Menus: support "underline" menu selection type (suggested in issue #49)

flatlaf-core/src/main/java/com/formdev/flatlaf/icons/FlatCheckBoxMenuItemIcon.java

@@ -30,7 +30,8 @@ import javax.swing.UIManager;
  *
  * @uiDefault MenuItemCheckBox.icon.checkmarkColor				Color
  * @uiDefault MenuItemCheckBox.icon.disabledCheckmarkColor		Color
- * @uiDefault Menu.selectionForeground							Color
+ * @uiDefault MenuItem.selectionForeground						Color
+ * @uiDefault MenuItem.selectionType							String
  *
  * @author Karl Tauber
  */
@@ -39,7 +40,7 @@ public class FlatCheckBoxMenuItemIcon
 {
 	protected final Color checkmarkColor = UIManager.getColor( "MenuItemCheckBox.icon.checkmarkColor" );
 	protected final Color disabledCheckmarkColor = UIManager.getColor( "MenuItemCheckBox.icon.disabledCheckmarkColor" );
-	protected final Color selectionForeground = UIManager.getColor( "Menu.selectionForeground" );
+	protected final Color selectionForeground = UIManager.getColor( "MenuItem.selectionForeground" );
 
 	public FlatCheckBoxMenuItemIcon() {
 		super( 15, 15, null );
@@ -67,9 +68,14 @@ public class FlatCheckBoxMenuItemIcon
 	}
 
 	private Color getCheckmarkColor( Component c ) {
-		if( c instanceof JMenuItem && ((JMenuItem)c).isArmed() )
+		if( c instanceof JMenuItem && ((JMenuItem)c).isArmed() && !isUnderlineSelection() )
 			return selectionForeground;
 
 		return c.isEnabled() ? checkmarkColor : disabledCheckmarkColor;
 	}
+
+	private boolean isUnderlineSelection() {
+		// not storing value of "MenuItem.selectionType" in class to allow changing at runtime
+		return "underline".equals( UIManager.getString( "MenuItem.selectionType" ) );
+	}
 }

flatlaf-core/src/main/java/com/formdev/flatlaf/icons/FlatMenuArrowIcon.java

@@ -32,6 +32,7 @@ import com.formdev.flatlaf.ui.FlatUIUtils;
  * @uiDefault Menu.icon.arrowColor				Color
  * @uiDefault Menu.icon.disabledArrowColor		Color
  * @uiDefault Menu.selectionForeground			Color
+ * @uiDefault MenuItem.selectionType			String
  *
  * @author Karl Tauber
  */
@@ -65,9 +66,14 @@ public class FlatMenuArrowIcon
 	}
 
 	private Color getArrowColor( Component c ) {
-		if( c instanceof JMenu && ((JMenu)c).isSelected() )
+		if( c instanceof JMenu && ((JMenu)c).isSelected() && !isUnderlineSelection() )
 			return selectionForeground;
 
 		return c.isEnabled() ? arrowColor : disabledArrowColor;
 	}
+
+	private boolean isUnderlineSelection() {
+		// not storing value of "MenuItem.selectionType" in class to allow changing at runtime
+		return "underline".equals( UIManager.getString( "MenuItem.selectionType" ) );
+	}
 }

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

@@ -55,6 +55,11 @@ public class FlatMenuItemRenderer
 	protected final int textAcceleratorGap;
 	protected final int textArrowGap;
 
+	protected final String selectionType = UIManager.getString( "MenuItem.selectionType" );
+	protected final Color underlineSelectionBackground = UIManager.getColor( "MenuItem.underlineSelectionBackground" );
+	protected final Color underlineSelectionColor = UIManager.getColor( "MenuItem.underlineSelectionColor" );
+	protected final int underlineSelectionHeight = UIManager.getInt( "MenuItem.underlineSelectionHeight" );
+
 	protected FlatMenuItemRenderer( JMenuItem menuItem, Icon checkIcon, Icon arrowIcon,
 		Font acceleratorFont, String acceleratorDelimiter )
 	{
@@ -226,8 +231,30 @@ debug*/
 	protected void paintBackground( Graphics g, Color selectionBackground ) {
 		boolean armedOrSelected = isArmedOrSelected( menuItem );
 		if( menuItem.isOpaque() || armedOrSelected ) {
-			g.setColor( armedOrSelected ? selectionBackground : menuItem.getBackground() );
-			g.fillRect( 0, 0, menuItem.getWidth(), menuItem.getHeight() );
+			int width = menuItem.getWidth();
+			int height = menuItem.getHeight();
+
+			// paint background
+			g.setColor( armedOrSelected
+				? (isUnderlineSelection() ? underlineSelectionBackground : selectionBackground)
+				: menuItem.getBackground() );
+			g.fillRect( 0, 0, width, height );
+
+			// paint underline
+			if( armedOrSelected && isUnderlineSelection() ) {
+				int underlineHeight = scale( underlineSelectionHeight );
+				g.setColor( underlineSelectionColor );
+				if( isTopLevelMenu( menuItem ) ) {
+					// paint underline at bottom
+					g.fillRect( 0, height - underlineHeight, width, underlineHeight );
+				} else if( menuItem.getComponentOrientation().isLeftToRight() ) {
+					// paint underline at left side
+					g.fillRect( 0, 0, underlineHeight, height );
+				} else {
+					// paint underline at right side
+					g.fillRect( width - underlineHeight, 0, underlineHeight, height );
+				}
+			}
 		}
 	}
 
