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Chapter 7: Creating an Operation
Overview of Creating an iTool Operation
iTool Developer’s Guide
Overview of Creating an iTool Operation
An operation is an iTool component object class that can be used to modify selected
data, change the way a visualization is displayed in the iTool window, or otherwise
affect the state of the iTool. Some examples of iTool operations are:
data, change the way a visualization is displayed in the iTool window, or otherwise
affect the state of the iTool. Some examples of iTool operations are:
•
performing the IDL SMOOTH operation on selected data,
•
rotating a selected visualization by a specified angle,
•
displaying data statistics.
A number of standard operations are predefined and included in the IDL iTools
package; if none of the predefined operations suits your needs, you can create your
own operation by subclassing either from the base IDLitOperation class on which all
of the predefined operations are based, from the IDLitDataOperation class, or from
one of the predefined operations.
package; if none of the predefined operations suits your needs, you can create your
own operation by subclassing either from the base IDLitOperation class on which all
of the predefined operations are based, from the IDLitDataOperation class, or from
one of the predefined operations.
The Operation Creation Process
To create a new iTool operation, you will do the following:
•
Choose an iTool operation class on which your new operation will be based. In
most cases, the operation will act on the data underlying a visualization; in
these cases, you will base your new operation on the IDLitDataOperation
class. If your operation will affect something other than data — the appearance
of visualizations in the iTool window, or the value of some property — you
will base your new class on the IDLitOperation class. Both classes provide
support for the iTool undo/redo system, but operations that do not deal directly
with data require additional code to properly allow for undoing and redoing the
operations.
most cases, the operation will act on the data underlying a visualization; in
these cases, you will base your new operation on the IDLitDataOperation
class. If your operation will affect something other than data — the appearance
of visualizations in the iTool window, or the value of some property — you
will base your new class on the IDLitOperation class. Both classes provide
support for the iTool undo/redo system, but operations that do not deal directly
with data require additional code to properly allow for undoing and redoing the
operations.
•
Define the properties of the operation, and set default property values.
•
If the new operation acts directly on data (that is, if it is based on the
IDLitDataOperation class), provide an Execute method that performs the
operation using the current property values. Similarly, if the new operation is
more general and is based on the IDLitOperation class, provide a DoAction
method.
IDLitDataOperation class), provide an Execute method that performs the
operation using the current property values. Similarly, if the new operation is
more general and is based on the IDLitOperation class, provide a DoAction
method.
•
Optionally provide a DoExecuteUI method to display a user interface for
operations that act directly on data.
operations that act directly on data.
•
For generalized operations, provide UndoOperation and RedoOperation
methods to undo and redo the operation. These methods may in turn require
methods to undo and redo the operation. These methods may in turn require