JavaFX fullscreen – resizing elements based upon screen size

There are a couple of ways to resize your UI.

Scale by Font Size

You can scale all controls by setting -fx-font-size in the .root of your scene’s style sheet.

For example, if you apply the following stylesheet to your scene, then all controls will be doubled in size (because the default font size is 13px).

.root {
-fx-font-size: 26px;
}

The above will work to scale controls, which is fine for things which are completely control based, but not so good for things which are graphic and shape based.

Scale by Transform

Apply a Scale transform pivoted at (0,0) to your scene’s root node.

Scale scale = new Scale(scaleFactor, scaleFactor);
scale.setPivotX(0);
scale.setPivotY(0);
scene.getRoot().getTransforms().setAll(scale);

To scale a game I developed which includes graphics and various shapes, I used a letter boxing technique which sized the game window to a constant aspect ratio, (similar to the letter boxing you see when you watch a 4:3 tv show on a 16:9 screen).

The SceneSizeChangeListener in the code below listens for changes to the scene size and scales the content of the scene appropriate to the available scene size.

import javafx.application.Application;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.fxml.FXMLLoader;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.layout.Pane;
import javafx.scene.transform.Scale;
import javafx.stage.Stage;
import org.jewelsea.games.supersnake.layout.LayoutController;

import java.io.IOException;
import java.util.ResourceBundle;

/* Main JavaFX application class */
public class SuperSnake extends Application {
  public static void main(String[] args) { launch(args); }

  @Override public void start(final Stage stage) throws IOException {
    FXMLLoader loader = new FXMLLoader(
        getClass().getResource("layout/layout.fxml"),
        ResourceBundle.getBundle("org.jewelsea.games.supersnake.layout.text")
    );
    Pane root = (Pane) loader.load();

    GameManager.instance().setLayoutController(loader.<LayoutController>getController());

    Scene scene = new Scene(new Group(root));
    stage.setScene(scene);
    stage.show();

    GameManager.instance().showMenu();

    letterbox(scene, root);
    stage.setFullScreen(true);
  }

  private void letterbox(final Scene scene, final Pane contentPane) {
    final double initWidth  = scene.getWidth();
    final double initHeight = scene.getHeight();
    final double ratio      = initWidth / initHeight;

    SceneSizeChangeListener sizeListener = new SceneSizeChangeListener(scene, ratio, initHeight, initWidth, contentPane);
    scene.widthProperty().addListener(sizeListener);
    scene.heightProperty().addListener(sizeListener);
  }

  private static class SceneSizeChangeListener implements ChangeListener<Number> {
    private final Scene scene;
    private final double ratio;
    private final double initHeight;
    private final double initWidth;
    private final Pane contentPane;

    public SceneSizeChangeListener(Scene scene, double ratio, double initHeight, double initWidth, Pane contentPane) {
      this.scene = scene;
      this.ratio = ratio;
      this.initHeight = initHeight;
      this.initWidth = initWidth;
      this.contentPane = contentPane;
    }

    @Override
    public void changed(ObservableValue<? extends Number> observableValue, Number oldValue, Number newValue) {
      final double newWidth  = scene.getWidth();
      final double newHeight = scene.getHeight();

      double scaleFactor =
          newWidth / newHeight > ratio
              ? newHeight / initHeight
              : newWidth / initWidth;

      if (scaleFactor >= 1) {
        Scale scale = new Scale(scaleFactor, scaleFactor);
        scale.setPivotX(0);
        scale.setPivotY(0);
        scene.getRoot().getTransforms().setAll(scale);

        contentPane.setPrefWidth (newWidth  / scaleFactor);
        contentPane.setPrefHeight(newHeight / scaleFactor);
      } else {
        contentPane.setPrefWidth (Math.max(initWidth,  newWidth));
        contentPane.setPrefHeight(Math.max(initHeight, newHeight));
      }
    }
  }
}

Here is a screenshot where you can see the letterboxing and scaling taking effect. The green grass in the middle is the main game content screen and scales up and down to fit the available screen area. The wood texture around the outside provides a flexibly sized border which fills in the area where the black letterbox bars would normally be if you were watching a tv program at a different aspect ratio to your screen. Note that the background in the screenshot below is blurry at the title page because I make it so, when the game starts, the blur effect is removed and the view is crisp regardless of the size.

Windowed version:

Scaled full screen version:

You might think that the scaling method above might make everything go all blocky and pixelated, but it doesn’t. All font’s and controls scale smoothly. All standard drawing and graphic commands and css based styles scale smoothly as they are all vector based. Even bitmapped images scale well because JavaFX uses fairly high quality filters when scaling the images.

One trick to get good scaling on images is to provide high resolution images, so that when the screen scales up, the JavaFX system has more raw data to work from. For example, if the preferred window size for an app is quarter of the screen size and it contains a 64×64 icon, instead use a 128×128 icon, so that when the app is put in full screen and all elements scaled, the scaler has more raw pixel data samples to use for interpolating values.

The scaling is also fast as it is hardware accelerated.

how can I remove the message and the effect on click the “esc” key to exit the fullscreen mode?

It’s not possible to remove the full screen exit message in JavaFX 2.2, it will be possible in JavaFX 8:

RT-15314 Allow trusted apps to disable the fullscreen overlay warning and disable the “Exit on ESC” behavior

It will be nice when that is done, because then my games won’t have that “look at me – I look like a beta” feel about them.