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2.3.3 OpenDoc Part Editors and Viewers

   Part editor and part handler are two terms that are used in the OpenDoc 
   literature in a synonymous way, just as the words parts and components. 

   There's little difference between the appearance of the OpenDoc window in 
   Figure 13 and that of a similar window in a page-layout application of 
   today; manipulation of the window contents, however, can be very 
   different.  When users interact with OpenDoc parts, the resulting behavior 
   is determined by part editors and part viewers.  A part editor is a 
   full-featured OpenDoc software component that allows the creation, 
   editing, and viewing of parts of a particular kind, just as a conventional 
   application allows manipulation of documents now. 


 


                                              



 
   Figure 13. An OpenDoc Document with Different Parts 

   Like applications, part editors are sold or licensed and are legally 
   protected from unauthorized copying and distribution.  You supply users 
   with the part editor (which the user installs in the Editors folder in the 
   System Folder) and also a stationery pad (which the user will double-click 
   or drag to create an OpenDoc document or part). 

   A part viewer is a special, limited type of part editor that can display 
   and print a particular kind of part but can't be used to create or edit 
   such a part.  Often a part viewer will just be a part editor with its 
   editing and part-creation capabilities removed.  It's important that part 
   viewers be widely available, to allow portability of OpenDoc compound 
   documents across machines and platforms.  Wide availability of a 
   particular part viewer encourages purchase and use of its equivalent part 
   editor, because users will know that other users will be able to view 
   parts created with that editor. 

    ___ Note: ______________________________________________________________  
   |                                                                        | 
   | It may be possible to view a part even when neither its editor nor its | 
   | viewer is present.  The application might have to translate the part   | 
   | to be able to use another compatible editor.  For example, suppose a   | 
   | user creates a document with a text editor named SurfWriter and sends  | 
   | it to someone who doesn't have the SurfWriter editor; the document is  | 
   | translated to a similar format supported by a text editor that the     | 
   | receiving user does have (see "Binding" in topic 2.4.1).               | 
   |                                                                        | 
   |________________________________________________________________________| 

   Users don't work with icons for part editors and part viewers the way they 
   work with application icons today.  Editors and viewers are not launched 
   by double-clicking.  The icons for editors and viewers have a unique 
   shape.  This shape provides maximum customizable space for your 
   identifying elements, with no required badges or identifiers such as hands 
   and pencils. 

   As a step toward becoming fully OpenDoc-compliant (that is, becoming part 
   editors themselves), some applications will be converted to container 
   applications, applications that allow parts to be embedded in their 
   documents, much as some documents today allow the embedding of QuickTime 
   format movies. 

   Many of today's applications have plug-in or extension APIs that may be 
   used to add functionality to the application.  These will continue to be 
   important to extending the capabilities of part editors. 

   OpenDoc part handlers are the applications in the OpenDoc architecture. 
   When a part is being displayed or edited, a part handler is invoked to 
   perform those tasks.  Just as an application performs basic editing, 
   display, and printing tasks for a given document, part handlers perform 
   these functions for parts. 

   Each part handler is responsible for the following basic functions: 

   °   Rendering the part (both on-screen and printing).  The part handler 
       may be asked to display the part on a dynamic medium such as a screen 
       or a static medium such as the printed page. 

   °   Editing the part.  The part handler must accept events and change the 
       state of the part so that you can edit and script the part. 

   °   Storage and memory management for the part.  The part handler is able 
       to read the part from the storage medium into the memory, and manages 
       its association with the part.  It is also able to write the part back 
       out to storage medium. 


   A part and its part handler together form the equivalent of a programmatic 
   object, in the object-oriented programming sense of the word.  The OpenDoc 
   part provides the data, while the part handler deals with the behavior of 
   the data.  When bound together, they form an editable segment of a 
   document. 

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