Keep desktop sidebar controls stable across panel changes (#2078)

* fix(app): stabilize desktop sidebar controls

Keep the left-window-controls toggle mounted across sidebar state changes so its position and tooltip state remain stable. Preserve browser placement and show an explicit Explorer close control only where native right-side controls do not provide one.

* fix(app): suppress inactive sidebar chrome

packages/app/src/utils/desktop-window.test.ts

@@ -1,6 +1,7 @@
 import { describe, expect, it } from "vitest";
 import {
   intersectWindowChromeCorners,
+  resolveHasOwnedWindowChromeObstruction,
   resolveWindowChromeObstruction,
   resolveWindowChromeSafeArea,
 } from "@/utils/desktop-window";
@@ -49,4 +50,33 @@ describe("window chrome", () => {
     expect(intersectWindowChromeCorners("top-right", "both")).toBe("top-right");
     expect(intersectWindowChromeCorners("top-left", "top-right")).toBe("none");
   });
+
+  it("reports an obstruction only when the surface owns its corner", () => {
+    const obstruction = {
+      topLeft: { width: 78, height: 45 },
+      topRight: { width: 140, height: 48 },
+    };
+
+    expect(
+      resolveHasOwnedWindowChromeObstruction({
+        obstruction,
+        corners: "top-left",
+        corner: "top-left",
+      }),
+    ).toBe(true);
+    expect(
+      resolveHasOwnedWindowChromeObstruction({
+        obstruction,
+        corners: "top-left",
+        corner: "top-right",
+      }),
+    ).toBe(false);
+    expect(
+      resolveHasOwnedWindowChromeObstruction({
+        obstruction: { topLeft: null, topRight: null },
+        corners: "both",
+        corner: "top-right",
+      }),
+    ).toBe(false);
+  });
 });

packages/app/src/utils/desktop-window.tsx

@@ -24,6 +24,8 @@ interface WindowChromeObstruction {
   topRight: WindowChromeCornerObstruction | null;
 }
 
+export type WindowChromeCorner = "top-left" | "top-right";
+
 type WindowChromeSafeAreaStyle = { height: number } | { paddingLeft: number; paddingRight: number };
 
 const EMPTY_OBSTRUCTION: WindowChromeObstruction = { topLeft: null, topRight: null };
@@ -37,6 +39,29 @@ function windowChromeCornersFromFlags(topLeft: boolean, topRight: boolean): Wind
   return "none";
 }
 
+export function windowChromeCornersInclude(
+  corners: WindowChromeCorners,
+  corner: WindowChromeCorner,
+): boolean {
+  return corners === "both" || corners === corner;
+}
+
+export function resolveHasOwnedWindowChromeObstruction(input: {
+  obstruction: WindowChromeObstruction;
+  corners: WindowChromeCorners;
+  corner: WindowChromeCorner;
+}): boolean {
+  if (!windowChromeCornersInclude(input.corners, input.corner)) return false;
+  return input.corner === "top-left"
+    ? input.obstruction.topLeft !== null
+    : input.obstruction.topRight !== null;
+}
+
+export function useHasWindowChromeObstruction(corner: WindowChromeCorner): boolean {
+  const obstruction = useContext(WindowChromeContext);
+  return corner === "top-left" ? obstruction.topLeft !== null : obstruction.topRight !== null;
+}
+
 export function intersectWindowChromeCorners(
   inherited: WindowChromeCorners,
   declared: WindowChromeCorners,
@@ -210,6 +235,17 @@ export function useWindowChromeCorners(): WindowChromeCorners {
   return useContext(WindowChromeCornersContext);
 }
 
+export function useOwnsWindowChromeCorner(corner: WindowChromeCorner): boolean {
+  const corners = useContext(WindowChromeCornersContext);
+  return windowChromeCornersInclude(corners, corner);
+}
+
+export function useHasOwnedWindowChromeObstruction(corner: WindowChromeCorner): boolean {
+  const obstruction = useContext(WindowChromeContext);
+  const corners = useContext(WindowChromeCornersContext);
+  return resolveHasOwnedWindowChromeObstruction({ obstruction, corners, corner });
+}
+
 type WindowChromeSafeAreaProps = ViewProps & {
   placement: WindowChromeSafeAreaPlacement;
   horizontalPadding?: number;