fix(sidebar): remeasure visible rows after density changes (#1489)

* fix(sidebar): remeasure visible rows after density changes

* test(credentials): avoid flaky Ed25519 key generation

src/ui/sidebar/tree/SidebarTree.tsx

@@ -861,6 +861,12 @@ export function SidebarTree({
   // and made the list visibly jump apart on every pointer move.
   useLayoutEffect(() => {
     virtualizer.measure();
+    // Rebuild the cleared size cache before measuring the mounted rows again.
+    virtualizer.getTotalSize();
+    // Unchanged rows will not trigger ResizeObserver after their cache is cleared.
+    parentRef.current
+      ?.querySelectorAll<HTMLElement>("[data-index]")
+      .forEach((element) => virtualizer.measureElement(element));
   }, [virtualizer, density, trayTrigger, showTags, showResourceBars]);
 
   if (loading) {

src/ui/tests/sidebar/tree/sidebar-density.test.tsx

@@ -0,0 +1,129 @@
+import { act, render } from "@testing-library/react";
+import { afterEach, beforeEach, expect, it, vi } from "vitest";
+import type { Host, HostFolder } from "@/types/ui-types";
+import { SidebarTree } from "@/sidebar/tree/SidebarTree";
+
+vi.mock("@/main-axios", () => ({}));
+vi.mock("@/api/plugins-api", () => ({}));
+vi.mock("@/settings/HostPluginSections", () => ({
+  usePluginHostSections: () => [],
+}));
+vi.mock("@/contexts/UiPreferencesContext", () => ({
+  useAreaPreferences: () => ({ showResourceBars: false, rowActions: "hover" }),
+}));
+vi.mock("@/sidebar/FolderMetadataDialog", () => ({
+  FolderMetadataDialog: () => null,
+}));
+vi.mock("@/sidebar/HostShareModal", () => ({ HostShareModal: () => null }));
+vi.mock("@/sidebar/tree/FolderItem/FolderItem", () => ({
+  FolderItem: () => <div>Folder</div>,
+  folderHostCount: () => 1,
+}));
+vi.mock("@/sidebar/tree/HostItem/HostItem", () => ({
+  HostItem: () => <div>Host</div>,
+}));
+
+const observers: Array<{
+  callback: ResizeObserverCallback;
+  nodes: Set<Element>;
+}> = [];
+let hostHeight = 55;
+function rect(element: Element): DOMRect {
+  const index = element.getAttribute("data-index");
+  const height = index === "0" ? 40 : index === "1" ? hostHeight : 600;
+  return {
+    x: 0,
+    y: 0,
+    width: 300,
+    height,
+    top: 0,
+    left: 0,
+    right: 300,
+    bottom: height,
+    toJSON() {},
+  };
+}
+function resize(rows: Element[]) {
+  act(() => {
+    for (const observer of observers) {
+      const entries = rows
+        .filter((row) => observer.nodes.has(row))
+        .map(
+          (target) =>
+            ({
+              target,
+              borderBoxSize: [
+                { blockSize: rect(target).height, inlineSize: 300 },
+              ],
+            }) as unknown as ResizeObserverEntry,
+        );
+      if (entries.length) observer.callback(entries, {} as ResizeObserver);
+    }
+  });
+}
+
+beforeEach(() => {
+  localStorage.setItem("hostOpenFolders", JSON.stringify(["group"]));
+  hostHeight = 55;
+  observers.length = 0;
+  vi.stubGlobal(
+    "ResizeObserver",
+    class {
+      nodes = new Set<Element>();
+      constructor(callback: ResizeObserverCallback) {
+        observers.push({ callback, nodes: this.nodes });
+      }
+      observe(node: Element) {
+        this.nodes.add(node);
+      }
+      unobserve(node: Element) {
+        this.nodes.delete(node);
+      }
+      disconnect() {
+        this.nodes.clear();
+      }
+    },
+  );
+  vi.spyOn(HTMLElement.prototype, "getBoundingClientRect").mockImplementation(
+    function () {
+      return rect(this);
+    },
+  );
+  vi.spyOn(HTMLElement.prototype, "offsetHeight", "get").mockReturnValue(600);
+  vi.spyOn(HTMLElement.prototype, "offsetWidth", "get").mockReturnValue(300);
+});
+afterEach(() => {
+  vi.restoreAllMocks();
+  vi.unstubAllGlobals();
+  localStorage.clear();
+});
+
+it("keeps an unchanged folder's measured height after changing density", () => {
+  const host = {
+    id: "1",
+    name: "Host",
+    ip: "example.com",
+    username: "test",
+  } as Host;
+  const children = [
+    { name: "group", path: "group", children: [host] },
+  ] as HostFolder[];
+  const props = {
+    children,
+    onOpenTab: vi.fn(),
+    onEditHost: vi.fn(),
+    selectionMode: false,
+    onToggleSelectionMode: vi.fn(),
+  };
+  const view = render(<SidebarTree {...props} density="comfortable" />);
+  const rows = () =>
+    Array.from(view.container.querySelectorAll("[data-index]"));
+  expect(rows()).toHaveLength(2);
+  resize(rows());
+  expect((rows()[1] as HTMLElement).style.transform).toBe("translateY(40px)");
+  hostHeight = 30;
+  view.rerender(<SidebarTree {...props} density="compact" />);
+  // Folder height is unchanged, so the browser only reports the host resize.
+  resize([rows()[1]]);
+  expect((rows()[1] as HTMLElement).style.transform).toBe("translateY(40px)");
+});