How To Create Lightweight Controls with Visual Basic 6.0

MORE INFORMATION

Lightweight, or windowless controls, are controls that are similar to regular controls except that lightweight controls do not have window handles. Because of they lack window handles, lightweight controls require less system resources, making them ideal for Internet applications, distributed applications, or any application where limited system resources may be an issue. Further, lightweight controls can be any shape and have true transparency properties.

When you create a lightweight control, the container can hold only other lightweight controls. If you try to place a regular control in a lightweight user control, you will receive the following error:

Can't have windowed child controls on a windowless control.

Regular controls always appear on top of lightweight controls because lightweight controls use the resources of the parent form. The ZOrder of a regular control changes only with respect to other regular controls.

Because lightweight controls do not have a Hwnd property, you cannot use these controls with Windows API functions that require an HWnd parameter. The HWnd property of the container is used instead, which may result in unpredictable results.

To make a control into a lightweight control, set the Windowless property of the control to True.

Visual Basic ships with intrinsic lightweight controls and other lightweight controls in the ActiveX component file MSWLess.ocx. For a list of these intrinsic controls and instructions on how to use the controls in the ActiveX component file MSWLess.ocx, please see the following article in the Microsoft Knowledge Base: The next section tells you how to create a sample project that contains a lightweight control. The sample project demonstrates that a lightweight control uses less resources than a regular control.

Creating the Sample Project

This section shows you how to create the sample project. The project measures the amount of time to load and unload a lightweight control as compared to a regular control. To create this project, you need to create a Standard EXE project, a lightweight control, and a regular control.

To Create the Standard EXE Program

1. Start a new Standard EXE project in Visual Basic. Form1 is created by default.
2. Add the following controls to the Form1 form and set the following properties to the appropriate controls:
   

         Control           Default Name     Property               Setting
         ---------------------------------------------------------------------
         Command Button    Command1         Name                    cmdWndLess
                                            Height                         375
                                            Left                           120
                                            Top                            840
                                            Width                         2535
   
         Command Button    Command2         Name                        cmdWnd
                                            Height                         375
                                            Left                          3000
                                            Top                            840
                                            Width                         2535
   
         TextBox           Text1            Name              txtNumofControls
                                            Height                         285
                                            Left                          1680
                                            Top                            120
                                            Width                          375
   
         Label             Label1           Name                lblWndLessLoad
                                            AutoSize                      True
                                            Height                         195
                                            Left                           120
                                            Top                           1320
   
         Label             Label2           Name              lblWndLessUnload
                                            AutoSize                      True
                                            Height                         195
                                            Left                           120
                                            Top                           1680
   
         Label             Label3           Name                    lblWndLoad
                                            AutoSize                      True
                                            Height                         195
                                            Left                          3000
                                            Top                           1320
   
         Label             Label4           Name                  lblWndUnload
                                            AutoSize                      True
                                            Height                         195
                                            Left                          3000
                                            Top                           1680
                                            Width                          480
   
         Label             Label5           Name                 lblStartTicks
                                            Alignment            Right Justify
                                            AutoSize                      True
                                            Caption               Start Ticker
                                            Height                         195
                                            Left                          4680
                                            Top                            480
                                            Width                          810
   
         Label             Label6           Name                   lblEndTicks
                                            Alignment            Right Justify
                                            AutoSize                      True
                                            Caption                 End Ticks:
                                            Height                         195
                                            Left                          4680
                                            Top                            120
   
   						

3. Copy the following code to the Code window of the Form1 form:
   

         Option Explicit
         Private Declare Function GetTickCount Lib "kernel32" () As Long
         Dim bLoadWnd As Boolean
         Dim bLoadWndLess As Boolean
         Dim lTickStart As Long
         Dim lTickEnd As Long
         Dim lResult As Long
         Dim colCtrlWnd As Collection
         Dim colCtrlWndLess As Collection
   
         Private Sub cmdWnd_Click()
         'This event loads and unloads regular controls.
            Dim tmpCtrlWnd As Control
            Dim lCounter As Long
   
            If bLoadWnd = True Then
               'Load Regular controls.
               lblWndLoad.Caption = "Loading Regular Controls"
               lTickStart = GetTickCount
               lblStartTicks.Caption = "Start: " & CStr(lTickStart) & " ms"
   
               For lCounter = 1 To Val(txtNumofControls.Text)
                  Set tmpCtrlWnd = Controls.Add("TestControls.ctrlWnd", _
                                                "ctrlWnd" & lCounter)
                  colCtrlWnd.Add tmpCtrlWnd
                  Set tmpCtrlWnd = Nothing
                  DoEvents
               Next
   
               lTickEnd = GetTickCount
               lblEndTicks.Caption = "End: " & CStr(lTickEnd) & " ms"
               lblWndLoad.Caption = "Load Time: " & _
                                    CStr(lTickEnd - lTickStart) & " ms"
               bLoadWnd = False
               cmdWnd.Caption = "Unload Regular Controls"
   
