Can't refresh rather than build

MidnightJa

I have a chart that will be refreshed very fast over a period of several seconds, and I want to minimze the flicker effect. I saw in the BIRT documentation that I could do a refresh rather than build and render on the Generator. But if I call refresh() on the Generator, I get a SWTException with the message "Graphic is disposed".

I can't find any way to avoid this, or even a suitable guard that prevents refresh() from being called when the exception will be thrown. Can someone tell me how do do a refresh as the documentation suggests? The documentation says to "Refer to the chart demo that illustrates how an animated chart may be computed with minimal overhead", but I haven't been able to find any such demo.

MidnightJa

Here's my code, which I should have posted yesterday. The code is adapted from an example I found online. It's a test case that plots a sine wave and changes the period of the wave every 500 msec. The code works, but there is some flicker with each update. If you un-comment the line in paintControl() that sets firstRender to false, it will attempt to refresh rather than build and render after the first paint operation. Then the SWTException I mentioned earlier will be thrown on gr.refresh(state).<br />
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<pre class='_prettyXprint _lang-auto _linenums:0'>public class SampleChartView extends ViewPart {

/**
* The ID of the view as specified by the extension.
*/
public static final String ID = "net.midnightjava.charttest.views.SampleChartView";

private static float p = 5;

private static GeneratedChartState state;

private static final class MyPaintListener implements PaintListener
{

boolean firstRender = true;

public void paintControl(PaintEvent e)
{
IDeviceRenderer deviceRenderer = null;
try {
deviceRenderer = PluginSettings.instance().getDevice("dv.SWT");
} catch (ChartException e1) {
e1.printStackTrace();
}
deviceRenderer
.setProperty(IDeviceRenderer.GRAPHICS_CONTEXT, e.gc);

Rectangle rect = ((Composite) e.widget).getClientArea();
Bounds bounds = BoundsImpl.create(rect.x + 2,
rect.y + 2,
rect.width - 4,
rect.height - 4);
bounds.scale(72d /
deviceRenderer.getDisplayServer().getDpiResolution());

Chart chart = null;
if (firstRender) {
chart = createSimpleLineChart();
}

Generator gr = Generator.instance();
try
{
if (firstRender) {
state = gr.build(deviceRenderer.getDisplayServer(),
chart,
bounds,
new RunTimeContext());

gr.render(deviceRenderer, state);
} else {
gr.refresh(state);
}
//firstRender = false;
}
catch (Exception ex)
{
ex.printStackTrace();
}
}
}

private Canvas canvas;

public SampleChartView() {
Job animator = new Job("Animator Job") {

@Override
protected IStatus run(IProgressMonitor monitor) {
if (p == 10) {
p = 5;
} else {
p++;
}
if (!PlatformUI.getWorkbench().getDisplay().isDisposed()) {
PlatformUI.getWorkbench().getDisplay().asyncExec(new Runnable() {

@Override
public void run() {
if (canvas != null && !canvas.isDisposed()) {
canvas.redraw();
}
}

});
}
schedule(500);
return Status.OK_STATUS;
}

};
animator.setSystem(true);
animator.schedule();
}

public void createPartControl(final Composite parent) {
canvas = new Canvas(parent, SWT.NONE);
canvas.addPaintListener(new MyPaintListener());
}

public static final Chart createSimpleLineChart()
{
ChartWithAxes cwaBar = ChartWithAxesImpl.create();
cwaBar.getBlock().setBackground(ColorDefinitionImpl.BLACK());
Plot plot = cwaBar.getPlot();
plot.getOutline().setVisible(false);
cwaBar.getTitle().getLabel().setVisible(false);

Legend lg = cwaBar.getLegend();
LineAttributes lia = lg.getOutline();
lg.getText().getFont().setSize(16);
lia.setStyle(LineStyle.SOLID_LITERAL);
lg.getInsets().set(10, 5, 0, 0);
lg.getOutline().setVisible(false);
lg.setAnchor(Anchor.NORTH_LITERAL);
lg.setVisible(false);

AxisImpl xAxisPrimary = (AxisImpl) cwaBar.getPrimaryBaseAxes()[0];
xAxisPrimary.setType(AxisType.LINEAR_LITERAL);
xAxisPrimary.getMajorGrid().getTickAttributes().setVisible(false);
xAxisPrimary.getOrigin().setType(IntersectionType.MIN_LITERAL);
xAxisPrimary.getTitle().setVisible(false);
xAxisPrimary.getLabel().setVisible(false);
xAxisPrimary.getLineAttributes().setVisible(false);

AxisImpl yAxisPrimary = (AxisImpl) cwaBar.getPrimaryOrthogonalAxis(xAxisPrimary);
yAxisPrimary.getMajorGrid().getTickAttributes().setVisible(false);
yAxisPrimary.getTitle().setVisible(false);
yAxisPrimary.setPercent(false);
yAxisPrimary.getLabel().setVisible(false);
yAxisPrimary.getLineAttributes().setVisible(false);

Vector<Integer> vs = new Vector<Integer>();
for (int i = 1; i <= 512; i++) {
vs.add(i);
}

ArrayList<Double> vn1 = new ArrayList<Double>();
for (float i = 1; i <= 512; i++) {
vn1.add(40 * Math.sin(i / p) + 40);
}

NumberDataSet categoryValues = NumberDataSetImpl.create(vs);
NumberDataSet orthoValues1 = NumberDataSetImpl.create(vn1);

Series seCategory = SeriesImpl.create();
seCategory.setDataSet(categoryValues);
seCategory.setVisible(false);

LineSeries ls = (LineSeries) LineSeriesImpl.create();
ls.setDataSet(orthoValues1);
ls.getLineAttributes().setColor(ColorDefinitionImpl.GREEN());
ls.getMarkers().get(0).setVisible(false);

SeriesDefinition sdX = SeriesDefinitionImpl.create();
sdX.getSeriesPalette().shift(0);
xAxisPrimary.getSeriesDefinitions().add(sdX);

SeriesDefinition sdY = SeriesDefinitionImpl.create();
sdY.getSeriesPalette().shift(0);
yAxisPrimary.getSeriesDefinitions().add(sdY);

sdX.getSeries().add(seCategory);
sdY.getSeries().add(ls);

return cwaBar;
}

@Override
public void setFocus() {
// TODO Auto-generated method stub

}
}</pre>