Windows API Guide: GetForegroundWindow Function


Declare Function GetSystemMenu Lib "user32.dll" (ByVal hWnd As Long, ByVal bRevert As Long) As Long

Platforms

  • Windows 95: Supported.
  • Windows 98: Supported.
  • Windows NT: Requires Windows NT 3.1 or later.
  • Windows 2000: Supported.
  • Windows CE: Requires Windows CE 1.0 or later.

Description & Usage

GetSystemMenu obtains a handle to a window's system menu (also known as its control menu). This menu is what appears when the application icon on the title bar is clicked, or when the title bar itself is right-clicked. Once you get a handle to a window's system menu, you can use the other menu functions to add or remove items from it. However, note that all items on a system menu send the WM_SYSCOMMAND message to the parent window instead of the usual WM_COMMAND message. Alternately, GetSystemMenu could also be used to restore the system menu to its default appearance, removing any modifications done to it.

Return Value

If the bRevert parameter is zero, GetSystemMenu returns a handle to the window's system menu. If bRevert is nonzero, this function returns 0.

Visual Basic-Specific Issues

None.

Parameters

hWnd
A handle to the window to locate the system menu of.
bRevert
If zero, the function obtains a handle to the window's system menu. If nonzero, the function instead reverts the system menu back to its default appearance.

