import javafx.application.Application;
import javafx.beans.binding.Bindings;
import javafx.beans.binding.DoubleBinding;
import javafx.beans.value.ObservableValue;
import javafx.geometry.Bounds;
import javafx.geometry.Insets;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.control.ScrollPane;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

/**
 * 1) Launch the application.
 * 2) Scroll vertically to the middle of the viewport.
 * 3) Maximize the window.
 * 4) Observe that the scrollpane is now empty.
 * 
 * @author lperkins
 */
public class ScrollPaneMaximizeBug extends Application
{

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

   @Override
   public void start(Stage stage) throws Exception
   {
      stage.setTitle("ScrollPane Bug");
      stage.setScene(new Scene(createContent()));
      stage.centerOnScreen();
      stage.show();
   }

   private Parent createContent()
   {
      VBox content = new VBox(5d);
      content.setPadding(new Insets(5d));
      content.setStyle("-fx-background-color: gold;");
      content.setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);

      for (int i = 0; i < 40; i++)
      {
         Label label = new Label(Integer.toString(i, 10));
         label.setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);
         label.setPrefWidth(350d);
         label.setStyle("-fx-background-color: cyan;");

         content.getChildren().add(label);
      }

      ScrollPane scrollPane = new ScrollPane();
      scrollPane.setContent(content);
      scrollPane.setPrefSize(300, 350);

      // ************************************************************************************************
      // ************************************************************************************************
      /*
       * This appears to be the trouble section of the code. If you comment out these
       * binds, you will not see the behavior. The purpose of the binding is two-fold:
       * 
       * 1) If the preferred size of the content is LESS THAN the viewport size, we want
       * to expand it to the width of the viewport (like setFitToWidth/Height)
       * 
       * -AND-
       * 
       * 2) If the preferred size of the content is GREATER THAN the viewport size, we
       * want to display a scrollbar (setFitToWidth/Height does not allow this).
       */
      ObservableValue<Bounds> viewportBoundsProperty = scrollPane.viewportBoundsProperty();
      content.minWidthProperty().bind(
               Bindings.max(content.prefWidthProperty(), new DimensionBinding(viewportBoundsProperty, true)));
      content.minHeightProperty().bind(
               Bindings.max(content.prefHeightProperty(), new DimensionBinding(viewportBoundsProperty, false)));
      // ************************************************************************************************
      // ************************************************************************************************

      BorderPane borderPane = new BorderPane();
      borderPane.setCenter(scrollPane);
      return borderPane;
   }

   private static class DimensionBinding extends DoubleBinding
   {
      private final ObservableValue<Bounds> property;

      private final boolean width;

      public DimensionBinding(ObservableValue<Bounds> property, boolean width)
      {
         this.property = property;
         this.width = width;

         bind(property);
      }

      @Override
      protected double computeValue()
      {
         Bounds bounds = property.getValue();
         if (bounds == null)
         {
            return 0d;
         }
         else
         {
            return width ? bounds.getWidth() : bounds.getHeight();
         }
      }
   } // end class DimensionBinding

}