DOCX

Windows 7 Brightness Control for Integrated Displays

By Bill Gonzalez,2014-08-10 06:52
7 views 0
Windows 7 Brightness Control for Integrated Displays

    Windows 7 Brightness Control for Integrated Displays

    January 9, 2009

    Abstract

    This paper provides information about integrated display brightness control for the Windows? family of operating systems. It provides guidelines for system manufacturers and firmware developers to expose brightness control infrastructure to Windows. The new brightness control user experiences for Windows 7 are discussed. Additionally, this paper provides power policy configuration information, including new policies for the adaptive display brightness feature and information on how to observe brightness control changes by using the PwrTest utility. This information applies to the Windows 7 operating system.

    References and resources discussed here are listed at the end of this paper. For the latest information, see:

     http://www.microsoft.com/whdc/system/pnppwr/powermgmt/BrightnessCtrl.mspx

    Windows 7 Brightness Control for Integrated Displays - 2

    Disclaimer: This is a preliminary document and may be changed substantially prior to final commercial release of the software described herein. The information contained in this document represents the current view of Microsoft Corporation on the issues discussed as of the date of publication. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information presented after the date of publication. This White Paper is for informational purposes only. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS DOCUMENT. Complying with all applicable copyright laws is the responsibility of the user. Without limiting the rights under copyright, no part of this document may be reproduced, stored in or introduced into a retrieval system, or transmitted in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise), or for any purpose, without the express written permission of Microsoft Corporation. Microsoft may have patents, patent applications, trademarks, copyrights, or other intellectual property rights covering subject matter in this document. Except as expressly provided in any written license agreement from Microsoft, the furnishing of this document does not give you any license to these patents, trademarks, copyrights, or other intellectual property. Unless otherwise noted, the example companies, organizations, products, domain names, e-mail addresses, logos, people, places and events depicted herein are fictitious, and no association with any real company, organization, product, domain name, email address, logo, person, place or event is intended or should be inferred. ? 2009 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Server, Windows Vista, and PowerPoint are either registered trademarks or trademarks of Microsoft Corporation in the United States and/or other countries. The names of actual companies and products mentioned herein may be the trademarks of their respective owners.

    Document History

     Date Change

    January 9, 2009 First publication

January 9, 2009 ? 2009 Microsoft Corporation. All rights reserved.

    Windows 7 Brightness Control for Integrated Displays - 3

    Contents

    Introduction ............................................................................................................... 4 Brightness Control User Experiences........................................................................... 4 Power Options........................................................................................................ 5 Windows Mobility Center ....................................................................................... 8 Hardware Hot Keys ................................................................................................. 8 Battery Meter Brightness Warnings ........................................................................ 9 Brightness Control Platform Infrastructure ................................................................. 9 ACPI-Based Brightness Control Interface ................................................................ 9 WDDM Driver DDI Brightness Control Interface .................................................... 10 Hot Key Integration .............................................................................................. 11 Fading Transitions ................................................................................................ 11 Brightness Control Policies and Actions .................................................................... 12 Default Display Brightness Policies ....................................................................... 12 Adaptive Display Brightness Policies ..................................................................... 12 Advanced Adaptive Display Brightness Policies ..................................................... 13 Best Practices for Brightness Control Policy Configuration ........................................ 14 Best Practices for Software Developers..................................................................... 15 Integration with Ambient Light Sensor Devices ......................................................... 15 Validation of Platform Brightness Control ................................................................. 15 The PwrTest MONITOR Scenario ........................................................................... 15 Observation of Brightness Level Changes with the MONITOR Scenario ................. 16

    Call to Action ............................................................................................................ 18 Resources ................................................................................................................. 19

January 9, 2009 ? 2009 Microsoft Corporation. All rights reserved.

    Windows 7 Brightness Control for Integrated Displays - 4

    Introduction

    During ordinary use, the integrated display in most portable computers is the greatest consumer of power. To reduce power consumption and extend battery life, Windows? provides an infrastructure for controlling the brightness of the display. Windows 7 simplifies the user experience for brightness control and configuration. Brightness controls are available in the Windows Mobility Center, the Control Panel Power Options application, and hot keys on the system keyboard. User adjustments to the brightness level are now applied to the current power policy, which preserves the user’s brightness level adjustment across sleep, resume, shutdown, and restart transitions. After a period of user inactivity, the display brightness automatically dims to help extend battery life.

    Windows supports two ways to integrate brightness control: Windows Display Driver Model (WDDM) miniport device driver interfaces (DDIs) and Advanced Configuration and Power Interface (ACPI) firmware control methods. ACPI control methods are the preferred implementation solution for new platforms. The underlying brightness control infrastructure is configured by using power policy settings. System manufacturers can customize these settings based on the target platforms or display technologies.

    System manufacturers and firmware developers should review this paper for details on the Windows brightness control infrastructure, new user experiences, and power policy configuration details for display brightness.

    Brightness Control User Experiences

    Windows 7 improves the brightness control configuration user experience by simplifying the interaction between the various methods to set the display brightness. Adjustments to the display brightness that a user makes through Windows Mobility Center or keyboard hot keys now persist across system power-state transitions (standby and resume). A user can also easily adjust the display brightness level by using a new slider control in the Control Panel Power Options application. If the

    display brightness is set to a level that is greater than the default display brightness of the On battery policy for the active power plan, a warning appears in the battery meter to advise the user of the effect of the display brightness setting on the battery life of a portable computer.

    January 9, 2009 ? 2009 Microsoft Corporation. All rights reserved.

    Windows 7 Brightness Control for Integrated Displays - 5

    Power Options

    The Control Panel Power Options application is the user’s primary interaction point for setting the display brightness. In Windows 7, a Display brightness adjustment

    slider is now available at the bottom of Power Options, as shown in Figure 1.