Smooth Scrolling: fixes too slow repeating block (page) scrolling (e.g. hold down PageUp key) for Tree, TextArea, TextPane and EditorPane

Author: DevCharly

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

@@ -31,6 +31,7 @@
 import javax.swing.plaf.ComponentUI;
 import javax.swing.plaf.basic.BasicEditorPaneUI;
 import javax.swing.text.Caret;
+import javax.swing.text.DefaultEditorKit;
 import javax.swing.text.JTextComponent;
 import com.formdev.flatlaf.FlatClientProperties;
 import com.formdev.flatlaf.ui.FlatStylingSupport.Styleable;
@@ -145,6 +146,21 @@ protected void uninstallListeners() {
 		focusListener = null;
 	}
 
+	@Override
+	protected void installKeyboardActions() {
+		super.installKeyboardActions();
+		installKeyboardActions( getComponent() );
+	}
+
+	static void installKeyboardActions( JTextComponent c ) {
+		FlatScrollPaneUI.installSmoothScrollingDelegateActions( c, false,
+			/* page-down */ DefaultEditorKit.pageDownAction,						// PAGE_DOWN
+			/* page-up */ DefaultEditorKit.pageUpAction,							// PAGE_UP
+			/* DefaultEditorKit.selectionPageDownAction */ "selection-page-down",	// shift PAGE_DOWN
+			/* DefaultEditorKit.selectionPageUpAction */ "selection-page-up"		// shift PAGE_UP
+		);
+	}
+
 	@Override
 	protected Caret createCaret() {
 		return new FlatCaret( null, false );
@@ -159,6 +175,11 @@ protected void propertyChange( PropertyChangeEvent e ) {
 
 		super.propertyChange( e );
 		propertyChange( getComponent(), e, this::installStyle );
+
+		// BasicEditorPaneUI.propertyChange() re-applied actions from editor kit,
+		// which removed our delegate actions
+		if( "editorKit".equals( propertyName ) )
+			installKeyboardActions( getComponent() );
 	}
 
 	static void propertyChange( JTextComponent c, PropertyChangeEvent e, Runnable installStyle ) {

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

@@ -34,7 +34,6 @@
 import javax.swing.JComponent;
 import javax.swing.JScrollBar;
 import javax.swing.JScrollPane;
-import javax.swing.JViewport;
 import javax.swing.SwingUtilities;
 import javax.swing.UIManager;
 import javax.swing.plaf.ComponentUI;
@@ -481,7 +480,8 @@ public void runAndSetValueAnimated( Runnable r ) {
 		// remember current scrollbar value so that we can start scroll animation from there
 		int oldValue = scrollbar.getValue();
 
-		runWithoutBlitting( scrollbar.getParent(), () ->{
+		// run given runnable, which computes and sets the new scrollbar value
+		FlatScrollPaneUI.runWithoutBlitting( scrollbar.getParent(), () ->{
 			// if invoked while animation is running, calculation of new value
 			// should start at the previous target value
 			if( targetValue != Integer.MIN_VALUE )
@@ -510,32 +510,16 @@ public void runAndSetValueAnimated( Runnable r ) {
 		inRunAndSetValueAnimated = false;
 	}
 
-	private void runWithoutBlitting( Container scrollPane, Runnable r ) {
-		// prevent the viewport to immediately repaint using blitting
-		JViewport viewport = null;
-		int oldScrollMode = 0;
-		if( scrollPane instanceof JScrollPane ) {
-			viewport = ((JScrollPane) scrollPane).getViewport();
-			if( viewport != null ) {
-				oldScrollMode = viewport.getScrollMode();
-				viewport.setScrollMode( JViewport.BACKINGSTORE_SCROLL_MODE );
-			}
-		}
-
-		try {
-			r.run();
-		} finally {
-			if( viewport != null )
-				viewport.setScrollMode( oldScrollMode );
-		}
-	}
-
 	private boolean inRunAndSetValueAnimated;
 	private Animator animator;
 	private int startValue = Integer.MIN_VALUE;
 	private int targetValue = Integer.MIN_VALUE;
 	private boolean useValueIsAdjusting = true;
 
+	int getTargetValue() {
+		return targetValue;
+	}
+
 	public void setValueAnimated( int initialValue, int value ) {
 		// do some check if animation already running
 		if( animator != null && animator.isRunning() && targetValue != Integer.MIN_VALUE ) {

