Fixes #58254: better logic for restoring top of viewport

src/vs/editor/common/viewModel/viewModelImpl.ts

@@ -35,7 +35,7 @@ export class ViewModel extends viewEvents.ViewEventEmitter implements IViewModel
 	private hasFocus: boolean;
 	private viewportStartLine: number;
 	private viewportStartLineTrackedRange: string;
-	private viewportStartLineTop: number;
+	private viewportStartLineDelta: number;
 	private readonly lines: IViewModelLinesCollection;
 	public readonly coordinatesConverter: ICoordinatesConverter;
 	public readonly viewLayout: ViewLayout;
@@ -51,7 +51,7 @@ export class ViewModel extends viewEvents.ViewEventEmitter implements IViewModel
 		this.hasFocus = false;
 		this.viewportStartLine = -1;
 		this.viewportStartLineTrackedRange = null;
-		this.viewportStartLineTop = 0;
+		this.viewportStartLineDelta = 0;
 
 		if (USE_IDENTITY_LINES_COLLECTION && this.model.isTooLargeForTokenization()) {
 
@@ -162,7 +162,7 @@ export class ViewModel extends viewEvents.ViewEventEmitter implements IViewModel
 		if (restorePreviousViewportStart && previousViewportStartModelPosition) {
 			const viewPosition = this.coordinatesConverter.convertModelPositionToViewPosition(previousViewportStartModelPosition);
 			const viewPositionTop = this.viewLayout.getVerticalOffsetForLineNumber(viewPosition.lineNumber);
-			this.viewLayout.deltaScrollNow(0, viewPositionTop - this.viewportStartLineTop);
+			this.viewLayout.setScrollPositionNow({ scrollTop: viewPositionTop + this.viewportStartLineDelta });
 		}
 	}
 
@@ -252,7 +252,7 @@ export class ViewModel extends viewEvents.ViewEventEmitter implements IViewModel
 				if (modelRange) {
 					const viewPosition = this.coordinatesConverter.convertModelPositionToViewPosition(modelRange.getStartPosition());
 					const viewPositionTop = this.viewLayout.getVerticalOffsetForLineNumber(viewPosition.lineNumber);
-					this.viewLayout.deltaScrollNow(0, viewPositionTop - this.viewportStartLineTop);
+					this.viewLayout.setScrollPositionNow({ scrollTop: viewPositionTop + this.viewportStartLineDelta });
 				}
 			}
 		}));
@@ -450,7 +450,9 @@ export class ViewModel extends viewEvents.ViewEventEmitter implements IViewModel
 		this.viewportStartLine = startLineNumber;
 		let position = this.coordinatesConverter.convertViewPositionToModelPosition(new Position(startLineNumber, this.getLineMinColumn(startLineNumber)));
 		this.viewportStartLineTrackedRange = this.model._setTrackedRange(this.viewportStartLineTrackedRange, new Range(position.lineNumber, position.column, position.lineNumber, position.column), TrackedRangeStickiness.NeverGrowsWhenTypingAtEdges);
-		this.viewportStartLineTop = this.viewLayout.getVerticalOffsetForLineNumber(startLineNumber);
+		const viewportStartLineTop = this.viewLayout.getVerticalOffsetForLineNumber(startLineNumber);
+		const scrollTop = this.viewLayout.getCurrentScrollTop();
+		this.viewportStartLineDelta = scrollTop - viewportStartLineTop;
 	}
 
 	public getActiveIndentGuide(lineNumber: number, minLineNumber: number, maxLineNumber: number): IActiveIndentGuideInfo {