Update ZenViewSplitter and session store to support tab splitting for empty tabs. Added 'allow-split' attribute handling in various components to enhance tab management functionality.

src/browser/base/zen-components/ZenKeyboardShortcuts.mjs

@@ -756,7 +756,7 @@ class ZenKeyboardShortcutsLoader {
 }
 
 class ZenKeyboardShortcutsVersioner {
-  static LATEST_KBS_VERSION = 8;
+  static LATEST_KBS_VERSION = 9;
 
   constructor() {}
 
@@ -937,6 +937,21 @@ class ZenKeyboardShortcutsVersioner {
         )
       );
     }
+    if (version < 9) {
+      // Migrate from 8 to 9
+      // In this new version, we add the "Add a Split New Tab to the Right" shortcut
+      data.push(
+        new KeyShortcut(
+          'zen-split-view-new-tab-to-right',
+          '+',
+          '',
+          ZEN_SPLIT_VIEW_SHORTCUTS_GROUP,
+          KeyShortcutModifiers.fromObject({ accel: true, shift: true }),
+          'code:gZenViewSplitter.createSplitNewTabToRight()',
+          'zen-split-view-shortcut-add-new-tab-to-right'
+        )
+      );
+    }
     return data;
   }
 }

src/browser/base/zen-components/ZenViewSplitter.mjs

@@ -133,7 +133,7 @@ class ZenViewSplitter extends ZenDOMOperatedFeature {
    */
   onTabSelect(event) {
     const previousTab = event.detail.previousTab;
-    if (previousTab && !previousTab.hasAttribute('zen-empty-tab')) {
+    if (previousTab && (!previousTab.hasAttribute('zen-empty-tab') || previousTab.hasAttribute('allow-split'))) {
       this._lastOpenedTab = previousTab;
     }
   }
@@ -178,7 +178,7 @@ class ZenViewSplitter extends ZenDOMOperatedFeature {
       // tab copy or move
       draggedTab = dt.mozGetDataAt(TAB_DROP_TYPE, 0);
       // not our drop then
-      if (!draggedTab || gBrowser.selectedTab.hasAttribute('zen-empty-tab')) {
+      if (!draggedTab || (gBrowser.selectedTab.hasAttribute('zen-empty-tab') && !gBrowser.selectedTab.hasAttribute('allow-split'))) {
         return;
       }
       draggedTab.container._finishMoveTogetherSelectedTabs(draggedTab);
@@ -893,7 +893,7 @@ class ZenViewSplitter extends ZenDOMOperatedFeature {
       return false;
     }
     for (const tab of window.gBrowser.selectedTabs) {
-      if (tab.splitView || tab.hasAttribute('zen-empty-tab') || tab.hasAttribute('zen-essential')) {
+      if (tab.splitView || (tab.hasAttribute('zen-empty-tab') && !tab.hasAttribute('allow-split')) || tab.hasAttribute('zen-essential')) {
         return false;
       }
     }
@@ -944,7 +944,7 @@ class ZenViewSplitter extends ZenDOMOperatedFeature {
    */
   splitTabs(tabs, gridType, initialIndex = 0) {
     // TODO: Add support for splitting essential tabs
-    tabs = tabs.filter((t) => !t.hidden && !t.hasAttribute('zen-empty-tab') && !t.hasAttribute('zen-essential'));
+    tabs = tabs.filter((t) => !t.hidden && (!t.hasAttribute('zen-empty-tab') || t.hasAttribute('allow-split')) && !t.hasAttribute('zen-essential'));
     if (tabs.length < 2 || tabs.length > this.MAX_TABS) {
       return;
     }
@@ -1506,6 +1506,74 @@ class ZenViewSplitter extends ZenDOMOperatedFeature {
     this.splitTabs(selected_tabs, gridType);
   }
 
