Q179137: Enable Default Processing in a Subclassed Button Control
Article: Q179137
Product(s): Microsoft C Compiler
Version(s): 5.0,6.0
Operating System(s):
Keyword(s): kbfile kbSample kbActiveX kbButton kbCOMt kbCtrlCreate kbDlg kbKeyAccel kbMFC kbVC500 k
Last Modified: 26-JUN-2002
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The information in this article applies to:
- Microsoft Visual C++, 32-bit Enterprise Edition, versions 5.0, 6.0
- Microsoft Visual C++, 32-bit Professional Edition, versions 5.0, 6.0
- Microsoft Visual C++, 32-bit Learning Edition, version 6.0
- Microsoft Visual C++.NET (2002)
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NOTE: Microsoft Visual C++ .NET (2002) supports both the managed code model that is provided by the Microsoft .NET Framework and the unmanaged native Microsoft Windows code model. The information in this article applies to unmanaged Visual C++ code only.
SUMMARY
=======
This article describes how to ensure default command processing when subclassing
the standard Windows Button control to create an MFC ActiveX control. It also
discusses how to determine when a control is the default command in both design-
and run-time modes so that the control is drawn correctly. Finally, the article
addresses how to ensure that the ENTER key gets routed to the current default
command.
MORE INFORMATION
================
The following files are available for download from the Microsoft Download
Center:
Visual C++ 6.0:
DownloadDownload Defbutn.exe now
(http://download.microsoft.com/download/vc60pro/Sample/1/NT4/EN-US/DefButn.exe)
For additional information about how to download Microsoft Support files, click
the following article number to view the article in the Microsoft Knowledge
Base:
Q119591 How to Obtain Microsoft Support Files from Online Services
Microsoft scanned this file for viruses. Microsoft used the most current
virus-detection software that was available on the date that the file was
posted. The file is stored on secure servers that prevent any unauthorized
changes to the file.
Visual C++ .NET:
The following file is available for download from the Microsoft Download Center:
DownloadDownload Defbutnvcnet.exe now
(http://download.microsoft.com/download/VisualStudioNET/Sample/1.4/WIN98MeXP/EN-US/Defbutnvcnet.exe)
Release Date: June 25, 2002
For additional information about how to download Microsoft Support files, click
the following article number to view the article in the Microsoft Knowledge
Base:
Q119591 How to Obtain Microsoft Support Files from Online Services
Microsoft scanned this file for viruses. Microsoft used the most current
virus-detection software that was available on the date that the file was
posted. The file is stored on secure servers that prevent any unauthorized
changes to the file.
The following sections and the DefButn.exe sample code describe how to:
- Make a Subclassed Control That Supports Extended Properties
- Set a Control to Be the Default Command at Run Time
- Use the Caption Property to Display the Command Text
- Draw Correctly Depending Upon Default Command Status
- Ensure That the ENTER Key Gets Routed to the Current Default Command
Make a Subclassed Control That Supports Extended Properties
-----------------------------------------------------------
To create a control that supports extended properties so that the container can
display its extended Default property in the Property Browser window when the
control is selected at design time, do the following:
1. Use the MFC ActiveX ControlWizard in Microsoft Visual C++ to create a new
project called DefBtn.
2. Accept all defaults in step 1.
3. In step 2, select the Button control in response to "Which window class, if
any, should this control subclass?" and accept all other defaults.
4. Click Finish to create the control.
5. In DefBtnctl.cpp add the following miscellaneous status bit to the
_dwDefBtnOleMisc bit mask:
OLEMISC_ACTSLIKEBUTTON
This allows a container that supports extended properties, such as Visual
Basic, to present the Default extended property in its Property Browser
window during design time. When using the control in an application, a
programmer can make your control the default command by setting this property
to "True." Note that in an environment that does not support extended
properties, such as Visual C++, this flag has no effect.
