Tip 201: Retrieving the Task List in Windows 95

December 5, 1995

Abstract
This article explains how to create a list of all currently running
taskson the Microsoft® Windows® 95 operating system.

Determining Which Tasks Are Running
With the Microsoft® Windows® 95 operating system, you can run any number
of applications simultaneously. Occasionally, you may need to determine
whichtasks are currently being run. This can be accomplished by using
severalWindows application programming interface (API) functions.

To find the names of all currently executing tasks, you must
firstdetermine the handle of the window that is currently at the top of
thez-order. This, of course, would be the window of your own Microsoft
VisualBasic® application. You can use the Windows API GetWindow function
toretrieve the handle of your application's window with the statement:

CurrWnd = GetWindow(Form1.hwnd, GW_HWNDFIRST)

The first argument of the GetWindow function is the handle of the
windowthat is at the top of the z-order. In this case, this is the
handle ofForm1.

The second argument of the GetWindow function specifies the window you
want to retrieve the handle for. This argument can have one of the
followingvalues:

GW_CHILD      Retrieve the handle for the child window.
GW_HWNDFIRST  Retrieve the handle for the window at the top of the
              z-order.
GW_HWNDLAST   Retrieve the handle for the window at the bottom of the
              z-order.
GW_HWNDNEXT   Retrieve the handle of the window below the specified window
              in the z-order.
GW_HWNDPREV   Retrieve the handle of the window above the specified window
              in the z-order.
GW_OWNER      Retrieve the handle of the window that owns the specified
              window, if any.

After you have retrieved the application's window handle, you can use the
Windows API GetParent function to retrieve this window's child window
handle. Next, you call the Windows API GetWindowText and
GetWindowTextLength functions to retrieve the text in the window's title
bar and the length of this text, respectively. You can then use the text
string in your own application. For example, you can save the title bar
text to a List Box control.

All of the above steps are repeated until you have processed all running
tasks. You know that you have gone through each task when the current
window is that of your own application.

Example Program
This program shows how to create a list of all currently running tasks in
Windows 95.

 1. Create a new project in Visual Basic. Form1 is created by default.
 2. Add the following Constant and Declare statements to the General
    Declarations section of Form1 (note that each Declare statement
    must be typed as a single line of code):

Private Declare Function GetWindow Lib "user32"
   (ByVal hwnd As Long, ByVal wCmd As Long) As Long
Private Declare Function GetParent Lib "user32"
   (ByVal hwnd As Long) As Long
Private Declare Function GetWindowTextLength Lib "user32"
   Alias "GetWindowTextLengthA" (ByVal hwnd As Long) As Long
Private Declare Function GetWindowText Lib "user32"
   Alias "GetWindowTextA" (ByVal hwnd As Long, ByVal lpString As String,
   ByVal cch As Long) As Long

Const GW_HWNDFIRST = 0
Const GW_HWNDNEXT = 2

 3. Add a Command Button control to Form1. Command1 is created by default.
 4. Add the following code to the Click event for Command1:

Private Sub Command1_Click()
    LoadTaskList
End Sub

 5. Add a List Box control to Form1. List1 is created by default.
 6. Create a new subroutine called LoadTaskList. Add the following code
    to this subroutine:

Sub LoadTaskList()
    Dim CurrWnd As Long
    Dim Length As Long
    Dim TaskName As String
    Dim Parent As Long

    List1.Clear
    CurrWnd = GetWindow(Form1.hwnd, GW_HWNDFIRST)

    While CurrWnd <> 0
        Parent = GetParent(CurrWnd)
        Length = GetWindowTextLength(CurrWnd)
        TaskName = Space$(Length + 1)
        Length = GetWindowText(CurrWnd, TaskName, Length + 1)
        TaskName = Left$(TaskName, Len(TaskName) - 1)

        If Length > 0 Then
            If TaskName <> Me.Caption Then
                List1.AddItem TaskName
            End If
        End If
        CurrWnd = GetWindow(CurrWnd, GW_HWNDNEXT)
        DoEvents
    Wend
End Sub

Run the example program by pressing F5. Click the Command Button control.
A list of all currently running tasks on the Windows 95 operating system
appears in the List Box control.