support MigLayout visualPadding

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

@@ -114,6 +114,15 @@ public class FlatButtonUI
 		toolbarPressedBackground = UIManager.getColor( prefix + "toolbar.pressedBackground" );
 
 		helpButtonIcon = UIManager.getIcon( "HelpButton.icon" );
+
+		MigLayoutVisualPadding.install( b, focusWidth );
+	}
+
+	@Override
+	protected void uninstallDefaults( AbstractButton b ) {
+		super.uninstallDefaults( b );
+
+		MigLayoutVisualPadding.uninstall( b );
 	}
 
 	static boolean isContentAreaFilled( Component c ) {

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

@@ -19,6 +19,7 @@ package com.formdev.flatlaf.ui;
 import java.awt.Dimension;
 import java.awt.Graphics;
 import java.awt.Rectangle;
+import javax.swing.AbstractButton;
 import javax.swing.JComponent;
 import javax.swing.plaf.ComponentUI;
 import javax.swing.plaf.metal.MetalCheckBoxUI;
@@ -39,6 +40,20 @@ public class FlatCheckBoxUI
 		return instance;
 	}
 
+	@Override
+	public void installDefaults( AbstractButton b ) {
+		super.installDefaults( b );
+
+		MigLayoutVisualPadding.install( b, null );
+	}
+
+	@Override
+	protected void uninstallDefaults( AbstractButton b ) {
+		super.uninstallDefaults( b );
+
+		MigLayoutVisualPadding.uninstall( b );
+	}
+
 	@Override
 	protected void paintFocus( Graphics g, Rectangle t, Dimension d ) {
 		// focus border painted in icon

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

@@ -106,6 +106,8 @@ public class FlatComboBoxUI
 
 		// scale
 		padding = UIScale.scale( padding );
+
+		MigLayoutVisualPadding.install( comboBox, focusWidth );
 	}
 
 	@Override
@@ -123,6 +125,8 @@ public class FlatComboBoxUI
 		buttonArrowColor = null;
 		buttonDisabledArrowColor = null;
 		buttonHoverArrowColor = null;
+
+		MigLayoutVisualPadding.uninstall( comboBox );
 	}
 
 	@Override

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

@@ -62,6 +62,15 @@ public class FlatPasswordFieldUI
 
 		focusWidth = UIManager.getInt( "Component.focusWidth" );
 		minimumWidth = UIManager.getInt( "Component.minimumWidth" );
+
+		MigLayoutVisualPadding.install( getComponent(), focusWidth );
+	}
+
+	@Override
+	protected void uninstallDefaults() {
+		super.uninstallDefaults();
+
+		MigLayoutVisualPadding.uninstall( getComponent() );
 	}
 
 	@Override

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

@@ -19,6 +19,7 @@ package com.formdev.flatlaf.ui;
 import java.awt.Dimension;
 import java.awt.Graphics;
 import java.awt.Rectangle;
+import javax.swing.AbstractButton;
 import javax.swing.JComponent;
 import javax.swing.plaf.ComponentUI;
 import javax.swing.plaf.metal.MetalRadioButtonUI;
@@ -39,6 +40,20 @@ public class FlatRadioButtonUI
 		return instance;
 	}
 
+	@Override
+	public void installDefaults( AbstractButton b ) {
+		super.installDefaults( b );
+
+		MigLayoutVisualPadding.install( b, null );
+	}
+
+	@Override
+	protected void uninstallDefaults( AbstractButton b ) {
+		super.uninstallDefaults( b );
+
+		MigLayoutVisualPadding.uninstall( b );
+	}
+
 	@Override
 	protected void paintFocus( Graphics g, Rectangle t, Dimension d ) {
 		// focus border painted in icon

