grid: resize views when branch is demoted

fixes #50675

src/vs/base/browser/ui/grid/gridview.ts

@@ -467,7 +467,7 @@ export class GridView implements IDisposable {
 		const sibling = parent.children[0];
 		parent.removeChild(0);
 
-		const sizes = grandParent.children.map(c => c.size);
+		const sizes = grandParent.children.map((_, i) => grandParent.getChildSize(i));
 		grandParent.removeChild(parentIndex, sizing);
 
 		if (sibling instanceof BranchNode) {
@@ -477,15 +477,15 @@ export class GridView implements IDisposable {
 				const child = sibling.children[i];
 				grandParent.addChild(child, child.size, parentIndex + i);
 			}
-
-			for (let i = 0; i < sizes.length; i++) {
-				grandParent.resizeChild(i, sizes[i]);
-			}
 		} else {
 			const newSibling = new LeafNode(sibling.view, orthogonal(sibling.orientation), sibling.size);
 			grandParent.addChild(newSibling, sibling.orthogonalSize, parentIndex);
 		}
 
+		for (let i = 0; i < sizes.length; i++) {
+			grandParent.resizeChild(i, sizes[i]);
+		}
+
 		return node.view;
 	}
 

src/vs/base/test/browser/ui/grid/grid.test.ts

@@ -264,6 +264,30 @@ suite('Grid', function () {
 		assert.deepEqual(view2.size, [200, 600]);
 		assert.deepEqual(view4.size, [200, 600]);
 	});
+
+	test('sizing should be correct after branch demotion #50675', function () {
+		const view1 = new TestView(50, Number.MAX_VALUE, 50, Number.MAX_VALUE);
+		const grid = new Grid(container, view1);
+		grid.layout(800, 600);
+
+		const view2 = new TestView(50, Number.MAX_VALUE, 50, Number.MAX_VALUE);
+		grid.addView(view2, Sizing.Distribute, view1, Direction.Down);
+
+		const view3 = new TestView(50, Number.MAX_VALUE, 50, Number.MAX_VALUE);
+		grid.addView(view3, Sizing.Distribute, view2, Direction.Down);
+
+		const view4 = new TestView(50, Number.MAX_VALUE, 50, Number.MAX_VALUE);
+		grid.addView(view4, Sizing.Distribute, view3, Direction.Right);
+		assert.deepEqual(view1.size, [800, 200]);
+		assert.deepEqual(view2.size, [800, 200]);
+		assert.deepEqual(view3.size, [400, 200]);
+		assert.deepEqual(view4.size, [400, 200]);
+
+		grid.removeView(view3, Sizing.Distribute);
+		assert.deepEqual(view1.size, [800, 200]);
+		assert.deepEqual(view2.size, [800, 200]);
+		assert.deepEqual(view4.size, [800, 200]);
+	});
 });
 
 class TestSerializableView extends TestView implements ISerializableView {