ADDITIONAL SYSTEM INFORMATION :
java 18.0.1.1
javafx-sdk-16 through 18.0.1 (latest)
macOS 12.3.1 (21E258)
iMac (Retina 5K, 27-inch, 2020)
72 GB 2133 MHz DDR4
3.8 GHz 8-Core Intel Core i7
AMD Radeon Pro 5500 XT 8 GB

A DESCRIPTION OF THE PROBLEM :
A visible flash occurs when the application is first activated.

I have a screen movie to show this.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Build a simple app.
2. Run the app from a Terminal window (not from inside Intellij IDEA, where it works) using e.g.
   /Library/Java/JavaVirtualMachines/jdk-18.0.1.1.jdk/Contents/Home/bin/java
3. Activate (switch to) the app by clicking it in the Dock or by clicking the app’s title bar or anywhere in the window

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The window should not “flash” when the app is first activated.
ACTUAL -
The window “flashes”, meaning that it goes completely transparent briefly then works normally.

---------- BEGIN SOURCE ----------
import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.geometry.Insets;
import javafx.scene.Cursor;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.Background;
import javafx.scene.layout.BackgroundFill;
import javafx.scene.layout.CornerRadii;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.stage.Stage;

public class FlashingProblem extends Application {

  @Override
  public void start(Stage primaryStage) {
    var root = new Pane();
    // The following line does not work around the bug.
    root.setBackground(new Background(new BackgroundFill(Color.AZURE, CornerRadii.EMPTY, Insets.EMPTY)));
    primaryStage.setScene(new Scene(root, 400, 350));
    primaryStage.show();
  }

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

CUSTOMER SUBMITTED WORKAROUND :
1. Run from inside Intellij IDEA
2. Use javafx-sdk-15.0.1 or earlier

FREQUENCY : always