Random Lines popping up while pane is moving through scene

Question

I am trying to make a very simple platformer game, but once I added the ability for platforms to move I started to get a really weird "glitch". For some reason, if I move a pane through the scene by an integer value (e.g. block.setLayoutX(block.getLayoutX() + 1)) there is no problem with the program, but once I use a double with decimal points (e.g. ```block.setLayoutX(block.getLayoutX() + 1.5) then random lines began showing up as the block moves throughout the scene.

The code below is a replica of what the issue is in my main program.

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.animation.AnimationTimer;
import javafx.stage.Stage;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.Group;
import javafx.scene.shape.Polygon;
import javafx.scene.shape.Shape;

public class GroupingIssue extends Application{
    public static Pane block = new Pane(PlatformMaker.createPlatform(50, 50, Color.WHITE));
    public static Group ObjectGroup = new Group(block);
    public static Group MainGroup = new Group(ObjectGroup);
    public static Scene MainScene;
    public static AnimationTimer rightDown;
    public static AnimationTimer leftUp;
    @Override public void start(Stage stage){
        MainScene = new Scene(MainGroup);
        rightDown = new AnimationTimer(){
            @Override public void handle(long e){
                block.setLayoutX(block.getLayoutX() + 1.25);
                block.setLayoutY(block.getLayoutY() + 1.25);
                if(block.getLayoutY() > 275){
                    block.setLayoutY(275);
                    block.setLayoutX(275);
                    leftUp.start();
                    stop();
                }
            }
        };
        
        leftUp = new AnimationTimer(){
            @Override public void handle(long e){
                block.setLayoutX(block.getLayoutX() - 1.25);
                block.setLayoutY(block.getLayoutY() - 1.25);
                if(block.getLayoutY() < 25){
                    block.setLayoutY(25);
                    block.setLayoutX(25);
                    rightDown.start();
                    stop();
                }
            }
        };
        
        block.setLayoutX(5);
        block.setLayoutY(5);
        
        stage.setScene(MainScene);
        stage.setWidth(300);
        stage.setHeight(300);
        stage.show();
        
        rightDown.start();
    }
}

class PlatformMaker{
    public static Pane createPlatform(double width, double height, Color c){
        Polygon p = new Polygon(new double[]{-width / 2, -height / 2, -width / 2, height / 2, width / 2, height / 2, width / 2 + 10, height / 2 - 10, width / 2 + 10, -height / 2 - 10, -width / 2 + 10, -height / 2 - 10});
        Polygon p1 = new Polygon(new double[]{width / 2 + 1, height / 2 - 2, width / 2 + 9, height / 2 - 11, width / 2 + 9, -height / 2 - 8, width / 2 + 1, -height / 2 + 1});
        p1.setFill(c);
        Polygon p2 = new Polygon(new double[]{-width / 2 + 2, -height / 2 - 1, width / 2 - 1, -height / 2 - 1, width / 2 + 8, -height / 2 - 9, -width / 2 + 11, -height / 2 - 9});
        p2.setFill(c);
        return new Pane(p, p1, p2);
    }
}

Some of the things I have tried to solve the issue is using a group or using a pane and I have also tried to see what happens if I use a regular rectangle instead of a group and there is no issue when I use a rectangle;

Answer 1

Replicates (sometimes) on:

• JavaFX 21.0.2
• OpenJDK 21.0.12
• OS X Sonoma 14.2.1
• Intel
• MacBook Pro
• Radeon Pro 5500M/Intel UHD 630

The issue seems independent of the graphics card used, as I switched graphics and behavior did not change.

I have two monitors, one is the HiDPI screen on the laptop. When displayed there, there is no visual glitch. If I drag the window to my external monitor, which is a widescreen non-HiDPI screen, I see visual glitches (sometimes).

The glitches will appear more reliably if I add the following line:

block.setCacheHint(CacheHint.QUALITY);

The glitches do not appear if I add the following line:

block.setCacheHint(CacheHint.SPEED);

I advise submitting a bug report. In the bug report you could link back to this question.