Inside Macintosh: Cyberdog Programmer's Kit / Part 2 - Programming in Cyberdog

Chapter 4 - Creating a Cyberdog Display Part

This chapter outlines the steps you take to create an editor for a Cyberdog display part. A Cyberdog display part is an OpenDoc part that can retrieve and display data from an Internet location specified by a Cyberdog item; for example, the contents of an HTTP or Gopher site. Specifically, a Cyberdog display part class is a subclass of ODPart that has a Cyberdog part extension.

You create a Cyberdog display part editor much as you create an editor for any OpenDoc part; for example, you specify how data is rendered and stored, and you specify its resources. However, creating a Cyberdog display part editor involves a few additional steps, as follows:

• Implement a Cyberdog part extension subclass to allow Cyberdog to communicate with your part editor.
• Implement the OpenDoc extension protocol in your part editor.
• Use window-position hints when your part is opened.
• Replace OpenDoc's Document menu with Cyberdog's Document menu.
• Access data referenced by a Cyberdog item; for example, by using a Cyberdog stream to download data for display.
• Allow Cyberdog to participate in closing your part's windows.
• Support Cyberdog's service menus, as described in "Displaying Cyberdog Menus" (page 105).
• Modify your part's name-mapping ('nmap') resource to support the Cyberdog part kind of data.

This chapter illustrates these steps using a sample Cyberdog display part, CybTxtViewer, which downloads and displays text. Cyberdog already provides a real display part for text; your display part would likely display other kinds of data or display text data some other way.

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Chapter Contents

Implementing Your Cyberdog Part Extension

Associating a Part Extension With a Display Part

Overriding Cyberdog Part Extension Methods

Implementing Your Cyberdog Display Part Class

Modifying Your ODPart Subclass

Implementing the OpenDoc Extension Protocol

Releasing the Part Extension

Creating and Destroying the Display Part Object

Supporting Cyberdog's Document Menu

Using Window-Position Hints

Creating a Stream for Downloading

Downloading From the Stream

Locating the Cyberdog Item's Window

Closing Your Display Part's Window

Modifying Your Name-Mapping Resource