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<title>Using The BIRT Chart Engine in Your Plug-in</title>
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<h1>Using the BIRT Chart Engine in Your Plug-in</h1>
<div class="summary">
<h2>Summary</h2>
<p>The BIRT Chart Engine is a powerful business chart generation
tool that can be used as a standalone charting component. This article
introduces the basic concepts of BIRT Chart Engine, explains what BIRT
Chart Engine is composed of, and illustrates how to create a chart and
use it as widget.</p>
<div class="author">By Qi Liang, IBM</div>
<div class="copyright">Copyright &copy; 2007 International
Business Machines Corp.</div>
<div class="date">May 14, 2007</div>
</div>
<div class="content">
<h2>Introduction</h2>
<p>Charts are a common and important way to display data in business
intelligence and other applications. Business Intelligence and Reporting
Tools (BIRT), an Eclipsed-based reporting tool, provides not only a nice
report designing tool, but a powerful charting engine. The BIRT Chart
Engine is a good choice for displaying charts in your Eclipse plug-ins,
Eclipse Rich Client Platform (RCP) applications, Java&trade;
applications, and more. It supports numerous chart types, and can be
rendered on SWT/Swing widgets and image files of many formats. In this
article, we show you some of the capabilities the BIRT Chart Engine
provides, and how to use it on an SWT widget in your plug-in.</p>
<h2>What the BIRT Chart Engine can provide</h2>
<p>The BIRT Chart Engine supports a variety of chart types. Here, we
take a look at some of the available chart choices. Note that only basic
and important charts are listed here; you can refer to BIRT
documentation for more details.</p>
<table class="no-border" width="60%" align="center" cellpadding="2">
<tr>
<td width="33%">
<div align="center"><a href="images/bar.png"><img
src="images/bar_s.png" width="128" height="96" border="0"></a></div>
</td>
<td width="33%">
<div align="center"><a href="images/multibar.png"><img
src="images/multibar_s.png" width="128" height="96" border="0"></a></div>
</td>
<td width="33%">
<div align="center"><a href="images/line.png"><img
src="images/line_s.png" border="0"></a></div>
</td>
</tr>
<tr>
<td>
<div align="center">Bar Chart</div>
</td>
<td>
<div align="center">Multi-Bar Chart</div>
</td>
<td>
<div align="center">Line Chart</div>
</td>
</tr>
<tr>
<td>
<div align="center"></div>
</td>
<td>
<div align="center"></div>
</td>
<td>
<div align="center"></div>
</td>
</tr>
<tr>
<td>
<div align="center"><a href="images/pie.png"><img
src="images/pie_s.png" width="128" height="96" border="0"></a></div>
</td>
<td>
<div align="center"><a href="images/stacked.png"><img
src="images/stacked_s.png" border="0"></a></div>
</td>
<td>
<div align="center"><a href="images/scatter.png"><img
src="images/scatter_s.png" border="0"></a></div>
</td>
</tr>
<tr>
<td>
<div align="center">Pie Chart</div>
</td>
<td>
<div align="center">Stacked Chart</div>
</td>
<td>
<div align="center">Scatter Chart</div>
</td>
</tr>
<tr>
<td>
<div align="center"></div>
</td>
<td>
<div align="center"></div>
</td>
<td>
<div align="center"></div>
</td>
</tr>
<tr>
<td>
<div align="center"><a href="images/stock.png"><img
src="images/stock_s.png" border="0"></a></div>
</td>
<td>
<div align="center"><a href="images/area.png"><img
src="images/area_s.png" border="0"></a></div>
</td>
<td>
<div align="center"></div>
</td>
</tr>
<tr>
<td>
<div align="center">Stock Chart</div>
</td>
<td>
<div align="center">Area Chart</div>
</td>
<td>
<div align="center"></div>
</td>
</tr>
</table>
<p align="center"><strong>Figure 1. Chart Samples</strong></p>
<h2>Preparation</h2>
<p>This article uses Eclipse SDK 3.2.2 and BIRT 2.1.1. The Eclipse <a
href="http://www.eclipse.org/callisto/discovery.php">Callisto
Discovery Site</a> can be used to install BIRT and its prerequisite plug-ins
by selecting &quot;Help &gt; Software Updates &gt; Find and
Install...&quot; and choosing &quot;Search for new features to
install&quot; in the update dialog. After selecting a mirror update
site, you can see all features under Callisto Discovery Site as follows.</p>
<p align="center"><img src="images/selectbirt.png"></p>
<p align="center"><strong>Figure 2. The Callisto Update
Site</strong></p>
<p>In this dialog box, select &quot;Eclipse BIRT Report Designer
Framework 2.1.2&quot; and click &quot;Select Required&quot;. Now BIRT
and all its dependency features are selected to install. Then click
&quot;Next&quot;, and install all these features.
