From 61e631902c37697dd61b31a0d051bb3743c5e213 Mon Sep 17 00:00:00 2001
From: Andrey Bochkarev <50177704+octaviusz@users.noreply.github.com>
Date: Sat, 20 Jun 2026 18:18:41 +0300
Subject: [PATCH] gh-14131: Prevent sidebar from flickering when moving a tab
 (gh-14293)

Co-authored-by: mr. m <mr.m@tuta.com>
---
 .../tabbrowser/content/tabs-js.patch          | 55 ++++++++++++-------
 src/zen/drag-and-drop/ZenDragAndDrop.js       | 11 +++-
 2 files changed, 43 insertions(+), 23 deletions(-)

diff --git a/src/browser/components/tabbrowser/content/tabs-js.patch b/src/browser/components/tabbrowser/content/tabs-js.patch
index 449d2bae1..167f6b882 100644
--- a/src/browser/components/tabbrowser/content/tabs-js.patch
+++ b/src/browser/components/tabbrowser/content/tabs-js.patch
@@ -1,8 +1,23 @@
 diff --git a/browser/components/tabbrowser/content/tabs.js b/browser/components/tabbrowser/content/tabs.js
-index 568f3a7cc7051ff8cb569f6bcb8018a5212f7072..3036768b8911b4fbc28df7528f7189d9ea21b6f6 100644
+index 568f3a7cc7051ff8cb569f6bcb8018a5212f7072..b9a1cfe3a4a5035d9b06b0b3826a97c52cfcb39e 100644
 --- a/browser/components/tabbrowser/content/tabs.js
 +++ b/browser/components/tabbrowser/content/tabs.js
-@@ -220,7 +220,7 @@
+@@ -197,8 +197,12 @@
+       XPCOMUtils.defineLazyPreferenceGetter(
+         this,
+         "_sidebarPositionStart",
+-        "sidebar.position_start",
+-        true
++        "zen.tabs.vertical.right-side",
++        true,
++        null,
++        newValue => {
++          return !newValue;
++        }
+       );
+ 
+       if (gMultiProcessBrowser) {
+@@ -220,7 +224,7 @@
  
        this.tooltip = "tabbrowser-tab-tooltip";
  
@@ -11,7 +26,7 @@ index 568f3a7cc7051ff8cb569f6bcb8018a5212f7072..3036768b8911b4fbc28df7528f7189d9
        this.tabDragAndDrop.init();
      }
  
-@@ -444,7 +444,7 @@
+@@ -444,7 +448,7 @@
        // and we're not hitting the scroll buttons.
        if (
          event.button != 0 ||
@@ -20,7 +35,7 @@ index 568f3a7cc7051ff8cb569f6bcb8018a5212f7072..3036768b8911b4fbc28df7528f7189d9
          event.composedTarget.localName == "toolbarbutton"
        ) {
          return;
-@@ -525,7 +525,6 @@
+@@ -525,7 +529,6 @@
              });
            }
          } else if (isTabGroupLabel(event.target)) {
@@ -28,7 +43,7 @@ index 568f3a7cc7051ff8cb569f6bcb8018a5212f7072..3036768b8911b4fbc28df7528f7189d9
          } else if (
            event.originalTarget.closest("scrollbox") &&
            !Services.prefs.getBoolPref(
-@@ -561,6 +560,9 @@
+@@ -561,6 +564,9 @@
      }
  
      on_keydown(event) {
@@ -38,7 +53,7 @@ index 568f3a7cc7051ff8cb569f6bcb8018a5212f7072..3036768b8911b4fbc28df7528f7189d9
        let { altKey, shiftKey } = event;
        let [accel, nonAccel] =
          AppConstants.platform == "macosx"
-@@ -755,7 +757,6 @@
+@@ -755,7 +761,6 @@
        this._updateCloseButtons();
  
        if (!this.#animatingGroups.size) {
@@ -46,7 +61,7 @@ index 568f3a7cc7051ff8cb569f6bcb8018a5212f7072..3036768b8911b4fbc28df7528f7189d9
        }
  
        document
-@@ -822,7 +823,7 @@
+@@ -822,7 +827,7 @@
      }
  
      get newTabButton() {
@@ -55,7 +70,7 @@ index 568f3a7cc7051ff8cb569f6bcb8018a5212f7072..3036768b8911b4fbc28df7528f7189d9
      }
  
      get verticalMode() {
-@@ -838,6 +839,7 @@
+@@ -838,6 +843,7 @@
      }
  
      get overflowing() {
@@ -63,7 +78,7 @@ index 568f3a7cc7051ff8cb569f6bcb8018a5212f7072..3036768b8911b4fbc28df7528f7189d9
        return this.hasAttribute("overflow");
      }
  
-@@ -851,29 +853,56 @@
+@@ -851,29 +857,56 @@
        if (pinnedChildren?.at(-1)?.id == "pinned-tabs-container-periphery") {
          pinnedChildren.pop();
        }
@@ -93,7 +108,7 @@ index 568f3a7cc7051ff8cb569f6bcb8018a5212f7072..3036768b8911b4fbc28df7528f7189d9
 +          } else if (!isTab(tab)) {
 +            tabs.splice(i, 1);
 +          }
-         }
++        }
 +      };
 +      expandTabs(pinnedTabs);
 +      expandTabs(unpinnedChildren);
@@ -114,7 +129,7 @@ index 568f3a7cc7051ff8cb569f6bcb8018a5212f7072..3036768b8911b4fbc28df7528f7189d9
 +          // remove the separator from the list
 +          allTabs.splice(i, 1);
 +          i--;
-+        }
+         }
 +        i++;
        }
 -
@@ -130,7 +145,7 @@ index 568f3a7cc7051ff8cb569f6bcb8018a5212f7072..3036768b8911b4fbc28df7528f7189d9
      }
  
      get allSplitViews() {
-@@ -958,29 +987,28 @@
+@@ -958,29 +991,28 @@
          return this.#focusableItems;
        }
  