+  /**
+   * Creates a vertical split with a new tab and focuses the URL bar
+   * Used for Ctrl+Shift+'+' shortcut
+   * Can be called repeatedly to add more tabs to the right
+   */
+  createSplitNewTabToRight() {
+    const currentTab = window.gBrowser.selectedTab;
+
+    if (currentTab.splitView) {
+      const groupIndex = this._data.findIndex((group) => group.tabs.includes(currentTab));
+      if (groupIndex >= 0) {
+        const group = this._data[groupIndex];
+        if (group.tabs.length < this.MAX_TABS) {
+          const newTab = this.openAndSwitchToTab('about:blank', { _forZenEmptyTab: true, _forZenEmptyTabAllowSplit: true });
+          group.tabs.push(newTab);
+
+          // Get the root node of the layout tree
+          const rootNode = group.layoutTree;
+
+          // For 'vsep' layout, add the new tab to the right end of the row
+          if (group.gridType === 'vsep' || rootNode.direction === 'row') {
+            // Calculate new sizes for all tabs
+            const newSize = 100 / (rootNode.children.length + 1);
+            const resizeFactor = newSize / (100 / rootNode.children.length);
+
+            // Resize existing tabs
+            rootNode.children.forEach((child) => {
+              child.sizeInParent *= resizeFactor;
+            });
+
+            // Add new tab at the end (not using addChild which puts it at the beginning)
+            const newNode = new SplitLeafNode(newTab, newSize);
+            newNode.parent = rootNode;
+            rootNode.children.push(newNode);
+
+            // Move tab to the group if needed
+            let splitGroup = this._getSplitViewGroup(group.tabs);
+            if (splitGroup) {
+              gBrowser.moveTabToGroup(newTab, splitGroup);
+            }
+
+            // Activate the updated layout
+            this.activateSplitView(group, true);
+
+            window.gBrowser.selectedTab = newTab;
+            window.gURLBar.select();
+            document.getElementById('Browser:OpenLocation').doCommand();
+            return;
+          }
+        }
+      }
+
+      // If we reached the maximum or layout isn't compatible, notify user
+      // (or silently do nothing)
+      return;
+    }
+
+    // First time pressing shortcut - create initial split
+    const newTab = this.openAndSwitchToTab('about:blank', { _forZenEmptyTab: true, _forZenEmptyTabAllowSplit: true });
+    this.splitTabs([currentTab, newTab], 'vsep');
+
+    window.gBrowser.selectedTab = newTab;
+
+    // Focus the URL bar
+    window.gURLBar.select();
+    document.getElementById('Browser:OpenLocation').doCommand();
+  }
+
   /**
    * @description removes the tab from the split
    * @param container - The container element

src/browser/components/sessionstore/SessionStore-sys-mjs.patch

@@ -7,7 +7,7 @@ index f814772114948f87cbb3c3a7231c95ea1f68d776..ae35daa518ca25f4fc95ef983519c390
        return;
      }
 -    if (aTab == aWindow.FirefoxViewHandler.tab) {
-+    if (aTab == aWindow.FirefoxViewHandler.tab || aTab.hasAttribute("zen-empty-tab")) {
++    if (aTab == aWindow.FirefoxViewHandler.tab || (aTab.hasAttribute("zen-empty-tab") && !aTab.hasAttribute("allow-split"))) {
        return;
      }
 
@@ -32,7 +32,7 @@ index f814772114948f87cbb3c3a7231c95ea1f68d776..ae35daa518ca25f4fc95ef983519c390
      // update the internal state data for this window
      for (let tab of tabs) {
 -      if (tab == aWindow.FirefoxViewHandler.tab) {
-+      if (tab == aWindow.FirefoxViewHandler.tab || tab.hasAttribute("zen-empty-tab")) {
++      if (tab == aWindow.FirefoxViewHandler.tab || (tab.hasAttribute("zen-empty-tab") && !tab.hasAttribute("allow-split"))) {
          continue;
        }
        let tabData = lazy.TabState.collect(tab, TAB_CUSTOM_VALUES.get(tab));
@@ -41,7 +41,7 @@ index f814772114948f87cbb3c3a7231c95ea1f68d776..ae35daa518ca25f4fc95ef983519c390
      // a window is closed, point to the first item in the tab strip instead (it will never be the Firefox View tab,
      // since it's only inserted into the tab strip after it's selected).
 -    if (aWindow.FirefoxViewHandler.tab?.selected) {
-+    if (aWindow.FirefoxViewHandler.tab?.selected || tabbrowser.selectedTab.hasAttribute("zen-empty-tab")) {
++    if (aWindow.FirefoxViewHandler.tab?.selected || (tabbrowser.selectedTab.hasAttribute("zen-empty-tab") && !tabbrowser.selectedTab.hasAttribute("allow-split"))) {
        selectedIndex = 1;
        winData.title = tabbrowser.tabs[0].label;
      }
@@ -54,6 +54,9 @@ index f814772114948f87cbb3c3a7231c95ea1f68d776..ae35daa518ca25f4fc95ef983519c390
 +    }
 +    if (tabData.zenIsEmpty) {
 +      tab.setAttribute("zen-empty-tab", "true");
++      if (tabData.zenAllowSplit) {
++        tab.setAttribute("allow-split", "true");
++      }
 +    }
 +    if (tabData.zenHasStaticLabel) {
 +      tab.setAttribute("zen-has-static-label", "true");

