ComboBox: fixed width of popup, which was too small if popup is wider…

… than combo box and vertical scroll bar is visible (issue #137)

CHANGELOG.md

@@ -15,6 +15,8 @@ FlatLaf Change Log
 - ToolTip: Do not show empty tooltip component if tooltip text is an empty
   string. (issue #134)
 - Button: Support specifying button border width.
+- ComboBox: Fixed width of popup, which was too small if popup is wider than
+  combo box and vertical scroll bar is visible. (issue #137)
 - ComboBox: Changed maximum row count of popup list to 15 (was 20). Set UI value
   `ComboBox.maximumRowCount` to any integer to use a different value.
 

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

@@ -47,6 +47,7 @@
 import javax.swing.JComponent;
 import javax.swing.JList;
 import javax.swing.JPanel;
+import javax.swing.JScrollBar;
 import javax.swing.JTextField;
 import javax.swing.KeyStroke;
 import javax.swing.ListCellRenderer;
@@ -544,13 +545,26 @@ protected FlatComboPopup( JComboBox combo ) {
 
 		@Override
 		protected Rectangle computePopupBounds( int px, int py, int pw, int ph ) {
-			// get maximum display size of all items
-			Dimension displaySize = getDisplaySize();
+			// get maximum display width of all items
+			int displayWidth = getDisplaySize().width;
+
+			// add border insets
+			for( Border border : new Border[] { scroller.getViewportBorder(), scroller.getBorder() } ) {
+				if( border != null ) {
+					Insets borderInsets = border.getBorderInsets( null );
+					displayWidth += borderInsets.left + borderInsets.right;
+				}
+			}
+
+			// add width of vertical scroll bar
+			JScrollBar verticalScrollBar = scroller.getVerticalScrollBar();
+			if( verticalScrollBar != null )
+				displayWidth += verticalScrollBar.getPreferredSize().width;
 
 			// make popup wider if necessary
-			if( displaySize.width > pw ) {
-				int diff = displaySize.width - pw;
-				pw = displaySize.width;
+			if( displayWidth > pw ) {
+				int diff = displayWidth - pw;
+				pw = displayWidth;
 
 				if( !comboBox.getComponentOrientation().isLeftToRight() )
 					px -= diff;