Set a Control to Be the Default Command at Run Time
---------------------------------------------------
To set the default command at run time in an MFC dialog-based container
application that does not support extended properties, add the following call to
the OnInitDialog processing:
CDialog::SetDefID
and pass in the control ID of DefBtn. This will override any other control that
was selected as the default command at design time. You do not need to make any
modifications to the control[ASCII 146]s source code nor to its property page.
Use the Caption Property to Display the Command Text
----------------------------------------------------
To display the command text both at run time and design time, do the following:
1. Expose the stock Caption property using ClassWizard. The subclassed control
automatically draws this property at run time.
2. To display the text at design time you have to include drawing code in the
CDefBtnCtrl::OnDraw member function to check whether the UserMode ambient
property is set to "False" (indicating design mode).
3. Use the CDC::GetInternalText member function to get the current value of the
Caption stock property and draw it using the CDC::DrawText member function.
Draw Correctly Depending Upon Default Command Status
----------------------------------------------------
ActiveX controls implement functionality that the older, pre-Ole Windows controls
(such as the Button control) do not. Because the MFC method of subclassing a
control is a way to support older technology, there tend to be inconsistencies
in certain operations (especially drawing) between subclassed controls and those
developed without subclassing. For example, the Button control does not draw its
border in accordance with Windows 95 user interface guidelines for a default
command.
You can add logic to a subclassed control so that its border is drawn to reflect
the default command status. Look at various CDC member functions such as
DrawEdge to do so. Note that the DefButn.exe sample does not include the code to
do this.
The DefButn.exe sample does include the logic to detect any change in the default
command status when overriding the CDefBtnCtrl::OnAmbientPropertyChange member
function. To determine when a control has been set as the default command on a
form at design time, and to draw correctly depending upon the default command
status in both design- and run-time modes, do the following:
1. If the DISPID of the ambient property passed in is:
DISPID_AMBIENT_DISPLAYASDEFAULT
then obtain the value it changed to by calling the GetAmbientProperty
function.
2. Pass in this DISPID and the address of a BOOL class member variable called
m_bDefault. If "True," the control becomes the default button; "False" means
it is no longer the default button.
3. Call the InvalidateControl function to redraw the control (use
CDefBtnCtrl::OnDraw) with the shadow outline border that indicates that a
command is the default. Use the value of m_bDefault to determine whether you
should draw the outline (True) or remove it (False).
Note that the control draws correctly with respect to focus (user has tabbed to
it). There is no need to manually draw the interior dotted rectangle.
Ensure That the ENTER Key Gets Routed to the Current Default Command
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This section describes how to receive the WM_COMMAND message when the ENTER key
is pressed, and the default command is a subclassed control. In Microsoft Visual
C++ Books Online, "Programming with MFC: Encyclopedia," the article called
"Keyboard Interface" contains the following paragraph:
The container traps the ENTER and ESC keys by including them in its
accelerator table. When one of these keys is pressed, the container
calls the standard method Click in the appropriate control's primary
dispatch interface. The standard Click method is described in Control
Methods.
If you want to do special processing within your control when the ENTER key is
pressed and your control is the default command, you must use the ClassWizard to
expose the DoClick custom method. You should send the Click event back to the
container when your control[ASCII 146]s DoClick method has been called. Use
ClassWizard to expose the Click stock event and call the FireClick() event from
within the CDefBtnCtrl::DoClick() member function to do this.
If no special processing is needed and you just want to ensure that the Click
event gets fired back to the container, then expose the DoClick stock method and
the Click stock event. In MFC's default processing, FireClick will be called for
you.
Additional query words: 4.20 Defbutn Defbutnvcnet
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Keywords : kbfile kbSample kbActiveX kbButton kbCOMt kbCtrlCreate kbDlg kbKeyAccel kbMFC kbVC500 kbVC600 kbWndwClass kbGrpDSMFCATL kbDialog kbAcceleratorKey
Technology : kbVCsearch kbAudDeveloper kbVC500 kbVC600 kbVC32bitSearch kbVCNET kbVC500Search
Version : :5.0,6.0
Issue type : kbhowto
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