Popup: no longer use popup.show() for already visible popup window to avoid that inactive owner window becomes active (issue #1037)

CHANGELOG.md

@@ -13,6 +13,8 @@ FlatLaf Change Log
 #### Fixed bugs
 
 - Tree and List: Fixed painting of rounded drop backgrounds. (issue #1023)
+- Popup: Showing tooltip in inactive window brought that window to front (made
+  it active) and potentially hid the previously active window. (issue #1037)
 - macOS: Fixed window "flashing" when switching from a light to a dark theme (or
   vice versa). Especially when using animated theme changer (see
   [FlatLaf Extras](flatlaf-extras)).

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

@@ -546,7 +546,15 @@ public class FlatPopupFactory
 			int x = popupWindow.getX();
 			int y = popupWindow.getY();
 
-			popup.show();
+			if( !popupWindow.isVisible() )
+				popup.show();
+			else {
+				// if the popup window is already visible (because it is reused),
+				// do not invoke Popup.show() because this would invoke Window.toFront(),
+				// which may have the side effect that an inactive owner window
+				// would be also moved to front and maybe hide previously active window
+				popupWindow.pack();
+			}
 
 			// restore popup window location if it has changed
 			// (probably scaled when screens use different scale factors)