@@ -252,16 +279,17 @@ debug*/
 		}
 
 		int mnemonicIndex = FlatLaf.isShowMnemonics() ? menuItem.getDisplayedMnemonicIndex() : -1;
+		Color foreground = menuItem.getForeground();
 
 		paintText( g, menuItem, textRect, text, mnemonicIndex, menuItem.getFont(),
-			menuItem.getForeground(), selectionForeground, disabledForeground );
+			foreground, isUnderlineSelection() ? foreground : selectionForeground, disabledForeground );
 	}
 
 	protected void paintAccelerator( Graphics g, Rectangle accelRect, String accelText,
 		Color foreground, Color selectionForeground, Color disabledForeground )
 	{
 		paintText( g, menuItem, accelRect, accelText, -1, acceleratorFont,
-			foreground, selectionForeground, disabledForeground );
+			foreground, isUnderlineSelection() ? foreground : selectionForeground, disabledForeground );
 	}
 
 	protected void paintArrowIcon( Graphics g, Rectangle arrowRect, Icon arrowIcon ) {
@@ -311,6 +339,10 @@ debug*/
 		return menuItem instanceof JMenu && ((JMenu)menuItem).isTopLevelMenu();
 	}
 
+	private boolean isUnderlineSelection() {
+		return "underline".equals( selectionType );
+	}
+
 	private Icon getIconForPainting() {
 		Icon icon = menuItem.getIcon();
 

flatlaf-core/src/main/resources/com/formdev/flatlaf/FlatDarkLaf.properties

@@ -29,6 +29,7 @@
 @disabledText=#777777
 @textComponentBackground=#45494A
 @menuBackground=darken(@background,5%)
+@menuHoverBackground=lighten(@menuBackground,10%)
 @menuCheckBackground=lighten(@menuBackground,15%)
 @cellFocusColor=#000000
 @icon=#adadad
@@ -171,7 +172,7 @@ Menu.icon.disabledArrowColor=#606060
 #---- MenuBar ----
 
 MenuBar.borderColor=#515151
-MenuBar.hoverBackground=lighten($MenuBar.background,10%)
+MenuBar.hoverBackground=@menuHoverBackground
 
 
 #---- MenuItemCheckBox ----

flatlaf-core/src/main/resources/com/formdev/flatlaf/FlatLaf.properties

@@ -319,6 +319,11 @@ MenuItem.textArrowGap=8
 MenuItem.acceleratorDelimiter=-
 [mac]MenuItem.acceleratorDelimiter=
 
+# for MenuItem.selectionType=underline
+MenuItem.underlineSelectionBackground=@menuHoverBackground
+MenuItem.underlineSelectionColor=$TabbedPane.underlineColor
+MenuItem.underlineSelectionHeight=3
+
 
 #---- OptionPane ----
 

flatlaf-core/src/main/resources/com/formdev/flatlaf/FlatLightLaf.properties

@@ -29,6 +29,7 @@
 @disabledText=#8C8C8C
 @textComponentBackground=#ffffff
 @menuBackground=#fff
+@menuHoverBackground=darken(@menuBackground,10%)
 @menuCheckBackground=darken(@menuBackground,15%)
 @cellFocusColor=#000000
 @icon=#afafaf
@@ -178,7 +179,7 @@ Menu.icon.disabledArrowColor=#ABABAB
 #---- MenuBar ----
 
 MenuBar.borderColor=#cdcdcd
-MenuBar.hoverBackground=darken($MenuBar.background,10%)
+MenuBar.hoverBackground=@menuHoverBackground
 
 
 #---- MenuItemCheckBox ----