src/browser/components/sessionstore/TabState-sys-mjs.patch

@@ -20,6 +20,7 @@ index 8f7ed557e6aa61e7e16ed4a8d785ad5fe651b3d8..aff63696d198055886960072a6130318
 +    tabData.zenPinnedIcon = tab.getAttribute("zen-pinned-icon");
 +    tabData.zenIsEmpty = tab.hasAttribute("zen-empty-tab");
 +    tabData.zenHasStaticLabel = tab.hasAttribute("zen-has-static-label");
++    tabData.zenAllowSplit = tab.hasAttribute("allow-split");
 +
      tabData.searchMode = tab.ownerGlobal.gURLBar.getSearchMode(browser, true);
 

src/browser/components/tabbrowser/content/browser-ctrlTab-js.patch

@@ -7,7 +7,7 @@ index e5d16e605b7edf11fc9f52b93e415087b76398f1..40b6e29d26c7f8d692a2a9a7d924b289
      // (Normally hidden tabs would be unhidden when selected, but that doesn't
      // happen for Firefox View).
 -    if (aTab.closing || (aTab.hidden && !aTab.selected)) {
-+    if (aTab.closing || (aTab.hidden && !aTab.selected) || aTab.hasAttribute("zen-empty-tab")) {
++    if (aTab.closing || (aTab.hidden && !aTab.selected) || (aTab.hasAttribute("zen-empty-tab") && !aTab.hasAttribute("allow-split"))) {
        return;
      }
 
@@ -16,7 +16,7 @@ index e5d16e605b7edf11fc9f52b93e415087b76398f1..40b6e29d26c7f8d692a2a9a7d924b289
      this._recentlyUsedTabs = Array.prototype.filter.call(
        gBrowser.tabs,
 -      tab => !tab.closing && !tab.hidden
-+      tab => !tab.closing && !tab.hidden && !tab.hasAttribute("zen-empty-tab")
++      tab => !tab.closing && !tab.hidden && (!tab.hasAttribute("zen-empty-tab") || tab.hasAttribute("allow-split"))
      );
      this._sortRecentlyUsedTabs();
    },

src/browser/components/tabbrowser/content/tab-js.patch

@@ -35,7 +35,7 @@ index 777eabb7524f2b021a03b3f54d69faee49b7381d..192d2fa058f7d9f043532c0ae6e4c081
 
      get visible() {
 -      return this.isOpen && !this.hidden && !this.group?.collapsed;
-+      return this.isOpen && !this.hidden && !this.group?.collapsed && !this.hasAttribute("zen-empty-tab");
++      return this.isOpen && !this.hidden && !this.group?.collapsed && (!this.hasAttribute("zen-empty-tab") || this.hasAttribute("allow-split"));
      }
 
      get hidden() {
@@ -44,7 +44,7 @@ index 777eabb7524f2b021a03b3f54d69faee49b7381d..192d2fa058f7d9f043532c0ae6e4c081
        }
 
 -      return true;
-+      return !this.hasAttribute("zen-empty-tab");
++      return !this.hasAttribute("zen-empty-tab") || this.hasAttribute("allow-split");
      }
 
      get lastAccessed() {

src/browser/components/tabbrowser/content/tabbrowser-js.patch

@@ -158,6 +158,7 @@ index 628aa6596627c85efe361fc1ece8fd58f7ee653e..06a4aae50ebe8a42d08d4689d8e80a63
        userContextId,
        skipLoad,
 +      _forZenEmptyTab,
++      _forZenEmptyTabAllowSplit,
      } = {}) {
        let b = document.createXULElement("browser");
        // Use the JSM global to create the permanentKey, so that if the
@@ -195,14 +196,15 @@ index 628aa6596627c85efe361fc1ece8fd58f7ee653e..06a4aae50ebe8a42d08d4689d8e80a63
          schemelessInput,
          hasValidUserGestureActivation = false,
          textDirectiveUserActivation = false,
-+        _forZenEmptyTab,
-       } = {}
-     ) {
-       // all callers of addTab that pass a params object need to pass
++                _forZenEmptyTab,
+        _forZenEmptyTabAllowSplit,
+      } = {}
+    ) {
+      // all callers of addTab that pass a params object need to pass
 @@ -2639,6 +2693,12 @@
-         );
-       }
- 
+        );
+      }
+
 +      let hasZenDefaultUserContextId = false;
 +      let zenForcedWorkspaceId = undefined;
 +      if (typeof ZenWorkspaces !== "undefined" && !_forZenEmptyTab) {
@@ -224,6 +226,9 @@ index 628aa6596627c85efe361fc1ece8fd58f7ee653e..06a4aae50ebe8a42d08d4689d8e80a63
 +        }
 +        if (_forZenEmptyTab) {
 +          t.setAttribute("zen-empty-tab", "true");
++          if (_forZenEmptyTabAllowSplit) {
++            t.setAttribute("allow-split", "true");
++          }
 +        }
          if (insertTab) {
            // insert the tab into the tab container in the correct position
@@ -233,6 +238,7 @@ index 628aa6596627c85efe361fc1ece8fd58f7ee653e..06a4aae50ebe8a42d08d4689d8e80a63
            openWindowInfo,
            skipLoad,
 +          _forZenEmptyTab,
++          _forZenEmptyTabAllowSplit,
          }));
 