<p>BIRT contains about fifty plug-ins, but if you use BIRT Chart
Engine in your application, you only need four of them (along with
several EMF prerequisite plug-ins). They are listed in the following
table. So you just need include these four when distributing your
application.</p>
<table width="80%" border="1" align="center">
<tr>
<td>
<div align="center"><strong>Plug-in Name</strong></div>
</td>
<td>
<div align="center"><strong>Description</strong></div>
</td>
</tr>
<tr>
<td width="37%">org.eclipse.birt.chart.device.extension</td>
<td width="59%">Allows third parties to extend the chart render
device</td>
</tr>
<tr>
<td>
<p>org.eclipse.birt.chart.engine.extension</p>
</td>
<td>Allows third parties to extend the chart engine.</td>
</tr>
<tr>
<td>org.eclipse.birt.chart.engine</td>
<td>Renders charts.</td>
</tr>
<tr>
<td>org.eclipse.birt.core</td>
<td>Provides basic functionalities for all BIRT plug-ins.</td>
</tr>
</table>
<p align="center"><strong>Table 1. BIRT Chart Engine
Plug-ins</strong></p>
<p>You will find all the code snippets shown in this article in the
sample code that you can download at <a
href="com.ibm.examples.chart.zip">com.ibm.examples.chart.zip</a>.</p>
<h2>Concepts</h2>
<p>Before we start to use the chart engine, let's go through the
basic concepts, which can help to understand the chart engine API
better. The following is a simple bar chart, which contains the basic
elements, like the title, axes, and so on.</p>
<p align="center"><img src="images/concepts.png" width="700"
height="500"></p>
<p align="center"><strong>Figure 3. Concepts in a Bar Chart</strong></p>
<table width="60%" border="1" align="center">
<tr>
<th>Concept</th>
<th>Description</th>
</tr>
<tr>
<td>Title Area</td>
<td>The area containing the chart's title.</td>
</tr>
<tr>
<td>Plot Area</td>
<td>The area with red border, containing X and Y axes, the axes
titles, and bars.</td>
</tr>
<tr>
<td>Legend Area</td>
<td>The area that is reserved to host the legend.</td>
</tr>
<tr>
<td>Legend Client Area</td>
<td>The area containing the legend to explain the meaning of each
bar with different series.</td>
</tr>
<tr>
<td>Title</td>
<td>Describes the data that the chart displays.</td>
</tr>
<tr>
<td>Major Grid</td>
<td>Indicates the major scale (minor Grid is supported, but not
displayed here).</td>
</tr>
<tr>
<td>X/Y Title</td>
<td>Describes the meaning of X/Y axis</td>
</tr>
<tr>
<td>X/Y Axis</td>
<td>Provides the label or scale value of X/Y axis</td>
</tr>
<tr>
<td>Series</td>
<td>Defines how to display data, bar, line, or pie, for example</td>
</tr>
</table>
<p align="center"><strong>Table 2. Some Concepts in Chart.</strong></p>
<p>Most charts have two or more axes, but some have none. One
example of a chart with no axis is pie chart. The horizontal axis is
