fix(zoom) desktop chrome clearance under text zoom

desktop/playwright.config.ts

@@ -50,6 +50,7 @@ export default defineConfig({
         "**/unread-pill.spec.ts",
         "**/sidebar-more-unread-overlap.spec.ts",
         "**/home-collapsed-top-chrome.spec.ts",
+        "**/top-chrome-zoom-clearance.spec.ts",
         "**/thread-unread.spec.ts",
         "**/workspace-rail.spec.ts",
         "**/thread-reply-anchor-roleplay.spec.ts",

desktop/src/app/AppTopChrome.tsx

@@ -21,10 +21,14 @@ type AppTopChromeProps = {
   hasWorkspaceRail?: boolean;
 };
 
+// Fixed px on purpose (button box + glyph): these controls sit beside the
+// native macOS traffic lights, which ignore the app's Cmd +/- text zoom, so
+// the row must not grow or shrink with the rem scale. Deliberate exception
+// to the rem-first rule.
 const TOP_CHROME_ICON_BUTTON_CLASS =
-  "h-7 w-7 rounded-[4px] text-sidebar-foreground/65 hover:bg-sidebar-accent hover:text-sidebar-accent-foreground [&_svg]:size-4";
+  "h-[28px] w-[28px] rounded-[4px] text-sidebar-foreground/65 hover:bg-sidebar-accent hover:text-sidebar-accent-foreground [&_svg]:size-[16px]";
 const HISTORY_ICON_BUTTON_CLASS =
-  "h-7 w-6 rounded-[4px] text-sidebar-foreground/65 hover:bg-sidebar-accent hover:text-sidebar-accent-foreground [&_svg]:size-4";
+  "h-[28px] w-[24px] rounded-[4px] text-sidebar-foreground/65 hover:bg-sidebar-accent hover:text-sidebar-accent-foreground [&_svg]:size-[16px]";
 
 function preventTopChromeWheel(event: WheelEvent) {
   event.preventDefault();
@@ -66,11 +70,15 @@ export function AppTopChrome({
   // x-position. When the workspace rail is present it already occupies the far
   // left, so the nav row only needs to clear the lights past the rail edge
   // rather than the full offset. In fullscreen those buttons hide.
+  //
+  // Fixed px on purpose: the native traffic lights do not scale with the app's
+  // Cmd +/- text zoom (rem), so rem-based clearance shrinks under them when
+  // zoomed out. This is a deliberate exception to the rem-first rule.
   const macChrome = isMacPlatform() && !isFullscreen;
   const navRowPaddingClass = macChrome
     ? hasWorkspaceRail
-      ? "pl-8"
-      : "pl-20"
+      ? "pl-[32px]"
+      : "pl-[80px]"
     : "pl-3";
   const navRowAlignmentClass = macChrome ? "translate-y-[3px]" : null;
 

desktop/src/features/sidebar/ui/WorkspaceRail.tsx

@@ -141,7 +141,7 @@ export function WorkspaceRail({
   // macOS traffic lights overlay the top-left, so start buttons below them (they hide in fullscreen).
   const topPaddingClass =
     isMacPlatform() && !isFullscreen
-      ? "pt-(--buzz-top-chrome-height,2.5rem)"
+      ? "pt-(--buzz-top-chrome-height,40px)"
       : "pt-3";
 
   return (

desktop/src/shared/layout/chromeLayout.ts

@@ -1,4 +1,8 @@
-export const TOP_CHROME_HEIGHT_DEFAULT = "2.5rem";
+// Fixed px on purpose: the top chrome strip hosts the fixed-size macOS
+// traffic lights and the px-pinned nav buttons (see `AppTopChrome`), so its
+// height must not follow the Cmd +/- rem text scale either. Deliberate
+// exception to the rem-first rule. 40px == the old 2.5rem at default zoom.
+export const TOP_CHROME_HEIGHT_DEFAULT = "40px";
 export const CHANNEL_CONTENT_TOP_PADDING_DEFAULT = "5.75rem";
 
 export const chromeCssVars = {
@@ -38,9 +42,9 @@ export const topChromeInset = {
 /** Tailwind class fragments for the global top chrome backdrop strip. */
 export const topChromeBackdrop = {
   /** Height matching the global top chrome search/drag strip. */
-  height: "h-(--buzz-top-chrome-height,2.5rem)",
+  height: "h-(--buzz-top-chrome-height,40px)",
   /** `after:` pseudo-element offset aligned to the bottom of top chrome. */
-  dividerTop: "after:top-(--buzz-top-chrome-height,2.5rem)",
+  dividerTop: "after:top-(--buzz-top-chrome-height,40px)",
 } as const;
 
