RootPane: undone commits 7b24842 and c6d1ed9 because it seems to have…

… no effect anymore

- on Windows with FlatLaf window decorations, maybe because of 7f02eb9
- on Windows with standard window decorations, it seems not to work (still shows "white lines" @2.25x on Windows 10; Java 17)
- macOS and Linux do not support fractional scaling and "white lines" shown never be shown on that platforms

flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatRootPaneUI.java

@@ -28,11 +28,8 @@
 import java.awt.LayoutManager;
 import java.awt.LayoutManager2;
 import java.awt.Window;
-import java.awt.event.ComponentAdapter;
-import java.awt.event.ComponentEvent;
 import java.awt.event.ComponentListener;
 import java.beans.PropertyChangeEvent;
-import java.beans.PropertyChangeListener;
 import java.util.function.Function;
 import javax.swing.JComponent;
 import javax.swing.JDialog;
@@ -41,7 +38,6 @@
 import javax.swing.JMenuBar;
 import javax.swing.JRootPane;
 import javax.swing.LookAndFeel;
-import javax.swing.SwingUtilities;
 import javax.swing.UIManager;
 import javax.swing.border.Border;
 import javax.swing.plaf.BorderUIResource;
@@ -88,8 +84,6 @@ public class FlatRootPaneUI
 
 	private Object nativeWindowBorderData;
 	private LayoutManager oldLayout;
-	private PropertyChangeListener ancestorListener;
-	private ComponentListener componentListener;
 	private ComponentListener macFullWindowContentListener;
 
 	public static ComponentUI createUI( JComponent c ) {
@@ -178,40 +172,6 @@ protected void uninstallDefaults( JRootPane c ) {
 	protected void installListeners( JRootPane root ) {
 		super.installListeners( root );
 
-		if( SystemInfo.isJava_9_orLater ) {
-			// On HiDPI screens, where scaling is used, there may be white lines on the
-			// bottom and on the right side of the window when it is initially shown.
-			// This is very disturbing in dark themes, but hard to notice in light themes.
-			// Seems to be a rounding issue when Swing adds dirty region of window
-			// using RepaintManager.nativeAddDirtyRegion().
-			//
-			// Note: Not using a HierarchyListener here, which would be much easier,
-			// because this causes problems with mouse clicks in heavy-weight popups.
-			// Instead, add a listener to the root pane that waits until it is added
-			// to a window, then add a component listener to the window.
-			// See: https://github.com/JFormDesigner/FlatLaf/issues/371
-			ancestorListener = e -> {
-				Object oldValue = e.getOldValue();
-				Object newValue = e.getNewValue();
-				if( newValue instanceof Window ) {
-					if( componentListener == null ) {
-						componentListener = new ComponentAdapter() {
-							@Override
-							public void componentShown( ComponentEvent e ) {
-								// add whole root pane to dirty regions when window is initially shown
-								root.getParent().repaint( root.getX(), root.getY(), root.getWidth(), root.getHeight() );
-							}
-						};
-					}
-					((Window)newValue).addComponentListener( componentListener );
-				} else if( newValue == null && oldValue instanceof Window ) {
-					if( componentListener != null )
-						((Window)oldValue).removeComponentListener( componentListener );
-				}
-			};
-			root.addPropertyChangeListener( "ancestor", ancestorListener );
-		}
-
 		if( SystemInfo.isMacFullWindowContentSupported )
 			macFullWindowContentListener = FullWindowContentSupport.macInstallListeners( root );
 	}
@@ -220,17 +180,6 @@ public void componentShown( ComponentEvent e ) {
 	protected void uninstallListeners( JRootPane root ) {
 		super.uninstallListeners( root );
 
-		if( SystemInfo.isJava_9_orLater ) {
-			if( componentListener != null ) {
-				Window window = SwingUtilities.windowForComponent( root );
-				if( window != null )
-					window.removeComponentListener( componentListener );
-				componentListener = null;
-			}
-			root.removePropertyChangeListener( "ancestor", ancestorListener );
-			ancestorListener = null;
-		}
-
 		if( SystemInfo.isMacFullWindowContentSupported ) {
 			FullWindowContentSupport.macUninstallListeners( root, macFullWindowContentListener );
 			macFullWindowContentListener = null;