called base axis. The base axis can be category axis or value axis. The
category axis just contains a sequence of labels, while the value axis
contains numeric or datetime values. The vertical axis is an orthogonal
axis, and it is always a value axis. The BIRT Chart Engine supports one
base axis, and one or more orthogonal axes, but only one orthogonal axis
is primary. The series determines how to show data. For example, a bar
series will show data with a bar graph, and a pie series shows data with
a pie chart. The series definition defines the color palette, label
displaying format, and the associated series. Each axis can have more
than one series definition, but typically only one series definition is
used. A series definition can itself have more than one series.</p>
<h2>Create Your First Chart</h2>
<p>Let's see how to create a simple bar chart to understand the
above concepts. This bar chart has one category base axis, and one
orthogonal value axis. It also contains a title and legend as follows:</p>
<p align="center"><img src="images/firstchart.png"></p>
<p align="center"><strong>Figure 4. A Sample Bar Chart.</strong></p>
<p>The complete source can be found in <code>com.ibm.examples.chart.widget.chart.TestChartBuilder</code>.</p>
<ol>
<li>Create chart instance <pre>
chart = ChartWithAxesImpl.create();
chart.setDimension(ChartDimension.TWO_DIMENSIONAL_WITH_DEPTH_LITERAL);</pre>
<p>A bar chart has two axes, so we call <code>ChartWithAxesImpl.create()</code>
to create it. The second statement sets dimension with <code>ChartDimension.TWO_DIMENSIONAL_WITH_DEPTH_LITERAL</code>,
so that the bar is shaded, which looks prettier.</p>
</li>
<li>Set background color of plot <pre> chart.getPlot().setBackground(ColorDefinitionImpl.ORANGE());
chart.getPlot().getClientArea().setBackground(ColorDefinitionImpl.YELLOW());
</pre>
<p>The background color of a plot or a plot's client area can be
changed. The above code sets the plot's background to orange, and sets
the client area's background to yellow.
</li>
<li>Enable legend <pre> chart.getLegend().setItemType(LegendItemType.CATEGORIES_LITERAL);
chart.getLegend().setVisible(true);
</pre>
<p>By default, the legend is disabled, so you need use <code>Legend.setVisible(true)</code>
to enable it. There are two legend types, <code>LegendItemType.CATEGORIES_LITERAL</code>
and <code>LegendItemType.SERIES_LITERAL</code>. The former shows a
different legend icon for each category, and the later shows different
icon for each series.</p>
</li>
<li>Set the chart title <pre> chart.getTitle().getLabel().getCaption().setValue(title);
chart.getTitle().getLabel().getCaption().getFont().setSize(14);
chart.getTitle().getLabel().getCaption().getFont().setName(FONT_NAME);
</pre>
<p>Setting the chart title is very simple, as the first line shows.
