Merge PR #790: Table header background is never restored after hover when the renderer background is null

CHANGELOG.md

@@ -33,10 +33,13 @@ FlatLaf Change Log
   - Fixed background of `boolean` columns when using alternating row colors.
     (issue #780)
   - Fixed border arc of components in complex table cell editors. (issue #786)
-- TableHeader: No longer temporary replace header cell renderer while painting.
-  This avoids a `StackOverflowError` in case that custom renderer does this too.
-  (see [NetBeans issue #6835](https://github.com/apache/netbeans/issues/6835))
-  This also improves compatibility with custom table header implementations.
+- TableHeader:
+  - No longer temporary replace header cell renderer while painting. This avoids
+    a `StackOverflowError` in case that custom renderer does this too. (see
+    [NetBeans issue #6835](https://github.com/apache/netbeans/issues/6835)) This
+    also improves compatibility with custom table header implementations.
+  - Header cell renderer background/foreground colors were not restored after
+    hover if renderer uses `null` for background/foreground. (PR #790)
 - TabbedPane:
   - Avoid unnecessary repainting whole tabbed pane content area when layouting
     leading/trailing components.

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

@@ -356,7 +356,7 @@ public class FlatTableHeaderUI
 			JLabel l = (JLabel) c;
 			Color oldBackground = null;
 			Color oldForeground = null;
-			Boolean oldOpaque = null;
+			boolean oldOpaque = false;
 			Icon oldIcon = null;
 			int oldHorizontalTextPosition = -1;
 
@@ -415,12 +415,12 @@ public class FlatTableHeaderUI
 			}
 
 			// restore modified renderer component properties
-			if( oldBackground != null )
+			if( background != null ) {
 				l.setBackground( oldBackground );
-			if( oldForeground != null )
-				l.setForeground( oldForeground );
-			if( oldOpaque != null )
 				l.setOpaque( oldOpaque );
+			}
+			if( foreground != null )
+				l.setForeground( oldForeground );
 			if( oldIcon != null )
 				l.setIcon( oldIcon );
 			if( oldHorizontalTextPosition >= 0 )