fixed jittery submenu rendering on Mac (issue #10)

CHANGELOG.md

@@ -5,6 +5,7 @@ FlatLaf Change Log
 
 - Support using IntelliJ platform themes (.theme.json files).
 - Fixed selection background of checkbox in table cell.
+- Fixed jittery submenu rendering on Mac. (issue #10)
 
 
 ## 0.18

flatlaf-core/src/main/java/com/formdev/flatlaf/FlatLaf.java

@@ -33,6 +33,7 @@ import javax.swing.AbstractButton;
 import javax.swing.JLabel;
 import javax.swing.JTabbedPane;
 import javax.swing.LookAndFeel;
+import javax.swing.PopupFactory;
 import javax.swing.SwingUtilities;
 import javax.swing.UIDefaults;
 import javax.swing.UIManager;
@@ -92,6 +93,11 @@ public abstract class FlatLaf
 
 		super.initialize();
 
+		// make sure that a plain popup factory is used (otherwise sub-menu rendering
+		// is "jittery" on Mac, where AquaLookAndFeel installs its own popup factory)
+		if( PopupFactory.getSharedInstance().getClass() != PopupFactory.class )
+			PopupFactory.setSharedInstance( new PopupFactory() );
+
 		// add mnemonic listener
 		mnemonicListener = e -> {
 			if( e.getKeyCode() == KeyEvent.VK_ALT )