ParaQ:API

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Revision as of 17:28, 21 October 2005 by Clinton (talk | contribs) (→‎Use Cases)
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Overview

We need to establish the architecture for how the GUI code interacts with the Server Manager.

Goals

The goals of designing this architecture are:

  • Establish a general method for how the GUI talks to the Server Manager.
  • Provide a way for the GUI to update correctly if a scripting client is modifying the server.
  • Be designed to minimize traffic with the server.
  • Decouple GUI from Server Manager to allow using of Qt Designer.
  • To provide functionality such that multiple inheritance of VTK & Qt objects is not necessary (toolkits have different object management schemes).
  • Allow GUI to control behavior. Meaning, Server Manager or API doesn't impose behavior on the GUI.

Use Cases

Description: Use case of API linking SM properties with Qt properties. Object controller controls behavior of GUI panel (vtkSphereSource). GUI panel could be generated or designed. API takes properties to set in bulk to minimize possible network traffic.
Description: Use case of a pipeline inspector/browser. API provides GUI with events for proxy creation. API also provides GUI with events for input/output connections between proxies. GUI calls SM directly to manipulate the pipeline.
Description: Use case of linked views. Can linked views be thought of as linked properties and a view watching for property changes?
 
Histogram Use case:
  Histogram will watch for modified
 events and then pull data through
 pipeline to display histogram.

Design

The GUI will call the Server Manager directly. It is likely a set of "helper" or "convenience" functions that can serve multiple parts of the GUI will be made to help the GUI talk to the Server Manager.

The bulk of our design time was spent on how the Server Manager updates the GUI. An "Event Relay" will be used to relay events from the Server Manager, and present them to the GUI in the way the GUI likes.

The Event Relay presents the GUI with two classes of events:

  • Server Manager Events
  • Object Events

Server Manager Events includes these events:

  • New Object instantiated
  • Object deleted
  • selection/pick

Object Events include these events:

  • object property changed
  • input/output object connection
  • object progress

ParaQAPIDesign.png

Assumptions

It is assumed that Compound Filters, Linked Views, and Histogram Data will be implemented in the Server Manager and the GUI can use the aforementioned events to get updated when those change.


Implementation Details

The Event Relay will contain Qt signals that Qt objects in the GUI can connect to. The signal signatures will be Qt friendly. For example, a property changed signal will have parameters of which property of an object changed and what the value of the property is. The Event Relay will translate events if necessary into a form the GUI would like. For example, if the Server Manager sends an event about object connections, the Event Relay will change that into an object input/output connection signal. In other words, Server Manager level events will be translated to object level events. The vtkEventQtSlotConnect class will be used by the Event Relay. It contains a generic signal signature to connect to. The Event Relay will change the parameters into ParaQ frirendly parameters.

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