Infinite JavaFX coordinate system pane

Question

I need to write a custom pane that behaves like an infinite two-dimensional cartesian coordinate system. When first showing I want 0,0 to be in the center of the pane. The user should be able to navigate the pane by holding down the left mouse button and dragging. It needs to have the ability to zoom in and out. I also have to be able to place nodes at specific coordinates.

Of course I am aware that this is a very specific control and I am not asking anyone to give me step-by-step instructions or write it for me.

I am just new to the world of JFX custom controls and don't know how to approach this problem, especially the whole infinity thing.

Answer 1

This is not so difficult to achieve as you may think. Just start with a simple Pane. That already gives you the infinte coordinate system. The only difference from your requirement is that the point 0/0 is in the upper left corner and not in the middle. This can be fixed by applying a translate transform to the pane. Zooming and panning can then be achieved in a similar way by adding the corresponding mouse listeners to the Pane.

Answer 2

One approach is to render arbitrary content in a Canvas, as suggested here. The corresponding GraphicsContext gives you maximum control of the coordinates. As a concrete example, jfreechart renders charts using jfreechart-fx, whose ChartViewer holds a ChartCanvas that extends Canvas. Starting from this example, the variation below sets the domain axis to span an interval centered on zero after adding corresponding points to the three series. Use the mouse wheel or context menu to zoom; see this related answer for more on zooming and panning.

for (double t = -3; t <= 3; t += 0.5) {
    series.add(t, Math.sin(t) + i);
}
…
xAxis.setRange(-Math.PI, Math.PI);
…
plot.setDomainPannable(true);

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.stage.Stage;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.axis.NumberAxis;
import org.jfree.chart.entity.ChartEntity;
import org.jfree.chart.entity.LegendItemEntity;
import org.jfree.chart.entity.XYItemEntity;
import org.jfree.chart.fx.ChartViewer;
import org.jfree.chart.fx.interaction.ChartMouseEventFX;
import org.jfree.chart.fx.interaction.ChartMouseListenerFX;
import org.jfree.chart.labels.StandardXYToolTipGenerator;
import org.jfree.chart.plot.XYPlot;
import org.jfree.chart.renderer.xy.XYLineAndShapeRenderer;
import org.jfree.data.xy.XYSeries;
import org.jfree.data.xy.XYSeriesCollection;

/**
 * @see https://stackoverflow.com/a/44967809/230513
 * @see https://stackoverflow.com/a/43286042/230513
 */
public class VisibleTest extends Application {

    @Override
    public void start(Stage stage) {
        XYSeriesCollection dataset = new XYSeriesCollection();
        for (int i = 0; i < 3; i++) {
            XYSeries series = new XYSeries("value" + i);
            for (double t = -3; t <= 3; t += 0.5) {
                series.add(t, Math.sin(t) + i);
            }
            dataset.addSeries(series);
        }
        NumberAxis xAxis = new NumberAxis("domain");
        xAxis.setRange(-Math.PI, Math.PI);
        NumberAxis yAxis = new NumberAxis("range");
        XYLineAndShapeRenderer renderer = new XYLineAndShapeRenderer(true, true);
        renderer.setBaseToolTipGenerator(new StandardXYToolTipGenerator());
        XYPlot plot = new XYPlot(dataset, xAxis, yAxis, renderer);
        JFreeChart chart = new JFreeChart("Test", plot);
        ChartViewer viewer = new ChartViewer(chart);
        viewer.addChartMouseListener(new ChartMouseListenerFX() {
            @Override
            public void chartMouseClicked(ChartMouseEventFX e) {
                ChartEntity ce = e.getEntity();
                if (ce instanceof XYItemEntity) {
                    XYItemEntity item = (XYItemEntity) ce;
                    renderer.setSeriesVisible(item.getSeriesIndex(), false);
                } else if (ce instanceof LegendItemEntity) {
                    LegendItemEntity item = (LegendItemEntity) ce;
                    Comparable key = item.getSeriesKey();
                    renderer.setSeriesVisible(dataset.getSeriesIndex(key), false);
                } else {
                    for (int i = 0; i < dataset.getSeriesCount(); i++) {
                        renderer.setSeriesVisible(i, true);
                    }
                }
            }

            @Override
            public void chartMouseMoved(ChartMouseEventFX e) {}
        });
        stage.setScene(new Scene(viewer));
        stage.setTitle("JFreeChartFX");
        stage.setWidth(640);
        stage.setHeight(480);
        stage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}