OK I could now solve the problem by adding a SWT paint listener which draws a text for every bar:
plotArea.addListener(SWT.Paint, new Listener() {
/**
* The x-axis offset
*/
private int xAxisOffset = 8;
/**
* The y-axis offset.
*/
private int yAxisOffset = 3;
@Override
public void handleEvent(final Event event) {
GC gc = event.gc;
ISeries[] series = chart.getSeriesSet().getSeries();
for (double xAxis : series[0].getXSeries()) {
double techTime = series[0].getYSeries()[(int) xAxis];
double thinkTime = series[1].getYSeries()[(int) xAxis];
int totalTime = (int) Math.round(techTime + thinkTime);
int xCoord = chart.getAxisSet().getXAxis(0).getPixelCoordinate(xAxis) - this.xAxisOffset;
int yCoord = chart.getAxisSet().getYAxis(0).getPixelCoordinate(totalTime / this.yAxisOffset);
gc.drawText(totalTime + " ms", yCoord, xCoord, SWT.DRAW_TRANSPARENT);
}
}
});
After that the SWT bar chart looks like this:

Furthermore to show the values for the dark blue bar and the light blue bar separately, I added a listener which shows the respective value in a tooltip text when hovering over it with the mouse:
plotArea.addListener(SWT.MouseHover, new Listener() {
@Override
public void handleEvent(final Event event) {
IAxis xAxis = chart.getAxisSet().getXAxis(0);
IAxis yAxis = chart.getAxisSet().getYAxis(0);
int x = (int) Math.round(xAxis.getDataCoordinate(event.y));
double y = yAxis.getDataCoordinate(event.x);
ISeries[] series = chart.getSeriesSet().getSeries();
double currentY = 0.0;
ISeries currentSeries = null;
/* over all series */
for (ISeries serie : series) {
double[] yS = serie.getYSeries();
if (x < yS.length && x >= 0) {
currentY += yS[x];
currentSeries = serie;
if (currentY > y) {
y = yS[x];
break;
}
}
}
if (currentY >= y) {
plotArea.setToolTipText(currentSeries.getDescription() + ": " + Math.round(y) + " ms");
} else {
plotArea.setToolTipText(null);
}
}
});