You can also set other attributes, like the font size, font name, font
style, and more.</p>
</li>
<li>Create axes <pre><img src="images/tag_1.gif" height=13
width=24 align=bottom> xAxis = ((ChartWithAxes) chart).getPrimaryBaseAxes()[0];
xAxis.getTitle().setVisible(true);
xAxis.getTitle().getCaption().setValue(xTitle);
<img src="images/tag_2.gif" height=13 width=24> yAxis = ((ChartWithAxes) chart).getPrimaryOrthogonalAxis(xAxis);
yAxis.getTitle().setVisible(true);
yAxis.getTitle().getCaption().setValue(yTitle);
yAxis.getScale().setStep(1.0);
</pre>
<p>We get <img src="images/tag_1.gif" height=13 width=24
align=bottom> the first primary base axis as the X axis, while <img
src="images/tag_2.gif" height=13 width=24> the Y axis is
orthogonal to the X axis. By default, the title of the axis is not
visible, so we enable that for both axes and set their titles. Finally,
we specify the scale step on Y axis as 1.</p>
</li>
<li>Create the X series <pre><img src="images/tag_1.gif"
height=13 width=24 align=bottom> TextDataSet categoryValues = TextDataSetImpl.create(dataSet.getCities());
<img src="images/tag_2.gif" height=13 width=24> Series seCategory = SeriesImpl.create();
seCategory.setDataSet(categoryValues);
<img src="images/tag_3.gif" height=13 width=24> SeriesDefinition sdX = SeriesDefinitionImpl.create();
sdX.getSeriesPalette().update(1);
<img src="images/tag_4.gif" height=13 width=24> xAxisPrimary.getSeriesDefinitions().add(sdX);
sdX.getSeries().add(seCategory);
</pre>
<p>The first thing to create the X series is <img
src="images/tag_1.gif" height=13 width=24 align=bottom> to
create the data set to bind. There are four types of data set: they are
<code>DataTimeDataSet</code>, <code>NumberDataSet</code>, <code>StockDataSet</code>,
and <code>TextDataSet</code>. In this example, the X axis is a category
axis, so we use <code>TextDataSet</code>. Then, <img
src="images/tag_2.gif" height=13 width=24> we create a series,
and bind the data set to it. In order to define what the series looks
like, we need to <img src="images/tag_3.gif" height=13 width=24>
create a series definition. The BIRT Chart Engine predefines two color
palettes. Here we choose the first series palette. Finally, we <img
src="images/tag_4.gif" height=13 width=24> add the series
definition to X axis, and add the series to the series definition.</p>
</li>
<li>Create the Y series <pre><img src="images/tag_1.gif"
height=13 width=24 align=bottom> NumberDataSet orthoValuesDataSet1 = NumberDataSetImpl.create(dataSet.getTechnitians());
BarSeries bs1 = (BarSeries) BarSeriesImpl.create();
bs1.setDataSet(orthoValuesDataSet1);
SeriesDefinition sdY = SeriesDefinitionImpl.create();
yAxisPrimary.getSeriesDefinitions().add(sdY);
sdY.getSeries().add(bs1);
</pre>
<p>Creation of the Y series is similar to that of the X series.
Here, the Y axis must be a value axis, so we use a <img
src="images/tag_1.gif" height=13 width=24 align=bottom> <code>NumberDataSet</code>.</p>
</li>
</ol>
<p>In the next section, we will see how to make this chart display
on an SWT canvas.</p>
<h2>Create the Chart Canvas</h2>
<p>The BIRT Chart Engine doesn't provide a SWT chart widget that can
be used directly, so we need create it by ourselves if we want to
display a chart in an editor or view. In the following example, we
create the <code>ChartCanvas</code> class, which extends from <code>Canvas</code>.</p>
<pre> public class ChartCanvas extends Canvas {
...
