ListView vs. Flowless

FlowlessBenchmark.java

import javafx.application.Application;
import javafx.application.Platform;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.ListCell;
import javafx.scene.control.ListView;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.Region;
import javafx.stage.Stage;

import org.fxmisc.flowless.Cell;
import org.fxmisc.flowless.VirtualFlow;

public class FlowlessBenchmark extends Application {

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

    private int counter = 0;
    private int layoutCounter = 0;
    private BorderPane bp = new BorderPane();

    @Override
    public void start(Stage primaryStage) {

        Scene scene = new Scene(bp, 200, 400);
        primaryStage.setScene(scene);
        primaryStage.show();

        System.out.println("\nNumber of LISTVIEW cell creations/layouts when:");
        ListView<String> lv = new ListView<>( getItems() );
        lv.setCellFactory( this::cellFactory );
        lv.setFixedCellSize( 16.0 );
        benchmark( lv, lv.getItems() );
        
        runLater( 1000, () -> {
            ObservableList<String> flowItems = getItems();
            System.out.println("\nNumber of VIRTUALFLOW cell creations/layouts when:");
            VirtualFlow<String, ?> flow = VirtualFlow.createVertical( flowItems, color -> reg(color) );
            benchmark( flow, flowItems );
        });
    }

    private ObservableList<String> getItems()
    {
        ObservableList<String> items = FXCollections.observableArrayList();
        for(int i = 0; i < 20; ++i) {
            items.addAll("red", "green", "blue", "purple");
        }
        return items;
    }
    
    private void benchmark( Parent listCtrl, ObservableList<String> items )
    {
        bp.setCenter( listCtrl );
        
        runLater( 125, () -> {
            // Reset counters
            counter = 0; layoutCounter = 0;
            // Updating an item in the viewport
            items.set(10, "yellow");
        });

        runLater( 250, () -> {
            // Print counters of previous operation
            System.out.println(" - updating an item in the viewport: " + counter + "/" + layoutCounter);
            // Reset counters
            counter = 0; layoutCounter = 0;
            // Updating an item outside the viewport
            items.set(30, "yellow");
        });

        runLater( 375, () -> {
            // Print counters of previous operation
            System.out.println(" - updating an item outside the viewport: " + counter + "/" + layoutCounter);
            // Reset counters
            counter = 0; layoutCounter = 0;
            // Deleting an item in the middle of the viewport
            items.remove(12);
        });

        runLater( 500, () -> {
            // Print counters of previous operation
            System.out.println(" - deleting an item in the middle of the viewport: " + counter + "/" + layoutCounter);
            // Reset counters
            counter = 0; layoutCounter = 0;
            // Adding an item in the middle of the viewport
            items.add(12, "yellow");
        });

        runLater( 725, () -> {
            // Print counters of previous operation
            System.out.println(" - adding an item in the middle of the viewport: " + counter + "/" + layoutCounter);
            // Reset counters
            counter = 0; layoutCounter = 0;
            // Scrolling 5 items down
            if ( listCtrl instanceof ListView )  ((ListView<?>) listCtrl).scrollTo(5);
            else ((VirtualFlow) listCtrl).showAsFirst( 5 );
        });

        runLater( 850, () -> {
            // Print counters of previous operation
            System.out.println(" - scrolling 5 items down: " + counter + "/" + layoutCounter);
            // Reset counters
            counter = 0; layoutCounter = 0;
            // Scrolling 50 items down
            if ( listCtrl instanceof ListView )  ((ListView<?>) listCtrl).scrollTo(55);
            else ((VirtualFlow) listCtrl).showAsFirst( 55 );
        });

        runLater( 975, () -> {
            // Print counters of previous operation
            System.out.println(" - scrolling 50 items down: " + counter + "/" + layoutCounter);
        });
    }

    private ListCell<String> cellFactory( ListView<String> lv )
    {
        return new ListCell<> () {
            { setStyle("-fx-padding: 0"); }

            @Override
            protected void updateItem(String color, boolean empty) {
                super.updateItem(color, empty);
                setText(null);
                if(empty) {
                    setGraphic(null);
                } else {
                    counter += 1;
                    Region reg = new Region() {
                        @Override
                        protected void layoutChildren() {
                            layoutCounter += 1;
                            super.layoutChildren();
                        }
                    };
                    reg.setPrefHeight(16);
                    reg.setStyle("-fx-background-color: " + color);
                    setGraphic(reg);
                }
            }
        };
    }
    
    private Cell<String, Region> reg(String color) {
        counter += 1;
        Region reg = new Region() {
            @Override
            protected void layoutChildren() {
                layoutCounter += 1;
                super.layoutChildren();
            }
        };
        reg.setPrefHeight(16);
        reg.setStyle("-fx-background-color: " + color);
        return Cell.wrapNode(reg);
    }

    /**
     * Delays the execution of a Runnable on the FX thread by <code>time</code> milliseconds.
     * @param time    Milliseconds to wait before executing <code>runFX</code>.
     * @param runFX Runnable to execute on the FX thread.
     */
    public void runLater( final long time, final Runnable runFX )
    {
        new Thread( () -> 
        {
            long  t0 = System.currentTimeMillis();
            long  t1 = t0 + time;
            
            while ( t0 < t1 ) try { Thread.sleep( t1 - t0 ); } catch ( Exception e ) {}
            finally { t0 = System.currentTimeMillis(); }
            
            Platform.runLater( runFX );
            
        }, "DelayedFx Thread" ).start();
    }
}

output.md

Tested with JDK 16.

ListViewBenchmark:

Number of LISTVIEW cell creations/layouts when:
 - updating an item in the viewport: 1/1
 - updating an item outside the viewport: 0/0
 - deleting an item in the middle of the viewport: 13/13
 - adding an item in the middle of the viewport: 13/13
 - scrolling 5 items down: 5/5
 - scrolling 50 items down: 25/25

FlowlessBenchmark:

Number of VIRTUALFLOW cell creations/layouts when:
 - updating an item in the viewport: 1/1
 - updating an item outside the viewport: 0/0
 - deleting an item in the middle of the viewport: 1/1
 - adding an item in the middle of the viewport: 1/1
 - scrolling 5 items down: 5/5
 - scrolling 50 items down: 25/25