From db983ef38e904e6da30198813056303e677defcd Mon Sep 17 00:00:00 2001
From: Christopher Hermann <christopher.hermann@sap.com>
Date: Fri, 12 Jul 2024 13:07:58 +0200
Subject: [PATCH] Don't scroll on caret movement to the end of editor

When the caret is moved to the end of the editor, the sticky scrolling does not need to adapt the visible source lines.
---
 .../stickyscroll/StickyScrollingControl.java  |  3 +-
 .../StickyScrollingControlTest.java           | 80 ++++++++++++++++++-
 2 files changed, 80 insertions(+), 3 deletions(-)

diff --git a/bundles/org.eclipse.ui.editors/src/org/eclipse/ui/internal/texteditor/stickyscroll/StickyScrollingControl.java b/bundles/org.eclipse.ui.editors/src/org/eclipse/ui/internal/texteditor/stickyscroll/StickyScrollingControl.java
index 59078bc5a88..0a5234b3ae7 100644
--- a/bundles/org.eclipse.ui.editors/src/org/eclipse/ui/internal/texteditor/stickyscroll/StickyScrollingControl.java
+++ b/bundles/org.eclipse.ui.editors/src/org/eclipse/ui/internal/texteditor/stickyscroll/StickyScrollingControl.java
@@ -507,7 +507,8 @@ public void keyReleased(KeyEvent e) {
 
 		@Override
 		public void caretMoved(CaretEvent event) {
-			if (event.caretOffset == 0) {
+			int offsetEndPosition = sourceViewer.getTextWidget().getText().length();
+			if (event.caretOffset == 0 || event.caretOffset == offsetEndPosition) {
 				return;
 			}
 			Display.getDefault().asyncExec(() -> {
diff --git a/tests/org.eclipse.ui.editors.tests/src/org/eclipse/ui/internal/texteditor/stickyscroll/StickyScrollingControlTest.java b/tests/org.eclipse.ui.editors.tests/src/org/eclipse/ui/internal/texteditor/stickyscroll/StickyScrollingControlTest.java
index 1dece650d71..06129dcea7e 100644
--- a/tests/org.eclipse.ui.editors.tests/src/org/eclipse/ui/internal/texteditor/stickyscroll/StickyScrollingControlTest.java
+++ b/tests/org.eclipse.ui.editors.tests/src/org/eclipse/ui/internal/texteditor/stickyscroll/StickyScrollingControlTest.java
@@ -69,7 +69,7 @@ public void setup() {
 		hoverColor = new Color(1, 1, 1);
 		backgroundColor = new Color(2, 2, 2);
 		separatorColor = new Color(3, 3, 3);
-		StickyScrollingControlSettings settings = new StickyScrollingControlSettings(5, lineNumberColor, hoverColor,
+		StickyScrollingControlSettings settings = new StickyScrollingControlSettings(2, lineNumberColor, hoverColor,
 				backgroundColor, separatorColor, true);
 		stickyScrollingControl = new StickyScrollingControl(sourceViewer, ruler, settings, null);
 	}
@@ -143,7 +143,7 @@ public void testCopyStyleRanges() {
 	}
 
 	@Test
-	public void testWithoutVeticalRuler() {
+	public void testWithoutVerticalRuler() {
 		sourceViewer = new SourceViewer(shell, null, SWT.None);
 		StickyScrollingControlSettings settings = new StickyScrollingControlSettings(5, lineNumberColor, hoverColor,
 				backgroundColor, separatorColor, true);
@@ -267,6 +267,77 @@ public void limitStickyLinesToTextWidgetHeight() {
 		assertEquals("", stickyLineText.getText());
 	}
 
+	@Test
+	public void testListenForCarretAfterKeyDown() {
+		// set height to 10 so that scrolling is needed
+		sourceViewer.getTextWidget().setBounds(0, 0, 200, 10);
+		String text = """
+				line 1
+				line 2
+				line 3
+				line 4
+				line 5
+				line 6
+				line 7
+				line 8
+				line 9""";
+		sourceViewer.setInput(new Document(text));
+		assertEquals(0, sourceViewer.getTextWidget().getTopPixel());
+
+		sourceViewer.getTextWidget().notifyListeners(SWT.KeyDown, new Event());
+		sourceViewer.getTextWidget().setCaretOffset(42);
+
+		drainDisplayEventQueue();
+		assertThat(sourceViewer.getTextWidget().getTopPixel(), greaterThan(0));
+	}
+
+	@Test
+	public void testDontListenForCaretWithoutKeyDown() {
+		// set height to 10 so that scrolling is needed
+		sourceViewer.getTextWidget().setBounds(0, 0, 200, 10);
+		String text = """
+				line 1
+				line 2
+				line 3
+				line 4
+				line 5
+				line 6
+				line 7
+				line 8
+				line 9""";
+		sourceViewer.setInput(new Document(text));
+		assertEquals(0, sourceViewer.getTextWidget().getTopPixel());
+
+		sourceViewer.getTextWidget().setCaretOffset(42);
+
+		drainDisplayEventQueue();
+		assertEquals(0, sourceViewer.getTextWidget().getTopPixel());
+	}
+
+	@Test
+	public void testDontMoveCaretAtDocumentEnd() {
+		// set height to 10 so that scrolling is needed
+		sourceViewer.getTextWidget().setBounds(0, 0, 200, 10);
+		String text = """
+				line 1
+				line 2
+				line 3
+				line 4
+				line 5
+				line 6
+				line 7
+				line 8
+				line 9""";
+		sourceViewer.setInput(new Document(text));
+		assertEquals(0, sourceViewer.getTextWidget().getTopPixel());
+
+		sourceViewer.getTextWidget().notifyListeners(SWT.KeyDown, new Event());
+		sourceViewer.getTextWidget().setCaretOffset(62);
+
+		drainDisplayEventQueue();
+		assertEquals(0, sourceViewer.getTextWidget().getTopPixel());
+	}
+
 	private Canvas getStickyControlCanvas(Composite composite) {
 		for (Control control : composite.getChildren()) {
 			if (control instanceof Canvas canvas) {
@@ -298,4 +369,9 @@ private Composite getStickyLineSeparator() {
 		return (Composite) canvas.getChildren()[2];
 	}
 
+	private void drainDisplayEventQueue() {
+		while (Display.getDefault().readAndDispatch()) {
+		}
+	}
+
 }