Auto-scroll with middle mouse button

recaf-ui/src/main/java/software/coley/recaf/ui/control/VirtualizedScrollPaneWrapper.java

@@ -1,11 +1,21 @@
 package software.coley.recaf.ui.control;
 
 import jakarta.annotation.Nonnull;
+import javafx.animation.AnimationTimer;
+import javafx.beans.property.BooleanProperty;
+import javafx.beans.property.DoubleProperty;
+import javafx.beans.property.SimpleBooleanProperty;
 import javafx.beans.property.SimpleDoubleProperty;
+import javafx.scene.Cursor;
+import javafx.scene.control.ScrollBar;
+import javafx.scene.input.MouseButton;
 import javafx.scene.layout.Region;
 import org.fxmisc.flowless.Virtualized;
 import org.fxmisc.flowless.VirtualizedScrollPane;
 import org.reactfx.value.Var;
+import software.coley.collections.Unchecked;
+import software.coley.recaf.util.NodeEvents;
+import software.coley.recaf.util.ReflectUtil;
 
 /**
  * Wrapper for {@link VirtualizedScrollPane} to properly expose properties with JavaFX's property types instead of
@@ -17,36 +27,144 @@
  * @author Matt Coley
  */
 public class VirtualizedScrollPaneWrapper<V extends Region & Virtualized> extends VirtualizedScrollPane<V> {
-	private final SimpleDoubleProperty xScroll = new SimpleDoubleProperty(0);
-	private final SimpleDoubleProperty yScroll = new SimpleDoubleProperty(0);
+	private static final double AUTO_SCROLL_MULTIPLIER = 0.1;
+	private static final double AUTO_SCROLL_BUFFER_PX = 5;
+	private final DoubleProperty xScrollProperty = new SimpleDoubleProperty(0);
+	private final DoubleProperty yScrollProperty = new SimpleDoubleProperty(0);
+	private final BooleanProperty canAutoScroll = new SimpleBooleanProperty(true);
+	private final ScrollBar horizontalScrollbar;
+	private final ScrollBar verticalScrollbar;
+	private Cursor preAutoScrollCursor;
+	private boolean isAutoScrolling;
+	private double autoScrollStartY;
+	private double autoScrollCurrentY;
+	private final AnimationTimer autoScrollTimer = new AnimationTimer() {
+		@Override
+		public void handle(long now) {
+			updateAutoScroll();
+		}
+	};
 
 	/**
 	 * @param content
 	 * 		Virtualized content.
 	 */
 	public VirtualizedScrollPaneWrapper(V content) {
 		super(content);
+
+		horizontalScrollbar = Unchecked.get(() -> ReflectUtil.quietGet(this, VirtualizedScrollPane.class.getDeclaredField("hbar")));
+		verticalScrollbar = Unchecked.get(() -> ReflectUtil.quietGet(this, VirtualizedScrollPane.class.getDeclaredField("vbar")));
+
 		setup();
 	}
 
