  source: canvasReference
}

• WebVR API homepage
• https://mixedreality.mozilla.org/ — demos, downloads, and other resources from the Mozilla VR team.