Fixes #27187: Keep the top-most visible line constant

src/vs/editor/browser/editorBrowser.ts

@@ -619,11 +619,6 @@ export interface ICodeEditor extends editorCommon.IEditor {
 	 */
 	getLayoutInfo(): editorOptions.EditorLayoutInfo;
 
-	/**
-	 * Returns the range that is currently centered in the view port.
-	 */
-	getCenteredRangeInViewport(): Range;
-
 	/**
 	 * Returns the ranges that are currently visible.
 	 * Does not account for horizontal scrolling.

src/vs/editor/common/commonCodeEditor.ts

@@ -253,13 +253,6 @@ export abstract class CommonCodeEditor extends Disposable {
 		}
 	}
 
-	public getCenteredRangeInViewport(): Range {
-		if (!this.hasView) {
-			return null;
-		}
-		return this.viewModel.getCenteredRangeInViewport();
-	}
-
 	public getVisibleRanges(): Range[] {
 		if (!this.hasView) {
 			return [];

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

@@ -33,6 +33,7 @@ export class ViewModel extends viewEvents.ViewEventEmitter implements IViewModel
 	private readonly configuration: editorCommon.IConfiguration;
 	private readonly model: ITextModel;
 	private hasFocus: boolean;
+	private viewportStartLine: number;
 	private viewportStartLineTrackedRange: string;
 	private viewportStartLineTop: number;
 	private readonly lines: IViewModelLinesCollection;
@@ -41,8 +42,6 @@ export class ViewModel extends viewEvents.ViewEventEmitter implements IViewModel
 
 	private readonly decorations: ViewModelDecorations;
 
-	private _centeredViewLine: number;
-
 	constructor(editorId: number, configuration: editorCommon.IConfiguration, model: ITextModel, scheduleAtNextAnimationFrame: (callback: () => void) => IDisposable) {
 		super();
 
@@ -50,6 +49,7 @@ export class ViewModel extends viewEvents.ViewEventEmitter implements IViewModel
 		this.configuration = configuration;
 		this.model = model;
 		this.hasFocus = false;
+		this.viewportStartLine = -1;
 		this.viewportStartLineTrackedRange = null;
 		this.viewportStartLineTop = 0;
 
@@ -89,8 +89,6 @@ export class ViewModel extends viewEvents.ViewEventEmitter implements IViewModel
 			}
 		}));
 
-		this._centeredViewLine = -1;
-
 		this.decorations = new ViewModelDecorations(this.editorId, this.model, this.configuration, this.lines, this.coordinatesConverter);
 
 		this._registerModelEvents();
@@ -130,8 +128,12 @@ export class ViewModel extends viewEvents.ViewEventEmitter implements IViewModel
 	private _onConfigurationChanged(eventsCollector: viewEvents.ViewEventsCollector, e: IConfigurationChangedEvent): void {
 
 		// We might need to restore the current centered view range, so save it (if available)
-		const previousCenteredModelRange = this.getCenteredRangeInViewport();
-		let revealPreviousCenteredModelRange = false;
+		let previousViewportStartModelPosition: Position = null;
+		if (this.viewportStartLine !== -1) {
+			let previousViewportStartViewPosition = new Position(this.viewportStartLine, this.getLineMinColumn(this.viewportStartLine));
+			previousViewportStartModelPosition = this.coordinatesConverter.convertViewPositionToModelPosition(previousViewportStartViewPosition);
+		}
+		let restorePreviousViewportStart = false;
 
 		const conf = this.configuration.editor;
 
@@ -144,7 +146,7 @@ export class ViewModel extends viewEvents.ViewEventEmitter implements IViewModel
 
 			if (this.viewLayout.getCurrentScrollTop() !== 0) {
 				// Never change the scroll position from 0 to something else...
-				revealPreviousCenteredModelRange = true;
+				restorePreviousViewportStart = true;
 			}
 		}
 
@@ -157,17 +159,10 @@ export class ViewModel extends viewEvents.ViewEventEmitter implements IViewModel
 		eventsCollector.emit(new viewEvents.ViewConfigurationChangedEvent(e));
 		this.viewLayout.onConfigurationChanged(e);
 
-		if (revealPreviousCenteredModelRange && previousCenteredModelRange) {
-			// modelLine -> viewLine
-			const newCenteredViewRange = this.coordinatesConverter.convertModelRangeToViewRange(previousCenteredModelRange);
-
-			// Send a reveal event to restore the centered content
-			eventsCollector.emit(new viewEvents.ViewRevealRangeRequestEvent(
-				newCenteredViewRange,
-				viewEvents.VerticalRevealType.Center,
-				false,
-				editorCommon.ScrollType.Immediate
-			));
+		if (restorePreviousViewportStart && previousViewportStartModelPosition) {
+			const viewPosition = this.coordinatesConverter.convertModelPositionToViewPosition(previousViewportStartModelPosition);
+			const viewPositionTop = this.viewLayout.getVerticalOffsetForLineNumber(viewPosition.lineNumber);
+			this.viewLayout.deltaScrollNow(0, viewPositionTop - this.viewportStartLineTop);
 		}
 	}
 
@@ -247,7 +242,7 @@ export class ViewModel extends viewEvents.ViewEventEmitter implements IViewModel
 			}
 
 			// Update the configuration and reset the centered view line
-			this._centeredViewLine = -1;
+			this.viewportStartLine = -1;
 			this.configuration.setMaxLineNumber(this.model.getLineCount());
 
 			// Recover viewport
@@ -332,16 +327,6 @@ export class ViewModel extends viewEvents.ViewEventEmitter implements IViewModel
 		}
 	}
 
-	public getCenteredRangeInViewport(): Range {
-		if (this._centeredViewLine === -1) {
-			// Never got rendered or not rendered since last content change event
-			return null;
-		}
-		let viewLineNumber = this._centeredViewLine;
-		let currentCenteredViewRange = new Range(viewLineNumber, this.getLineMinColumn(viewLineNumber), viewLineNumber, this.getLineMaxColumn(viewLineNumber));
-		return this.coordinatesConverter.convertViewRangeToModelRange(currentCenteredViewRange);
-	}
-
 	public getVisibleRanges(): Range[] {
 		const visibleViewRange = this.getCompletelyVisibleViewRange();
 		const visibleRange = this.coordinatesConverter.convertViewRangeToModelRange(visibleViewRange);
@@ -458,9 +443,9 @@ export class ViewModel extends viewEvents.ViewEventEmitter implements IViewModel
 	 * Gives a hint that a lot of requests are about to come in for these line numbers.
 	 */
 	public setViewport(startLineNumber: number, endLineNumber: number, centeredLineNumber: number): void {
-		this._centeredViewLine = centeredLineNumber;
 		this.lines.warmUpLookupCache(startLineNumber, endLineNumber);
 
+		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);

src/vs/monaco.d.ts

@@ -3782,10 +3782,6 @@ declare namespace monaco.editor {
 		 * Get the layout info for the editor.
 		 */
 		getLayoutInfo(): EditorLayoutInfo;
-		/**
-		 * Returns the range that is currently centered in the view port.
-		 */
-		getCenteredRangeInViewport(): Range;
 		/**
 		 * Returns the ranges that are currently visible.
 		 * Does not account for horizontal scrolling.