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

@@ -30,6 +30,7 @@ import javax.swing.JComponent;
 import javax.swing.JScrollPane;
 import javax.swing.JViewport;
 import javax.swing.ScrollPaneLayout;
+import javax.swing.UIManager;
 import javax.swing.plaf.ComponentUI;
 import javax.swing.plaf.UIResource;
 import javax.swing.plaf.basic.BasicScrollPaneUI;
@@ -54,6 +55,8 @@ public class FlatScrollPaneUI
 
 		if( scrollpane.getLayout() instanceof UIResource )
 			scrollpane.setLayout( new FlatScrollPaneLayout() );
+
+		MigLayoutVisualPadding.install( scrollpane, UIManager.getInt( "Component.focusWidth" ) );
 	}
 
 	@Override
@@ -61,6 +64,8 @@ public class FlatScrollPaneUI
 		if( scrollpane.getLayout() instanceof FlatScrollPaneLayout )
 			scrollpane.setLayout( new ScrollPaneLayout.UIResource() );
 
+		MigLayoutVisualPadding.uninstall( scrollpane );
+
 		super.uninstallUI( c );
 	}
 

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

@@ -101,6 +101,8 @@ public class FlatSpinnerUI
 
 		// scale
 		padding = scale( padding );
+
+		MigLayoutVisualPadding.install( spinner, focusWidth );
 	}
 
 	@Override
@@ -116,6 +118,8 @@ public class FlatSpinnerUI
 		buttonDisabledArrowColor = null;
 		buttonHoverArrowColor = null;
 		padding = null;
+
+		MigLayoutVisualPadding.uninstall( spinner );
 	}
 
 	@Override

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

@@ -107,6 +107,8 @@ public class FlatTabbedPaneUI
 		tabHeight = scale( tabHeight );
 		tabSelectionHeight = scale( tabSelectionHeight );
 		contentSeparatorHeight = scale( contentSeparatorHeight );
+
+		MigLayoutVisualPadding.install( tabPane, null );
 	}
 
 	@Override
@@ -120,6 +122,8 @@ public class FlatTabbedPaneUI
 		hoverColor = null;
 		focusColor = null;
 		contentAreaColor = null;
+
+		MigLayoutVisualPadding.uninstall( tabPane );
 	}
 
 	@Override

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

@@ -59,6 +59,15 @@ public class FlatTextFieldUI
 
 		focusWidth = UIManager.getInt( "Component.focusWidth" );
 		minimumWidth = UIManager.getInt( "Component.minimumWidth" );
+
+		MigLayoutVisualPadding.install( getComponent(), focusWidth );
+	}
+
+	@Override
+	protected void uninstallDefaults() {
+		super.uninstallDefaults();
+
+		MigLayoutVisualPadding.uninstall( getComponent() );
 	}
 
