Allow background painting if no border is painted.

core/src/main/java/com/github/weisj/darklaf/ui/button/DarkButtonUI.java

@@ -28,7 +28,6 @@ import java.awt.*;
 import java.awt.geom.RoundRectangle2D;
 
 import javax.swing.*;
-import javax.swing.border.Border;
 import javax.swing.plaf.ComponentUI;
 import javax.swing.plaf.UIResource;
 import javax.swing.plaf.basic.BasicButtonListener;
@@ -286,8 +285,7 @@ public class DarkButtonUI extends BasicButtonUI implements ButtonConstants {
     }
 
     protected boolean shouldDrawBackground(final AbstractButton c) {
-        Border border = c.getBorder();
-        return c.isEnabled() && border != null && button.isContentAreaFilled();
+        return button.isContentAreaFilled();
     }
 
     protected int getArc(final Component c) {

core/src/test/java/ui/button/AbstractButtonDemo.java

@@ -106,6 +106,18 @@ public abstract class AbstractButtonDemo<T extends AbstractButton> implements Co
                 addActionListener(e -> button.setContentAreaFilled(isSelected()));
             }
         });
+        controlPanel.add(new JCheckBox("Border painted") {
+            {
+                setSelected(button.isBorderPainted());
+                addActionListener(e -> button.setBorderPainted(isSelected()));
+            }
+        });
+        controlPanel.add(new JCheckBox("Focus Painted") {
+            {
+                setSelected(button.isFocusPainted());
+                addActionListener(e -> button.setFocusPainted(isSelected()));
+            }
+        });
         controlPanel.add(new JCheckBox("Button.defaultButtonFollowsFocus") {
             {
                 setSelected(UIManager.getBoolean("Button.defaultButtonFollowsFocus"));