[StickyScrolling] Prevent out of bounds errors by validating sticky line number

Handle cases where the sticky line number exceeds the total number of lines to prevent out of bounds errors. Since widgetLineNumber is 0-based, ensure it is not equal to or greater than the line count.

Fixes #2765

Author: Christopher-Hermann

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

@@ -55,7 +55,7 @@ public StyleRange[] getStyleRanges() {
 		StyledText textWidget= sourceViewer.getTextWidget();
 		int widgetLineNumber = getWidgetLineNumber();
 
-		if (widgetLineNumber > textWidget.getLineCount()) {
+		if (widgetLineNumber >= textWidget.getLineCount()) {
 			return null;
 		}
 

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

@@ -441,7 +441,7 @@ public void controlMoved(ControlEvent e) {
 	private boolean areStickyLinesOutDated(StyledText textWidget) {
 		if (stickyLines.size() > 0) {
 			int lastStickyLineNumber = stickyLines.get(stickyLines.size() - 1).getLineNumber();
-			return lastStickyLineNumber > textWidget.getLineCount();
+			return lastStickyLineNumber >= textWidget.getLineCount();
 		}
 		return false;
 	}

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

@@ -100,9 +100,10 @@ public void testGetStyleRangesIgnoresOutOfBoundLines() {
 		textWidget.setText("line1\nline2\nline3");
 
 		StickyLine stickyLineOutOfBound = new StickyLine(10, sourceViewer);
-		StyleRange[] styleRanges = stickyLineOutOfBound.getStyleRanges();
+		assertNull(stickyLineOutOfBound.getStyleRanges());
 
-		assertNull(styleRanges);
+		stickyLineOutOfBound = new StickyLine(3, sourceViewer);
+		assertNull(stickyLineOutOfBound.getStyleRanges());
 	}
 
 	@Test

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

@@ -256,7 +256,7 @@ public void testLayoutStickyLinesCanvasOnResize() {
 	public void testDontLayoutOutDatedStickyLinesOnResize() {
 		sourceViewer.getTextWidget().setBounds(0, 0, 200, 200);
 
-		List<IStickyLine> stickyLines = List.of(new StickyLineStub("line 10", 10));
+		List<IStickyLine> stickyLines = List.of(new StickyLineStub("line 1", 1));
 		stickyScrollingControl.setStickyLines(stickyLines);
 
 		Canvas stickyControlCanvas = getStickyControlCanvas(shell);