--- a/browser/base/content/tabbrowser.xml
+++ b/browser/base/content/tabbrowser.xml
@@ -6434,25 +6434,25 @@
 
           if (this.getAttribute("movingtab") != "true") {
             requestAnimationFrame(() => {
               this.setAttribute("movingtab", "true");
               this.selectedItem = draggedTab;
             });
           }
 
-          if (!("animLastScreenX" in draggedTab._dragData))
-            draggedTab._dragData.animLastScreenX = draggedTab._dragData.screenX;
-
-          let screenX = event.screenX;
-          if (screenX == draggedTab._dragData.animLastScreenX)
+          if (!("animLastClientX" in draggedTab._dragData))
+            draggedTab._dragData.animLastClientX = draggedTab._dragData.clientX;
+
+          let clientX = event.clientX;
+          if (clientX == draggedTab._dragData.animLastClientX)
             return;
 
           (async () => {
-            draggedTab._dragData.animLastScreenX = screenX;
+            draggedTab._dragData.animLastClientX = clientX;
 
             let tabWidth, rtl;
             let newIndex = -1;
             let oldIndex = "animDropIndex" in draggedTab._dragData ?
                            draggedTab._dragData.animDropIndex : draggedTab._tPos;
 
             let pinned = draggedTab.pinned;
             let numPinned = this.tabbrowser._numPinnedTabs;
@@ -6466,51 +6466,51 @@
                 tabs.reverse();
               tabWidth = draggedTab.getBoundingClientRect().width;
               draggedTab._dragData.tabWidth = tabWidth;
 
               // Move the dragged tab based on the mouse position.
 
               let leftTab = tabs[0];
               let rightTab = tabs[tabs.length - 1];
-              let tabScreenX = draggedTab.boxObject.screenX;
-              let translateX = screenX - draggedTab._dragData.screenX;
+              let tabClientX = draggedTab.boxObject.x;
+              let translateX = clientX - draggedTab._dragData.clientX;
               if (!pinned)
                 translateX += this.mTabstrip.scrollPosition - draggedTab._dragData.scrollX;
-              let leftBound = leftTab.boxObject.screenX - tabScreenX;
-              let rightBound = (rightTab.boxObject.screenX + rightTab.boxObject.width) -
-                               (tabScreenX + tabWidth);
+              let leftBound = leftTab.boxObject.x - tabClientX;
+              let rightBound = (rightTab.boxObject.x + rightTab.boxObject.width) -
+                               (tabClientX + tabWidth);
               translateX = Math.max(translateX, leftBound);
               translateX = Math.min(translateX, rightBound);
 
               requestAnimationFrame(() => {
                 draggedTab.style.transform = "translateX(" + translateX + "px)";
                 draggedTab._dragData.translateX = translateX;
               });
 
               // Determine what tab we're dragging over.
               // * Point of reference is the center of the dragged tab. If that
               //   point touches a background tab, the dragged tab would take that
               //   tab's position when dropped.
               // * We're doing a binary search in order to reduce the amount of
               //   tabs we need to check.
 
-              let tabCenter = tabScreenX + translateX + tabWidth / 2;
+              let tabCenter = tabClientX + translateX + tabWidth / 2;
               let low = 0;
               let high = tabs.length - 1;
               while (low <= high) {
                 let mid = Math.floor((low + high) / 2);
                 if (tabs[mid] == draggedTab &&
                     ++mid > high)
                   break;
                 let boxObject = tabs[mid].boxObject;
-                screenX = boxObject.screenX + getTabShift(tabs[mid], oldIndex);
-                if (screenX > tabCenter) {
+                clientX = boxObject.x + getTabShift(tabs[mid], oldIndex);
+                if (clientX > tabCenter) {
                   high = mid - 1;
-                } else if (screenX + boxObject.width < tabCenter) {
+                } else if (clientX + boxObject.width < tabCenter) {
                   low = mid + 1;
                 } else {
                   newIndex = tabs[mid]._tPos;
                   break;
                 }
               }
             });
 
@@ -7032,17 +7032,17 @@
         function clientX(ele) {
           return ele.getBoundingClientRect().left;
         }
         let tabOffsetX = clientX(tab) - clientX(this);
         tab._dragData = {
           offsetX: event.screenX - window.screenX - tabOffsetX,
           offsetY: event.screenY - window.screenY,
           scrollX: this.mTabstrip.scrollPosition,
-          screenX: event.screenX
+          clientX: event.clientX
         };
 
         event.stopPropagation();
       ]]></handler>
 
       <handler event="dragover"><![CDATA[
         var effects = this._getDropEffectForTabDrag(event);