[Sticky Scrolling] Dispatch scrolling to source viewer

Scrolling on the sticky lines control is dispatched to the linked source viewer. With this change the source viewer's scrolling behavior remains consistent, regardless of whether sticky scrolling is enalbed or not.

Follow up for eclipse-platform#1894

Author: Christopher-Hermann

bundles/org.eclipse.ui.editors/src/org/eclipse/ui/internal/texteditor/stickyscroll/StickyScrollingControl.java

@@ -39,7 +39,10 @@
 import org.eclipse.swt.widgets.Canvas;
 import org.eclipse.swt.widgets.Composite;
 import org.eclipse.swt.widgets.Display;
+import org.eclipse.swt.widgets.Event;
 import org.eclipse.swt.widgets.Label;
+import org.eclipse.swt.widgets.Listener;
+import org.eclipse.swt.widgets.ScrollBar;
 
 import org.eclipse.core.runtime.ICoreRunnable;
 import org.eclipse.core.runtime.jobs.Job;
@@ -98,11 +101,15 @@ public class StickyScrollingControl {
 
 	private final static int BOTTOM_SEPARATOR_SPACING= 2;
 
+	private StickyScrollingHandler stickyScrollingHandler;
+
 	public StickyScrollingControl(ISourceViewer sourceViewer, StickyScrollingControlSettings settings) {
-		this(sourceViewer, null, settings);
+		this(sourceViewer, null, settings, null);
 	}
 
-	public StickyScrollingControl(ISourceViewer sourceViewer, IVerticalRuler verticalRuler, StickyScrollingControlSettings settings) {
+	public StickyScrollingControl(ISourceViewer sourceViewer, IVerticalRuler verticalRuler,
+			StickyScrollingControlSettings settings, StickyScrollingHandler stickyScrollingHandler) {
+		this.stickyScrollingHandler= stickyScrollingHandler;
 		this.stickyLines= new ArrayList<>();
 		this.sourceViewer= sourceViewer;
 		this.verticalRuler= verticalRuler;
@@ -441,6 +448,10 @@ public void mouseExit(MouseEvent e) {
 				stickyLineText.setLineBackground(0, getNumberStickyLines(), null);
 			}
 		});
+
+		ScrollingDispatchingListener scrollingDispatchingListener= new ScrollingDispatchingListener();
+		canvas.addListener(SWT.MouseHorizontalWheel, scrollingDispatchingListener);
+		canvas.addListener(SWT.MouseVerticalWheel, scrollingDispatchingListener);
 	}
 
 	/**
@@ -479,6 +490,42 @@ public void caretMoved(CaretEvent event) {
 				ensureSourceViewerLineVisible(line);
 			});
 		}
+	}
+
+	/**
+	 * A mouse wheel listener that is dispatching the scrolling on the sticky lines canvas to the
+	 * source viewer. The calculation of the scrolling steps is copied from
+	 * {@link Composite}#scrollWheel.
+	 */
+	class ScrollingDispatchingListener implements Listener {
 
+		@Override
+		public void handleEvent(Event event) {
+			StyledText textWidget= sourceViewer.getTextWidget();
+
+			ScrollBar bar= event.type == SWT.MouseHorizontalWheel ? textWidget.getHorizontalBar() : textWidget.getVerticalBar();
+			if (bar == null) {
+				return;
+			}
+
+			int deltaY= event.count;
+			if (-1 < deltaY && deltaY < 0) {
+				deltaY= -1;
+			}
+			if (0 < deltaY && deltaY < 1) {
+				deltaY= 1;
+			}
+
+			int pixel= Math.max(0, (int) (0.5f + bar.getSelection() - bar.getIncrement() * deltaY));
+
+			if (event.type == SWT.MouseHorizontalWheel) {
+				sourceViewer.getTextWidget().setHorizontalPixel(pixel);
+			} else {
+				sourceViewer.getTextWidget().setTopPixel(pixel);
+				if (stickyScrollingHandler != null) {
+					stickyScrollingHandler.viewportChanged(pixel);
+				}
+			}
+		}
 	}
 }

bundles/org.eclipse.ui.editors/src/org/eclipse/ui/internal/texteditor/stickyscroll/StickyScrollingHandler.java

@@ -85,7 +85,7 @@ public StickyScrollingHandler(ISourceViewer sourceViewer, IVerticalRuler vertica
 		this.stickyLinesProvider= stickyLinesProvider;
 
 		StickyScrollingControlSettings settings= loadAndListenForProperties(preferenceStore);
-		stickyScrollingControl= new StickyScrollingControl(sourceViewer, verticalRuler, settings);
+		stickyScrollingControl= new StickyScrollingControl(sourceViewer, verticalRuler, settings, this);
 
 		sourceViewer.addViewportListener(this);
 	}

tests/org.eclipse.ui.editors.tests/src/org/eclipse/ui/internal/texteditor/stickyscroll/StickyScrollingControlTest.java

