ComboBox: fixed popup location if shown above of combo box (Java 8 only)

CHANGELOG.md

@@ -21,6 +21,7 @@ FlatLaf Change Log
   `StringBuilder`, `StringBuffer`, or any other object that returns HTML text in
   method `toString()`. (similar to issue #12)
 - ComboBox: Fixed popup border painting on HiDPI screens (e.g. at 150% scaling).
+- ComboBox: Fixed popup location if shown above of combo box (Java 8 only).
 - ComboBox (editable): Fixed wrong border of internal text field under special
   circumstances.
 - Spinner: Fixed painting of border corners on left side. (issue #382;

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

@@ -730,6 +730,21 @@ public class FlatComboBoxUI
 			return height;
 		}
 
+		@Override
+		public void show( Component invoker, int x, int y ) {
+			// Java 8: fix y coordinate if popup is shown above the combobox
+			// (already fixed in Java 9+ https://bugs.openjdk.java.net/browse/JDK-7072653)
+			if( y < 0 && !SystemInfo.isJava_9_orLater ) {
+				Border popupBorder = getBorder();
+				if( popupBorder != null ) {
+					Insets insets = popupBorder.getBorderInsets( this );
+					y -= insets.top + insets.bottom;
+				}
+			}
+
+			super.show( invoker, x, y );
+		}
+
 		@Override
 		protected void paintChildren( Graphics g ) {
 			super.paintChildren( g );