ITT Rule IDL Version 7.0 User Manual download pdf (Page 68)

68 Chapter 4: Property Management

About the Properties Interface iTool Developer’s Guide

About the Properties Interface

Object properties are used to store settings and values that relate to visualizations,

data, and other components of an iTool. The iTools system presents a graphical

property sheet interface to tool users; see “Property Sheets” (Chapter 6, iTool User’s

Guide) for a description of the property sheet interface. As a tool developer, you can

manage individual property values, as well as the property set that is visible to users

of your application, programmatically.

Note

In most cases, you do not need to manage updates to visualizations or data that

result from a user’s modifications to values in a property sheet. See “Property

Update Mechanism” on page 84 for details.

What is a Property?

A property is a value that is associated with an object instance. Examples of property

values commonly associated with iTool objects are Boolean True/False flags, text

strings, color values stored as RGB triplets, and integer and floating point values. For

example, a plot visualization object might have a Color property that defines the line

color as an RGB triplet, a Line thickness property that defines the thickness of the

line drawn as an integer value in pixels, and a Name property that defines how the

plot is referred to in iTool browser windows.

Properties vs. Preferences

In the case of objects that have a visual representation (plots, annotations, surfaces,

axes, etc.), properties apply to a single instance of an object. When a new instance of

the same type of object is created, any property changes applied to the first object are

not applied to the second. For example, if you change the color of a plot line to red,

subsequent plot lines will still be created with the default line color.

In the case of non-visual objects (operations, file readers and writers, and

manipulators) only one instance of the object is created no matter how many times

the object is requested. As a result, properties set on these objects will “stick” until

changed again. For example, if you change the value of the Width property of the

Smooth operation, the property will retain the value you set until you change it again

or close that iTool.

Finally, properties that apply to all iTools and which are preserved between iTool

sessions are known as preferences. Preferences include default values for properties

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ITT Rule IDL Version 7.0 User Manual Page 68