From e118cc1a206497a34f2dc766f4ca8c040e6a292c Mon Sep 17 00:00:00 2001
From: "mr. m" <91018726+mr-cheffy@users.noreply.github.com>
Date: Sat, 3 Jan 2026 02:42:17 +0100
Subject: [PATCH] chore: Motion to native animatiosn migration, p=#11796

* chore: Motion to native animatiosn migration, b=no-bug, c=common, glance, split-view

* Discard changes to src/zen/glance/zen-glance.css

* Discard changes to src/zen/glance/ZenGlanceManager.mjs
---
 src/zen/common/modules/ZenUIManager.mjs | 43 +++++++++++++++++++
 src/zen/drag-and-drop/ZenDragAndDrop.js | 57 +++++++++----------------
 src/zen/split-view/ZenViewSplitter.mjs  |  1 +
 3 files changed, 65 insertions(+), 36 deletions(-)

diff --git a/src/zen/common/modules/ZenUIManager.mjs b/src/zen/common/modules/ZenUIManager.mjs
index 93b9649fb..5976e8c2e 100644
--- a/src/zen/common/modules/ZenUIManager.mjs
+++ b/src/zen/common/modules/ZenUIManager.mjs
@@ -65,6 +65,49 @@ window.gZenUIManager = {
     ZenMenubar.init();
   },
 
+  /**
+   * Animate an element using Element.animate API.
+   * This is not using gZenUIManager.motion, because motion library has some issues
+   * with certain properties and we want to have a simple wrapper for that.
+   */
+  async elementAnimate(element, rawKeyframes, ...args) {
+    rawKeyframes = { ...rawKeyframes };
+    // Convert 'y' property to 'transform' with translateY and 'x' to translateX,
+    // and 'scale' to 'transform' with scale.
+    if ((rawKeyframes.y || rawKeyframes.x || rawKeyframes.scale) && !rawKeyframes.transform) {
+      const yValues = rawKeyframes.y || [];
+      const xValues = rawKeyframes.x || [];
+      const scaleValues = rawKeyframes.scale || [];
+      delete rawKeyframes.y;
+      delete rawKeyframes.x;
+      delete rawKeyframes.scale;
+      rawKeyframes.transform = [];
+      console.assert(
+        yValues.length === 0 || xValues.length === 0 || yValues.length === xValues.length,
+        'y and x keyframes must have the same length'
+      );
+      const length = Math.max(yValues.length, xValues.length, scaleValues.length);
+      for (let i = 0; i < length; i++) {
+        const y = yValues[i] !== undefined ? `translateY(${yValues[i]}px)` : '';
+        const x = xValues[i] !== undefined ? `translateX(${xValues[i]}px)` : '';
+        const scale = scaleValues[i] !== undefined ? `scale(${scaleValues[i]})` : '';
+        rawKeyframes.transform.push(`${x} ${y} ${scale}`.trim());
+      }
+    }
+    let keyframes = [];
+    for (let i = 0; i < Object.values(rawKeyframes)[0].length; i++) {
+      let frame = {};
+      for (const [property, values] of Object.entries(rawKeyframes)) {
+        frame[property] = values[i];
+      }
+      keyframes.push(frame);
+    }
+    return await new Promise((resolve) => {
+      const animation = element.animate(keyframes, ...args);
+      animation.onfinish = () => resolve();
+    });
+  },
+
   _addNewCustomizableButtonsIfNeeded() {
     const kPref = 'zen.ui.migration.compact-mode-button-added';
     let navbarPlacements = CustomizableUI.getWidgetIdsInArea('zen-sidebar-top-buttons');
diff --git a/src/zen/drag-and-drop/ZenDragAndDrop.js b/src/zen/drag-and-drop/ZenDragAndDrop.js
index 4fb343638..17ee6f82f 100644
--- a/src/zen/drag-and-drop/ZenDragAndDrop.js
+++ b/src/zen/drag-and-drop/ZenDragAndDrop.js
@@ -97,9 +97,7 @@
       const { offsetX, offsetY } = this.#getDragImageOffset(event, tab, draggingTabs);
       const dragImage = this.#createDragImageForTabs(draggingTabs);
       this.originalDragImageArgs = [dragImage, offsetX, offsetY];
-      setTimeout(() => {
-        dt.setDragImage(...this.originalDragImageArgs);
-      }, 0);
+      dt.setDragImage(...this.originalDragImageArgs);
     }
 
