Table Of Contents

Graph IDE ► Overview ► Event Qualifier

Event Qualifiers are used to implement hit detection and subsequent processing by an algorithm you implement. For example, place two Circles on a Graphic View, implement the Event Qualifiers for those circles and then when the circle is clicked on an algorithm can be called to control a device such as a valve. Event Qualifiers work on data as well so you can hit a data point on a graph and interact with parameters associated with that data point. For example, a price and earnings scatter plot of symbols shows distributions and a user can click on a symbol to process results. The default behavior is to present a Information Selector such as in the following figure.

In practice, the behavior you implement can be as simple as using the Information Selector or can be very specific and integrated. Once you have Event Qualifiers running on a document within Graph IDE then you can embed that document's Graphic View into a Custom Application to make a precise interface. The example above can be implemented on a Mac or iPhone so an operator can control a process at a station in a control center or can be driving to a remote location while touching a circle to control the process.

The capabilities of Event Qualifiers are too enormous to discuss in full detail so this section is merely concerned with an overview of the implementation, not the domain-specific details. To experiment with Event Qualifier processing select the menu item Graph IDE ► Palettes ► Event Qualifiers ► Conglomerate. That shows hit processing behavior for several objects including circles, 3D graphs and 2D graphs.

To implement the example shown in the figure above follow these steps:

• Add the circles, rectangles, text and lines to a document.

• Select each circle individually and enter the following into the circle's Program Inspector Editor and click the Apply button.

  @@class() Circle:Object @@method(public, class) (id)stored; @@end { id myCircle; myCircle = [Circle stored]; }

• Turn on Execute During Animation.

• Drag select some graphics to bring forward the layer inspector editor and in its Program Inspector Editor enter the following and click the Apply button.

  @@class() Layer:Object @@method(public, class) (id)stored; @@method(public, instance) (void)enableEventQualifier; @@end { id myLayer, myEventQualifier; myLayer = [Layer stored]; [myLayer enableEventQualifier]; }

• Execute During Animation is on by default for layers so you do not have to explicitly turn it on.

To engage the event qualifiers select the menu item Graph IDE ► Tools ► Programming ► Enable Event Qualifiers. To execute the programs select the menu item Graph IDE ► Tools ► Programming ► Execute Program. All normal event processing is now intercepted by the event qualifiers so when you mouse over a circle the Information Selector is shown. To turn off event qualifiers and restore normal event editing select the menu item Graph IDE ► Tools ► Programming ► Disable Event Qualifiers.

The following are a few things to consider when programming event qualifiers.

• Event Qualifier could have been implemented without programming. However, the idea is that a Plugin will be used to overload the Event Qualifier methods to implement your specific processing and that eventually the code for that plugin will be used by a Custom Application.

• The Information Selector behavior is optional and can be disengaged so that only your precise processing can be implemented. The Information Selector shows the parameters that are available for processing. Those parameters can include hit graphic index, hit coordinates, data point index and segment index.

• This event qualifier implementation may appear elaborate and unnecessarily complicated. However, the value that can be accessed by using it looms over the modest implementation details.

To read about the programmatic aspects of event qualifiers see the section Custom Application ► Event Qualifier.