Limit visible sticky lines to text widget height

When the editor is very small, the sticky lines should not be displayed or the amount of sticky lines should be reduced so that the original source code can be seen.

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

@@ -77,6 +77,15 @@
  */
 public class StickyScrollingControl {
 
+	/**
+	 * This threshold represents the minimum number of source lines that must remain visible in the
+	 * editor. If the StickyScrollingControl's size would result in fewer than this number of lines
+	 * being visible, the height of the StickyScrollingControl will be reduced to ensure visibility
+	 * of at least this many lines. Thus, it guarantees a minimum visibility threshold for the
+	 * source content in the editor underneath the StickyScrollingControl.
+	 */
+	private final static int MIN_VISIBLE_EDITOR_LINES_THRESHOLD= 3;
+
 	private List<StickyLine> stickyLines;
 
 	private ISourceViewer sourceViewer;
@@ -103,6 +112,8 @@ public class StickyScrollingControl {
 
 	private StickyScrollingHandler stickyScrollingHandler;
 
+	private int maximumVisibleStickyLines= Integer.MAX_VALUE;
+
 	public StickyScrollingControl(ISourceViewer sourceViewer, StickyScrollingControlSettings settings) {
 		this(sourceViewer, null, settings, null);
 	}
@@ -185,6 +196,7 @@ private void createControls() {
 		bottomSeparator.setEnabled(false);
 
 		layoutLineNumbers();
+		limitVisibleStickyLinesToTextWidgetHeight(sourceViewer.getTextWidget());
 
 		stickyLinesCanvas.pack();
 		stickyLinesCanvas.moveAbove(null);
@@ -379,7 +391,9 @@ private void ensureSourceViewerLineVisible(int line) {
 	}
 
 	private int getNumberStickyLines() {
-		return Math.min(settings.maxCountStickyLines(), this.stickyLines.size());
+		int numberStickyLines= Math.min(settings.maxCountStickyLines(), this.stickyLines.size());
+		numberStickyLines= Math.min(maximumVisibleStickyLines, numberStickyLines);
+		return numberStickyLines;
 	}
 
 	/**
@@ -412,7 +426,12 @@ private void addSourceViewerListeners() {
 		controlListener= new ControlListener() {
 			@Override
 			public void controlResized(ControlEvent e) {
+				StyledText textWidget= sourceViewer.getTextWidget();
+				limitVisibleStickyLinesToTextWidgetHeight(textWidget);
 				layoutStickyLines();
+				if (stickyScrollingHandler != null) {
+					stickyScrollingHandler.viewportChanged(textWidget.getTopPixel());
+				}
 			}
 
 			@Override
@@ -423,6 +442,16 @@ public void controlMoved(ControlEvent e) {
 		sourceViewer.getTextWidget().addControlListener(controlListener);
 	}
 
+	private void limitVisibleStickyLinesToTextWidgetHeight(StyledText textWidget) {
+		int lineHeight= textWidget.getLineHeight() + textWidget.getLineSpacing();
+		int textWidgetHeight= textWidget.getBounds().height;
+
+		int visibleLinesInTextWidget= textWidgetHeight / lineHeight;
+
+		maximumVisibleStickyLines= Math.max(0, visibleLinesInTextWidget - MIN_VISIBLE_EDITOR_LINES_THRESHOLD);
+		updateStickyScrollingControls();
+	}
+
 	/**
 	 * Sets the cursor on the canvas to {@link SWT#CURSOR_HAND} and adds several mouse listeners to
 	 * the canvas.<br>

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

@@ -62,6 +62,7 @@ public void setup() {
 		ruler = new CompositeRuler();
 		sourceViewer = new SourceViewer(shell, ruler, SWT.V_SCROLL | SWT.H_SCROLL);
 		sourceViewer.setDocument(new Document());
+		sourceViewer.getTextWidget().setBounds(0, 0, 200, 200);
 
 		lineNumberColor = new Color(0, 0, 0);
 		hoverColor = new Color(1, 1, 1);
@@ -116,12 +117,10 @@ public void testLimitStickyLinesCount() {
 		stickyScrollingControl.applySettings(settings);
 
 		StyledText stickyLineNumber = getStickyLineNumber();
-		String expLineNumber = """
-				10""";
+		String expLineNumber = "10";
 		assertEquals(expLineNumber, stickyLineNumber.getText());
 		StyledText stickyLineText = getStickyLineText();
-		String expStickyLineText = """
-				line 10""";
+		String expStickyLineText = "line 10";
 		assertEquals(expStickyLineText, stickyLineText.getText());
 	}
 
@@ -215,6 +214,7 @@ public void testNavigateToStickyLine() {
 
 	@Test
 	public void testVerticalScrollingIsDispatched() {
+		sourceViewer.getTextWidget().setBounds(0, 0, 200, 0);
 		Canvas stickyControlCanvas = getStickyControlCanvas(shell);
 		String text = """
 				line 1
@@ -232,6 +232,7 @@ public void testVerticalScrollingIsDispatched() {
 
 	@Test
 	public void testHorizontalScrollingIsDispatched() {
+		sourceViewer.getTextWidget().setBounds(0, 0, 0, 200);
 		Canvas stickyControlCanvas = getStickyControlCanvas(shell);
 		String text = """
 				line 1
@@ -247,6 +248,20 @@ public void testHorizontalScrollingIsDispatched() {
 		assertEquals(10, sourceViewer.getTextWidget().getHorizontalPixel());
 	}
 
+	@Test
+	public void limitStickyLinesToTextWidgetHeight() {
+		sourceViewer.getTextWidget().setBounds(0, 0, 200, 200);
+		List<StickyLine> stickyLines = List.of(new StickyLine("line 2", 1));
+		stickyScrollingControl.setStickyLines(stickyLines);
+
+		StyledText stickyLineText = getStickyLineText();
+		assertEquals("line 2", stickyLineText.getText());
+
+		sourceViewer.getTextWidget().setBounds(0, 0, 200, 20);
+		stickyLineText = getStickyLineText();
+		assertEquals("", stickyLineText.getText());
+	}
+
 	private Canvas getStickyControlCanvas(Composite composite) {
 		for (Control control : composite.getChildren()) {
 			if (control instanceof Canvas canvas) {

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

@@ -64,6 +64,7 @@ public void setup() {
 		ruler = new CompositeRuler();
 		sourceViewer = new SourceViewer(shell, ruler, SWT.None);
 		sourceViewer.setDocument(new Document());
+		sourceViewer.getTextWidget().setBounds(0, 0, 200, 200);
 
 		lineNumberColor = new Color(0, 0, 0);
 		hoverColor = new Color(1, 1, 1);