add StableEditorBottomScrollState so that inline chat moves lines of interest less (microsoft#209637)

there is still some movement because the height of the zone changes through out the request

Author: jrieken

src/vs/editor/browser/stableEditorScroll.ts

@@ -62,3 +62,44 @@ export class StableEditorScrollState {
 		editor.setScrollTop(editor.getScrollTop() + offset);
 	}
 }
+
+
+export class StableEditorBottomScrollState {
+
+	public static capture(editor: ICodeEditor): StableEditorBottomScrollState {
+		if (editor.hasPendingScrollAnimation()) {
+			// Never mess with the scroll if there is a pending scroll animation
+			return new StableEditorBottomScrollState(editor.getScrollTop(), editor.getContentHeight(), null, 0);
+		}
+
+		let visiblePosition: Position | null = null;
+		let visiblePositionScrollDelta = 0;
+		const visibleRanges = editor.getVisibleRanges();
+		if (visibleRanges.length > 0) {
+			visiblePosition = visibleRanges.at(-1)!.getEndPosition();
+			const visiblePositionScrollBottom = editor.getBottomForLineNumber(visiblePosition.lineNumber);
+			visiblePositionScrollDelta = (editor.getScrollTop() + editor.getLayoutInfo().height) - visiblePositionScrollBottom;
+		}
+		return new StableEditorBottomScrollState(editor.getScrollTop(), editor.getContentHeight(), visiblePosition, visiblePositionScrollDelta);
+	}
+
+	constructor(
+		private readonly _initialScrollTop: number,
+		private readonly _initialContentHeight: number,
+		private readonly _visiblePosition: Position | null,
+		private readonly _visiblePositionScrollDelta: number,
+	) {
+	}
+
+	public restore(editor: ICodeEditor): void {
+		if (this._initialContentHeight === editor.getContentHeight() && this._initialScrollTop === editor.getScrollTop()) {
+			// The editor's content height and scroll top haven't changed, so we don't need to do anything
+			return;
+		}
+
+		if (this._visiblePosition) {
+			const visiblePositionScrollBottom = editor.getBottomForLineNumber(this._visiblePosition.lineNumber);
+			editor.setScrollTop(visiblePositionScrollBottom - (this._visiblePositionScrollDelta + editor.getLayoutInfo().height));
+		}
+	}
+}

src/vs/workbench/contrib/inlineChat/browser/inlineChatZoneWidget.ts

@@ -9,7 +9,7 @@ import { assertType } from 'vs/base/common/types';
 import { ICodeEditor } from 'vs/editor/browser/editorBrowser';
 import { EditorLayoutInfo, EditorOption } from 'vs/editor/common/config/editorOptions';
 import { Position } from 'vs/editor/common/core/position';
-import { IRange } from 'vs/editor/common/core/range';
+import { IRange, Range } from 'vs/editor/common/core/range';
 import { ZoneWidget } from 'vs/editor/contrib/zoneWidget/browser/zoneWidget';
 import { localize } from 'vs/nls';
 import { IContextKey, IContextKeyService } from 'vs/platform/contextkey/common/contextkey';
@@ -18,6 +18,8 @@ import { ACTION_ACCEPT_CHANGES, ACTION_REGENERATE_RESPONSE, ACTION_TOGGLE_DIFF,
 import { EditorBasedInlineChatWidget } from './inlineChatWidget';
 import { MenuId } from 'vs/platform/actions/common/actions';
 import { isEqual } from 'vs/base/common/resources';
+import { StableEditorBottomScrollState } from 'vs/editor/browser/stableEditorScroll';
+import { ScrollType } from 'vs/editor/common/editorCommon';
 
 
 export class InlineChatZoneWidget extends ZoneWidget {
@@ -128,13 +130,17 @@ export class InlineChatZoneWidget extends ZoneWidget {
 	override show(position: Position): void {
 		assertType(this.container);
 
+		const scrollState = StableEditorBottomScrollState.capture(this.editor);
 		const info = this.editor.getLayoutInfo();
 		const marginWithoutIndentation = info.glyphMarginWidth + info.decorationsWidth + info.lineNumbersWidth;
 		this.container.style.marginLeft = `${marginWithoutIndentation}px`;
 
 		super.show(position, this._computeHeightInLines());
 		this._setWidgetMargins(position);
 		this.widget.focus();
+
+		scrollState.restore(this.editor);
+		this.editor.revealRangeNearTopIfOutsideViewport(Range.fromPositions(position.delta(-1)), ScrollType.Immediate);
 	}
 
 	override updatePositionAndHeight(position: Position): void {