@@ -170,7 +185,7 @@ index 568f3a7cc7051ff8cb569f6bcb8018a5212f7072..3036768b8911b4fbc28df7528f7189d9
        this.#focusableItems = focusableItems;
  
        return this.#focusableItems;
-@@ -993,6 +1021,7 @@
+@@ -993,6 +1025,7 @@
       * focusable (ex, we don't want the splitview container to be focusable, only its children).
       */
      get dragAndDropElements() {
@@ -178,7 +193,7 @@ index 568f3a7cc7051ff8cb569f6bcb8018a5212f7072..3036768b8911b4fbc28df7528f7189d9
        if (this.#dragAndDropElements) {
          return this.#dragAndDropElements;
        }
-@@ -1063,6 +1092,7 @@
+@@ -1063,6 +1096,7 @@
      _invalidateCachedTabs() {
        this.#allTabs = null;
        this._invalidateCachedVisibleTabs();
@@ -186,7 +201,7 @@ index 568f3a7cc7051ff8cb569f6bcb8018a5212f7072..3036768b8911b4fbc28df7528f7189d9
      }
  
      _invalidateCachedVisibleTabs() {
-@@ -1082,7 +1112,8 @@
+@@ -1082,7 +1116,8 @@
  
      isContainerVerticalPinnedGrid(tab) {
        return (
@@ -196,7 +211,7 @@ index 568f3a7cc7051ff8cb569f6bcb8018a5212f7072..3036768b8911b4fbc28df7528f7189d9
          this.verticalMode &&
          this.hasAttribute("expanded") &&
          !this.expandOnHover
-@@ -1176,7 +1207,7 @@
+@@ -1176,7 +1211,7 @@
  
        if (node == null) {
          // We have a container for non-tab elements at the end of the scrollbox.
@@ -205,7 +220,7 @@ index 568f3a7cc7051ff8cb569f6bcb8018a5212f7072..3036768b8911b4fbc28df7528f7189d9
        }
  
        node.before(tab);
-@@ -1271,7 +1302,7 @@
+@@ -1271,7 +1306,7 @@
            // There are separate "new tab" buttons for horizontal tabs toolbar, vertical tabs and
            // for when the tab strip is overflowed (which is shared by vertical and horizontal tabs);
            // Attach the long click popup to all of them.
@@ -214,7 +229,7 @@ index 568f3a7cc7051ff8cb569f6bcb8018a5212f7072..3036768b8911b4fbc28df7528f7189d9
            const newTab2 = this.newTabButton;
            const newTabVertical = document.getElementById(
              "vertical-tabs-newtab-button"
-@@ -1376,8 +1407,10 @@
+@@ -1376,8 +1411,10 @@
       */
      _handleTabSelect(aInstant) {
        let selectedTab = this.selectedItem;
@@ -225,7 +240,7 @@ index 568f3a7cc7051ff8cb569f6bcb8018a5212f7072..3036768b8911b4fbc28df7528f7189d9
        selectedTab._notselectedsinceload = false;
      }
  
-@@ -1386,7 +1419,7 @@
+@@ -1386,7 +1423,7 @@
       * @param {boolean} [shouldScrollInstantly=false]
       */
      #ensureTabIsVisible(tab, shouldScrollInstantly = false) {
@@ -234,7 +249,7 @@ index 568f3a7cc7051ff8cb569f6bcb8018a5212f7072..3036768b8911b4fbc28df7528f7189d9
        if (arrowScrollbox?.overflowing) {
          arrowScrollbox.ensureElementIsVisible(tab, shouldScrollInstantly);
        }
-@@ -1513,7 +1546,7 @@
+@@ -1513,7 +1550,7 @@
      }
  
      _notifyBackgroundTab(aTab) {
diff --git a/src/zen/drag-and-drop/ZenDragAndDrop.js b/src/zen/drag-and-drop/ZenDragAndDrop.js
index 05f31ac9c..67cf9a238 100644
--- a/src/zen/drag-and-drop/ZenDragAndDrop.js
+++ b/src/zen/drag-and-drop/ZenDragAndDrop.js
@@ -723,8 +723,11 @@
       const { isNearLeftEdge, isNearRightEdge } =
         this.#shouldSwitchSpace(event);
       if (isNearLeftEdge || isNearRightEdge) {
-        if (!this.#changeSpaceTimer) {
+        if (!this.#changeSpaceTimer && !this.#isOutOfWindow) {
           this.#changeSpaceTimer = setTimeout(() => {
+            if (this.#isOutOfWindow) {
+              return;
+            }
             this.clearDragOverVisuals();
             gZenWorkspaces
               .changeWorkspaceShortcut(
@@ -956,8 +959,10 @@
       if (ownerGlobal?.gZenCompactModeManager) {
         // Sometimes, dragend doesn't always get called when dragging
         // to different windows, see gh-8643.
-        delete ownerGlobal.gZenCompactModeManager._isTabBeingDragged;
-        ownerGlobal.gZenCompactModeManager._clearAllHoverStates();
+        requestAnimationFrame(() => {
+          delete ownerGlobal.gZenCompactModeManager._isTabBeingDragged;
+          ownerGlobal.gZenCompactModeManager._clearAllHoverStates();
+        });
       }
       this.clearSpaceSwitchTimer();
       gZenFolders.highlightGroupOnDragOver(null);