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XPFC - Cross Platform Foundation Classes

Contents

• Overview
• Design
• Dependencies
• Architecture
  • View
  • Parser
  • Layout
  • Shell
  • Model
  • Miscellaneous
• Change History

Overview

The Cross Platform Foundation Classes (XPFC) are a set of interfaces and underlying implementations for supporting applications in a platform-independent manner with code reuse and modularity at the heart of its design.

Information on how resources are defined is here.

Design

The design of XPFC encompasses the following major features:

• Platform Independence - currently running on Win95/98/NT, IRIX & Linux.
• XML based user interface layout design
• XML based user interface widgets (dialogs, toolbars, menubars, buttons, custom ui, etc...)
• Platform-independent Javascript & RDF based localizeable resources
• Full UI definitions available via the internet
• MC support of all UI elements
• Application level downloadable widgets (ie toolbars, menubars, etc...)
• Command based widget communication, which supports multiple levels of Undo throughout the UI
• Plugginable Layout Managers
• Embeddable component support (currently embeds HTML via raptor, and trex calendar)
• Builtin TCP/IP protocol for remotely controlling dynamic UI content

Dependencies

XPFC has 'core' dependencies on the following modules:

• XPCOM
• NSPR 2.0
• Base
• Gfx
• Widget
• XML Parser

In addition, additionally functionality can be dynamically loaded with dependencies on the following modules:

• webshell (aka raptor)
• netlib
• libpref
• javascript

Architecture

The following diagram depicts the general relationship of core XPFC with other modules:

Figure 1: XPFC Module Relationship

Within XPFC, there are several subsystems which play a major role. Their relationship is depicted in the following diagram:

Figure 2: XPFC Subsystems

View Subsystem

This system is comprised of all the visual runtime elements. All visual elements are instances of the core Canvas class.  This class, which aggregates the nsIWidget interface, is the lowest level base class that all system can expect to QueryInterface.

Supporting Containers include Dialogs, Toolbars and Menubars. Supporting widgets include those typically found in application toolbars and dialogs, such as buttons and textfield. The widgets and containers aggregate the Canvas implementation.  Thus, ALL UI elements in the View Subsystem Support the nsIWidget AND nsIXPFCCanvas interfaces.

 

Layout Subsystem

This system is comprised objects that know how to lay out Canvas's. Currently, X/Y Box layout is the only implementation.  Table layout is possible, and width modifications to the Parser Subsystem, the raptor Layout engine could be used here.

Parser Subsystem

This system is comprised of both the XML DTD for XPFC and the ContentSink for the View Subsystem.  The raptor xml parser is used for the majority of this system.

Shell Subsystem

This system is is the entry point for your main application, written as XP code. It offers the toplevel event loop, as well as application level services.

Model Subsystem

This system offers access to predefined runtime definitions of tokenized XML. Multiple UI definitions and parts can be loaded into memory and be referenced by the View subsystem for display.

Miscellaneous

There are a variety of supporting classes in XPFC:

1. ObserverManager: For supporting Subjetc/Observer interfaces
2. CanvasManager: For managing the relationships between canvas'
3. Command System: For supporting arbitrary command passing between objects for multiple levels of Undo
4. Toolkit: The global object accessor
5. Utility:  For stacks, vectors and iterators

Change History