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.
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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
|
4a. Visual Basic: Press the F5 key to run the project.
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.
|
The constant CC_PREVENTFULLOPEN, with a decimal value of 4, can be used in
the flags element of the CHOOSECOLOR structure if you wish to prevent the
Custom Colors part of the Dialog from being displayed.
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.
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Microsoft Visual Basic Programmer's Guide, Chapter 11, P.325-332.
Win32 SDK.
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