Example

' This code is licensed according to the terms and conditions listed here. ' Declarations and such needed for the example: ' (Copy them to the (declarations) section of a module.) ' There's quite a few declarations for this example, but it's worth it! Public Declare Function GetSystemMenu Lib "user32.dll" (ByVal hWnd As Long, ByVal bRevert _ As Long) As Long Public Declare Function GetMenuItemCount Lib "user32.dll" (ByVal hMenu As Long) As Long Public Type MENUITEMINFO cbSize As Long fMask As Long fType As Long fState As Long wID As Long hSubMenu As Long hbmpChecked As Long hbmpUnchecked As Long dwItemData As Long dwTypeData As String cch As Long End Type Public Const MIIM_STATE = &H1 Public Const MIIM_ID = &H2 Public Const MIIM_TYPE = &H10 Public Const MFT_SEPARATOR = &H800 Public Const MFT_STRING = &H0 Public Const MFS_ENABLED = &H0 Public Const MFS_CHECKED = &H8 Public Declare Function InsertMenuItem Lib "user32.dll" Alias "InsertMenuItemA" (ByVal _ hMenu As Long, ByVal uItem As Long, ByVal fByPosition As Long, lpmii _ As MENUITEMINFO) As Long Public Declare Function SetMenuItemInfo Lib "user32.dll" Alias "SetMenuItemInfoA" (ByVal _ hMenu As Long, ByVal uItem As Long, ByVal fByPosition As Long, lpmii _ As MENUITEMINFO) As Long Public Declare Function SetWindowPos Lib "user32.dll" (ByVal hWnd As Long, ByVal _ hWndInsertAfter As Long, ByVal x As Long, ByVal y As Long, ByVal cx As Long, ByVal _ cy As Long, ByVal wFlags As Long) As Long Public Const HWND_TOPMOST = -1 Public Const HWND_NOTOPMOST = -2 Public Const SWP_NOMOVE = &H2 Public Const SWP_NOSIZE = &H1 Public Declare Function SetWindowLong Lib "user32.dll" Alias "SetWindowLongA" (ByVal hWnd _ As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long Public Const GWL_WNDPROC = -4 Public Declare Function CallWindowProc Lib "user32.dll" Alias "CallWindowProcA" (ByVal _ lpPrevWndFunc As Long, ByVal hWnd As Long, ByVal Msg As Long, ByVal wParam _ As Long, ByVal lParam As Long) As Long Public Const WM_SYSCOMMAND = &H112 Public Const WM_INITMENU = &H116 ' Add an option to make window Form1 "Always On Top" to the bottom of its system ' menu.  A check mark appears next to this option when active.  The menu item acts as a toggle. ' Note how subclassing the window is necessary to process the two messages needed ' to give the added system menu item its full functionality. ' *** Place the following code in a module. *** Public pOldProc As Long  ' pointer to Form1's previous window procedure Public ontop As Boolean  ' identifies if Form1 is always on top or not ' The following function acts as Form1's window procedure to process messages. Public Function WindowProc (ByVal hwnd As Long, ByVal uMsg As Long, ByVal wParam _ As Long, ByVal lParam As Long) As Long Dim hSysMenu As Long     ' handle to Form1's system menu Dim mii As MENUITEMINFO  ' menu item information for Always On Top Dim retval As Long       ' return value Select Case uMsg Case WM_INITMENU ' Before displaying the system menu, make sure that the Always On Top ' option is properly checked. hSysMenu = GetSystemMenu(hwnd, 0) With mii ' Size of the structure. .cbSize = Len(mii) ' Only use what needs to be changed. .fMask = MIIM_STATE ' If Form1 is now always on top, check the item. .fState = MFS_ENABLED Or IIf(ontop, MFS_CHECKED, 0) End With retval = SetMenuItemInfo(hSysMenu, 1, 0, mii) WindowProc = 0 Case WM_SYSCOMMAND ' If Always On Top (ID = 1) was selected, change the on top/not on top ' setting of Form1 to match. If wParam = 1 Then ' Reverse the setting and make it the current one. ontop = Not ontop retval = SetWindowPos(hwnd, IIf(ontop, HWND_TOPMOST, HWND_NOTOPMOST), _ 0, 0, 0, 0, SWP_NOMOVE Or SWP_NOSIZE) WindowProc = 0 Else ' Some other item was selected.  Let the previous window procedure ' process it. WindowProc = CallWindowProc(pOldProc, hwnd, uMsg, wParam, lParam) End If Case Else ' If this is some other message, let the previous procedure handle it. WindowProc = CallWindowProc(pOldProc, hwnd, uMsg, wParam, lParam) End Select End Function ' *** Place the following code inside Form1. *** ' When Form1 loads, add Always On Top to the system menu and set up the ' new window procedure. Private Sub Form_Load() Dim hSysMenu As Long     ' handle to the system menu Dim count As Long        ' the number of items initially on the menu Dim mii As MENUITEMINFO  ' describes a menu item to add Dim retval As Long       ' return value ' Get a handle to the system menu. hSysMenu = GetSystemMenu(Form1.hWnd, 0) ' See how many items are currently in it. count = GetMenuItemCount(hSysMenu) ' Add a separator bar and then Always On Top to the system menu. With mii ' The size of the structure. .cbSize = Len(mii) ' What parts of the structure to use. .fMask = MIIM_ID Or MIIM_TYPE ' This is a separator. .fType = MFT_SEPARATOR ' It has an ID of 0. .wID = 0 End With ' Add the separator to the end of the system menu. retval = InsertMenuItem(hSysMenu, count, 1, mii) ' Likewise, add the Always On Top command. With mii .fMask = MIIM_STATE Or MIIM_ID Or MIIM_TYPE ' This is a regular text item. .fType = MFT_STRING ' The option is enabled. .fState = MFS_ENABLED ' It has an ID of 1 (this identifies it in the window procedure). .wID = 1 ' The text to place in the menu item. .dwTypeData = "&Always On Top" .cch = Len(.dwTypeData) End With ' Add this to the bottom of the system menu. retval = InsertMenuItem(hSysMenu, count + 1, 1, mii) ' Set the custom window procedure to process Form1's messages. ontop = False pOldProc = SetWindowLong(Form1.hWnd, GWL_WNDPROC, AddressOf WindowProc) End Sub ' Before unloading, restore the default system menu and remove the ' custom window procedure. Private Sub Form_Unload(Cancel As Integer) Dim retval As Long  ' return value ' Replace the previous window procedure to prevent crashing. retval = SetWindowLong(Form1.hWnd, GWL_WNDPROC, pOldProc) ' Remove the modifications made to the system menu. retval = GetSystemMenu(Form1.hWnd, 1) End Sub

See Also

GetMenu

Category

Menus

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Last Modified: June 4, 2000
This page is copyright © 2000 Paul Kuliniewicz. Copyright Information Revised October 29, 2000
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Windows API Guide
Windows API Guide - Reference - Volume 1: Version 3.0 For the MS-DOS and PC-DOS Operating Systems
ISBN: B001V0KQIY
EAN: N/A
Year: 1998
Pages: 610

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