Popup: added drop shadows to all popups (menu, combobox and tooltip) on all platforms (issue #94)

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

@@ -56,6 +56,7 @@ import javax.swing.plaf.UIResource;
 import javax.swing.plaf.basic.BasicLookAndFeel;
 import javax.swing.text.StyleContext;
 import javax.swing.text.html.HTMLEditorKit;
+import com.formdev.flatlaf.ui.FlatPopupFactory;
 import com.formdev.flatlaf.util.GrayFilter;
 import com.formdev.flatlaf.util.MultiResolutionImageSupport;
 import com.formdev.flatlaf.util.SystemInfo;
@@ -78,6 +79,7 @@ public abstract class FlatLaf
 	private static boolean aquaLoaded;
 	private static boolean updateUIPending;
 
+	private PopupFactory oldPopupFactory;
 	private MnemonicHandler mnemonicHandler;
 
 	private Consumer<UIDefaults> postInitialization;
@@ -144,6 +146,10 @@ public abstract class FlatLaf
 
 		super.initialize();
 
+		// install popup factory
+		oldPopupFactory = PopupFactory.getSharedInstance();
+		PopupFactory.setSharedInstance( new FlatPopupFactory() );
+
 		// install mnemonic handler
 		mnemonicHandler = new MnemonicHandler();
 		mnemonicHandler.install();
@@ -200,6 +206,12 @@ public abstract class FlatLaf
 			desktopPropertyListener = null;
 		}
 
+		// uninstall popup factory
+		if( oldPopupFactory != null ) {
+			PopupFactory.setSharedInstance( oldPopupFactory );
+			oldPopupFactory = null;
+		}
+
 		// uninstall mnemonic handler
 		if( mnemonicHandler != null ) {
 			mnemonicHandler.uninstall();

