JavaFX LineChart Performance

Question

I\'ve been trying to improve the performance of LineChart in JavaFX but without great success. I also have found that this seems to be a common problem that some programmers hav

Answer 1

I am also using JavaFX charts for a scientific application with tens of thounsands of data points, and have been able to achieve real-time speeds for updating and drawing a graph. There are two main things you need to do.

Firstly, the Ramer-Douglas-Peucker algorithm is unnecessarily complex, I think. Assuming you're working with a nice simple continuous function it's much easier to observe that we only have a limited display resolution and we don't need more than at most three or four data points for every pixel in the domain to convey as much information as possible. For example, one each for the first and last data point to occur within a pixel, and one each for the maximum and minimum within the pixel.

There are a few variations you can try on this strategy but the basic idea is just a nice quick single-pass downsample, and it should basically be lossless. (Or more accurately, it should add no extra representational loss on top of that of rasterisation.) It also limits the number of points to something manageable, and in my experience is fast enough to redraw on zoom or for real-time data updates. It may however cause problems if you have display scaling for HiDPI or are otherwise scaling your graph components for any reason.

The second part is just as important: even if you set the css to not draw the data point shapes, it still takes an inexplicably long time to add the nodes to the scene. To address this it seems sufficient to subclass LineChart and override the dataItemAdded method to be a no-op in the case that you don't want shapes drawn. You should also re-use the data points which are already added to the series where possible rather than add new ones, i.e. prefer series.getData().get(i).setXValue(...) and series.getData().get(i).setYValue(...) to series.setData(...) or series.getData().add(...).