HOWTO: Use the OLE_COLOR Property Data Type

• Microsoft Visual Basic Control Creation, Learning, Professional, and Enterprise Editions for Windows, version 5.0

SUMMARY

An ActiveX control property can be any valid data type, such as long or string. Visual Basic provides some special data types for ActiveX control properties, such as OLE_COLOR. This article demonstrates how to use the OLE_COLOR data type.

MORE INFORMATION

The OLE_COLOR data type is internally represented as a 32-bit long integer. However, what makes OLE_COLOR data type unique is that when a property of this type is selected, Visual Basic displays the color palette in the Visual Basic property window and accepts a selection, the same way that the color palette is displayed for the BackColor property of a Form.

An OLE_COLOR property can also be used with the standard color selection window in a custom property page.

The steps below describe how to create a simple ActiveX control with a property of type OLE_COLOR.

Create ActiveX Control

The following steps describe how to create an ActiveX control, with a property name ControlColor of type OLE_COLOR. The control will be designed so the BackColor of the custom control is set to the ControlColor property.

1. In Visual Basic 5.0, create a new ActiveX Control project.

2. From the Project menu, choose Project1 Properties. In the Project Name field, type "OleColorControl" without the quotes. Click OK.

3. View the code for the UserControl and copy the following code:

         Option Explicit
         Private CurrentColor As OLE_COLOR
   

         Public Property Get ControlColor() As OLE_COLOR
            'Retrieve the current value of ControlColor
   
            ControlColor = CurrentColor
   
         End Property
   
         Public Property Let ControlColor(ByVal NewColor As OLE_COLOR)
            CurrentColor = NewColor
            UserControl.BackColor = NewColor
            PropertyChanged "ControlColor"
   
         End Property
   
         Private Sub UserControl_InitProperties()
            'The InitProperties in this example is optional, however the
            'ReadProperties and WriteProperties are required.
            '
            'Set the default ControlColor value to gray.
   
            Me.ControlColor = &H8000000F
         PropertyChanged "ControlColor"
   
         End Sub
   
         Private Sub UserControl_ReadProperties(PropBag As PropertyBag)
            'Without ReadProperties & WriteProperties the ControlColor
            'property would only work in the design environment.
            'The following line of code reads the BackColor property from the
            'PropertyBag. If there is no value for the BackColor property in
            'the PropertyBag, the default is set to &H8000000F (gray).
   
            Me.ControlColor = PropBag.ReadProperty("BackColor", &H8000000F)
   
         End Sub
   
         Private Sub UserControl_WriteProperties(PropBag As PropertyBag)
            'The following line of code saves the BackColor property to the
            'PropertyBag if the ControlColor property is not set, then set to
            'the default, gray.
   
            Call PropBag.WriteProperty("BackColor", Me.ControlColor,
         &H8000000F)
   
         End Sub
   
   

4. Save the Project and compile the OleColorControl.Ocx.

Creating the Test Container

The test container is designed to test the OleColorControl created in the steps above.

1. Create a new Standard EXE project in Visual Basic 5.0. Form1 is created by default.

2. From the Project menu, choose Components. Select the OleColorControl created in the above steps.

3. Add a OleColorControl to Form1.

4. From the Properties Window, choose the ControlColor property. Note that the Color Palette is displayed. Make a selection.

5. Run the Project.

   NOTE: Without the use of ReadProperties and WriteProperties, the control would still change colors when you selected a new color for ControlColor in the design environment. However, because the control gets reinitialized when the form is executed, the color would return to gray when the form is run.

Keywords          : vb5all vb5howto
Version           : WINDOWS:5.0
Platform          : WINDOWS
Issue type        : kbhowto