COM principle and application----ActiveX control

1. ActiveX control

ActiveX control is a powerful program design and development technology provided by Microsoft. ActiveX control is both an Automation object (and, of course, a standard COM object) and an interface element, as is common control in Windows.

ActiveX control is a comprehensive technology that involves many of the technical essences of COM and OLE, and is closely integrated with Windows operating systems, as an extension of Windows standard control.

Microsoft's use of this Internet control, together with OCX, is collectively known as ActiveX control, and all technologies based on COM and OLE and Internet-related technology are collectively referred to as ActiveX technologies.

2, the technical basis of ActiveX control

The main technical base of ActiveX control is OLE compound document technology, which involves almost all the techniques of interaction between OLE embedded objects and the containment program, including structured storage technology, automation technology, field activation (in-place activation, primarily for embedded objects), property page technology , permanent object technology, the connection object mechanism, and so on.

3. Field activation

field activation (In-place activation) refers to an interface feature of an OLE object that can be edited directly inside the Package container window, so sometimes we also call this feature field editor (In-place editing) or visual editing (visual editing).

In order to implement the field activation feature, it is required that the OLE object and the containment program must adhere to strict interface conventions.

4, Property Page

The property page is a technique for OLE that has become the basic means of expressing properties on a Windows 32-bit platform. An attribute sheet (property sheet) consists of multiple property pages, each of which has a title (also known as a label), usually a modal dialog box, and a property sheet is a modeless window embedded in the Property sheet dialog box.

Property page technology involves four aspects: Client side, COM object, property sheet, and property page. The communication between them is implemented by a set of predefined COM interfaces and API functions.

5. Notification of Property change

Property change notification includes two scenarios: first, when an object changes its properties, it sends a request to the customer asking if the customer is allowed to change the attribute; second, when the object has changed the attribute, it sends a notification to the customer informing the customer that the attribute has been changed.

6, the basic requirements of ActiveX control

Property and method Management, event mechanism, user interface characteristics (visibility), state permanence mechanism.

7. ActiveX Control Basic structure

8. Package Container

An ActiveX-controlled containment program is usually a form or dialog box, or a visual window (view) or Document object for a composite document. Package containers typically manage multiple ActiveX controls, or other Windows common controls.

The basic function of the containment device: layout function, permanent feature, Environment attribute, event handling mechanism, extended control, keyboard function.

The package container program supports different scenarios, called design patterns and run patterns, respectively.