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

@@ -17,10 +17,12 @@
 package com.formdev.flatlaf.ui;
 
 import java.awt.Component;
+import java.awt.Container;
 import java.awt.Graphics;
 import java.awt.Insets;
 import java.awt.KeyboardFocusManager;
 import java.awt.Rectangle;
+import java.awt.event.ActionEvent;
 import java.awt.event.ContainerEvent;
 import java.awt.event.ContainerListener;
 import java.awt.event.FocusEvent;
@@ -31,6 +33,8 @@
 import java.beans.PropertyChangeListener;
 import java.util.Map;
 import java.util.concurrent.atomic.AtomicBoolean;
+import javax.swing.Action;
+import javax.swing.ActionMap;
 import javax.swing.BorderFactory;
 import javax.swing.JButton;
 import javax.swing.JComponent;
@@ -458,17 +462,39 @@ protected void syncScrollPaneWithViewport() {
 		// if the viewport has been scrolled by using JComponent.scrollRectToVisible()
 		// (e.g. by moving selection), then it is necessary to update the scroll bar values
 		if( isSmoothScrollingEnabled() ) {
-			runAndSyncScrollBarValueAnimated( scrollpane.getVerticalScrollBar(), 0, () -> {
-				runAndSyncScrollBarValueAnimated( scrollpane.getHorizontalScrollBar(), 1, () -> {
+			runAndSyncScrollBarValueAnimated( scrollpane.getVerticalScrollBar(), 0, false, () -> {
+				runAndSyncScrollBarValueAnimated( scrollpane.getHorizontalScrollBar(), 1, false, () -> {
 					super.syncScrollPaneWithViewport();
 				} );
 			} );
 		} else
 			super.syncScrollPaneWithViewport();
 	}
 
-	private void runAndSyncScrollBarValueAnimated( JScrollBar sb, int i, Runnable r ) {
-		if( inRunAndSyncValueAnimated[i] || sb == null ) {
+	/**
+	 * Runs the given runnable, if smooth scrolling is enabled, with disabled
+	 * viewport blitting mode and with scroll bar value set to "target" value.
+	 * This is necessary when calculating new view position during animation.
+	 * Otherwise calculation would use wrong view position and (repeating) scrolling
+	 * would be much slower than without smooth scrolling.
+	 */
+	private void runWithScrollBarsTargetValues( boolean blittingOnly, Runnable r ) {
+		if( isSmoothScrollingEnabled() ) {
+			runWithoutBlitting( scrollpane, () -> {
+				if( blittingOnly )
+					r.run();
+				else {
+					runAndSyncScrollBarValueAnimated( scrollpane.getVerticalScrollBar(), 0, true, () -> {
+						runAndSyncScrollBarValueAnimated( scrollpane.getHorizontalScrollBar(), 1, true, r );
+					} );
+				}
+			} );
+		} else
+			r.run();
+	}
+
+	private void runAndSyncScrollBarValueAnimated( JScrollBar sb, int i, boolean useTargetValue, Runnable r ) {
+		if( inRunAndSyncValueAnimated[i] || sb == null || !(sb.getUI() instanceof FlatScrollBarUI) ) {
 			r.run();
 			return;
 		}
@@ -480,6 +506,10 @@ private void runAndSyncScrollBarValueAnimated( JScrollBar sb, int i, Runnable r
 		int oldMinimum = sb.getMinimum();
 		int oldMaximum = sb.getMaximum();
 
+		FlatScrollBarUI ui = (FlatScrollBarUI) sb.getUI();
+		if( useTargetValue && ui.getTargetValue() != Integer.MIN_VALUE )
+			sb.setValue( ui.getTargetValue() );
+
 		r.run();
 
 		int newValue = sb.getValue();
@@ -490,14 +520,61 @@ private void runAndSyncScrollBarValueAnimated( JScrollBar sb, int i, Runnable r
 			sb.getMaximum() == oldMaximum &&
 			sb.getUI() instanceof FlatScrollBarUI )
 		{
-			((FlatScrollBarUI)sb.getUI()).setValueAnimated( oldValue, newValue );
+			ui.setValueAnimated( oldValue, newValue );
 		}
 
 		inRunAndSyncValueAnimated[i] = false;
 	}
 
 	private final boolean[] inRunAndSyncValueAnimated = new boolean[2];
 