 	private void setup() {
-		xScroll.bind(estimatedScrollXProperty());
-		yScroll.bind(estimatedScrollYProperty());
+		xScrollProperty.bind(estimatedScrollXProperty());
+		yScrollProperty.bind(estimatedScrollYProperty());
+
+		// Handle middle mouse press to start auto-scrolling.
+		// - Press initiates the auto-scroll
+		// - Drag changes the auto-scroll speed
+		// - Release stops the auto-scroll
+		NodeEvents.addMousePressHandler(getContent(), e -> {
+			if (canAutoScroll.get() && e.getButton() == MouseButton.MIDDLE) {
+				preAutoScrollCursor = getContent().getCursor();
+				autoScrollStartY = e.getScreenY();
+				autoScrollCurrentY = autoScrollStartY;
+			}
+		});
+		NodeEvents.addMouseReleaseHandler(getContent(), e -> {
+			if (e.getButton() == MouseButton.MIDDLE && isAutoScrolling()) {
+				getContent().setCursor(preAutoScrollCursor);
+				autoScrollTimer.stop();
+				autoScrollCurrentY = -1;
+				isAutoScrolling = false;
+			}
+		});
+		NodeEvents.addMouseDraggedHandler(getContent(), e -> {
+			if (e.getButton() == MouseButton.MIDDLE) {
+				autoScrollCurrentY = e.getScreenY();
+
+				// Only begin the auto-scroll after the user has moved a couple of pixels away.
+				//
+				// We do this because the 'content' node may have middle click behavior similar
+				// to how a browser opens/closes tabs when using the middle mouse button on links.
+				// By not initiating until we're sure the user intends to move around via auto-scroll
+				// we don't mess with the UX of the existing behavior in the 'content' node.
+				if (!isAutoScrolling && Math.abs(autoScrollCurrentY - autoScrollStartY) > AUTO_SCROLL_BUFFER_PX) {
+					isAutoScrolling = true;
+					autoScrollTimer.start();
+					getContent().setCursor(Cursor.V_RESIZE);
+				}
+			}
+		});
+	}
+
+	private void updateAutoScroll() {
+		double deltaY = autoScrollCurrentY - autoScrollStartY;
+
+		// Get current scroll values
+		double value = verticalScrollbar.getValue();
+		double min = verticalScrollbar.getMin();
+		double max = verticalScrollbar.getMax();
+
+		// Calculate scroll amount based on viewport size
+		double viewportHeight = getHeight();
+		double scrollAmount = (deltaY * AUTO_SCROLL_MULTIPLIER);
+		if (Math.abs(scrollAmount) > 0.1) {
+			// Calculate new scroll position
+			double newValue = value + scrollAmount;
+			newValue = Math.max(min, Math.min(max, newValue));
+
+			// Update scroll position
+			verticalScrollbar.setValue(newValue);
+		}
+	}
+
+	/**
+	 * @return {@code true} when this scroll pane is auto-scrolling.
+	 */
+	public boolean isAutoScrolling() {
+		return isAutoScrolling;
+	}
+
+	/**
+	 * @return Horizontal scrollbar.
+	 */
+	@Nonnull
+	public ScrollBar getHorizontalScrollbar() {
+		return horizontalScrollbar;
+	}
+
+	/**
+	 * @return Vertical scrollbar.
+	 */
+	@Nonnull
+	public ScrollBar getVerticalScrollbar() {
+		return verticalScrollbar;
 	}
 
 	/**
 	 * @return Horizontal scroll property.
 	 */
 	@Nonnull
-	public SimpleDoubleProperty horizontalScrollProperty() {
-		return xScroll;
+	public DoubleProperty horizontalScrollProperty() {
+		return xScrollProperty;
 	}
 
 	/**
 	 * @return Vertical scroll property.
 	 */
 	@Nonnull
-	public SimpleDoubleProperty verticalScrollProperty() {
-		return yScroll;
+	public DoubleProperty verticalScrollProperty() {
+		return yScrollProperty;
+	}
+
+	/**
+	 * @return Can auto-scroll property.
+	 */
+	@Nonnull
+	public BooleanProperty canAutoScrollProperty() {
+		return canAutoScroll;
 	}
 }

