OLE Controls and Control Containers Guidelines

• Microsoft Visual FoxPro for Windows, versions 3.0, 5.0

SUMMARY

This article explains how to get a document in Microsoft Word version 6.0 for Windows format that provides guidelines for implementing OLE controls and containers that will interoperate well with other controls and containers.

Download Ole-cont.exe, a self-extracting file, from the Microsoft Software Library (MSL) on the following services:

• Microsoft Download Service (MSDL)

        Dial (206) 936-6735 to connect to MSDL
        Download Ole-cont.exe (size: 36832 bytes) 
  

• Internet (anonymous FTP)

        ftp ftp.microsoft.com
        Change to the \softlib\mslfiles directory
        Get Ole-cont.exe (size: 36832 bytes) 
  

MORE INFORMATION

Following is an overview from the document:

The purpose of this document is to provide guidelines for implementing OLE controls and containers that will interoperate well with other controls and containers. This document defines the minimum set of interfaces, methods, and features that are required of OLE Controls and Containers to accomplish seamless and useful interoperability.

These guidelines define the minimum set of functionality that is required of a control and container; it therefore also describes the minimum set of functionality that a control can expect of a container and vice versa. This enables controls and container developers to assume a standard set of functionality and to reasonably rely on the existence of that functionality. Of course, OLE standard return-checking conventions should always be followed.

There are many optional features that OLE controls and OLE control containers can choose to implement, which may or may not be essential to correct operation of the control or container. Some optional features are grouped into function groups. A control or a control container can choose to implement any of these function groups; function groups are not cumulative, so a control or container can support one group without necessarily supporting another. It is important for a control or container to degrade gracefully if a feature or function group it uses is not available. If an optional feature that is essential for correct operation is not available, then the control or container should alert the user and/or should not instantiate itself.

It is important for controls and containers that require optional features (or features specific to a certain container) to be marketed and packaged as such. For example, a control that requires Visual Basic's data-bound list box should be marketed as a Visual Basic-specific control because it cannot run in other containers.

These guidelines explicitly define those features, interfaces, methods, and properties that are mandatory for OLE controls and control containers. Any feature, interface, method, property, or function group that is not explicitly stated as mandatory in these guidelines should be considered optional.