+	/**
+	 * Runs the given runnable with disabled viewport blitting mode.
+	 * If blitting mode is enabled, the viewport immediately repaints parts of the
+	 * view if the view position is changed via JViewport.setViewPosition().
+	 * This causes scrolling artifacts if smooth scrolling is enabled and the view position
+	 * is "temporary" changed to its new target position, changed back to its old position
+	 * and again moved animated to the target position.
+	 */
+	static void runWithoutBlitting( Container scrollPane, Runnable r ) {
+		// prevent the viewport to immediately repaint using blitting
+		JViewport viewport = null;
+		int oldScrollMode = 0;
+		if( scrollPane instanceof JScrollPane ) {
+			viewport = ((JScrollPane) scrollPane).getViewport();
+			if( viewport != null ) {
+				oldScrollMode = viewport.getScrollMode();
+				viewport.setScrollMode( JViewport.BACKINGSTORE_SCROLL_MODE );
+			}
+		}
+
+		try {
+			r.run();
+		} finally {
+			if( viewport != null )
+				viewport.setScrollMode( oldScrollMode );
+		}
+	}
+
+	public static void installSmoothScrollingDelegateActions( JComponent c, boolean blittingOnly, String... actionKeys ) {
+		// get shared action map, used for all components of same type
+		ActionMap map = SwingUtilities.getUIActionMap( c );
+		if( map == null )
+			return;
+
+		// install actions, but only if not already installed
+		for( String actionKey : actionKeys )
+			installSmoothScrollingDelegateAction( map, blittingOnly, actionKey );
+	}
+
+	private static void installSmoothScrollingDelegateAction( ActionMap map, boolean blittingOnly, String actionKey ) {
+		Action oldAction = map.get( actionKey );
+		if( oldAction == null || oldAction instanceof SmoothScrollingDelegateAction )
+			return; // not found or already installed
+
+		map.put( actionKey, new SmoothScrollingDelegateAction( oldAction, blittingOnly ) );
+	}
+
 	//---- class Handler ------------------------------------------------------
 
 	/**
@@ -529,4 +606,34 @@ public void focusLost( FocusEvent e ) {
 			scrollpane.repaint();
 		}
 	}
+
+	//---- class SmoothScrollingDelegateAction --------------------------------
+
+	/**
+	 * Used to run component actions with disabled blitting mode and
+	 * with scroll bar target values.
+	 */
+	private static class SmoothScrollingDelegateAction
+		extends FlatUIAction
+	{
+		private final boolean blittingOnly;
+
+		private SmoothScrollingDelegateAction( Action delegate, boolean blittingOnly ) {
+			super( delegate );
+			this.blittingOnly = blittingOnly;
+		}
+
+		@Override
+		public void actionPerformed( ActionEvent e ) {
+			Object source = e.getSource();
+			JScrollPane scrollPane = (source instanceof Component)
+				? (JScrollPane) SwingUtilities.getAncestorOfClass( JScrollPane.class, (Component) source )
+				: null;
+			if( scrollPane != null && scrollPane.getUI() instanceof FlatScrollPaneUI ) {
+				((FlatScrollPaneUI)scrollPane.getUI()).runWithScrollBarsTargetValues( blittingOnly,
+					() -> delegate.actionPerformed( e ) );
+			} else
+				delegate.actionPerformed( e );
+		}
+	}
 }

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

@@ -141,6 +141,12 @@ protected void uninstallListeners() {
 		focusListener = null;
 	}
 
+	@Override
+	protected void installKeyboardActions() {
+		super.installKeyboardActions();
+		FlatEditorPaneUI.installKeyboardActions( getComponent() );
+	}
+
 	@Override
 	protected Caret createCaret() {
 		return new FlatCaret( null, false );

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

@@ -142,6 +142,12 @@ protected void uninstallListeners() {
 		focusListener = null;
 	}
 
+	@Override
+	protected void installKeyboardActions() {
+		super.installKeyboardActions();
+		FlatEditorPaneUI.installKeyboardActions( getComponent() );
+	}
+
 	@Override
 	protected Caret createCaret() {
 		return new FlatCaret( null, false );
@@ -156,6 +162,11 @@ protected void propertyChange( PropertyChangeEvent e ) {
 
 		super.propertyChange( e );
 		FlatEditorPaneUI.propertyChange( getComponent(), e, this::installStyle );
+
+		// BasicEditorPaneUI.propertyChange() re-applied actions from editor kit,
+		// which removed our delegate actions
+		if( "editorKit".equals( propertyName ) )
+			FlatEditorPaneUI.installKeyboardActions( getComponent() );
 	}
 
 	/** @since 2 */

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

@@ -238,6 +238,22 @@ protected void uninstallDefaults() {
 		oldStyleValues = null;
 	}
 
+	@Override
+	protected void installKeyboardActions() {
+		super.installKeyboardActions();
+
+		FlatScrollPaneUI.installSmoothScrollingDelegateActions( tree, false,
+			"scrollDownChangeSelection",	// PAGE_DOWN
+			"scrollUpChangeSelection",		// PAGE_UP
+			"scrollDownChangeLead",			// ctrl PAGE_DOWN
+			"scrollUpChangeLead",			// ctrl PAGE_UP
+			"scrollDownExtendSelection",	// shift PAGE_DOWN, shift ctrl PAGE_DOWN
+			"scrollUpExtendSelection",		// shift PAGE_UP, shift ctrl PAGE_UP
+			"selectNextChangeLead",			// ctrl DOWN
+			"selectPreviousChangeLead"		// ctrl UP
+		);
+	}
+
 	@Override
 	protected void updateRenderer() {
 		super.updateRenderer();