Q137354: Using Enumerated Properties in an OLE Control
Article: Q137354
Product(s): Microsoft C Compiler
Version(s):
Operating System(s):
Keyword(s): kbfile kbole kbSample kbActiveX kbCOMt kbCtrl kbMFC kbVC100 kbGrpDSMFCATL
Last Modified: 02-FEB-2002
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The information in this article applies to:
- The Microsoft Foundation Classes (MFC), used with:
- Microsoft OLE Control Developer's Kit (CDK)
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SUMMARY
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This is the Visual C++ 1.5x and 2.x version of this sample. There is an
equivalent Visual C++ 4.x 32-bit sample available under the name ENPROP32.
The Enumprop sample illustrates using enumerated properties in an OLE control.
MORE INFORMATION
================
The following files are available for download from the Microsoft Download
Center:
Enprop.exe
For additional information about how to download Microsoft Support files, click
the article number below to view the article in the Microsoft Knowledge Base:
Q119591 How to Obtain Microsoft Support Files from Online Services
Microsoft used the most current virus detection software available on the date of
posting to scan this file for viruses. Once posted, the file is housed on secure
servers that prevent any unauthorized changes to the file.
After downloading Enprop.exe, run it in an empty directory using the -d switch
(as follows) to automatically create subdirectories to hold the many files it
contains:
ENPROP.EXE -d
The ENUMPROP sample illustrates how to use enumerated properties in an OLE
control. An enumerated property is one that has a specific set of possible
values. For example, an OLE control might support a property named FillPattern,
which it uses to determine the type of brush to use when drawing the control and
limit the values the FillPattern property could be set to. Accepted values for a
FillPattern property might be cross-hatched, vertical lines, horizontal lines,
and so on.
An OLE control can limit a user's possible choices for a property by presenting a
drop list combo box that lists the possibilities on its property page. However,
another mechanism is needed to enable a property browser provided by another
application to be able to provide the same type of interface when editing the
property.
There are two ways to implement an enumerated property so that a property browser
can gather enough information about the property to provide the right editing
interface. One method involves declaring an enum type in the OLE control's .odl
file and manually editing the property's declaration to make it be of that type.
For example:
...
typedef enum
{
[helpstring("Solid")] Solid = 0,
[helpstring("Dash")] Dash = 1,
[helpstring("Dot")] Dot = 2,
[helpstring("Dash-Dot")] DashDot = 3,
[helpstring("Dash-Dot-Dot")] DashDotDot = 4,
} enumLineStyle;
...
properties:
// NOTE - ClassWizard will maintain property information here.
// Use extreme caution when editing this section.
//{{AFX_ODL_PROP(CEnumCtrl)
[id(1)] enumLineStyle LineStyle;
//}}AFX_ODL_PROP
...
Another method involves overriding the COleControl methods
OnGetPredefinedStrings, OnGetPredefinedValue, and OnGetDisplayString.
The ENUMPROP sample illustrates using both methods. The OLE control implemented
in the sample supports two custom properties, LineStyle and FillPattern. The
LineStyle property is declared as an enum in the control's .odl file. Support
for using the FillPattern property as an enumerated property is handled by using
overrides of the OnGetPredefinedStrings, OnGetPredefinedValue, and
OnGetDisplayString methods.
ENUMPROP is based on a ControlWizard-generated OLE control. Files included with
the sample, which are directly related to using enumerated properties, are:
Enum.odl - Shows declaring the enum type for the LineStyle property.
Enumctl.cpp - Illustrates overriding the COleControl members
OnGetPredefinedStrings, OnGetPredefinedValue, and
OnGetDisplayString.
NOTE: When building the sample, the MKTYPLIB utility will generate the following
warning when compiling the .odl file:
warning M0002: Warning near line 35 column 35: specified type is not
supported by IDispatch::Invoke
MKTYPLIB is issuing the warning because the enumLineStyle type is not one of the
predefined types supported by IDispatch::Invoke. You can ignore the warning
because the actual value of the LineStyle property is a short, which is a type
supported by IDispatch::Invoke.
NOTE: The test container tool provided with the CDK does not implement a drop
list combo box on its property browser page when editing an enumerated property.
To see the full benefits of using an enumerated property, use an OLE control
container application that provides a property browser with this capability.
RFERENCES
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For more information, please see the Per-Property Browsing section in Appendix D,
OLE Controls Architecture, in the CDK Books Online.
Additional query words: enprop32 kbole kbfile
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Keywords : kbfile kbole kbSample kbActiveX kbCOMt kbCtrl kbMFC kbVC100 kbGrpDSMFCATL
Technology : kbAudDeveloper kbMFC
Version : :
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