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This chapter is from the book

Writing event handlers for charts

While a chart is a report item, it is a much more complex report item than any other. The set of events for a chart is much greater than for any other report item. As with all report items, chart scripting is supported in both Java and JavaScript.

Chart events

All chart Java event handlers receive a chart script context object, IChartScriptContext. The chart script context object has methods to get the chart instance, the locale, and the external context. Some chart event handler methods have arguments of the type Chart, Series, Block, MarkerRange, ISeriesRenderer, GeneratedChartState, DataSet, and IDataSetProcessor.

The chart has a different set of events for which you can write event handlers than the other report items. Table 8-2 lists the chart event handler methods and describes when they are called.

Table 8-2. Chart event handler methods

Method

Called

afterDataSetFilled(Series series, DataSet dataSet, IChartScriptContext icsc)

After populating the series data set

afterDrawAxisLabel(Axis axis, Label label, IChartScriptContext icsc)

After rendering each label on a given axis

afterDrawAxisTitle(Axis axis, Label label, IChartScriptContext icsc)

After rendering the title of an axis

afterDrawBlock(Block block, IChartScriptContext icsc)

After drawing each block

afterDrawDataPoint(DataPointHints dph, Fill fill, IChartScriptContext icsc)

After drawing each data point graphical representation or marker

afterDrawDataPointLabel(DataPointHints dph, Label label, IChartScriptContext icsc)

After rendering the label for each data point

afterDrawFittingCurve(CurveFitting cf, IChartScriptContext icsc)

After rendering curve fitting

afterDrawLegendEntry(Label label, IChartScriptContext icsc)

After drawing each entry in the legend

afterDrawMarkerLine(Axis axis, MarkerLine mLine, IChartScriptContext icsc)

After drawing each marker line in an axis

afterDrawMarkerRange(Axis axis, MarkerRange mRange, IChartScriptContext icsc)

After drawing each marker range in an axis

afterDrawSeries(Series series, ISeriesRenderer isr, IChartScriptContext icsc)

After rendering the series

afterDrawSeriesTitle(Series series, Label label, IChartScriptContext icsc)

After rendering the title of a series

afterGeneration(GeneratedChartState gcs, IChartScriptContext icsc)

After generation of a chart model to GeneratedChartState

afterRendering(GeneratedChartState gcs, IChartScriptContext icsc)

After the chart is rendered

beforeDataSetFilled(Series series, IDataSetProcessor idsp, IChartScriptContext icsc)

Before populating the series data set using the DataSetProcessor

beforeDrawAxisLabel(Axis axis, Label label, IChartScriptContext icsc)

Before rendering each label on a given axis

beforeDrawAxisTitle(Axis axis, Label label, IChartScriptContext icsc)

Before rendering the title of an axis

beforeDrawBlock(Block block, IChartScriptContext icsc)

Before drawing each block

beforeDrawDataPoint(DataPointHints dph, Fill fill, IChartScriptContext icsc)

Before drawing each datapoint graphical representation or marker

beforeDrawDataPointLabel(DataPointHints dph, Label label, IChartScriptContext icsc)

Before rendering the label for each datapoint

beforeDrawFittingCurve(CurveFitting cf, IChartScriptContext icsc)

Before rendering curve fitting

beforeDrawLegendEntry(Label label, IChartScriptContext icsc)

Before drawing each entry in the legend

beforeDrawMarkerLine(Axis axis, MarkerLine mLine, IChartScriptContext icsc)

Before drawing each marker line in an axis

beforeDrawMarkerRange(Axis axis, MarkerRange mRange, IChartScriptContext icsc)

Before drawing each marker range in an axis

beforeDrawSeries(Series series, ISeriesRenderer isr, IChartScriptContext icsc)

Before rendering the series

beforeDrawSeriesTitle(Series series, Label label, IChartScriptContext icsc)

Before rendering the title of a series

beforeGeneration(Chart cm, IChartScriptContext icsc)

Before generation of a chart model to GeneratedChartState

beforeRendering(GeneratedChartState gcs, IChartScriptContext icsc)

Before the chart is rendered

Chart script context

All chart event handler methods for both Java and JavaScript receive a chart script context argument in the form of a ChartScriptContext object. The chart script context object provides access to the chart instance object, the Locale and ULocale objects, a logging object, and an external context object. You can also use the ChartScriptContext object to set the external context, the chart instance, and the ULocale.