<br> public ChartCanvas(Composite parent, int style) {
super(parent, style);
// initialize the SWT rendering device
try {
<img src="images/tag_1.gif" height=13 width=24 align=bottom> PluginSettings ps = PluginSettings.instance();
render = ps.getDevice(&quot;dv.SWT&quot;);
} catch (ChartException pex) {
DefaultLoggerImpl.instance().log(pex);
}
...</pre>
<p>In the constructor, <img src="images/tag_1.gif" height=13
width=24 align=CENTER> we need to get the device renderer for
SWT. The device renderer is responsible for rendering a chart onto a
target device. The target device can be an image file or widget toolkit
like SWT or Swing. The BIRT Chart Engine defines nine device renderers
in <code>org.eclipse.birt.chart.util.PluginSettings</code>; they are
shown below:</p>
<table width="55%" border="1" align="center">
<tr>
<th>Device Name</th>
<th>Description</th>
</tr>
<tr>
<td>dv.SWING</td>
<td>Renders a charts using Swing's <code>java.awt.Graphics2D</code>.</td>
</tr>
<tr>
<td>dv.SWT</td>
<td>Renders a chart using SWT's <code>org.eclipse.swt.graphics.GC</code>.</td>
</tr>
<tr>
<td>dv.PNG24</td>
<td>Renders a chart to a 24-bit PNG file (deprecated).</td>
</tr>
<tr>
<td>dv.GIF8</td>
<td>Renders a chart to an 8-bit GIF file (deprecated).</td>
</tr>
<tr>
<td>dv.PNG</td>
<td>Renders a chart to a PNG file.</td>
</tr>
<tr>
<td>dv.GIF</td>
<td>Renders a chart to GIF file.</td>
</tr>
<tr>
<td>dv.JPEG/dv.JPG</td>
<td>Renders a chart to a JPEG file.</td>
</tr>
<tr>
<td>dv.BMP</td>
<td>Renders a chart to a BMP file</td>
</tr>
<tr>
<td>dv.SVG</td>
<td>Renders a chart to an SVG file (requires the <code>org.eclipse.birt.chart.device.svg</code>
plug-in).</td>
</tr>
</table>
<p align="center"><strong>Table 3. Available Device
Renderers.</strong></p>
<p>We selected <code>dv.SWT</code> as our device renderer, since we
will render chart on an SWT widget. In the constructor, we add one paint
listener to do the actual painting work.</p>
<pre><img src="images/tag_1.gif" height=13 width=24> addPaintListener(new PaintListener() {
public void paintControl(PaintEvent e) {
Composite co = (Composite) e.getSource();
final Rectangle rect = co.getClientArea();
if (cachedImage == null) {
<br><img src="images/tag_2.gif" height=13 width=24> buildChart();
<img src="images/tag_3.gif" height=13 width=24> drawToCachedImage(rect);
}
<br><img src="images/tag_4.gif" height=13 width=24> e.gc.drawImage(cachedImage,
0, 0,
cachedImage.getBounds().width,
cachedImage.getBounds().height,
0, 0,
rect.width,
rect.height);
}
});
</pre>
<p>We use double-buffering to draw the chart on the canvas to avoid
flickering while the chart is being drawn. In the paint listener <img
src="images/tag_1.gif" height=13 width=24 align=bottom>, if this
is the first time to get paint event, we <img src="images/tag_2.gif"
height=13 width=24 align=bottom> build the chart via the <code>buildChart()</code>
method, and then <img src="images/tag_3.gif" height=13 width=24
align=bottom> draw the chart on an <code>org.eclipse.swt.graphics.Image</code>
named <code>cachedImage</code> through the <code>drawToCachedImage(...)
method.</code>. Thereafter, the cached image is used to draw the chart with a
call to <code>GC.drawImage(...)</code> <img src="images/tag_4.gif"
height=13 width=24 align=bottom> to draw the cached image on the
widget. The <code>buildChart()</code>, and <code>drawToCachedImage(...)</code>
follow:</p>
<pre> private void buildChart() {<br> Point size = getSize();<br> Bounds bo = BoundsImpl.create(0, 0, size.x, size.y);<br> int resolution = render.getDisplayServer().getDpiResolution();<br><img
src="images/tag_1.gif" height=13 width=24 align=CENTER> bo.scale(72d / resolution);<br> try {<br><img
src="images/tag_2.gif" height=13 width=24 align=CENTER> Generator gr = Generator.instance();<br><img
src="images/tag_3.gif" height=13 width=24 align=CENTER> state = gr.build(render.getDisplayServer(),<br> chart,<br> bo,<br> null,<br> null,<br> null);<br> } catch (ChartException ex) {<br> DefaultLoggerImpl.instance().log(ex);<br> }<br> }<br></pre>
<p>The <code>buildChart()</code> method is responsible for building
the runtime chart state with the render display server. One important
thing to do is to scale the bounds of chart from pixel to point. SWT and
other screen based renders always use pixels as the logical unit.