@@ -37,6 +37,7 @@
 import org.eclipse.swt.widgets.Control;
 import org.eclipse.swt.widgets.Display;
 import org.eclipse.swt.widgets.Event;
+import org.eclipse.swt.widgets.ScrollBar;
 import org.eclipse.swt.widgets.Shell;
 
 import org.eclipse.jface.text.Document;
@@ -59,14 +60,14 @@ public void setup() {
 		shell.setSize(200, 200);
 		shell.setLayout(new FillLayout());
 		ruler = new CompositeRuler();
-		sourceViewer = new SourceViewer(shell, ruler, SWT.None);
+		sourceViewer = new SourceViewer(shell, ruler, SWT.V_SCROLL | SWT.H_SCROLL);
 
 		lineNumberColor = new Color(0, 0, 0);
 		hoverColor = new Color(1, 1, 1);
 		backgroundColor = new Color(2, 2, 2);
 		StickyScrollingControlSettings settings = new StickyScrollingControlSettings(5, lineNumberColor, hoverColor,
 				backgroundColor, true);
-		stickyScrollingControl = new StickyScrollingControl(sourceViewer, ruler, settings);
+		stickyScrollingControl = new StickyScrollingControl(sourceViewer, ruler, settings, null);
 	}
 
 	@After
@@ -177,20 +178,20 @@ public void testLayoutStickyLinesCanvasOnResize() {
 		Canvas stickyControlCanvas = getStickyControlCanvas(shell);
 		assertEquals(0, stickyControlCanvas.getBounds().x);
 		assertEquals(0, stickyControlCanvas.getBounds().y);
-		assertEquals(201, stickyControlCanvas.getBounds().width);
+		assertEquals(getExpectedWitdh(200), stickyControlCanvas.getBounds().width);
 		assertThat(stickyControlCanvas.getBounds().height, greaterThan(0));
 
 		sourceViewer.getTextWidget().setBounds(0, 0, 150, 200);
 
 		stickyControlCanvas = getStickyControlCanvas(shell);
 		assertEquals(0, stickyControlCanvas.getBounds().x);
 		assertEquals(0, stickyControlCanvas.getBounds().y);
-		assertEquals(151, stickyControlCanvas.getBounds().width);
+		assertEquals(getExpectedWitdh(150), stickyControlCanvas.getBounds().width);
 		assertThat(stickyControlCanvas.getBounds().height, greaterThan(0));
 	}
 
 	@Test
-	public void navigateToStickyLine() {
+	public void testNavigateToStickyLine() {
 		String text = """
 				line 1
 				line 2""";
@@ -209,6 +210,40 @@ public void navigateToStickyLine() {
 		assertEquals(0, selectedRange.y);
 	}
 
+	@Test
+	public void testVerticalScrollingIsDispatched() {
+		Canvas stickyControlCanvas = getStickyControlCanvas(shell);
+		String text = """
+				line 1
+				line 2""";
+		sourceViewer.getTextWidget().setText(text);
+		sourceViewer.getTextWidget().getVerticalBar().setIncrement(10);
+		assertEquals(0, sourceViewer.getTextWidget().getTopPixel());
+
+		Event event = new Event();
+		event.count = -1;
+		stickyControlCanvas.notifyListeners(SWT.MouseVerticalWheel, event);
+
+		assertEquals(10, sourceViewer.getTextWidget().getTopPixel());
+	}
+
+	@Test
+	public void testHorizontalScrollingIsDispatched() {
+		Canvas stickyControlCanvas = getStickyControlCanvas(shell);
+		String text = """
+				line 1
+				line 2""";
+		sourceViewer.getTextWidget().setText(text);
+		sourceViewer.getTextWidget().getHorizontalBar().setIncrement(10);
+		assertEquals(0, sourceViewer.getTextWidget().getHorizontalPixel());
+
+		Event event = new Event();
+		event.count = -1;
+		stickyControlCanvas.notifyListeners(SWT.MouseHorizontalWheel, event);
+
+		assertEquals(10, sourceViewer.getTextWidget().getHorizontalPixel());
+	}
+
 	private Canvas getStickyControlCanvas(Composite composite) {
 		for (Control control : composite.getChildren()) {
 			if (control instanceof Canvas canvas) {
@@ -233,4 +268,13 @@ private StyledText getStickyLineText() {
 		return (StyledText) canvas.getChildren()[1];
 	}
 
+	private int getExpectedWitdh(int textWidgetWitdth) {
+		ScrollBar verticalBar = sourceViewer.getTextWidget().getVerticalBar();
+		if (verticalBar.isVisible()) {
+			return textWidgetWitdth - verticalBar.getSize().x + 1;
+		} else {
+			return textWidgetWitdth + 1;
+		}
+	}
+
 }