            Else
               'Unload regular controls.
               lblWndUnload.Caption = "Unloading Regular Controls"
               lTickStart = GetTickCount
               lblStartTicks.Caption = "Start: " & CStr(lTickStart) & " ms"
               '  UnLoad controls.
               For lCounter = colCtrlWnd.Count To 1 Step -1
                  Controls.Remove colCtrlWnd.Item(lCounter).Name
                  colCtrlWnd.Remove (lCounter)
               Next
               lTickEnd = GetTickCount
               lblEndTicks.Caption = "End: " & CStr(lTickEnd) & " ms"
               lblWndUnload.Caption = "Unload Time: " & _
                                       CStr(lTickEnd - lTickStart) & " ms"
               bLoadWnd = True
               cmdWnd.Caption = "Load Regular Controls"
   
            End If
   
         End Sub
   
         Private Sub cmdWndless_Click()
         'This command button loads and unloads the lightweight controls.
   
            Dim tmpCtrlWndLess As Control
            Dim lCounter As Long
            If bLoadWndLess = True Then
               lblWndLessLoad.Caption = "Loading Lightweight Controls"
               lTickStart = GetTickCount
               lblStartTicks.Caption = "Start: " & CStr(lTickStart) & " ms"
   
               '  Load controls.
               For lCounter = 1 To Val(txtNumofControls.Text)
                  Set tmpCtrlWndLess = _
                                   Controls.Add("TestControls.ctrlWndLess", _
                                   "ctrlWndLess" & lCounter)
                  colCtrlWndLess.Add tmpCtrlWndLess
                  Set tmpCtrlWndLess = Nothing
                  DoEvents
               Next
   
               lTickEnd = GetTickCount
               lblEndTicks.Caption = "End: " & CStr(lTickEnd) & " ms"
               lblWndLessLoad.Caption = "Load Time: " & _
                                        CStr(lTickEnd - lTickStart) & " ms"
               bLoadWndLess = False
               cmdWndless.Caption = "Unload Windowless Controls"
            Else
               lblWndLessUnload.Caption = "Unloading Lightweight Controls"
               lTickStart = GetTickCount
               lblStartTicks.Caption = "Start: " & CStr(lTickStart) & " ms"
   
               '  UnLoad controls.
               For lCounter = colCtrlWndLess.Count To 1 Step -1
                  Controls.Remove colCtrlWndLess.Item(lCounter).Name
                  colCtrlWndLess.Remove (lCounter)
               Next
   
               lTickEnd = GetTickCount
               lblEndTicks.Caption = "End: " & CStr(lTickEnd) & " ms"
               lblWndLessUnload.Caption = "Unload Time: " & _
                                        CStr(lTickEnd - lTickStart) & " ms"
               bLoadWndLess = True
               cmdWndless.Caption = "Load Windowless Controls"
            End If
         End Sub
   
         Private Sub Form_Load()
            Set colCtrlWnd = New Collection
            Set colCtrlWndLess = New Collection
            cmdWndless.Caption = "Load Lightweight Controls"
            bLoadWndLess = True
            cmdWnd.Caption = "Load Regular Controls"
            bLoadWnd = True
            txtNumofControls.Text = "20"
         End Sub
   
   						

4. On the Run menu, click Start or press the F5 key to start the program. If the form successfully launches, then you have completed creating the standard executable program in this project.

The next section shows you how to create the regular and lightweight controls that the standard executable program uses.

To Create the Regular and Lightweight Controls

1. Add an ActiveX Control project to your project group.
   
   
   1. On the File menu, click Add Project. The Add Project dialog box appears.
   2. In the New Tab, select ActiveX Control.
   3. Click Open to add the project to your project group and to close the Add Project dialog box. UserControl1 is created by default.
   4. Change the name of UserControl1 to ctrlWnd. This will be your regular control.
2. Add a combo box to the ctrlWnd control. Save the control.
3. Add another UserControl by completing the following steps. This will be your lightweight control:
   
   
   1. On the Project Menu, click Add User Control. The Add User Control dialog box appears with User Control highlighted.
   2. Click Open to add the User Control to the project and close the Add User Control dialog box. UserControl1 is created by default.
   3. Change the name of UserControl1 to ctrlWndLess.
   4. Set the Windowless property to True.
4. Save the control.
5. Rename the Project to TestControls. Save the project.

You have completed creating the ActiveX controls required by this project. To run the project, press F5 or from the Run menu, click Start. You can set the number of controls and compare the load and unload times.