JavaFX setFitHeight()/setFitWidth() for an image used within a scrollPane disables panning

Question

So I am creating a map in JavaFX and I would like to have the whole map visible at times. However, the issue is that after I set the imageView to fit the screen size then adding it to the scrollPane my zoom function works fine, but once I zoom in I am not allowed to pan around the image. Below is the code that I have written.

package gameaspects;

import java.awt.GraphicsDevice;
import java.awt.GraphicsEnvironment;

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.ScrollPane;
import javafx.scene.control.ScrollPane.ScrollBarPolicy;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.input.ScrollEvent;
import javafx.scene.layout.AnchorPane;
import javafx.stage.Stage;

public class SourceCodeVersion8 extends Application{

final double SCALE_DELTA = 1.1;
public double SCALE_TOTAL = 1;

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

@Override
public void start(Stage primaryStage) throws Exception {
    AnchorPane mapAnchorO = addMapAnchor();
    Scene mapScene = new Scene(mapAnchorO);
    primaryStage.setScene(mapScene);
    primaryStage.setFullScreen(true);
    primaryStage.setResizable(false);
    primaryStage.show();
}

//Creates an AnchorPane for the map
private AnchorPane addMapAnchor()
{
    AnchorPane mapAnchor = new AnchorPane();
    ScrollPane mapScrollO = addMapScroll();
    mapAnchor.getChildren().add(mapScrollO);
    AnchorPane.setLeftAnchor(mapScrollO, 0.0);
    AnchorPane.setTopAnchor(mapScrollO, 0.0);
    AnchorPane.setBottomAnchor(mapScrollO, 0.0);
    AnchorPane.setRightAnchor(mapScrollO, 0.0);
    return mapAnchor;
}

//Creates an ImageView for the map
private ImageView addMapView()
{
    Image mapImage = new Image("WorldProvincialMap-v1.01.png");
    ImageView mapView = new ImageView(mapImage);
    GraphicsDevice gd =               GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice();
    int width = gd.getDisplayMode().getWidth();
    int height = gd.getDisplayMode().getHeight();
    mapView.setFitHeight(height);
    mapView.setFitWidth(width);
    return mapView;
}

//Creates a scrollPane for the map
private ScrollPane addMapScroll()
{
    ScrollPane mapScroll = new ScrollPane();
    ImageView mapViewO = addMapView();
    mapScroll.setContent(mapViewO);
    mapScroll.setPannable(true);
    mapScroll.setVbarPolicy(ScrollBarPolicy.NEVER);
    mapScroll.setHbarPolicy(ScrollBarPolicy.NEVER);
    mapScroll.addEventFilter(ScrollEvent.ANY, e ->{
        e.consume();
        if(e.getDeltaY() == 0)
        {
            return;
        }
        double scaleFactor =
                  (e.getDeltaY() > 0)
                    ? SCALE_DELTA
                    : 1/SCALE_DELTA;

        if(scaleFactor * SCALE_TOTAL >= 1)
        {
            mapScroll.setScaleX(mapScroll.getScaleX() * scaleFactor);
            mapScroll.setScaleY(mapScroll.getScaleY() * scaleFactor);
            SCALE_TOTAL *= scaleFactor;
        }
    });
    return mapScroll;
    }
}

Answer 1

You're scaling the ScrollPane instead of the content. Furthermore even if you scale the ImageView, scaleX and scaleY are not taken into account when it comes to calculating the content's size. Therefore the ImageView should also be wrapped in a Group:

private ScrollPane addMapScroll() {
    ScrollPane mapScroll = new ScrollPane();
    ImageView mapViewO = addMapView();
    mapScroll.setContent(new Group(mapViewO));
    mapScroll.setPannable(true);
    mapScroll.setVbarPolicy(ScrollBarPolicy.NEVER);
    mapScroll.setHbarPolicy(ScrollBarPolicy.NEVER);
    mapScroll.addEventFilter(ScrollEvent.ANY, e -> {
        e.consume();
        if (e.getDeltaY() == 0) {
            return;
        }
        double scaleFactor
                = (e.getDeltaY() > 0)
                        ? SCALE_DELTA
                        : 1 / SCALE_DELTA;

        if (scaleFactor * SCALE_TOTAL >= 1) {
            mapViewO.setScaleX(mapViewO.getScaleX() * scaleFactor);
            mapViewO.setScaleY(mapViewO.getScaleY() * scaleFactor);
            SCALE_TOTAL *= scaleFactor;
        }
    });
    return mapScroll;
}

To "keep the center centered" you need to adjust he scroll positions accordingly:

if (scaleFactor * SCALE_TOTAL >= 1) {
    Bounds viewPort = mapScroll.getViewportBounds();
    Bounds contentSize = mapViewO.getBoundsInParent();

    double centerPosX = (contentSize.getWidth() - viewPort.getWidth()) * mapScroll.getHvalue() + viewPort.getWidth() / 2;
    double centerPosY = (contentSize.getHeight() - viewPort.getHeight()) * mapScroll.getVvalue() + viewPort.getHeight() / 2;

    mapViewO.setScaleX(mapViewO.getScaleX() * scaleFactor);
    mapViewO.setScaleY(mapViewO.getScaleY() * scaleFactor);
    SCALE_TOTAL *= scaleFactor;

    double newCenterX = centerPosX * scaleFactor;
    double newCenterY = centerPosY * scaleFactor;

    mapScroll.setHvalue((newCenterX - viewPort.getWidth()/2) / (contentSize.getWidth() * scaleFactor - viewPort.getWidth()));
    mapScroll.setVvalue((newCenterY - viewPort.getHeight()/2) / (contentSize.getHeight() * scaleFactor  -viewPort.getHeight()));
}