@Override
	protected void installDefaults( JRootPane c ) {
		super.installDefaults( c );

		// Give the root pane useful background, foreground and font.
		// Background is used for title bar and menu bar if native window decorations
		// and unified background are enabled.
		// Foreground and font are usually not used, but set for completeness.
		// Not using LookAndFeel.installColorsAndFont() here because it will not work
		// because the properties are null by default but inherit non-null values from parent.
		if( !c.isBackgroundSet() || c.getBackground() instanceof UIResource )
			c.setBackground( UIManager.getColor( "RootPane.background" ) );
		if( !c.isForegroundSet() || c.getForeground() instanceof UIResource )
			c.setForeground( UIManager.getColor( "RootPane.foreground" ) );
		if( !c.isFontSet() || c.getFont() instanceof UIResource )
			c.setFont( UIManager.getFont( "RootPane.font" ) );

		// Update background color of JFrame or JDialog parent to avoid bad border
		// on HiDPI screens when switching from light to dark Laf.
		// Window background color is also used in native window decorations
		// to fill background when window is initially shown or when resizing window.
		// The background of JFrame is initialized in JFrame.frameInit() and
		// the background of JDialog in JDialog.dialogInit(),
		// but it was not updated when switching Laf.
		Container parent = c.getParent();
		if( parent instanceof JFrame || parent instanceof JDialog ) {
			Color background = parent.getBackground();
			if( background == null || background instanceof UIResource )
				parent.setBackground( UIManager.getColor( "control" ) );
		}

		macClearBackgroundForTranslucentWindow( c );
	}
Provides the Flat LaF UI delegate for {@link javax.swing.JRootPane}.

<!-- FlatRootPaneUI -->

@uiDefault RootPane.border								Border
@uiDefault RootPane.activeBorderColor					Color
@uiDefault RootPane.inactiveBorderColor					Color
@uiDefault TitlePane.borderColor							Color	optional

<!-- FlatWindowResizer -->

@uiDefault RootPane.font									Font	unused
@uiDefault RootPane.background							Color
@uiDefault RootPane.foreground							Color	unused
@uiDefault RootPane.borderDragThickness					int
@uiDefault RootPane.cornerDragWidth						int
@uiDefault RootPane.honorFrameMinimumSizeOnResize		boolean
@uiDefault RootPane.honorDialogMinimumSizeOnResize		boolean

@author Karl Tauber
flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatRootPaneUI.java