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

@@ -0,0 +1,168 @@
+/*
+ * Copyright 2020 FormDev Software GmbH
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.formdev.flatlaf.ui;
+
+import java.awt.Color;
+import java.awt.Component;
+import java.awt.Container;
+import java.awt.Dimension;
+import java.awt.Window;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import javax.swing.JComponent;
+import javax.swing.Popup;
+import javax.swing.PopupFactory;
+import javax.swing.SwingUtilities;
+import javax.swing.border.Border;
+import com.formdev.flatlaf.util.SystemInfo;
+
+/**
+ * A popup factory that adds drop shadows to popups on Windows and Linux.
+ * On macOS, heavy weight popups (without drop shadow) are produced and the
+ * operating system automatically adds drop shadows.
+ *
+ * @author Karl Tauber
+ */
+public class FlatPopupFactory
+	extends PopupFactory
+{
+	private Method java8getPopupMethod;
+	private Method java9getPopupMethod;
+
+	@Override
+	public Popup getPopup( Component owner, Component contents, int x, int y )
+		throws IllegalArgumentException
+	{
+		// always use heavy weight popup because the drop shadow increases
+		// the popup size and may overlap the window bounds
+		Popup popup = getHeavyWeightPopup( owner, contents, x, y );
+
+		// failed to get heavy weight popup --> do not add drop shadow
+		if( popup == null )
+			return super.getPopup( owner, contents, x, y );
+
+		// macOS adds drop shadow to heavy weight popups
+		if( SystemInfo.IS_MAC )
+			return popup;
+
+		// create drop shadow popup
+		return new DropShadowPopup( popup, contents );
+	}
+
+	/**
+	 * There is no API in Java 8 to force creation of heavy weight popups,
+	 * but it is possible with reflection. Java 9 provides a new method.
+	 *
+	 * When changing FlatLaf system requirements to Java 9+,
+	 * then this method can be replaced with:
+	 *    return getPopup( owner, contents, x, y, true );
+	 */
+	private Popup getHeavyWeightPopup( Component owner, Component contents, int x, int y )
+		throws IllegalArgumentException
+	{
+		try {
+			if( SystemInfo.IS_JAVA_9_OR_LATER ) {
+				if( java9getPopupMethod == null ) {
+					java9getPopupMethod = PopupFactory.class.getDeclaredMethod(
+						"getPopup", Component.class, Component.class, int.class, int.class, boolean.class );
+				}
+				return (Popup) java9getPopupMethod.invoke( this, owner, contents, x, y, true );
+			} else {
+				// Java 8
+				if( java8getPopupMethod == null ) {
+					java8getPopupMethod = PopupFactory.class.getDeclaredMethod(
+						"getPopup", Component.class, Component.class, int.class, int.class, int.class );
+					java8getPopupMethod.setAccessible( true );
+				}
+				return (Popup) java8getPopupMethod.invoke( this, owner, contents, x, y, /*HEAVY_WEIGHT_POPUP*/ 2 );
+			}
+		} catch( NoSuchMethodException | SecurityException | IllegalAccessException | InvocationTargetException ex ) {
+			// ignore
+			return null;
+		}
+	}
+
+	//---- class DropShadowPopup ----------------------------------------------
+
+	private static class DropShadowPopup
+		extends Popup
+	{
+		private Popup delegate;
+
+		private JComponent parent;
+		private Border oldBorder;
+		private boolean oldOpaque;
+
+		private Window window;
+		private Color oldBackground;
+
+		DropShadowPopup( Popup delegate, Component contents ) {
+			this.delegate = delegate;
+
+			if( delegate.getClass().getName().endsWith( "MediumWeightPopup" ) )
+				return;
+
+			Dimension size = contents.getPreferredSize();
+			if( size.width <= 0 || size.height <= 0 )
+				return;
+
+			Container p = contents.getParent();
+			if( !(p instanceof JComponent) )
+				return;
+
+			parent = (JComponent) p;
+			oldBorder = parent.getBorder();
+			oldOpaque = parent.isOpaque();
+			parent.setBorder( new FlatDropShadowBorder( null, 4, 4, 32 ) ); //TODO
+			parent.setOpaque( false );
+
+			window = SwingUtilities.windowForComponent( contents );
+			if( window != null ) {
+				oldBackground = window.getBackground();
+				window.setBackground( new Color( 0, true ) );
+				window.setSize( window.getPreferredSize() );
+			} else
+				parent.setSize( parent.getPreferredSize() );
+		}
+
+		@Override
+		public void show() {
+			delegate.show();
+		}
+
+		@Override
+		public void hide() {
+			if( delegate == null )
+				return;
+
+			delegate.hide();
+
+			if( parent != null ) {
+				parent.setBorder( oldBorder );
+				parent.setOpaque( oldOpaque );
+				parent = null;
+			}
+
+			if( window != null ) {
+				window.setBackground( oldBackground );
+				window = null;
+			}
+
+			delegate = null;
+		}
+	}
+}

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

@@ -19,7 +19,6 @@ package com.formdev.flatlaf.ui;
 import javax.swing.JComponent;
 import javax.swing.plaf.ComponentUI;
 import javax.swing.plaf.basic.BasicPopupMenuUI;
-import com.formdev.flatlaf.util.SystemInfo;
 
 /**
  * Provides the Flat LaF UI delegate for {@link javax.swing.JPopupMenu}.
@@ -36,28 +35,7 @@ import com.formdev.flatlaf.util.SystemInfo;
 public class FlatPopupMenuUI
 	extends BasicPopupMenuUI
 {
-	private boolean oldLightWeightPopupEnabled;
-
 	public static ComponentUI createUI( JComponent c ) {
 		return new FlatPopupMenuUI();
 	}
-
-	@Override
-	public void installDefaults() {
-		super.installDefaults();
-
-		// use heavy-weight popups on macOS to get nice drop shadow from OS
-		if( SystemInfo.IS_MAC ) {
-			oldLightWeightPopupEnabled = popupMenu.isLightWeightPopupEnabled();
-			popupMenu.setLightWeightPopupEnabled( false );
-		}
-	}
-
-	@Override
-	protected void uninstallDefaults() {
-		super.uninstallDefaults();
-
-		if( SystemInfo.IS_MAC )
-			popupMenu.setLightWeightPopupEnabled( oldLightWeightPopupEnabled );
-	}
 }