The JavaFX FileChooser doesn't work well when multiselecting many files (say, 100).

Sample code:


import java.io.File;
import java.util.List;
import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TextArea;
import javafx.scene.control.TextAreaBuilder;
import javafx.scene.layout.VBox;
import javafx.scene.layout.VBoxBuilder;
import javafx.stage.FileChooser;
import javafx.stage.Stage;

public class Bug extends Application
{
    public static void main(String[] args)
    {
        launch(args);
    }

    @Override
    public void start(final Stage primaryStage)
    {
        primaryStage.setTitle("bug");
        Group root = new Group();

        final TextArea textArea = TextAreaBuilder.create().prefWidth(400).wrapText(true).build();

        Button buttonLoad = new Button("open files");
        buttonLoad.setOnAction(new EventHandler<ActionEvent>()
        {

            @Override
            public void handle(ActionEvent arg0)
            {
                FileChooser fileChooser = new FileChooser();

                // Show save file dialog
                List<File> files = fileChooser.showOpenMultipleDialog(primaryStage);
                System.out.println(files.size());
                textArea.setText("Ok, done - " + files.size());
                System.out.println("setText call finished");
            }
        });

        VBox vBox = VBoxBuilder.create().children(buttonLoad, textArea).build();

        root.getChildren().add(vBox);
        primaryStage.setScene(new Scene(root, 500, 400));
        primaryStage.show();
    }
}

So, if you click the button to display the file chooser, it comes up as expected. Multiselect many files (say, about 100).
You will the "System.out.println(files.size());" print to the console immediately after you click ok on the file chooser.
At this point, the file chooser should be hidden - it has already handed us the file list.

However, what I observe is the file chooser stays on the screen for about 10 seconds. CPU Usage goes to 100%, and the entire JavaFX app stops repainting.

About 10 seconds later, the file chooser finally goes away, and the FX app starts repainting per normal.

I have been unable to determine what on earth the FX thread is doing during these 10 seconds.