Window decorations:

- use window border color from UI defaults
- support "active" and "inactive" window border colors
- better window border colors for dark themes

CHANGELOG.md

@@ -4,6 +4,8 @@ FlatLaf Change Log
 ## Unreleased
 
 - Hide focus indicator when window is inactive.
+- Improved/fixed window border color in dark themes in custom window
+  decorations.
 
 
 ## 0.37

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

@@ -25,7 +25,7 @@ import java.awt.Graphics2D;
 import java.awt.Insets;
 import java.awt.LayoutManager;
 import java.awt.LayoutManager2;
-import java.awt.Toolkit;
+import java.awt.Window;
 import java.beans.PropertyChangeEvent;
 import java.util.function.Function;
 import javax.swing.JComponent;
@@ -51,6 +51,8 @@ import com.formdev.flatlaf.util.SystemInfo;
  * <!-- FlatRootPaneUI -->
  *
  * @uiDefault RootPane.border								Border
+ * @uiDefault RootPane.activeBorderColor					Color
+ * @uiDefault RootPane.inactiveBorderColor					Color
  *
  * <!-- FlatWindowResizer -->
  *
@@ -323,19 +325,20 @@ public class FlatRootPaneUI
 	public static class FlatWindowBorder
 		extends BorderUIResource.EmptyBorderUIResource
 	{
+		protected final Color activeBorderColor = UIManager.getColor( "RootPane.activeBorderColor" );
+		protected final Color inactiveBorderColor = UIManager.getColor( "RootPane.inactiveBorderColor" );
+		protected final Color baseBorderColor = UIManager.getColor( "Panel.background" );
+
 		public FlatWindowBorder() {
 			super( 1, 1, 1, 1 );
 		}
 
 		@Override
 		public void paintBorder( Component c, Graphics g, int x, int y, int width, int height ) {
-			Object borderColorObj = Toolkit.getDefaultToolkit().getDesktopProperty(
+			Container parent = c.getParent();
-				"win.frame.activeBorderColor" );
+			boolean active = parent instanceof Window ? ((Window)parent).isActive() : false;
-			Color borderColor = (borderColorObj instanceof Color)
-				? (Color) borderColorObj
-				: UIManager.getColor( "windowBorder" );
 
-			g.setColor( borderColor );
+			g.setColor( FlatUIUtils.deriveColor( active ? activeBorderColor : inactiveBorderColor, baseBorderColor ) );
 			HiDPIUtils.paintAtScale1x( (Graphics2D) g, x, y, width, height, this::paintImpl );
 		}
 

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

@@ -385,6 +385,16 @@ public class FlatTitlePane
 		g.fillRect( 0, 0, getWidth(), getHeight() );
 	}
 
+	protected void repaintWindowBorder() {
+		int width = rootPane.getWidth();
+		int height = rootPane.getHeight();
+		Insets insets = rootPane.getInsets();
+		rootPane.repaint( 0, 0, width, insets.top ); // top
+		rootPane.repaint( 0, 0, insets.left, height ); // left
+		rootPane.repaint( 0, height - insets.bottom, width, insets.bottom ); // bottom
+		rootPane.repaint( width - insets.right, 0, insets.right, height ); // right
+	}
+
 	/**
 	 * Iconifies the window.
 	 */
@@ -613,6 +623,8 @@ public class FlatTitlePane
 
 			if( hasJBRCustomDecoration() )
 				JBRWindowTopBorder.getInstance().repaintBorder( FlatTitlePane.this );
+
+			repaintWindowBorder();
 		}
 
 		@Override
@@ -622,6 +634,8 @@ public class FlatTitlePane
 
 			if( hasJBRCustomDecoration() )
 				JBRWindowTopBorder.getInstance().repaintBorder( FlatTitlePane.this );
+
+			repaintWindowBorder();
 		}
 
 		@Override

flatlaf-core/src/main/resources/com/formdev/flatlaf/FlatDarkLaf.properties

@@ -239,6 +239,12 @@ ProgressBar.selectionBackground=@foreground
 RadioButton.icon[filled].centerDiameter=5
 
 
+#---- RootPane ----
+
+RootPane.activeBorderColor=darken(@background,7%,derived)
+RootPane.inactiveBorderColor=darken(@background,5%,derived)
+
+
 #---- ScrollBar ----
 
 ScrollBar.track=lighten(@background,1%,derived noAutoInverse)

flatlaf-core/src/main/resources/com/formdev/flatlaf/FlatLightLaf.properties

@@ -251,6 +251,12 @@ ProgressBar.selectionBackground=@foreground
 RadioButton.icon[filled].centerDiameter=5
 
 
+#---- RootPane ----
+
+RootPane.activeBorderColor=#707070
+RootPane.inactiveBorderColor=lighten($RootPane.activeBorderColor,20%)
+
+
 #---- ScrollBar ----
 
 ScrollBar.track=lighten(@background,1%,derived noAutoInverse)

flatlaf-testing/src/main/resources/com/formdev/flatlaf/testing/uidefaults/FlatDarkLaf_1.8.0_202.txt

@@ -752,6 +752,7 @@ Resizable.resizeBorder         [lazy] 4,4,4,4  false    com.formdev.flatlaf.ui.F
 
 #---- RootPane ----
 
+RootPane.activeBorderColor     #4d5154    com.formdev.flatlaf.util.DerivedColor [UI]    darken(7% autoInverse)
 RootPane.border                [lazy] 1,1,1,1  false    com.formdev.flatlaf.ui.FlatRootPaneUI$FlatWindowBorder [UI]
 RootPane.borderDragThickness   5
 RootPane.cornerDragWidth       16
@@ -765,6 +766,7 @@ RootPane.defaultButtonWindowKeyBindings length=8    [Ljava.lang.Object;
     [6] ctrl released ENTER
     [7] release
 RootPane.honorMinimumSizeOnResize true
+RootPane.inactiveBorderColor   #484c4e    com.formdev.flatlaf.util.DerivedColor [UI]    darken(5% autoInverse)
 RootPaneUI                     com.formdev.flatlaf.ui.FlatRootPaneUI
 
 

flatlaf-testing/src/main/resources/com/formdev/flatlaf/testing/uidefaults/FlatLightLaf_1.8.0_202.txt

@@ -757,6 +757,7 @@ Resizable.resizeBorder         [lazy] 4,4,4,4  false    com.formdev.flatlaf.ui.F
 
 #---- RootPane ----
 
+RootPane.activeBorderColor     #707070    javax.swing.plaf.ColorUIResource [UI]
 RootPane.border                [lazy] 1,1,1,1  false    com.formdev.flatlaf.ui.FlatRootPaneUI$FlatWindowBorder [UI]
 RootPane.borderDragThickness   5
 RootPane.cornerDragWidth       16
@@ -770,6 +771,7 @@ RootPane.defaultButtonWindowKeyBindings length=8    [Ljava.lang.Object;
     [6] ctrl released ENTER
     [7] release
 RootPane.honorMinimumSizeOnResize true
+RootPane.inactiveBorderColor   #a3a3a3    javax.swing.plaf.ColorUIResource [UI]
 RootPaneUI                     com.formdev.flatlaf.ui.FlatRootPaneUI