You have seen that you can alter the
appearance of symbols by using parameters and conditions. This
ability is useful for creating rich graphic objects such as dials
or meters, for monitoring activities.You can also make GUI objects
respond to user actions by using interactors. You use an interactor
to create interactive objects by specifying how user actions can
alter the value of a symbol parameter.
This mechanism works as a loop. A user
interaction modifies the value of a parameter, this new value is
processed by the symbol in order to give the appropriate visual
feedback. Both actions in this loop are completely independent,
that is, the interaction does not need to 'know' what the visual
effect is.
The interactor workflow
A symbol interactor detects and processes
input done by the user on a symbol. This input is in the form of
mouse events on the graphical representation of a symbol.
An interactor does one of two things:
- Uses the mouse event to change the value of a parameter in the symbol. Objects bound to the parameter are transformed according to this change in value.
- Passes the event to the object as a condition. This is used for Push and Discrete interactors.
The different kinds of interactions
available are as follows:
- Discrete: Increments or decrements the value of a parameter by a specific amount on a mouse click event. Parameter change is limited by maximum and minimum values.
- Push: Reacts to mouse BUTTON_UP, BUTTON_DOWN, and BUTTON_CLICKED events on a symbol. It sets the value of a string parameter in order to indicate the new state that the symbol could display.
- Horizontal: Changes the value of a parameter when an object is clicked and dragged horizontally. The change in parameter value depends on the distance the object is dragged. Parameter change is limited by maximum and minimum values.
- Vertical: Changes the value of a parameter when an object is clicked and dragged vertically. The change in parameter value depends on the distance the object is dragged. Parameter change is limited by maximum and minimum values.
- Rotation: Changes the value of a parameter when an object is clicked and rotated. The change in parameter value depends on the distance the object is dragged. Parameter change is limited by maximum and minimum values.
Discrete, Horizontal, Vertical, and Rotation
interactors work in the same way. They respond to a mouse event by
changing the value of a symbol parameter. This means that, although
the interactor is applied to a specific object, the change occurs
to any object bound to the parameter. Push interactors use
conditions to transform the object clicked. When a condition has
been created for a push interactor, it can be used to make
simultaneous changes in multiple objects.