Preserve diffr context when applying review lenses

apps/whiteboard-desktop/code-oss/src/vs/editor/common/diff/documentDiffProvider.ts

@@ -99,6 +99,11 @@ export interface IDocumentDiff {
 	};
 	/** Optional authoritative zero-based source row correspondence. Null denotes padding. */
 	readonly contextGaps?: readonly IDocumentContextGap[];
+	/** Syntax scopes supplied by the context plugin, as zero-based half-open line ranges. */
+	readonly contextScopes?: {
+		readonly original: readonly (readonly [number, number])[];
+		readonly modified: readonly (readonly [number, number])[];
+	};
 	readonly sourceLineAlignment?: readonly (readonly [number | null, number | null])[];
 	/**
 	 * If true, both text models are identical (byte-wise).

apps/whiteboard-desktop/code-oss/src/vs/whiteboard/common/whiteboardLens.ts

@@ -14,6 +14,29 @@ export function lensContextGaps(diff: IDocumentDiff, originalCount: number, modi
 	}));
 	// Context follows alignment rows, keeping both sides synchronized around insertions.
 	const context = visible.map((_, index) => visible.slice(Math.max(0, index - 3), index + 4).some(Boolean));
+	if (diff.contextScopes) {
+		// A lens must not clip context that diffr kept around its selected code.
+		// Seed enclosing scope boundaries, then retain each visible context run
+		// touching a seed. Never expand through a collapsed provider band.
+		const scopes = [diff.contextScopes.original, diff.contextScopes.modified];
+		const enclosing = scopes.map((sideScopes, side) => sideScopes.filter(([start, end]) =>
+			rows.some((row, index) => visible[index] && row[side] !== null && row[side]! >= start && row[side]! < end)));
+		const open = rows.map(row => row.every((line, side) => line === null || !(diff.contextGaps ?? []).some(gap => {
+			if (gap.collapsed === false) return false;
+			const start = side === 0 ? gap.originalStart : gap.modifiedStart;
+			const count = side === 0 ? gap.originalCount : gap.modifiedCount;
+			return line + 1 >= start && line + 1 < start + count;
+		})));
+		const seeds = rows.map((row, index) => visible[index] || row.some((line, side) =>
+			line !== null && enclosing[side].some(([start, end]) => line === start || line === end - 1)));
+		for (let start = 0; start < rows.length;) {
+			if (!open[start]) { start++; continue; }
+			let end = start + 1;
+			while (end < rows.length && open[end]) end++;
+			if (seeds.slice(start, end).some(Boolean)) context.fill(true, start, end);
+			start = end;
+		}
+	}
 	const gaps: IDocumentContextGap[] = [];
 	let left = 1, right = 1;
 	for (let index = 0; index < rows.length;) {

apps/whiteboard-desktop/code-oss/src/vs/whiteboard/common/whiteboardStructuralDiff.ts

@@ -33,6 +33,24 @@ export function regionLines(region: StructuralRegion): { start: number; end: num
 	return { start: region.start.line, end: region.end.column === 0 ? region.end.line : region.end.line + 1 };
 }
 
+/** Preserve the context plugin's scope boundaries for lens projection. */
+export function structuralContextScopes(diff: StructuralTextDiff) {
+	const scopes = (source: StructuralSource | undefined) => {
+		const result: [number, number][] = [];
+		const visit = (region: StructuralRegion) => {
+			if (region.kind !== "fold") return;
+			if (region.tags?.includes("context:scope")) {
+				const { start, end } = regionLines(region);
+				result.push([start, end]);
+			}
+			region.children.forEach(visit);
+		};
+		source?.regions?.forEach(visit);
+		return result;
+	};
+	return { original: scopes(diff.lhs), modified: scopes(diff.rhs) };
+}
+
 export function structuralLeaves(regions: readonly StructuralRegion[] | undefined): StructuralLeaf[] {
 	const leaves: StructuralLeaf[] = [];
 	const walk = (region: StructuralRegion) => {

apps/whiteboard-desktop/code-oss/src/vs/whiteboard/services/whiteboardStructuralDiff.ts

@@ -22,6 +22,7 @@ import { autorun, derived, type IObservable } from "../../base/common/observable
 import type { UnchangedRegion } from "../../editor/browser/widget/diffEditor/diffEditorViewModel.js";
 import {
 	structuralContextGaps,
+	structuralContextScopes,
 	structuralRows,
 	structuralHighlights,
 } from "../common/whiteboardStructuralDiff.js";
@@ -122,6 +123,7 @@ export class StructuralDiffProvider implements IDocumentDiffProvider {
 			identical: left === right,
 			quitEarly: false,
 			sourceLineAlignment: rows,
+			contextScopes: structuralContextScopes(diff),
 			// Every collapsed region is a hidden-region band, labelled by the wire.
 			contextGaps: structuralContextGaps(
 				diff,