However, the BIRT Chart Engine uses points, which is an absolute unit (1
point = 1/72 inch). We need to <img src="images/tag_1.gif" height=13
width=24 align=CENTER> scale the bounds of chart from pixels to
points. Another important step is to <img src="images/tag_2.gif"
height=13 width=24> get a <code>Generator</code> instance and <img
src="images/tag_3.gif" height=13 width=24 align=CENTER> build the
runtime chart state with the given chart model and display server. So
the generated runtime chart state takes all necessary information to
render, which includes the <code>DisplayServer</code>, chart model, and
the bounds. The <code>DisplayServer</code> provides rendering-related
information, like DPI (Dots Per Inch) resolution. The bounds define the
area that the generated chart will be drawn on.</p>
<pre> public void drawToCachedImage(Rectangle size) {<br> GC gc = null;<br> try {<br> if (cachedImage != null)<br> cachedImage.dispose();<br> cachedImage = new Image(Display.getCurrent(), imageData);<br>
<img src="images/tag_1.gif" height=13 width=24 align=CENTER> gc = new GC(cachedImage);<br><img
src="images/tag_2.gif" height=13 width=24 align=CENTER> render.setProperty(IDeviceRenderer.GRAPHICS_CONTEXT, gc);
<br> Generator gr = Generator.instance();<br><img
src="images/tag_3.gif" height=13 width=24> gr.render(render, state);<br> } catch (ChartException ex) {<br> DefaultLoggerImpl.instance().log(ex);<br> } finally {<br> if (gc != null)<br> gc.dispose();<br> }<br></pre>
<p>In the <code>drawToCachedImage(...)</code> method we draw the
generated runtime chart state on the cached image. First, we <img
src="images/tag_1.gif" height=13 width=24 align=CENTER> create a
<code>GC</code> for the cached image, and <img src="images/tag_2.gif"
height=13 width=24 align=CENTER> set it into the renderer with
the property name <code>IDeviceRenderer.GRAPHICS_CONTEXT</code>. Then,
generator <img src="images/tag_3.gif" height=13 width=24> asks the
renderer to perform actual rendering with the generated runtime chart
state. Finally, we dispose the <code>GC</code> to ensure that underlying
system resources are released.</p>
<p>Next, we get a SWT canvas widget to display chart and also go
through the process to render the chart to a specific device. Now you
can create an instance of <code>ChartCanvas</code>, assign a chart
instance to it, and insert this canvas into the view.</p>
<h2>Others</h2>
<p><strong>Render Chart to File</strong></p>
<p>The BIRT Chart Engine also supports the rendering of a charts
directly to a file. The process is similar to the above. The difference
is the render device and you needn't use a cached image. First, get the
render device for PNG files. Then, set the render property, <code>IDeviceRender.FILE_IDENTIFIER</code>,
with file name. The other steps are as same as rendering chart on
screen.</p>
<pre> try {
PluginSettings ps = PluginSettings.instance();
render = ps.getDevice(&quot;dv.PNG&quot;);
render.setProperty(IDeviceRenderer.FILE_IDENTIFIER, &quot;chart.png&quot;);
} catch (ChartException ex) {
DefaultLoggerImpl.instance().log(ex);
}
</pre>
<h2><strong>Conclusion</strong></h2>
<p>This article introduces the whole process of using the BIRT Chart
Engine in plug-in development. BIRT Chart Engine supports almost all
types of chart, including bar charts, pie charts, and more. It also has
good abstraction for device renderers, and supports many rendering
devices, including SWT widgets, SWING components, numerous file formats
(JPEG, GIF, and PNG), and more. Although this article focuses on
rendering chart on SWT canvas, the concepts and process to render on
other devices are similar.</p>
</div>
<div class="notices">
<h2>Notices</h2>
Java and all Java-based trademarks and logos are trademarks or
registered trademarks of Sun Microsystems, Inc. in the United States,
other countries, or both.</div>
</body>
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