chore: Started working on browser swaping, b=(no-bug), c=workspaces

src/zen/workspaces/ZenWorkspaces.mjs

@@ -2930,6 +2930,8 @@ var ZenWorkspaces = new (class extends ZenMultiWindowFeature {
     #ignoreNextEvents = false;
     #waitForPromise = null;
 
+    lastSelectedWindow = false;
+
     constructor() {
       super();
       if (!window.closed) {
@@ -2941,6 +2943,8 @@ var ZenWorkspaces = new (class extends ZenMultiWindowFeature {
       await ZenWorkspaces.promiseInitialized;
       this.#makeSureAllTabsHaveIds();
       this.#setUpEventListeners();
+
+      this.lastSelectedWindow = ZenMultiWindowFeature.isActiveWindow;
     }
 
     #makeSureAllTabsHaveIds() {
@@ -2971,12 +2975,60 @@ var ZenWorkspaces = new (class extends ZenMultiWindowFeature {
       for (const event of kEvents) {
         window.addEventListener(event, eventListener);
       }
+
+      window.addEventListener('unload', () => {
+        for (const event of kEvents) {
+          window.removeEventListener(event, eventListener);
+        }
+      });
+
+      window.addEventListener('focus', this.#onWindowFocus.bind(this));
     }
 
     #handleEvent(event) {
       this.#propagateToOtherWindows(event);
     }
 
+    #getLastSelectedWindow() {
+      return new Promise(async (resolve) => {
+        await this.foreachWindowAsActive(async (browser) => {
+          if (browser.gZenWorkspaceWindowSync && browser.gZenWorkspaceWindowSync.lastSelectedWindow) {
+            resolve(browser);
+          }
+        });
+        resolve(null);
+      });
+    }
+
+    async #onWindowFocus(event) {
+      const lastSelectedWindow = await this.#getLastSelectedWindow();
+      if (lastSelectedWindow && lastSelectedWindow !== window) {
+        lastSelectedWindow.gZenWorkspaceWindowSync.lastSelectedWindow = false;
+        this.lastSelectedWindow = true;
+        this.#replaceBrowsersWithLastSelectedWindow(lastSelectedWindow);
+      } else {
+        this.lastSelectedWindow = false;
+      }
+    }
+
+    #replaceBrowsersWithLastSelectedWindow(lastSelectedWindow) {
+      // Replace all `linkedBrowser` elements with the last selected window's browsers
+      // from all the tabs in the current window
+      const allTabs = lastSelectedWindow.ZenWorkspaces.allStoredTabs;
+      for (const oldTab of allTabs) {
+        const tabId = this.#getTabId(oldTab);
+        const targetTab = this.#getTabWithId(tabId);
+        if (targetTab) {
+          const browserToReplace = oldTab.linkedBrowser;
+          const browserReplaced = targetTab.linkedBrowser;
+          const parentNode = browserReplaced.parentNode;
+          if (browserToReplace && parentNode) {
+            gBrowser.swapBrowsers(browserToReplace, browserReplaced);
+          }
+        }
+      }
+    }
+
     async #propagateToOtherWindows(event) {
       if (this.#ignoreNextEvents) {
         return;
@@ -3148,7 +3200,6 @@ var ZenWorkspaces = new (class extends ZenMultiWindowFeature {
 
     async #onTabOpen(event) {
       await new Promise((resolve) => {
-        setTimeout(() => {
         const targetTab = event.target;
         const isPinned = targetTab.pinned;
         const isEssential = isPinned && targetTab.hasAttribute('zen-essential');
@@ -3163,7 +3214,6 @@ var ZenWorkspaces = new (class extends ZenMultiWindowFeature {
 
         gBrowser.moveTabTo(duplicatedTab, { tabIndex, forceUngrouped: !!targetTab.group });
         resolve();
-        }, 0);
       });
     }
   }