Pick Packet (edgPickPacket)

Software Customisation Reference Manual

Event Driven Graphics : Pick Packet (edgPickPacket)

Whereas the event packet edgPacket defines what happens before and after a pick or picks have been performed, the pick packet defines the actual pick sequence and types of pick that are to be performed before the action of the event packet is executed.

A pick packet can be defined simple as a single basic pick, pick element, pline, ppoint, etc. Or it can be used to define several consecutive picks, either of the same time or of different types.

Only when all picks within a pick packet have been performed, will the system return control to the owning event packet. This allows the developer to define a standard set of picks required for an interaction, without the need to handle every graphic canvas pick in the utility they are writing.

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Administration data

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Actions

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Pick sequence definitions

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Input Data

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Output Data

Currently the main interface into the object is via members, however, there are several methods available for defining the most common pick types.

Administration Data

Unlike the administrative members of the event object, these members of this object are only for interrogation by the developer and do not perform or define any characteristics of the pick packet, they are only for information.

Actions

There is only one action member of the pick packet object .action this defines the action that is carried out once all the picks within the pick packet definition have been completed.

Where a developer wish to define an action that is triggered on the completion of all picks, then refer to the event packet action section, as the same principles apply to the definition of the pick packet action.

Pick Sequence Definitions

For each pick required by the pick packet, the sequence definition array .picks, must contain one or more pick type objects edgPickType, which define the pick to be carried out by the system. This means that where a pick packet requires two pick, then the sequence definition array .picks will contain two entries.

There are several predefined methods available to the object that allows commonly required pick sequences to be defined. The defined methods describe the pick packet object in their entirety and should not require any modification.

In most instances the predefined methods within the object can be used via a method on the event packet object edgPacket (refer to Pick Sequence Methods). Therefore, in most cases the use of the pick packet predefined methods should not be required.

Input Data

The input data mechanism is identical to that of the event packet input mechanism, i.e. if data is to be passed about within the pick packet definition, then it should be via the .input array (refer to Input Data).

Even though the input member has been included in the system, it currently has not been used within any of the EDG developed so far. Therefore, even though the mechanism is available it has not been extensively tested.

Output Data

The output data mechanism is identical to that of the event packet object (refer to Output Data).