 	@Override

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

@@ -0,0 +1,162 @@
+/*
+ * Copyright 2019 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
+ *
+ *     http://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 static com.formdev.flatlaf.util.UIScale.scale2;
+import java.awt.Insets;
+import java.beans.PropertyChangeListener;
+import java.util.function.Function;
+import javax.swing.JComponent;
+
+/**
+ * Support for MigLayout visual paddings.
+ *
+ * Visual paddings are used by MigLayout to ignore the usually invisible space
+ * around some components (e.g. buttons) that is used to paint a focus border.
+ *
+ * @author Karl Tauber
+ */
+public class MigLayoutVisualPadding
+{
+	/**
+	 * Key of visual padding client property.
+	 * Value must be either an integer array of size 4, or java.awt.Insets.
+	 *
+	 * Same as net.miginfocom.layout.PlatformDefaults.VISUAL_PADDING_PROPERTY,
+	 * but we don't want to depend on miglayout library.
+	 */
+	public static String VISUAL_PADDING_PROPERTY = "visualPadding";
+
+	private static final FlatMigInsets ZERO = new FlatMigInsets( 0, 0, 0, 0 );
+	private static final boolean migLayoutAvailable;
+
+	static {
+		// check whether MigLayout is available
+		boolean available = false;
+		try {
+			Class.forName( "net.miginfocom.swing.MigLayout" );
+			available = true;
+		} catch( ClassNotFoundException ex ) {
+			// ignore
+		}
+		migLayoutAvailable = available;
+	}
+
+	/**
+	 * Sets the client property to the given insets.
+	 */
+	public static void install( JComponent c, Insets insets ) {
+		if( !migLayoutAvailable )
+			return;
+
+		setVisualPadding( c, insets );
+	}
+
+	/**
+	 * Convenience method that checks whether component border is a FlatBorder.
+	 */
+	public static void install( JComponent c, int focusWidth ) {
+		if( !migLayoutAvailable )
+			return;
+
+		install( c, c2 -> {
+			return (c2.getBorder() instanceof FlatBorder)
+				? new Insets( focusWidth, focusWidth, focusWidth, focusWidth )
+				: null;
+		}, "border" );
+	}
+
+	/**
+	 * Invokes the given function to retrieve the actual visual paddings and sets
+	 * the client property. Also adds property change listener to component and
+	 * re-invokes the function if one of the given properties have changed.
+	 */
+	public static void install( JComponent c, Function<JComponent, Insets> getPaddingFunction, String... propertyNames ) {
+		if( !migLayoutAvailable )
+			return;
+
+		// set client property
+		setVisualPadding( c, getPaddingFunction.apply( c ) );
+
+		// add listener
+		c.addPropertyChangeListener( (FlatMigListener) e -> {
+			String propertyName = e.getPropertyName();
+			for( String name : propertyNames ) {
+				if( name == propertyName ) {
+					setVisualPadding( c, getPaddingFunction.apply( c ) );
+					break;
+				}
+			}
+		} );
+	}
+
+	private static void setVisualPadding( JComponent c, Insets visualPadding ) {
+		Object oldPadding = c.getClientProperty( VISUAL_PADDING_PROPERTY );
+		if( oldPadding == null || oldPadding instanceof FlatMigInsets ) {
+			FlatMigInsets flatVisualPadding = (visualPadding != null)
+				? new FlatMigInsets( scale2( visualPadding.top ), scale2( visualPadding.left ),
+					scale2( visualPadding.bottom ), scale2( visualPadding.right ) )
+				: ZERO;
+
+			c.putClientProperty( VISUAL_PADDING_PROPERTY, flatVisualPadding );
+		}
+	}
+
+	/**
+	 * Removes listeners and restores client property.
+	 */
+	public static void uninstall( JComponent c ) {
+		if( !migLayoutAvailable )
+			return;
+
+		// remove listener
+		for( PropertyChangeListener l : c.getPropertyChangeListeners() ) {
+			if( l instanceof FlatMigListener ) {
+				c.removePropertyChangeListener( l );
+				break;
+			}
+		}
+
+		// remove client property
+		if( c.getClientProperty( VISUAL_PADDING_PROPERTY ) instanceof FlatMigInsets )
+			c.putClientProperty( VISUAL_PADDING_PROPERTY, null );
+	}
+
+	//---- class FlatMigInsets ------------------------------------------------
+
+	/**
+	 * Marker class to identify our visual paddings and leaf paddings,
+	 * which were set from outside, untouched.
+	 */
+	private static class FlatMigInsets
+		extends Insets
+	{
+		FlatMigInsets( int top, int left, int bottom, int right ) {
+			super( top, left, bottom, right );
+		}
+	}
+
+	//---- class FlatMigListener ----------------------------------------------
+
+	/**
+	 * Marker interface needed for listener removal.
+	 */
+	private interface FlatMigListener
+		extends PropertyChangeListener
+	{
+	}
+}

flatlaf-core/src/main/java/com/formdev/flatlaf/util/UIScale.java

@@ -188,6 +188,13 @@ public class UIScale
 		return (scaleFactor == 1) ? value : Math.round( value * scaleFactor );
 	}
 
+	/**
+	 * Similar as scale(int) but always "rounds down".
+	 */
+	public static int scale2( int value ) {
+		return (scaleFactor == 1) ? value : (int) (value * scaleFactor);
+	}
+
 	public static float unscale( float value ) {
 		return (scaleFactor == 1f) ? value : (value / scaleFactor);
 	}