GetKeyState function does not work when you use the AttachThreadInput function to attach an input processing mechanism to a thread in Windows 7 or in Windows Server 2008 R2

Applies to: Windows 7 EnterpriseWindows 7 Home PremiumWindows 7 Professional

Symptoms


Consider the following scenario:
  • You use the AttachThreadInput function to attach the input processing mechanism of a thread to the input processing mechanism of another thread.
  • You press a key or click a mouse button.
  • When the input notification message (such as WM_KEYDOWN, WM_SYSKEYDOWN, or WM_LBUTTONDOWN) is being processed, you perform one of the following operations:
    • You use the AttachThreadInput function to reattach the input processing mechanism to the current thread.
    • You create a window that is owned by a window in a different thread or process.
  • A call is made to the GetKeyState function.
In this scenario, the GetKeyState function returns a key or mouse button state that is not the down state. However, the key or the mouse button should remain in the down state until a corresponding key or mouse button release message (such as WM_KEYUP, WMSYSKEYUP, WM_LBUTTONUP) is processed.

Notes
  • This issue affects any application that uses the GetKeyState function or the KeyState property in this scenario.
  • This issue does not affect the GetMessage and PeekMessage functions.
  • This issue may affect the TranslateMessage function and the keyboard character messages if the key that you press is a modifier key (such as Alt, Shift, Ctrl, or Caps Lock).

Cause


This issue occurs because Windows creates a new input queue without copying the KeyState property in the scenario that is described in the "Symptoms" section. Therefore, the KeyState property of the new input queue has a null value. In this situation, every key and mouse button is in the up state or in the not toggled state.

Resolution


Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing the problem described in this article. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site: Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.

Prerequisites

To apply this hotfix, you must be running Windows 7 Service Pack 1 (SP1) or Windows Server 2008 R2 Service Pack 1 (SP1).

For more information about how to obtain a Windows 7 or Windows Server 2008 R2 service pack, click the following article number to view the article in the Microsoft Knowledge Base:

976932 Information about Service Pack 1 for Windows 7 and for Windows Server 2008 R2

Registry information

To use the hotfix in this package, you do not have to make any changes to the registry.

Restart requirement

You must restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace a previously released hotfix.

Status


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

More Information


For more information about the AttachThreadInput function, visit the following Microsoft website:For more information about the TranslateMessage function, visit the following Microsoft website:For more information about the GetKeyState function, visit the following Microsoft website:For more information about owned windows, visit the following Microsoft website:For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:

824684 Description of the standard terminology that is used to describe Microsoft software updates