From 91a1d4d2ca88e06789c0f7845adf6262eb8f755a Mon Sep 17 00:00:00 2001
From: "mr. m" <91018726+mr-cheffy@users.noreply.github.com>
Date: Thu, 20 Aug 2026 21:38:09 +0200
Subject: [PATCH] gh-14470: Run sweep animation on first sync (gh-15036)

---
 src/zen/common/modules/ZenStartup.mjs     |  9 +++++++++
 src/zen/common/modules/ZenUpdates.mjs     |  8 ++++++++
 src/zen/sync/ZenSpacesSyncApplier.sys.mjs | 17 +++++++++++++++++
 3 files changed, 34 insertions(+)

diff --git a/src/zen/common/modules/ZenStartup.mjs b/src/zen/common/modules/ZenStartup.mjs
index a1683d6ad..5766774df 100644
--- a/src/zen/common/modules/ZenStartup.mjs
+++ b/src/zen/common/modules/ZenStartup.mjs
@@ -4,6 +4,7 @@
 
 import checkForZenUpdates, {
   createWindowUpdateAnimation,
+  playWindowSweepAnimation,
 } from "chrome://browser/content/ZenUpdates.mjs";
 
 class ZenStartup {
@@ -195,6 +196,14 @@ class ZenStartup {
     checkForZenUpdates();
     return await createWindowUpdateAnimation();
   }
+
+  /**
+   * Entry point for privileged modules (e.g. the sync applier) to play the
+   * update sweep animation in this window.
+   */
+  playWindowSweepAnimation() {
+    return playWindowSweepAnimation();
+  }
 }
 
 window.gZenStartup = new ZenStartup();
diff --git a/src/zen/common/modules/ZenUpdates.mjs b/src/zen/common/modules/ZenUpdates.mjs
index f0631e022..94599bdee 100644
--- a/src/zen/common/modules/ZenUpdates.mjs
+++ b/src/zen/common/modules/ZenUpdates.mjs
@@ -61,6 +61,14 @@ export async function createWindowUpdateAnimation() {
     return;
   }
   Services.prefs.setStringPref(ZEN_BUILD_ID_PREF, appID);
+  await playWindowSweepAnimation();
+}
+
+/**
+ * Plays the full-window sweep shown after updates. Also used the first
+ * time incoming sync data is applied on this profile.
+ */
+export async function playWindowSweepAnimation() {
   await gZenWorkspaces.promiseInitialized;
   const appWrapper = document.getElementById("zen-main-app-wrapper");
   const element = document.createElement("div");
diff --git a/src/zen/sync/ZenSpacesSyncApplier.sys.mjs b/src/zen/sync/ZenSpacesSyncApplier.sys.mjs
index 398df24c2..555abd2ce 100644
--- a/src/zen/sync/ZenSpacesSyncApplier.sys.mjs
+++ b/src/zen/sync/ZenSpacesSyncApplier.sys.mjs
@@ -22,6 +22,8 @@ ChromeUtils.defineESModuleGetters(lazy, {
     "moz-src:///toolkit/components/contextualidentity/ContextualIdentityService.sys.mjs",
 });
 
+const FIRST_SYNC_ANIMATION_PREF = "zen.spaces-sync.first-sync-animation-shown";
+
 /**
  * Applies batches of incoming Spaces records to the local browser.
  */
@@ -112,6 +114,7 @@ class nsZenSpacesSyncApplier {
       }
     } else {
       await win.gZenWorkspaces.promiseInitialized;
+      this.#maybePlayFirstSyncAnimation(win);
       const removals = this.#routeTombstones(win, deletions);
       this.#deleteTabs(win, removals.tabs, fail);
       this.#deleteSplits(win, removals.splits, fail);
@@ -141,6 +144,20 @@ class nsZenSpacesSyncApplier {
     return [...failed];
   }
 
+  /**
+   * Plays the update sweep animation over the window the first time
+   * incoming sync data lands on this profile.
+   *
+   * @param {Window} win
+   */
+  #maybePlayFirstSyncAnimation(win) {
+    if (Services.prefs.getBoolPref(FIRST_SYNC_ANIMATION_PREF, false)) {
+      return;
+    }
+    Services.prefs.setBoolPref(FIRST_SYNC_ANIMATION_PREF, true);
+    win.gZenStartup.playWindowSweepAnimation();
+  }
+
   /**
    * Tombstones have no payload. Whatever local thing owns the id decides
    * what kind of deletion this is. Ids with no local counterpart need no