Menus: scroll large menus using mouse wheel or up/down arrows (issue #225)

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

@@ -16,18 +16,58 @@
 
 package com.formdev.flatlaf.ui;
 
+import java.awt.BorderLayout;
+import java.awt.Color;
+import java.awt.Component;
 import java.awt.Container;
 import java.awt.Dimension;
+import java.awt.EventQueue;
+import java.awt.Graphics;
+import java.awt.GraphicsConfiguration;
+import java.awt.GraphicsDevice;
+import java.awt.GraphicsEnvironment;
+import java.awt.Insets;
 import java.awt.LayoutManager;
+import java.awt.Point;
+import java.awt.Rectangle;
+import java.awt.Toolkit;
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import java.awt.event.MouseEvent;
+import java.awt.event.MouseListener;
+import java.awt.event.MouseWheelEvent;
+import java.awt.event.MouseWheelListener;
 import java.beans.PropertyChangeListener;
 import java.util.Map;
 import java.util.concurrent.atomic.AtomicBoolean;
 import javax.swing.BoxLayout;
+import javax.swing.JButton;
 import javax.swing.JComponent;
+import javax.swing.JMenuItem;
+import javax.swing.JPanel;
+import javax.swing.JPopupMenu;
+import javax.swing.JScrollPane;
+import javax.swing.JViewport;
+import javax.swing.MenuElement;
+import javax.swing.MenuSelectionManager;
+import javax.swing.Popup;
+import javax.swing.PopupFactory;
+import javax.swing.SwingConstants;
+import javax.swing.SwingUtilities;
+import javax.swing.Timer;
+import javax.swing.UIManager;
+import javax.swing.event.MenuKeyEvent;
+import javax.swing.event.MenuKeyListener;
+import javax.swing.event.PopupMenuEvent;
+import javax.swing.event.PopupMenuListener;
+import javax.swing.plaf.ButtonUI;
 import javax.swing.plaf.ComponentUI;
 import javax.swing.plaf.UIResource;
+import javax.swing.plaf.basic.BasicComboPopup;
+import javax.swing.plaf.basic.BasicMenuItemUI;
 import javax.swing.plaf.basic.BasicPopupMenuUI;
 import javax.swing.plaf.basic.DefaultMenuLayout;
+import com.formdev.flatlaf.ui.FlatStylingSupport.Styleable;
 import com.formdev.flatlaf.ui.FlatStylingSupport.StyleableUI;
 import com.formdev.flatlaf.util.LoggingFacade;
 
@@ -41,12 +81,22 @@ import com.formdev.flatlaf.util.LoggingFacade;
  * @uiDefault PopupMenu.foreground						Color
  * @uiDefault PopupMenu.border							Border
  *
+ * <!-- FlatPopupMenuUI -->
+ *
+ * @uiDefault Component.arrowType					String	chevron (default) or triangle
+ * @uiDefault PopupMenu.scrollArrowColor			Color
+ * @uiDefault PopupMenu.hoverScrollArrowBackground	Color	optional
+ *
  * @author Karl Tauber
  */
 public class FlatPopupMenuUI
 	extends BasicPopupMenuUI
 	implements StyleableUI
 {
+	/** @since 2.1 */ @Styleable protected String arrowType;
+	/** @since 2.1 */ @Styleable protected Color scrollArrowColor;
+	/** @since 2.1 */ @Styleable protected Color hoverScrollArrowBackground;
+
 	private PropertyChangeListener propertyChangeListener;
 	private Map<String, Object> oldStyleValues;
 	private AtomicBoolean borderShared;
@@ -74,11 +124,23 @@ public class FlatPopupMenuUI
 	public void installDefaults() {
 		super.installDefaults();
 
+		arrowType = UIManager.getString( "Component.arrowType" );
+		scrollArrowColor = UIManager.getColor( "PopupMenu.scrollArrowColor" );
+		hoverScrollArrowBackground = UIManager.getColor( "PopupMenu.hoverScrollArrowBackground" );
+
 		LayoutManager layout = popupMenu.getLayout();
 		if( layout == null || layout instanceof UIResource )
 			popupMenu.setLayout( new FlatMenuLayout( popupMenu, BoxLayout.Y_AXIS ) );
 	}
 
