CreateDesktopA function (winuser.h)

Creates a new desktop, associates it with the current window station of the calling process, and assigns it to the calling thread. The calling process must have an associated window station, either assigned by the system at process creation time or set by the SetProcessWindowStation function.

To specify the size of the heap for the desktop, use the CreateDesktopEx function.

Syntax

HDESK CreateDesktopA(
  [in]           LPCSTR                lpszDesktop,
                 LPCSTR                lpszDevice,
                 DEVMODEA              *pDevmode,
  [in]           DWORD                 dwFlags,
  [in]           ACCESS_MASK           dwDesiredAccess,
  [in, optional] LPSECURITY_ATTRIBUTES lpsa
);

Parameters

[in] lpszDesktop

The name of the desktop to be created. Desktop names are case-insensitive and may not contain backslash characters (\).

lpszDevice

Reserved; must be NULL.

pDevmode

Reserved; must be NULL.

[in] dwFlags

This parameter can be zero or the following value.

[in] dwDesiredAccess

The access to the desktop. For a list of values, see Desktop Security and Access Rights.

This parameter must include the DESKTOP_CREATEWINDOW access right, because internally CreateDesktop uses the handle to create a window.

[in, optional] lpsa

A pointer to a SECURITY_ATTRIBUTES structure that determines whether the returned handle can be inherited by child processes. If lpsa is NULL, the handle cannot be inherited.

The lpSecurityDescriptor member of the structure specifies a security descriptor for the new desktop. If this parameter is NULL, the desktop inherits its security descriptor from the parent window station.

Return value

If the function succeeds, the return value is a handle to the newly created desktop. If the specified desktop already exists, the function succeeds and returns a handle to the existing desktop. When you are finished using the handle, call the CloseDesktop function to close it.

If the function fails, the return value is NULL. To get extended error information, call GetLastError.

Remarks

If the dwDesiredAccess parameter specifies the READ_CONTROL, WRITE_DAC, or WRITE_OWNER standard access rights, you must also request the DESKTOP_READOBJECTS and DESKTOP_WRITEOBJECTS access rights.

The number of desktops that can be created is limited by the size of the system desktop heap, which is 48 MB. Desktop objects use the heap to store resources. You can increase the number of desktops that can be created by reducing the default heap reserved for each desktop in the interactive window station. This value is specified in the "SharedSection" substring of the following registry value: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\SubSystems\Windows. The default data for this registry value is as follows:

"%SystemRoot%\system32\csrss.exe ObjectDirectory=\Windows SharedSection=1024,3072,512 Windows=On SubSystemType=Windows ServerDll=basesrv,1 ServerDll=winsrv:UserServerDllInitialization,3 ServerDll=winsrv:ConServerDllInitialization,2 ProfileControl=Off MaxRequestThreads=16"

The values for the "SharedSection" substring are described as follows:

• The first "SharedSection" value is the size of the shared heap common to all desktops, in kilobytes.
• The second "SharedSection" value is the size of the desktop heap needed for each desktop that is created in the interactive window station, WinSta0, in kilobytes.
• The third "SharedSection" value is the size of the desktop heap needed for each desktop that is created in a noninteractive window station, in kilobytes.

Requirements

See also

CloseDesktop

CreateDesktopEx

Desktops

SECURITY_ATTRIBUTES

SetProcessWindowStation

SwitchDesktop

Window Station and Desktop Functions