Use correct background color on DefaultTreeCellRenderer.

core/src/main/java/com/github/weisj/darklaf/ui/cell/CellUtil.java

@@ -27,7 +27,10 @@ package com.github.weisj.darklaf.ui.cell;
 import java.awt.*;
 
 import javax.swing.*;
+import javax.swing.plaf.UIResource;
+import javax.swing.tree.DefaultTreeCellRenderer;
 
+import com.github.weisj.darklaf.graphics.ColorWrapper;
 import com.github.weisj.darklaf.ui.list.DarkListUI;
 import com.github.weisj.darklaf.ui.table.DarkTableUI;
 import com.github.weisj.darklaf.ui.table.renderer.IconWrapper;
@@ -334,7 +337,14 @@ public class CellUtil {
 
     public static void setupTreeBackground(final Component comp, final JTree parent, final boolean selected,
                                            final int row) {
-        setupBackground(comp, getTreeBackground(comp, parent, selected, row));
+        Color bg = getTreeBackground(comp, parent, selected, row);
+        setupBackground(comp, bg);
+        if (comp instanceof DefaultTreeCellRenderer) {
+            Color c = comp.getBackground();
+            if (c == null || c instanceof UIResource || c instanceof NonUIResourceColorWrapper) {
+                comp.setBackground(new NonUIResourceColorWrapper(bg));
+            }
+        }
     }
 
     public static Color getTreeBackground(final JTree tree, final boolean selected, final int row) {
@@ -554,4 +564,11 @@ public class CellUtil {
         Rectangle rect = table.getVisibleRect();
         return table.rowAtPoint(rect.getLocation());
     }
+
+    private static class NonUIResourceColorWrapper extends ColorWrapper {
+
+        public NonUIResourceColorWrapper(final Color color) {
+            super(color);
+        }
+    }
 }

core/src/main/java/com/github/weisj/darklaf/ui/tree/DarkTreeCellRendererDelegate.java

@@ -74,6 +74,7 @@ public class DarkTreeCellRendererDelegate extends TreeCellRendererDelegate imple
             renderer = super.getTreeCellRendererComponent(tree, value, selected, expanded, leaf, row, isFocused);
         }
         CellUtil.setupTreeForeground(renderer, tree, selected);
+        CellUtil.setupTreeBackground(renderer, tree, selected, row);
         return renderer;
     }
 

core/src/test/java/ui/table/TableDemo.java

@@ -31,14 +31,14 @@ import javax.swing.*;
 import javax.swing.table.JTableHeader;
 import javax.swing.table.TableCellEditor;
 
+import ui.ComponentDemo;
+import ui.DemoPanel;
+
 import com.github.weisj.darklaf.ui.table.DarkTableUI;
 import com.github.weisj.darklaf.ui.table.renderer.DarkTableCellEditor;
 import com.github.weisj.darklaf.util.PropertyKey;
 import com.github.weisj.darklaf.util.PropertyUtil;
 
-import ui.ComponentDemo;
-import ui.DemoPanel;
-
 public class TableDemo implements ComponentDemo {
 
     public static void main(final String[] args) {

utils/src/main/java/com/github/weisj/darklaf/util/PropertyUtil.java

@@ -38,18 +38,12 @@ public class PropertyUtil {
 
     public static void installBackground(final Component component, final Color color) {
         if (component == null || color == null) return;
-        Color c = component.getBackground();
-        if (c == null || c instanceof UIResource) {
-            component.setBackground(color);
-        }
+        component.setBackground(chooseColor(component.getBackground(), color));
     }
 
     public static void installForeground(final Component component, final Color color) {
         if (component == null || color == null) return;
-        Color c = component.getForeground();
-        if (c == null || c instanceof UIResource) {
-            component.setForeground(color);
-        }
+        component.setForeground(chooseColor(component.getForeground(), color));
     }
 
     public static void installBorder(final JComponent component, final Border border) {
@@ -187,4 +181,9 @@ public class PropertyUtil {
                    .map(type::cast)
                    .collect(Collectors.toList());
     }
+
+    public static Color chooseColor(final Color currentColor, final Color newColor) {
+        if (currentColor == null || currentColor instanceof UIResource) return newColor;
+        return currentColor;
+    }
 }