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WinBioAcquireFocus function (winbio.h)

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Acquires window focus.

Syntax

HRESULT WinBioAcquireFocus();

Return value

If the function succeeds, it returns S_OK. If the function fails, it returns an HRESULT value that indicates the error. Possible values include, but are not limited to, those in the following table. For a list of common error codes, see Common HRESULT Values.

Return code Description
E_ACCESSDENIED
 The calling process must be running under the Local System account.

Remarks

The Windows Biometric Framework uses window focus to arbitrate among multiple sessions connected to the system pool.

The manner in which you acquire focus depends on the type of application you are writing. For example, if you are creating a GUI application you can implement a message handler that captures a WM_ACTIVATE, WM_SETFOCUS, or other appropriate message. If you are writing a CUI application, call GetConsoleWindow to retrieve a handle to the console window and pass that handle to the SetForegroundWindow function to force the console window into the foreground and assign it focus. If your application is running in a detached process or is a Windows service and has no window, use WinBioAcquireFocus and WinBioReleaseFocus to manually control focus.

The following list summarizes the major points to consider before calling this function.

  • The calling process must be running under the Local System account.
  • A process that directly displays a user interface should not call this function. See the preceding discussion to determine how to acquire focus for GUI and CUI applications.
  • Only a service or a detached process that does not directly display a user interface during biometric API calls should call this function.
  • If the function succeeds, you must call WinBioReleaseFocus to release focus.
If you do not acquire focus when calling the following functions, they will behave in unexpected ways:

Requirements

Requirement Value
Minimum supported client Windows 7 [desktop apps only]
Minimum supported server Windows Server 2008 R2 [desktop apps only]
Target Platform Windows
Header winbio.h (include Winbio.h)
Library Winbio.lib
DLL Winbio.dll

See also

Client Application Functions

WinBioEnrollBegin