Unlike what was described in the documentation, it's not permissible to call capture() while 'ready' or isReadyForCapture() is false. All backends emit an error in that case. Updated the documentation to reflect that behavior. Change-Id: Icb326e65376b65eadd4c68b67e0ee30beddf1a04 Reviewed-by: Venugopal Shivashankar <venugopal.shivashankar@digia.com> Reviewed-by: Christian Stromme <christian.stromme@theqtcompany.com>