Table 8-3 lists the methods of the chart script context object and their functions.

Table 8-3. Chart script context event handler methods

Method

Function

getChartInstance( )

Returns the chart instance object.

getExternalContext( )

Returns the IExternalContext object that provides access to a scriptable external object. External scriptable objects are defined in the user application.

getLocale( )

Returns the Locale object for the locale currently in use.

getLogger( )

Returns the Logger object, which can be used for logging messages and errors.

getULocale( )

Returns the ULocale object for the locale currently in use.

setChartInstance(Chart )

Sets the chart instance.

setExternalContext(IEXternalContext)

Sets the external context.

setLogger(ILogger)

Sets the logger.

setULocale(ULocale)

Sets the ULocale.

Chart instance object

As explained in the previous section, you get a chart instance object from the chart script context object. The chart instance object contains methods that provide chart modification functionality. Use the chart instance object to get properties, change properties, and test properties.

Chart instance getter methods

The chart instance getter methods allow you to get various properties of a chart.

Table 8-4 lists the chart instance getter methods and the property values they return.

Table 8-4. Chart instance getter methods

Method

Gets

getBlock( )

The value of the Block containment reference

getDescription( )

The value of the Description containment reference

getDimension( )

The value of the Dimension attribute

getExtendedProperties( )

The value of the Extended Properties containment reference list

getGridColumnCount( )

The value of the Grid Column Count attribute

getInteractivity( )

The value of the Interactivity containment reference

getLegend( )

The Legend block

getPlot( )

The Plot block

getSampleData( )

The value of the Sample Data containment reference

getScript( )

The value of the Script attribute

getSeriesForLegend( )

An array of series whose captions or markers are rendered in the Legend

getSeriesThickness( )

The value of the Series Thickness attribute

getStyles( )

The value of the Styles containment reference list

getSubType( )

The value of the Sub Type attribute

getTitle( )

The Title block for the chart

getType( )

The value of the Type attribute

getUnits( )

The value of the Units attribute

getVersion( )

The value of the Version attribute

Chart instance setter methods

The chart instance setter methods allow you to set various properties of a chart. Table 8-5 lists the chart instance setter methods and the values they set.

Table 8-5. Chart instance setter methods

Method

Sets

setBlock(Block value)

The value of the Block containment reference

setDescription(Text value)

The value of the Description containment reference

setDimension(Chart Dimension value)

The value of the Dimension attribute

setGridColumnCount(int value)

The value of the GridColumnCount attribute

setInteractivity(Interactivity value)

The value of the Interactivity containment reference

setSampleData( )

The value of the Sample Data containment reference

setScript( )

The value of the Script attribute

setSeriesThickness( )

The value of the Series Thickness attribute

setSubType( )

The value of the Sub Type attribute

setType( )

The value of the Type attribute

setUnits( )

The value of the Units attribute

setVersion( )

The value of the Version attribute

Writing a Java chart event handler

Writing a Java chart event handler is not different from writing a Java event handler for any other kind of report item. For more information about writing Java event handlers, see Chapter 10, "Using Java to Write an Event Handler."

Writing a JavaScript chart event handler

The process of writing a JavaScript chart event handler differs from the process of writing an event handler for other report items. The primary difference is that the Script tab does not contain a selectable list of chart events. For chart events, you must include every event handler script for the chart in one place.

The Script tab of the BIRT Report Designer for a chart contains a set of function stubs to assist you in writing a chart event handler. The set of stubs is a subset of the chart events, consisting only of the before events, such as beforeDataSetFilled( ). Figure 8-12 shows the Script tab as it appears before any event handlers have been typed.

Figure 8-12

Figure 8-12 Script tab

The before events are the most common events to script. If you need to write an after event handler, such as afterDataSetFilled( ), you can find the signature of the event handler earlier in this chapter or by viewing the interface IChartEventHandler in the Chart Engine API Reference in the BIRT online help.

To write handler code for one of the before chart events, uncomment the appropriate function statement in the Script tab and type the code between the parentheses, as shown in Figure 8-13.

Figure 8-13

Figure 8-13 Chart event handler code with a standard function declaration

If you want to write an event handler that does not have a stub in the Script tab, you must type the function declaration yourself. When typing a new function declaration, follow the format of the function declarations in the stubs.

Figure 8-14 shows the entry of an afterDrawElement( ) script.

Figure 8-14

Figure 8-14 Chart event handler code with a custom function declaration

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