 /** Tailwind class fragments for measured channel header chrome. */

desktop/tests/e2e/top-chrome-zoom-clearance.spec.ts

@@ -0,0 +1,138 @@
+import { expect, test } from "@playwright/test";
+
+import { installMockBridge } from "../helpers/bridge";
+
+// The macOS traffic lights are native chrome: with `trafficLightPosition`
+// x:16 they occupy roughly x 16–68 regardless of the app's Cmd +/- text
+// zoom. The top-chrome nav row must clear that band in fixed px, so the
+// clearance cannot shrink when the root font size scales down.
+const TRAFFIC_LIGHT_RIGHT_EDGE = 72;
+
+async function spoofMacPlatform(page: import("@playwright/test").Page) {
+  await page.addInitScript(() => {
+    Object.defineProperty(navigator, "platform", { get: () => "MacIntel" });
+  });
+}
+
+async function firstNavButtonX(page: import("@playwright/test").Page) {
+  const toggle = page.locator('[data-testid="app-top-chrome"] button').first();
+  await expect(toggle).toBeVisible();
+  const box = await toggle.boundingBox();
+  expect(box).not.toBeNull();
+  return box?.x ?? 0;
+}
+
+// The chrome buttons are styled to visually match the fixed-size native
+// controls, so their box must not follow the rem text scale either. The
+// sidebar toggle is 28px square; the back/forward history buttons share the
+// height but are deliberately narrower (24px).
+const NAV_BUTTON_SIZE = 28;
+const HISTORY_BUTTON_WIDTH = 24;
+
+// The grabber/drag strip hosting the buttons must hold its height too —
+// otherwise Cmd+ balloons the bar around the fixed-size buttons and Cmd-
+// collapses it.
+const TOP_CHROME_BAR_HEIGHT = 40;
+
+async function expectTopChromeFixedHeight(
+  page: import("@playwright/test").Page,
+) {
+  const bar = page.getByTestId("app-top-chrome");
+  await expect(bar).toBeVisible();
+  const box = await bar.boundingBox();
+  expect(box).not.toBeNull();
+  expect(box?.height ?? 0).toBe(TOP_CHROME_BAR_HEIGHT);
+}
+
+async function expectNavButtonsFixedSize(
+  page: import("@playwright/test").Page,
+) {
+  const buttons = page.locator('[data-testid="app-top-chrome"] button');
+  const count = await buttons.count();
+  expect(count).toBeGreaterThan(0);
+  for (let i = 0; i < count; i += 1) {
+    const button = buttons.nth(i);
+    const label = await button.getAttribute("aria-label");
+    const isHistoryButton = label === "Go back" || label === "Go forward";
+    const box = await button.boundingBox();
+    expect(box).not.toBeNull();
+    expect(box?.width ?? 0).toBe(
+      isHistoryButton ? HISTORY_BUTTON_WIDTH : NAV_BUTTON_SIZE,
+    );
+    expect(box?.height ?? 0).toBe(NAV_BUTTON_SIZE);
+  }
+}
+
+async function seedTextScale(
+  page: import("@playwright/test").Page,
+  scale: number,
+) {
+  await page.addInitScript((value) => {
+    window.localStorage.setItem("buzz:text-scale", String(value));
+  }, scale);
+}
+
+async function expectRootFontSize(
+  page: import("@playwright/test").Page,
+  fontSize: string,
+) {
+  await expect
+    .poll(() =>
+      page.evaluate(() => getComputedStyle(document.documentElement).fontSize),
+    )
+    .toBe(fontSize);
+}
+
+test.describe("top chrome macOS traffic-light clearance under text zoom", () => {
+  test("nav buttons clear the traffic lights at default zoom", async ({
+    page,
+  }) => {
+    await spoofMacPlatform(page);
+    await installMockBridge(page);
+    await page.goto("/");
+
+    expect(await firstNavButtonX(page)).toBeGreaterThanOrEqual(
+      TRAFFIC_LIGHT_RIGHT_EDGE,
+    );
+    await expectNavButtonsFixedSize(page);
+    await expectTopChromeFixedHeight(page);
+  });
+
+  test("nav buttons still clear the traffic lights when zoomed out", async ({
+    page,
+  }) => {
+    await spoofMacPlatform(page);
+    // Seed the minimum Cmd- text scale (0.75). The old rem-based clearance
+    // (pl-20 = 5rem) shrank to 60px here, sliding the buttons under the
+    // fixed-position native controls.
+    await seedTextScale(page, 0.75);
+    await installMockBridge(page);
+    await page.goto("/");
+
+    // Confirm the zoomed-out scale actually applied to the root font size.
+    await expectRootFontSize(page, "12px");
+
+    expect(await firstNavButtonX(page)).toBeGreaterThanOrEqual(
+      TRAFFIC_LIGHT_RIGHT_EDGE,
+    );
+    await expectNavButtonsFixedSize(page);
+    await expectTopChromeFixedHeight(page);
+  });
+
+  test("nav buttons keep their fixed size when zoomed in", async ({ page }) => {
+    await spoofMacPlatform(page);
+    // Seed the maximum Cmd+ text scale (1.5). Rem-sized buttons (h-7 = 42px
+    // here) grew visibly taller than the fixed-size traffic lights.
+    await seedTextScale(page, 1.5);
+    await installMockBridge(page);
+    await page.goto("/");
+
+    await expectRootFontSize(page, "24px");
+
+    expect(await firstNavButtonX(page)).toBeGreaterThanOrEqual(
+      TRAFFIC_LIGHT_RIGHT_EDGE,
+    );
+    await expectNavButtonsFixedSize(page);
+    await expectTopChromeFixedHeight(page);
+  });
+});