     #createDragImageForTabs(movingTabs) {
@@ -520,18 +518,7 @@
       let dropElementGroup = dropElement?.group;
       let colorCode = dropElementGroup?.color;
 
-      let lastUnmovingTabInGroup = dropElementGroup?.tabs.findLast((t) => !movingTabsSet.has(t));
-      if (
-        isTab(dropElement) &&
-        dropElementGroup &&
-        dropElement == lastUnmovingTabInGroup &&
-        !dropBefore
-      ) {
-        // Dragging tab over the last tab of a tab group, but not enough
-        // for it to drop into the tab group. Drop it after the tab group instead.
-        dropElement = dropElementGroup;
-        colorCode = undefined;
-      } else if (isTabGroupLabel(dropElement)) {
+      if (isTabGroupLabel(dropElement)) {
         // Dropping right before the first tab in the tab group.
         dropElement = dropElementGroup.tabs[0];
         dropBefore = true;
@@ -711,7 +698,6 @@
           !gZenStartup.isReady ||
           gReduceMotion ||
           !dropElement ||
-          dropElement.group !== draggedTab.group ||
           dropElement.hasAttribute('zen-essential') ||
           draggedTab.hasAttribute('zen-essential') ||
           draggedTab.getAttribute('zen-workspace-id') != gZenWorkspaces.activeWorkspace
@@ -725,26 +711,24 @@
         }
         const animateElement = (ele, translateY) => {
           ele.style.transform = `translateY(${translateY}px)`;
-          setTimeout(() => {
-            setTimeout(() => {
-              animations.push(
-                gZenUIManager.motion
-                  .animate(
-                    ele,
-                    {
-                      y: [translateY, 0],
-                    },
-                    {
-                      duration: 0.1,
-                      bounce: 0,
-                    }
-                  )
-                  .then(() => {
-                    ele.style.transform = '';
-                  })
-              );
-            });
-          });
+          let animateInternal = (resolve) => {
+            gZenUIManager
+              .elementAnimate(ele, { y: [translateY, 0] }, { duration: 100, easing: 'ease-out' })
+              .then(() => {
+                ele.style.transform = '';
+                ele.style.zIndex = '';
+              })
+              .finally(resolve);
+          };
+          // Wait for the next event loop tick to ensure the initial transform style is applied.
+          // We need to ensure the element has already been moved in the DOM before starting the animation.
+          animations.push(
+            new Promise((resolve) =>
+              setTimeout(() => {
+                setTimeout(() => animateInternal(resolve), 0);
+              })
+            )
+          );
         };
         const items = this._tabbrowserTabs.ariaFocusableItems;
         let rect = window.windowUtils.getBoundsWithoutFlushing(draggedTab);
@@ -781,6 +765,7 @@
             : -rect.height * tabsInBetween.length;
         draggedTabTranslateY +=
           extraTranslate * (draggedTab.elementIndex > dropElement.elementIndex ? 1 : -1);
+        draggedTab.style.zIndex = '9';
         animateElement(draggedTab, draggedTabTranslateY);
       } catch (e) {
         console.error(e);
diff --git a/src/zen/split-view/ZenViewSplitter.mjs b/src/zen/split-view/ZenViewSplitter.mjs
index 28e3c9cf2..c22b4bd65 100644
--- a/src/zen/split-view/ZenViewSplitter.mjs
+++ b/src/zen/split-view/ZenViewSplitter.mjs
@@ -335,6 +335,7 @@ class nsZenViewSplitter extends nsZenDOMOperatedFeature {
       }
       const side = event.clientX - threshold > halfWidth ? 'right' : 'left';
       for (const browser of gBrowser.browsers) {
+        if (!browser) continue;
         const width = browser.getBoundingClientRect().width;
         // Only apply it to the left side because if we add it to the right side,
         // we wont be able to move the element to the left.