Tree: fill cell background if DefaultTreeCellRenderer.setBackgroundNonSelectionColor(Color) was used (issue #322)

CHANGELOG.md

@@ -44,6 +44,9 @@ FlatLaf Change Log
     internal frames in dock.
 - PopupFactory: Fixed occasional `NullPointerException` in
   `FlatPopupFactory.fixToolTipLocation()`. (issue #305)
+- Tree: Fill cell background if
+  `DefaultTreeCellRenderer.setBackgroundNonSelectionColor(Color)` was used.
+  (issue #322)
 - IntelliJ Themes: Fixed background colors of DesktopPane and DesktopIcon in all
   themes.
 - Native window decorations: Fixed occasional double window title bar when

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

@@ -107,6 +107,8 @@ public class FlatTreeUI
 	protected boolean wideSelection;
 	protected boolean showCellFocusIndicator;
 
+	private Color defaultCellNonSelectionBackground;
+
 	public static ComponentUI createUI( JComponent c ) {
 		return new FlatTreeUI();
 	}
@@ -125,6 +127,8 @@ public class FlatTreeUI
 		wideSelection = UIManager.getBoolean( "Tree.wideSelection" );
 		showCellFocusIndicator = UIManager.getBoolean( "Tree.showCellFocusIndicator" );
 
+		defaultCellNonSelectionBackground = UIManager.getColor( "Tree.textBackground" );
+
 		// scale
 		int rowHeight = FlatUIUtils.getUIInt( "Tree.rowHeight", 16 );
 		if( rowHeight > 0 )
@@ -144,6 +148,8 @@ public class FlatTreeUI
 		selectionInactiveBackground = null;
 		selectionInactiveForeground = null;
 		selectionBorderColor = null;
+
+		defaultCellNonSelectionBackground = null;
 	}
 
 	@Override
@@ -306,24 +312,24 @@ public class FlatTreeUI
 				}
 			} else {
 				// non-wide selection
-				int xOffset = 0;
-				int imageOffset = 0;
-
-				if( rendererComponent instanceof JLabel ) {
-					JLabel label = (JLabel) rendererComponent;
-					Icon icon = label.getIcon();
-					imageOffset = (icon != null && label.getText() != null)
-						? icon.getIconWidth() + Math.max( label.getIconTextGap() - 1, 0 )
-						: 0;
-					xOffset = label.getComponentOrientation().isLeftToRight() ? imageOffset : 0;
-				}
-
-				g.fillRect( bounds.x + xOffset, bounds.y, bounds.width - imageOffset, bounds.height );
+				paintCellBackground( g, rendererComponent, bounds );
 			}
 
 			// this is actually not necessary because renderer should always set color
 			// before painting, but doing anyway to avoid any side effect (in bad renderers)
 			g.setColor( oldColor );
+		} else {
+			// paint cell background if DefaultTreeCellRenderer.getBackgroundNonSelectionColor() is set
+			if( rendererComponent instanceof DefaultTreeCellRenderer ) {
+				DefaultTreeCellRenderer renderer = (DefaultTreeCellRenderer) rendererComponent;
+				Color bg = renderer.getBackgroundNonSelectionColor();
+				if( bg != null && !bg.equals( defaultCellNonSelectionBackground ) ) {
+					Color oldColor = g.getColor();
+					g.setColor( bg );
+					paintCellBackground( g, rendererComponent, bounds );
+					g.setColor( oldColor );
+				}
+			}
 		}
 
 		// paint renderer
@@ -337,6 +343,22 @@ public class FlatTreeUI
 			((DefaultTreeCellRenderer)rendererComponent).setBorderSelectionColor( oldBorderSelectionColor );
 	}
 
+	private void paintCellBackground( Graphics g, Component rendererComponent, Rectangle bounds ) {
+		int xOffset = 0;
+		int imageOffset = 0;
+
+		if( rendererComponent instanceof JLabel ) {
+			JLabel label = (JLabel) rendererComponent;
+			Icon icon = label.getIcon();
+			imageOffset = (icon != null && label.getText() != null)
+				? icon.getIconWidth() + Math.max( label.getIconTextGap() - 1, 0 )
+				: 0;
+			xOffset = label.getComponentOrientation().isLeftToRight() ? imageOffset : 0;
+		}
+
+		g.fillRect( bounds.x + xOffset, bounds.y, bounds.width - imageOffset, bounds.height );
+	}
+
 	/**
 	 * Checks whether dropping on a row.
 	 * See DefaultTreeCellRenderer.getTreeCellRendererComponent().

flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/FlatComponents2Test.java

@@ -1200,10 +1200,27 @@ public class FlatComponents2Test
 		extends DefaultTreeCellRenderer
 	{
 		public TestDefaultTreeCellRenderer() {
-			setBackgroundNonSelectionColor( Color.red );
 			setBackgroundSelectionColor( Color.green );
 			setTextSelectionColor( Color.blue );
 		}
+
+		@Override
+		public Component getTreeCellRendererComponent( JTree tree, Object value, boolean sel, boolean expanded,
+			boolean leaf, int row, boolean hasFocus )
+		{
+			Color nonSelectionBg = null;
+			Color nonSelectionFg = null;
+			switch( String.valueOf( value ) ) {
+				case "blue":		nonSelectionFg = Color.blue; break;
+				case "red":		nonSelectionFg = Color.red; break;
+				case "yellow":	nonSelectionBg = Color.yellow; break;
+				case "violet":	nonSelectionBg = Color.magenta; break;
+			}
+			setBackgroundNonSelectionColor( nonSelectionBg );
+			setTextNonSelectionColor( (nonSelectionFg != null) ? nonSelectionFg : UIManager.getColor( "Tree.textForeground" ) );
+
+			return super.getTreeCellRendererComponent( tree, value, sel, expanded, leaf, row, hasFocus );
+		}
 	}
 
 	//---- class TestLabelTreeCellRenderer ------------------------------------