+	@Override
+	protected void uninstallDefaults() {
+		super.uninstallDefaults();
+
+		scrollArrowColor = null;
+		hoverScrollArrowBackground = null;
+	}
+
 	@Override
 	protected void installListeners() {
 		super.installListeners();
@@ -122,6 +184,52 @@ public class FlatPopupMenuUI
 		return FlatStylingSupport.getAnnotatedStyleableInfos( this, popupMenu.getBorder() );
 	}
 
+	@Override
+	public Popup getPopup( JPopupMenu popup, int x, int y ) {
+		// do not add scroller to combobox popups or to popups that already have a scroll pane
+		if( popup instanceof BasicComboPopup ||
+			(popup.getComponentCount() > 0 && popup.getComponent( 0 ) instanceof JScrollPane) )
+		  return super.getPopup( popup, x, y );
+
+		// do not add scroller if popup fits into screen
+		Dimension prefSize = popup.getPreferredSize();
+		int screenHeight = getScreenHeightAt( x, y );
+		if( prefSize.height <= screenHeight )
+			return super.getPopup( popup, x, y );
+
+		// create scroller
+		FlatPopupScroller scroller = new FlatPopupScroller( popup );
+		scroller.setPreferredSize( new Dimension( prefSize.width, screenHeight ) );
+
+		// create popup
+		PopupFactory popupFactory = PopupFactory.getSharedInstance();
+		return popupFactory.getPopup( popup.getInvoker(), scroller, x, y );
+	}
+
+	private int getScreenHeightAt( int x, int y ) {
+		// find GraphicsConfiguration at popup location (similar to JPopupMenu.getCurrentGraphicsConfiguration())
+		GraphicsConfiguration gc = null;
+		for( GraphicsDevice device : GraphicsEnvironment.getLocalGraphicsEnvironment().getScreenDevices() ) {
+			if( device.getType() == GraphicsDevice.TYPE_RASTER_SCREEN ) {
+				GraphicsConfiguration dgc = device.getDefaultConfiguration();
+				if( dgc.getBounds().contains( x, y ) ) {
+					gc = dgc;
+					break;
+				}
+			}
+		}
+		if( gc == null && popupMenu.getInvoker() != null )
+			gc = popupMenu.getInvoker().getGraphicsConfiguration();
+
+		// compute screen height
+		// (always subtract screen insets because there is no API to detect whether
+		// the popup can overlap the taskbar; see JPopupMenu.canPopupOverlapTaskBar())
+		Toolkit toolkit = Toolkit.getDefaultToolkit();
+		Rectangle screenBounds = (gc != null) ? gc.getBounds() : new Rectangle( toolkit.getScreenSize() );
+		Insets screenInsets = Toolkit.getDefaultToolkit().getScreenInsets( gc );
+		return screenBounds.height - screenInsets.top - screenInsets.bottom;
+	}
+
 	//---- class FlatMenuLayout -----------------------------------------------
 