          if (focusUrlBar) {
@@ -280,7 +286,8 @@ index 628aa6596627c85efe361fc1ece8fd58f7ee653e..06a4aae50ebe8a42d08d4689d8e80a63
            openWindowInfo,
            name,
            skipLoad,
-+          _forZenEmptyTab
++          _forZenEmptyTab,
++          _forZenEmptyTabAllowSplit
          });
        }
 
@@ -293,6 +300,9 @@ index 628aa6596627c85efe361fc1ece8fd58f7ee653e..06a4aae50ebe8a42d08d4689d8e80a63
 +          }
 +          if (tabData.zenIsEmpty) {
 +            tab.setAttribute("zen-empty-tab", "true");
++            if (tabData.zenAllowSplit) {
++              tab.setAttribute("allow-split", "true");
++            }
 +          }
 +          if (tabData.zenHasStaticLabel) {
 +            tab.setAttribute("zen-has-static-label", "true");
@@ -333,6 +343,9 @@ index 628aa6596627c85efe361fc1ece8fd58f7ee653e..06a4aae50ebe8a42d08d4689d8e80a63
 +          }
 +          if (tabData.zenIsEmpty) {
 +            tab.setAttribute("zen-empty-tab", "true");
++            if (tabData.zenAllowSplit) {
++              tab.setAttribute("allow-split", "true");
++            }
 +          }
 +          if (tabData.zenHasStaticLabel) {
 +            tab.setAttribute("zen-has-static-label", "true");

src/browser/components/tabbrowser/content/tabs-js.patch

@@ -199,7 +199,7 @@ index fa96568d366fd3608f9bd583fa793150bd815c8b..1c940a3b162919256ca73fa867c5c261
      get visibleTabs() {
        if (!this.#visibleTabs) {
 -        this.#visibleTabs = this.openTabs.filter(tab => tab.visible);
-+        this.#visibleTabs = this.openTabs.filter(tab => tab.visible && !tab.hasAttribute("zen-empty-tab"));
++        this.#visibleTabs = this.openTabs.filter(tab => tab.visible && (!tab.hasAttribute("zen-empty-tab") || tab.hasAttribute("allow-split")));
        }
        return this.#visibleTabs;
      }

src/browser/modules/URILoadingHelper-sys-mjs.patch

@@ -7,7 +7,7 @@ index 313e895980c502d79f64f5a6ab838f6a96c83835..8a1a853567aeae2c368005d375781579
        // we'll open a new tab instead.
        let tab = w.gBrowser.getTabForBrowser(targetBrowser);
 -      if (tab == w.FirefoxViewHandler.tab) {
-+      if (tab == w.FirefoxViewHandler.tab || tab.hasAttribute("zen-empty-tab")) {
++      if (tab == w.FirefoxViewHandler.tab || (tab.hasAttribute("zen-empty-tab") && !tab.hasAttribute("allow-split"))) {
          where = "tab";
          targetBrowser = null;
        } else if (

src/toolkit/content/widgets/tabbox-js.patch

@@ -25,7 +25,7 @@ index 033582a3badb65d50f58a11f8a259e28eaa04ef3..ef634d76549f0fa4d5789e2bbfb9409f
            return null;
          }
 -        if (filter(tab)) {
-+        if (filter(tab) && !tab.hasAttribute("zen-glance-tab") && !tab.hasAttribute("zen-empty-tab")) {
++        if (filter(tab) && !tab.hasAttribute("zen-glance-tab") && (!tab.hasAttribute("zen-empty-tab") || tab.hasAttribute("allow-split"))) {
            return tab;
          }
        }