dataset.addDataStyle not working for bar charts

[edkennard]

Hi,

I have a single DefaultErrorDataSet added to a bar chart that's using a HistogramRenderer configured as follows:

val renderer = new HistogramRenderer()
renderer.setDrawBars(true)
renderer.setErrorType(ErrorStyle.NONE)
renderer.setPolyLineStyle(LineStyle.NONE)
renderer.setShiftBar(false)
renderer.setRoundedCorner(false)

I want some bars in the dataset to be rendered one colour, and others another colour. I've tried using dataset.addDataStyle(index, "strokeColor=#FF4C1E;") but the chart ignores these settings.

Instead, as a workaround I've had to create two separate datasets, one for each colour, with blank values in each dataset set to 0.0. I've then applied the different colours using dataSet.setStyle("strokeColor=#FF4C1E;"). This creates some undesirable side-effects though, for example with tooltips.

Should dataset.addDataStyle work in this scenario, or is my workaround actually the recommended approach?

Thanks!

Ed

[wirew0rm]

Hey Ed,

it seems like the Renderer only implements setting the line style (which you disabled) but not the fill:
https://github.com/GSI-CS-CO/chart-fx/blob/master/chartfx-chart/src/main/java/de/gsi/chart/renderer/spi/HistogramRenderer.java#L270
If you look into the implementation of DefaultRendererColorScheme::setLineScheme you can see that the fill is only set based on the dataset index and the point style has no effect.
This is because the DefaultRendererColorScheme is shared with other renderers, which use different routines for drawing the lines and the surfaces.
Please feel free to add a PR for adding this or convert this discussion to an appropriate issue so we can fix this ourself.

As for workarounds, you could switch to use outline bars instead of filled bars. Or just override the renderer method to also call DefaultRendererColorScheme::setFill until this is fixed in ChartFx.

[edkennard]

@wirew0rm Thanks so much for your swift reply, it's a really positive point when working with your library. I was able to join our daily team meeting this morning armed with a clear path to completion on my work integrating chart-fx into our project :)

I will submit a PR to you with a fix which I've already tested and is working well. I added a line to HistogramRenderer immediately after the one you highlighted previously, as follows:

if (dataPointStyle != null) {
  gc.save();
  DefaultRenderColorScheme.setMarkerScheme(gc, dataPointStyle, lindex);
  DefaultRenderColorScheme.setLineScheme(gc, dataPointStyle, lindex);
  DefaultRenderColorScheme.setFillScheme(gc, dataPointStyle, lindex);              //   <-- Added this line
  DefaultRenderColorScheme.setGraphicsContextAttributes(gc, dataPointStyle);
}

The calling code now does this:

dataset.addDataStyle(index, "fillColor=#FF4C1E;")

The original tests all pass, but I will update them to reflect this change before submitting the PR

Cheers

Ed

[edkennard]

The fix for this has now been submitted - #500