 	protected static class FlatMenuLayout
@@ -138,4 +246,206 @@ public class FlatPopupMenuUI
 			return super.preferredLayoutSize( target );
 		}
 	}
+
+	//---- class FlatPopupScroller --------------------------------------------
+
+	private class FlatPopupScroller
+		extends JPanel
+		implements MouseWheelListener, PopupMenuListener, MenuKeyListener
+	{
+		private final JPopupMenu popup;
+
+		private final JScrollPane scrollPane;
+		private final JButton scrollUpButton;
+		private final JButton scrollDownButton;
+		private int unitIncrement;
+
+		FlatPopupScroller( JPopupMenu popup ) {
+			super( new BorderLayout() );
+			this.popup = popup;
+
+			// this panel is required to avoid that JPopupMenu.setLocation() will be invoked
+			// while scrolling, because this would call JPopupMenu.showPopup()
+			JPanel view = new JPanel( new BorderLayout() );
+			view.add( popup, BorderLayout.CENTER );
+
+			scrollPane = new JScrollPane( view, JScrollPane.VERTICAL_SCROLLBAR_NEVER, JScrollPane.HORIZONTAL_SCROLLBAR_NEVER );
+			scrollPane.setBorder( null );
+
+			scrollUpButton = new ArrowButton( SwingConstants.NORTH );
+			scrollDownButton = new ArrowButton( SwingConstants.SOUTH );
+
+			add( scrollPane, BorderLayout.CENTER );
+			add( scrollUpButton, BorderLayout.NORTH );
+			add( scrollDownButton, BorderLayout.SOUTH );
+
+			setBackground( popup.getBackground() );
+			setBorder( popup.getBorder() );
+			popup.setBorder( null );
+
+			popup.addPopupMenuListener( this );
+			popup.addMouseWheelListener( this );
+			popup.addMenuKeyListener( this );
+
+			updateArrowButtons();
+		}
+
+		void scroll( int unitsToScroll ) {
+			if( unitIncrement == 0 )
+				unitIncrement = new JMenuItem( "X" ).getPreferredSize().height;
+
+			JViewport viewport = scrollPane.getViewport();
+			Point viewPosition = viewport.getViewPosition();
+			int newY = viewPosition.y + (unitIncrement * unitsToScroll);
+			if( newY < 0 )
+				newY = 0;
+			else
+				newY = Math.min( newY, viewport.getViewSize().height - viewport.getExtentSize().height );
+			viewport.setViewPosition( new Point( viewPosition.x, newY ) );
+
+			updateArrowButtons();
+		}
+
+		void updateArrowButtons() {
+			JViewport viewport = scrollPane.getViewport();
+			Point viewPosition = viewport.getViewPosition();
+
+			scrollUpButton.setVisible( viewPosition.y > 0 );
+			scrollDownButton.setVisible( viewPosition.y < viewport.getViewSize().height - viewport.getExtentSize().height );
+		}
+
+		//---- interface PopupMenuListener ----
+
+		@Override
+		public void popupMenuWillBecomeInvisible( PopupMenuEvent e ) {
+			// restore popup border
+			popup.setBorder( getBorder() );
+
+			popup.removePopupMenuListener( this );
+			popup.removeMouseWheelListener( this );
+			popup.removeMenuKeyListener( this );
+		}
+
+		@Override public void popupMenuWillBecomeVisible( PopupMenuEvent e ) {}
+		@Override public void popupMenuCanceled( PopupMenuEvent e ) {}
+
+		//---- interface MouseWheelListener ----
+
+		/**
+		 * Scroll when user rotates mouse wheel.
+		 */
+		@Override
+		public void mouseWheelMoved( MouseWheelEvent e ) {
+			// convert mouse location before scrolling
+			Point mouseLocation = SwingUtilities.convertPoint( (Component) e.getSource(), e.getPoint(), this );
+
+			// scroll
+			scroll( e.getUnitsToScroll() );
+
+			// select menu item at mouse location
+			Component c = SwingUtilities.getDeepestComponentAt( this, mouseLocation.x, mouseLocation.y );
+			if( c instanceof JMenuItem ) {
+				ButtonUI ui = ((JMenuItem)c).getUI();
+				if( ui instanceof BasicMenuItemUI )
+					MenuSelectionManager.defaultManager().setSelectedPath( ((BasicMenuItemUI)ui).getPath() );
+			}
+
+			// this avoids that the popup is closed when running on Java 8
