fix(desktop): skip community view transition on Linux WebKitGTK to avoid UI-process segfault

desktop/src/app/communityViewTransition.test.mjs

@@ -5,20 +5,49 @@ import {
   completeCommunityViewTransition,
   replaceCommunityDestinationRoute,
   runCommunityViewTransition,
+  shouldSkipCommunityViewTransition,
 } from "./communityViewTransition.ts";
 
 const originalDocument = globalThis.document;
 const originalWindow = globalThis.window;
+const originalNavigator = Object.getOwnPropertyDescriptor(
+  globalThis,
+  "navigator",
+);
+
+const WEBKITGTK_UA =
+  "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.0 Safari/605.1.15";
+const MAC_UA =
+  "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.4 Safari/605.1.15";
 
 afterEach(() => {
   globalThis.document = originalDocument;
   globalThis.window = originalWindow;
+  if (originalNavigator) {
+    Object.defineProperty(globalThis, "navigator", originalNavigator);
+  } else {
+    delete globalThis.navigator;
+  }
   mock.restoreAll();
 });
 
+// `undefined` removes navigator entirely, so `typeof navigator === "undefined"`.
+// afterEach puts the real one back.
+function setNavigator(value) {
+  if (value === undefined) {
+    delete globalThis.navigator;
+    return;
+  }
+  Object.defineProperty(globalThis, "navigator", { configurable: true, value });
+}
+
 function installBrowser(startViewTransition) {
   globalThis.window = { clearTimeout, setTimeout };
   globalThis.document = { startViewTransition };
+  // node reports navigator.platform as "Linux x86_64", which is exactly what
+  // the crash guard skips the transition for. Default these tests to a
+  // platform that keeps the animation path; the linux cases set their own.
+  setNavigator({ platform: "MacIntel", userAgent: MAC_UA });
 }
 
 function transitionFor(callback) {
@@ -33,6 +62,48 @@ test("replaceCommunityDestinationRoute uses router history and encodes the chann
   assert.deepEqual(replacements, ["/channels/channel%2Fwith%20spaces"]);
 });
 
+test("the transition is skipped on linux and kept everywhere else", () => {
+  setNavigator({ platform: "Linux x86_64", userAgent: WEBKITGTK_UA });
+  assert.equal(shouldSkipCommunityViewTransition(), true);
+
+  // Chromium on Linux is skipped too. The guard fails closed on purpose: it
+  // cannot tell a WebKitGTK webview from a Linux browser without sniffing the
+  // user agent, and losing an animation costs less than a segfault.
+  setNavigator({
+    platform: "Linux x86_64",
+    userAgent:
+      "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/126.0.0.0 Safari/537.36",
+  });
+  assert.equal(shouldSkipCommunityViewTransition(), true);
+
+  setNavigator({ platform: "MacIntel", userAgent: MAC_UA });
+  assert.equal(shouldSkipCommunityViewTransition(), false);
+
+  // Android reports a Linux platform but is not a WebKitGTK desktop webview.
+  setNavigator({
+    platform: "Linux armv8l",
+    userAgent:
+      "Mozilla/5.0 (Linux; Android 14) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/126.0.0.0 Mobile Safari/537.36",
+  });
+  assert.equal(shouldSkipCommunityViewTransition(), false);
+
+  setNavigator(undefined);
+  assert.equal(shouldSkipCommunityViewTransition(), false);
+});
+
+test("linux runs the update without starting a transition", async () => {
+  const startViewTransition = mock.fn((callback) => transitionFor(callback));
+  installBrowser(startViewTransition);
+  setNavigator({ platform: "Linux x86_64", userAgent: WEBKITGTK_UA });
+
+  let updated = false;
+  await runCommunityViewTransition(async () => {
+    updated = true;
+  });
+  assert.equal(updated, true);
+  assert.equal(startViewTransition.mock.callCount(), 0);
+});
+
 test("unsupported browsers execute the update and contain rejection", async () => {
   installBrowser(undefined);
   const expected = new Error("navigation failed");

desktop/src/app/communityViewTransition.ts

@@ -1,3 +1,5 @@
+import { isLinuxPlatform } from "@/shared/lib/platform";
+
 const COMMUNITY_TRANSITION_TIMEOUT_MS = 5_000;
 
 let finishPendingTransition: (() => void) | null = null;
@@ -13,11 +15,31 @@ export function replaceCommunityDestinationRoute(
   history.replace(`/channels/${encodeURIComponent(channelId)}`);
 }
 
+// WebKitGTK (the engine under every Linux Tauri webview) crashes the UI
+// process when a view transition is the first thing to demand accelerated
+// compositing on a machine whose accelerated backing store could not be
+// created (X11 sessions, dmabuf transport disabled or unavailable): the
+// missing-store guard is a debug ASSERT that release builds compile out, so
+// document.startViewTransition() segfaults instead of animating. Reproduced
+// 100% outside Buzz on WebKitGTK 2.52 regardless of the dmabuf env vars —
+// see #3488, #4142, and https://bugs.webkit.org/show_bug.cgi?id=321683.
+//
+// Keyed on the platform alone, deliberately: this guards a UI-process
+// segfault, so it has to fail closed. Narrowing it to WebKitGTK would mean
+// sniffing the user agent for the engine, and a UA test that quietly stops
+// matching re-enables the crash with nothing pointing back at this line. On
+// Tauri, Linux means WebKitGTK anyway, so the cost of over-matching is only a
+// missing cross-fade in a Linux browser session — a crash is not a tradeoff
+// worth taking for an animation.
+export function shouldSkipCommunityViewTransition(): boolean {
+  return isLinuxPlatform();
+}
+
 export async function runCommunityViewTransition(
   update: () => Promise<void> | void,
   options: { timeoutMs?: number } = {},
 ): Promise<void> {
-  if (!document.startViewTransition) {
+  if (!document.startViewTransition || shouldSkipCommunityViewTransition()) {
     try {
       await update();
     } catch (error) {