HOWTO: Use Color Dialog from COMDLG32.DLL in VB and Access

• Microsoft Visual Basic Professional and Enterprise Editions for Windows, version 5.0
• Microsoft Visual Basic Standard, Professional, and Enterprise Editions, 32-bit only, for Windows, version 4.0
• Microsoft Access versions 7.0, 97

SUMMARY

Making use of the COMDLG32.DLL is a good reuse of resources under Windows because Windows always has COMDLG32.DLL loaded. If you use the COMDLG32.OCX control instead, your program must load the OCX into memory and you must also distribute an additional 90K file to your customers. The OCX control provides an easy-to-use interface to predefined dialog boxes, but is a more expensive hit on performance and resources. To optimize performance and reduce resource usage, you should minimize the use of controls in your applications and use the Win32 API calls directly. Below is a code sample of how to use the Choose Color dialog box in the COMDLG32.DLL.

MORE INFORMATION

1a. Visual Basic: Start a new project. Form1 is created by default.

1b. Access: Open a database and create a new form.

1. Add a CommandButton (Command1) to the form.

2. Add the following code to the General Declarations section of the form:

   Option Explicit

   Private Type CHOOSECOLOR

        lStructSize As Long
        hwndOwner As Long
        hInstance As Long
        rgbResult As Long
        lpCustColors As String
        flags As Long
        lCustData As Long
        lpfnHook As Long
        lpTemplateName As String
   

   End Type

      Private Declare Function ChooseColorAPI Lib "comdlg32.dll" Alias _
        "ChooseColorA" (pChoosecolor As CHOOSECOLOR) As Long
   
      Dim CustomColors() As Byte
   
      Private Sub Command1_Click()
          Dim cc As CHOOSECOLOR
          Dim Custcolor(16) As Long
          Dim lReturn As Long
          cc.lStructSize = Len(cc)
          cc.hwndOwner = Me.hWnd
          cc.hInstance = 0
          cc.lpCustColors = StrConv(CustomColors, vbUnicode)
          cc.flags = 0
          lReturn = ChooseColorAPI(cc)
          If lReturn <> 0 Then
              Me.Caption = "RGB Value User Chose: " & Str$(cc.rgbResult)
              Me.BackColor = cc.rgbResult            ' Visual Basic only ****
              Me.Section(0).BackColor = cc.rgbResult ' Access only **********
              CustomColors = StrConv(cc.lpCustColors, vbFromUnicode)
          Else
              MsgBox "User chose the Cancel Button"
          End If
      End Sub
   
      Private Sub Form_Load()
          ReDim CustomColors(0 To 16 * 4 - 1) As Byte
          Dim i As Integer
   
          For i = LBound(CustomColors) To UBound(CustomColors)
              CustomColors(i) = 0
          Next i
      End Sub
   
   

4b. Access: Use the View|Form menu to open the form and run it.

1. Click the CommandButton and the Color dialog box will be displayed. When you choose a color and press OK, the background color of the form will change to your selected color.

NOTE: In the Command1_Click routine above, the code to set the background color of an Access form and a Visual Basic form is slightly different. Both commands are included and commented. Only type the command that is appropriate for the product you are using.

REFERENCES

Microsoft Visual Basic Programmer's Guide, Chapter 11, P.325-332.

Win32 SDK.