recaf-ui/src/main/java/software/coley/recaf/ui/control/richtext/Editor.java

@@ -16,10 +16,13 @@
 import javafx.scene.text.Text;
 import org.fxmisc.flowless.Cell;
 import org.fxmisc.flowless.VirtualFlow;
-import org.fxmisc.flowless.VirtualizedScrollPane;
 import org.fxmisc.richtext.CodeArea;
 import org.fxmisc.richtext.GenericStyledArea;
-import org.fxmisc.richtext.model.*;
+import org.fxmisc.richtext.model.PlainTextChange;
+import org.fxmisc.richtext.model.ReadOnlyStyledDocument;
+import org.fxmisc.richtext.model.StyleSpans;
+import org.fxmisc.richtext.model.StyledDocument;
+import org.fxmisc.richtext.model.TwoDimensional;
 import org.reactfx.Change;
 import org.reactfx.EventStream;
 import org.reactfx.EventStreams;
@@ -72,8 +75,7 @@ public class Editor extends BorderPane {
 	private static final StyleResult FALLBACK_STYLE_RESULT = new StyleResult(StyleSpans.singleton(Collections.emptyList(), 0), 0);
 	private final StackPane stackPane = new StackPane();
 	private final CodeArea codeArea = new SafeCodeArea();
-	private final ScrollBar horizontalScrollbar;
-	private final ScrollBar verticalScrollbar;
+	private final VirtualizedScrollPaneWrapper<CodeArea> codeScrollWrapper;
 	private final VirtualFlow<?, ?> virtualFlow;
 	private final MemoizationList<Cell<?, ?>> virtualCellList;
 	private final ExecutorService syntaxPool = ThreadPoolFactory.newSingleThreadExecutor("syntax-highlight");
@@ -92,17 +94,16 @@ public class Editor extends BorderPane {
 	public Editor() {
 		// Get the reflection hacks out of the way first.
 		//  - Want to have access to scrollbars & the internal 'virtualFlow'
-		VirtualizedScrollPaneWrapper<CodeArea> scrollPane = new VirtualizedScrollPaneWrapper<>(codeArea);
-		horizontalScrollbar = Unchecked.get(() -> ReflectUtil.quietGet(scrollPane, VirtualizedScrollPane.class.getDeclaredField("hbar")));
-		verticalScrollbar = Unchecked.get(() -> ReflectUtil.quietGet(scrollPane, VirtualizedScrollPane.class.getDeclaredField("vbar")));
+		codeScrollWrapper = new VirtualizedScrollPaneWrapper<>(codeArea);
+
 		virtualFlow = Unchecked.get(() -> ReflectUtil.quietGet(codeArea, GenericStyledArea.class.getDeclaredField("virtualFlow")));
 		Object virtualCellManager = Unchecked.get(() -> ReflectUtil.quietGet(virtualFlow, VirtualFlow.class.getDeclaredField("cellListManager")));
 		virtualCellList = ReflectUtil.quietInvoke(virtualCellManager.getClass(), virtualCellManager, "getLazyCellList", new Class[0], new Object[0]);
 
 		// Initial layout / style.
 		getStylesheets().add("/style/code-editor.css");
 		setCenter(stackPane);
-		stackPane.getChildren().add(scrollPane);
+		stackPane.getChildren().add(codeScrollWrapper);
 
 		// Do not want text wrapping in a code editor.
 		codeArea.setWrapText(false);
@@ -643,15 +644,15 @@ public boolean isParagraphVisible(int line) {
 	 */
 	@Nonnull
 	public ScrollBar getHorizontalScrollbar() {
-		return horizontalScrollbar;
+		return codeScrollWrapper.getHorizontalScrollbar();
 	}
 
 	/**
 	 * @return {@link #getCodeArea() Code area's} vertical scrollbar.
 	 */
 	@Nonnull
 	public ScrollBar getVerticalScrollbar() {
-		return verticalScrollbar;
+		return codeScrollWrapper.getVerticalScrollbar();
 	}
 
 	/**

recaf-ui/src/main/java/software/coley/recaf/util/NodeEvents.java

@@ -115,6 +115,17 @@ public static void addMouseMoveHandler(@Nonnull Node node, @Nonnull EventHandler
 		addHandler(node, handler, Unchecked.cast(original), Node::setOnMouseMoved);
 	}
 
+	/**
+	 * @param node
+	 * 		Node to add to.
+	 * @param handler
+	 * 		Handler to add.
+	 */
+	public static void addMouseDraggedHandler(@Nonnull Node node, @Nonnull EventHandler<MouseEvent> handler) {
+		Function<Node, EventHandler<? super MouseEvent>> original = Node::getOnMouseDragged;
+		addHandler(node, handler, Unchecked.cast(original), Node::setOnMouseDragged);
+	}
+
 	/**
 	 * @param node
 	 * 		Node to add to.