+			// https://bugs.openjdk.java.net/browse/JDK-8075063
+			e.consume();
+		}
+
+		//---- interface MenuKeyListener ----
+
+		/**
+		 * Scroll when user presses Up or Down keys.
+		 */
+		@Override
+		public void menuKeyPressed( MenuKeyEvent e ) {
+			// use invokeLater() because menu selection is not yet updated because
+			// this listener is invoked before another listener that updates the menu selection
+			EventQueue.invokeLater( () -> {
+				if( !isDisplayable() )
+					return;
+
+				MenuElement[] path = MenuSelectionManager.defaultManager().getSelectedPath();
+				if( path.length == 0 )
+					return;
+
+				// scroll selected menu item to visible area
+				Component c = path[path.length - 1].getComponent();
+				JViewport viewport = scrollPane.getViewport();
+				Point pt = SwingUtilities.convertPoint( c, 0, 0, viewport );
+				viewport.scrollRectToVisible( new Rectangle( pt, c.getSize() ) );
+
+				// update arrow buttons
+				boolean upVisible = scrollUpButton.isVisible();
+				updateArrowButtons();
+				if( !upVisible && scrollUpButton.isVisible() ) {
+					// if "up" button becomes visible, make sure that bottom menu item stays visible
+					Point viewPosition = viewport.getViewPosition();
+					int newY = viewPosition.y + scrollUpButton.getPreferredSize().height;
+					viewport.setViewPosition( new Point( viewPosition.x, newY ) );
+				}
+			} );
+		}
+
+		@Override public void menuKeyTyped( MenuKeyEvent e ) {}
+		@Override public void menuKeyReleased( MenuKeyEvent e ) {}
+
+		//---- class ArrowButton ----------------------------------------------
+
+		private class ArrowButton
+			extends FlatArrowButton
+			implements MouseListener, ActionListener
+		{
+			private Timer timer;
+
+			ArrowButton( int direction ) {
+				super( direction, arrowType, scrollArrowColor, null, null, hoverScrollArrowBackground, null, null );
+
+				addMouseListener( this );
+			}
+
+			@Override
+			public void paint( Graphics g ) {
+				// always fill background to paint over border on HiDPI screens
+				g.setColor( popup.getBackground() );
+				g.fillRect( 0, 0, getWidth(), getHeight() );
+
+				super.paint( g );
+			}
+
+			//---- interface MouseListener ----
+
+			@Override public void mouseClicked( MouseEvent e ) {}
+			@Override public void mousePressed( MouseEvent e ) {}
+			@Override public void mouseReleased( MouseEvent e ) {}
+
+			@Override
+			public void mouseEntered( MouseEvent e ) {
+				if( timer == null )
+					timer = new Timer( 50, this );
+				timer.start();
+			}
+
+			@Override
+			public void mouseExited( MouseEvent e ) {
+				if( timer != null )
+					timer.stop();
+			}
+
+			//---- interface ActionListener ----
+
+			@Override
+			public void actionPerformed( ActionEvent e ) {
+				if( timer != null && !isDisplayable() ) {
+					timer.stop();
+					return;
+				}
+
+				scroll( direction == SwingConstants.NORTH ? -1 : 1 );
+			}
+		}
+	}
 }

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

@@ -252,6 +252,7 @@ Popup.dropShadowOpacity = 0.25
 #---- PopupMenu ----
 
 PopupMenu.borderColor = tint(@background,17%)
+PopupMenu.hoverScrollArrowBackground = lighten(@background,5%)
 
 
 #---- ProgressBar ----

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

@@ -500,6 +500,7 @@ Popup.dropShadowInsets = -4,-4,4,4
 PopupMenu.border = com.formdev.flatlaf.ui.FlatPopupMenuBorder
 PopupMenu.borderInsets = 4,1,4,1
 PopupMenu.background = @menuBackground
+PopupMenu.scrollArrowColor = @buttonArrowColor
 
 
 #---- PopupMenuSeparator ----

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

@@ -259,6 +259,7 @@ Popup.dropShadowOpacity = 0.15
 #---- PopupMenu ----
 
 PopupMenu.borderColor = shade(@background,28%)
+PopupMenu.hoverScrollArrowBackground = darken(@background,5%)
 
 
 #---- ProgressBar ----