Under some conditions, the Y axis of XYChart instances is taking too much horizontal space.

package test;

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.chart.LineChart;
import javafx.scene.chart.NumberAxis;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

public class Test_ChartYAxis extends Application {
    
    @Override
    public void start(Stage primaryStage) {
        final NumberAxis xAxis = new NumberAxis(0, 10, 1);
        final NumberAxis yAxis = new NumberAxis(0, 2.2, 0.2);
        yAxis.setStyle("-fx-border-color: green;");
        final LineChart chart = new LineChart(xAxis, yAxis);
        final StackPane root = new StackPane();
        root.getChildren().add(chart);
        final Scene scene = new Scene(root, 500, 3000);
        primaryStage.setTitle("Test");
        primaryStage.setScene(scene);
        primaryStage.show();
    }

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

In JDK8u40, the Y axis on this test chart is 105 pixels wide. This leaves a huge blank space on the left side of the chart.

If instead you use a Y axis definition such as :

final NumberAxis yAxis = new NumberAxis(0, 10, 1);

Then the axis is only 22 pixels wide instead.

It looks like, when pre-calculating its width, the axis class is producing tmp labels, texts or strings that contains non-rounded floating points values so they are way longer than the ones that end up being generated on screen. This is probably why the Y axis' width is way too large under some conditions.