HOWTO: Use Icons with the Windows 95 System Tray

• Standard, Professional, and Enterprise Editions of Microsoft Visual Basic, 32-bit only, for Windows, version 4.0

SUMMARY

The Windows API provides the ability to add, modify, and remove icons from the system tray available in the Windows 95 shell. This functionality can be provided using only the Shell_NotifyIcon function that is exported by Shell32.dll. This API function also provides the ability to specify a text string for the ToolTip that is displayed when a user pauses with the mouse pointer over the icon. The step-by-step example in this article creates a Visual Basic program which demonstrates how to use this API function.

The ability to take some action if the icon in the systray is clicked depends on a callback function. Because Visual Basic does not support callback functions directly, there is no way to show a form or execute some code using solely Visual Basic. A number of options are available that can provide callback functionality, including the Message Blaster OCX, the OCX mentioned in the MSJ article referenced below, or the Callback OLE server detailed in Bruce McKinney's book, "Hardcore Visual Basic," published by Microsoft Press. For more information on any of these options, see the REFERENCES section at the end of this article. Because these products do not ship with Visual Basic, Microsoft Technical Support does not support their use.

MORE INFORMATION

The following example creates a one-form Visual Basic project that shows how to use the Shell_NotifyIcon API function.

Step-by-Step Example

1. Start Visual Basic. Form1 is created by default.

2. Change the form's icon property to the icon that should be shown in the systray.

3. Draw three CommandButtons onto the form.

4. Select Module from the Insert menu to add a single code module to the project.

5. Add the following code, consisting of function, type, and constant declarations, to Module1:

         Type NOTIFYICONDATA
             cbSize As Long
             hWnd As Long
             uID As Long
             uFlags As Long
             uCallbackMessage As Long
             hIcon As Long
             szTip As String * 64
         End Type
   
         Global Const NIM_ADD = 0
         Global Const NIM_MODIFY = 1
         Global Const NIM_DELETE = 2
         Global Const NIF_MESSAGE = 1
         Global Const NIF_ICON = 2
         Global Const NIF_TIP = 4
   
         Declare Function Shell_NotifyIconA Lib "SHELL32" _
         (ByVal dwMessage As Long,  lpData As NOTIFYICONDATA) As Integer
   
   

6. The following code is a function that takes the parameters that need to be set for the NOTIFYICONDATA type and returns a variable of this type. Add to Form1:

         Private Function setNOTIFYICONDATA(hWnd As Long, ID As Long, _
             Flags As Long, CallbackMessage As Long, Icon As Long, _
             Tip As String) As NOTIFYICONDATA
   
             Dim nidTemp As NOTIFYICONDATA
   
             nidTemp.cbSize = Len(nidTemp)
             nidTemp.hWnd = hWnd
             nidTemp.uID = ID
             nidTemp.uFlags = Flags
             nidTemp.uCallbackMessage = CallbackMessage
             nidTemp.hIcon = Icon
             nidTemp.szTip = Tip & Chr$(0)
   
             setNOTIFYICONDATA = nidTemp
         End Function
   
   

7. The three procedures in this block of code call the function created in step 5 to add, modify, and remove systray icons. Add this code to Form1 also:

         Private Sub Command1_Click()
             'Add an icon.  This procedure uses the icon specified in
             'the Icon property of Form1. This can be modified as desired.
   
             Dim i As Integer
             Dim s As String
             Dim nid As NOTIFYICONDATA
   
             s = InputBox("Enter string:")
             nid = setNOTIFYICONDATA(hWnd:=Form1.hWnd, _
                                     ID:=vbNull, _
                                     Flags:=NIF_MESSAGE Or NIF_ICON _
                                     Or NIF_TIP, _
                                     CallbackMessage:=vbNull, _
                                     Icon:=Form1.Icon, _
                                     Tip:=s)
   
                i = Shell_NotifyIconA(NIM_ADD, nid)
            End Sub
   
            Private Sub Command2_Click()
                'Modify an existing icon. This procedure uses the icon
                'specified in the Icon property of Form1. This can be modified
                'as desired.
   
                Dim i As Integer
                Dim s As String
                Dim nid As NOTIFYICONDATA
   
                s = InputBox("Enter string:")
                nid = setNOTIFYICONDATA(hWnd:=Form1.hWnd, _
                                        ID:=vbNull, _
                                        Flags:=NIF_MESSAGE Or NIF_ICON _
                                        Or NIF_TIP, _
                                        CallbackMessage:=vbNull, _
                                        Icon:=Form1.Icon, _
                                        Tip:=s)
   
                i = Shell_NotifyIconA(NIM_MODIFY, nid)
            End Sub
   
            Private Sub Command3_Click()
                'Delete an existing icon.
   
                Dim i As Integer
                Dim nid As NOTIFYICONDATA
   
             nid = setNOTIFYICONDATA(hWnd:=Form1.hWnd, _
                                     ID:=vbNull, _
                                     Flags:=NIF_MESSAGE Or NIF_ICON _
                                     Or NIF_TIP, _
                                     CallbackMessage:=vbNull, _
                                     Icon:=Form1.Icon, _
                                     Tip:="")
   
             i = Shell_NotifyIconA(NIM_DELETE, nid)
         End Sub
   
   

8. Press the F5 key or select Start from the Run menu to run the application. Click the first button and enter a text string to add an icon. Click the second button to modify an existing icon, and the third to delete the icon.

REFERENCES

Hardcore Visual Basic, Bruce McKinney, Microsoft Press 1995. Microsoft Win32 SDK, Shell_NotifyIcon and NOTIFYICONDATA. Microsoft Systems Journal, February 1996, The Visual Programmer, page 93. Visual Basic Programmer's Journal, March 1996, Q&A, page 136.

Keywords          : PrgOther vb432 VB4WIN
Version           : 4.0
Platform          : NT WINDOWS
Issue type        : kbhowto