Fixes microsoft#197553

Author: hediet

src/vs/editor/browser/widget/diffEditor/diffEditorViewModel.ts

@@ -418,7 +418,7 @@ export class UnchangedRegion {
 	private readonly _shouldHideControls = derived(this, reader => /** @description isVisible */
 		this.visibleLineCountTop.read(reader) + this.visibleLineCountBottom.read(reader) === this.lineCount && !this.isDragged.read(reader));
 
-	public readonly isDragged = observableValue<boolean>(this, false);
+	public readonly isDragged = observableValue<undefined | 'bottom' | 'top'>(this, undefined);
 
 	constructor(
 		public readonly originalLineNumber: number,

src/vs/editor/browser/widget/diffEditor/hideUnchangedRegionsFeature.ts

@@ -258,6 +258,30 @@ class CollapsedCodeOverlayWidget extends ViewZoneOverlayWidget {
 			reset(this._nodes.first);
 		}
 
+		this._register(autorun(reader => {
+			const isFullyRevealed = this._unchangedRegion.visibleLineCountTop.read(reader) + this._unchangedRegion.visibleLineCountBottom.read(reader) === this._unchangedRegion.lineCount;
+
+			this._nodes.bottom.classList.toggle('canMoveTop', !isFullyRevealed);
+			this._nodes.bottom.classList.toggle('canMoveBottom', this._unchangedRegion.visibleLineCountBottom.read(reader) > 0);
+			this._nodes.top.classList.toggle('canMoveTop', this._unchangedRegion.visibleLineCountTop.read(reader) > 0);
+			this._nodes.top.classList.toggle('canMoveBottom', !isFullyRevealed);
+			const isDragged = this._unchangedRegion.isDragged.read(reader);
+			const domNode = this._editor.getDomNode();
+			if (domNode) {
+				domNode.classList.toggle('draggingUnchangedRegion', !!isDragged);
+				if (isDragged === 'top') {
+					domNode.classList.toggle('canMoveTop', this._unchangedRegion.visibleLineCountTop.read(reader) > 0);
+					domNode.classList.toggle('canMoveBottom', !isFullyRevealed);
+				} else if (isDragged === 'bottom') {
+					domNode.classList.toggle('canMoveTop', !isFullyRevealed);
+					domNode.classList.toggle('canMoveBottom', this._unchangedRegion.visibleLineCountBottom.read(reader) > 0);
+				} else {
+					domNode.classList.toggle('canMoveTop', false);
+					domNode.classList.toggle('canMoveBottom', false);
+				}
+			}
+		}));
+
 		const editor = this._editor;
 
 		this._register(addDisposableListener(this._nodes.top, 'mousedown', e => {
@@ -270,7 +294,7 @@ class CollapsedCodeOverlayWidget extends ViewZoneOverlayWidget {
 			const startTop = e.clientY;
 			let didMove = false;
 			const cur = this._unchangedRegion.visibleLineCountTop.get();
-			this._unchangedRegion.isDragged.set(true, undefined);
+			this._unchangedRegion.isDragged.set('top', undefined);
 
 			const window = getWindow(this._nodes.top);
 
@@ -289,7 +313,7 @@ class CollapsedCodeOverlayWidget extends ViewZoneOverlayWidget {
 				}
 				this._nodes.top.classList.toggle('dragging', false);
 				this._nodes.root.classList.toggle('dragging', false);
-				this._unchangedRegion.isDragged.set(false, undefined);
+				this._unchangedRegion.isDragged.set(undefined, undefined);
 				mouseMoveListener.dispose();
 				mouseUpListener.dispose();
 			});
@@ -305,7 +329,7 @@ class CollapsedCodeOverlayWidget extends ViewZoneOverlayWidget {
 			const startTop = e.clientY;
 			let didMove = false;
 			const cur = this._unchangedRegion.visibleLineCountBottom.get();
-			this._unchangedRegion.isDragged.set(true, undefined);
+			this._unchangedRegion.isDragged.set('bottom', undefined);
 
 			const window = getWindow(this._nodes.bottom);
 
@@ -322,7 +346,7 @@ class CollapsedCodeOverlayWidget extends ViewZoneOverlayWidget {
 			});
 
 			const mouseUpListener = addDisposableListener(window, 'mouseup', e => {
-				this._unchangedRegion.isDragged.set(false, undefined);
+				this._unchangedRegion.isDragged.set(undefined, undefined);
 
 				if (!didMove) {
 					const top = editor.getTopForLineNumber(this._unchangedRegionRange.endLineNumberExclusive);

src/vs/editor/browser/widget/diffEditor/style.css

@@ -29,7 +29,25 @@
 	background-clip: padding-box;
 	border-bottom: 2px solid transparent;
 	border-top: 4px solid transparent;
-	cursor: ns-resize;
+	/*cursor: n-resize;*/
+}
+
+.monaco-editor.draggingUnchangedRegion.canMoveTop:not(.canMoveBottom) *,
+.monaco-editor .diff-hidden-lines .top.canMoveTop:not(.canMoveBottom),
+.monaco-editor .diff-hidden-lines .bottom.canMoveTop:not(.canMoveBottom) {
+	cursor: n-resize !important;
+}
+
+.monaco-editor.draggingUnchangedRegion:not(.canMoveTop).canMoveBottom *,
+.monaco-editor .diff-hidden-lines .top:not(.canMoveTop).canMoveBottom,
+.monaco-editor .diff-hidden-lines .bottom:not(.canMoveTop).canMoveBottom {
+	cursor: s-resize !important;
+}
+
+.monaco-editor.draggingUnchangedRegion.canMoveTop.canMoveBottom *,
+.monaco-editor .diff-hidden-lines .top.canMoveTop.canMoveBottom,
+.monaco-editor .diff-hidden-lines .bottom.canMoveTop.canMoveBottom {
+	cursor: ns-resize !important;
 }
 
 .monaco-editor .diff-hidden-lines .top {