PositionObserver rework

clauderic · Sep 12, 2024 · 9479be0 · 9479be0
1 parent 8053e4b
commit 9479be0
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diff --git a/.changeset/collision-observer.md b/.changeset/collision-observer.md
@@ -1,5 +1,6 @@
 ---
 '@dnd-kit/abstract': patch
+'@dnd-kit/dom': patch
 ---
 
-Reduce the how frequently collisions are re-computed when the position of the drag operation does not change.
+Rework how collisions are detected and how the position of elements is observed using a new `PositionObserver`.
diff --git a/packages/abstract/src/core/collision/observer.ts b/packages/abstract/src/core/collision/observer.ts
@@ -1,4 +1,4 @@
-import {batch, signal, untracked, type Signal, effects} from '@dnd-kit/state';
+import {signal, untracked, type Signal, effects} from '@dnd-kit/state';
 import type {Coordinates} from '@dnd-kit/geometry';
 
 import type {DragDropManager} from '../manager/index.ts';
@@ -49,25 +49,9 @@ export class CollisionObserver<
     );
   }
 
-  forceUpdateCount = signal(0);
-
-  public forceUpdate(refresh = true) {
+  public forceUpdate() {
     untracked(() => {
-      const {source} = this.manager.dragOperation;
-
-      batch(() => {
-        if (refresh) {
-          for (const droppable of this.manager.registry.droppables) {
-            if (source && !droppable.accepts(source)) {
-              continue;
-            }
-
-            droppable.refreshShape();
-          }
-        }
-
-        this.#collisions.value = this.computeCollisions();
-      });
+      this.#collisions.value = this.computeCollisions();
     });
   }
 

diff --git a/packages/abstract/src/core/entities/droppable/droppable.ts b/packages/abstract/src/core/entities/droppable/droppable.ts
@@ -90,8 +90,4 @@ export class Droppable<
   public get isDropTarget() {
     return this.manager?.dragOperation.target?.id === this.id;
   }
-
-  public refreshShape() {
-    // To be implemented by subclasses
-  }
 }
diff --git a/packages/dom/src/core/entities/droppable/droppable.ts b/packages/dom/src/core/entities/droppable/droppable.ts
@@ -5,14 +5,9 @@ import type {
 } from '@dnd-kit/abstract';
 import {defaultCollisionDetection} from '@dnd-kit/collision';
 import type {CollisionDetector} from '@dnd-kit/collision';
-import {Signal, reactive, signal, untracked} from '@dnd-kit/state';
+import {reactive, untracked} from '@dnd-kit/state';
 import type {Shape} from '@dnd-kit/geometry';
-import {
-  DOMRectangle,
-  getDocument,
-  scheduler,
-  getFirstScrollableAncestor,
-} from '@dnd-kit/dom/utilities';
+import {DOMRectangle, PositionObserver} from '@dnd-kit/dom/utilities';
 
 import type {DragDropManager} from '../../manager/manager.ts';
 
@@ -33,6 +28,25 @@ export class Droppable<T extends Data = Data> extends AbstractDroppable<
     manager: DragDropManager | undefined
   ) {
     const {collisionDetector = defaultCollisionDetection} = input;
+    const updateShape = (boundingClientRect?: DOMRectReadOnly | null) => {
+      const {element} = this;
+
+      if (!element || boundingClientRect === null) {
+        this.shape = undefined;
+        return undefined;
+      }
+
+      const updatedShape = new DOMRectangle(element);
+
+      const shape = untracked(() => this.shape);
+      if (updatedShape && shape?.equals(updatedShape)) {
+        return shape;
+      }
+
+      this.shape = updatedShape;
+
+      return updatedShape;
+    };
 
     super(
       {
@@ -45,74 +59,25 @@ export class Droppable<T extends Data = Data> extends AbstractDroppable<
             if (!manager) return;
 
             const {dragOperation} = manager;
-
-            if (element && dragOperation.status.initialized) {
-              const scrollableAncestor = getFirstScrollableAncestor(element);
-              const doc = getDocument(element);
-              const root =
-                scrollableAncestor === doc.scrollingElement
-                  ? doc
-                  : scrollableAncestor;
-              const intersectionObserver = new IntersectionObserver(
-                (entries) => {
-                  const [entry] = entries.slice(-1);
-                  const {width, height} = entry.boundingClientRect;
-
-                  if (!width && !height) {
-                    return;
-                  }
-
-                  this.visible = entry.isIntersecting;
-                },
-                {
-                  root: root ?? doc,
-                  rootMargin: '40%',
-                }
-              );
-
-              const mutationObserver = new MutationObserver(() =>
-                scheduler.schedule(this.refreshShape)
+            const {source} = dragOperation;
+            const observePosition =
+              source &&
+              dragOperation.status.initialized &&
+              element &&
+              this.accepts(source);
+
+            if (observePosition) {
+              const positionObserver = new PositionObserver(
+                element,
+                updateShape
               );
 
-              const resizeObserver = new ResizeObserver(() =>
-                scheduler.schedule(this.refreshShape)
-              );
-
-              if (element.parentElement) {
-                mutationObserver.observe(element.parentElement, {
-                  childList: true,
-                });
-              }
-
-              resizeObserver.observe(element);
-              intersectionObserver.observe(element);
-
               return () => {
+                positionObserver.disconnect();
                 this.shape = undefined;
-                this.visible = undefined;
-                resizeObserver.disconnect();
-                mutationObserver.disconnect();
-                intersectionObserver.disconnect();
               };
             }
           },
-          () => {
-            const {manager} = this;
-
-            if (!manager) return;
-
-            const {dragOperation} = manager;
-            const {status} = dragOperation;
-            const source = untracked(() => dragOperation.source);
-
-            if (status.initialized) {
-              if (source?.type != null && !this.accepts(source)) {
-                return;
-              }
-
-              scheduler.schedule(this.refreshShape);
-            }
-          },
           () => {
             if (this.manager?.dragOperation.status.initialized) {
               return () => {
@@ -125,54 +90,11 @@ export class Droppable<T extends Data = Data> extends AbstractDroppable<
       manager
     );
 
-    this.internal = {
-      element: signal(element),
-    };
-    this.refreshShape = this.refreshShape.bind(this);
-
-    /*
-     * If a droppable target mounts during a drag operation, assume it is visible
-     * so that we can update its shape immediately.
-     */
-    if (this.manager?.dragOperation.status.initialized) {
-      this.visible = true;
-    }
+    this.refreshShape = () => updateShape();
   }
 
   @reactive
-  public accessor visible: Boolean | undefined;
-
-  @reactive
-  public accessor placeholder: Element | undefined;
-
-  public set element(value: Element | undefined) {
-    this.internal.element.value = value;
-  }
-
-  public get element() {
-    return this.placeholder ?? this.internal?.element.value;
-  }
-
-  public refreshShape(ignoreTransform?: boolean): Shape | undefined {
-    const {element, shape} = this;
-
-    if (!element || this.visible === false) {
-      this.shape = undefined;
-      return undefined;
-    }
-
-    const updatedShape = new DOMRectangle(element, ignoreTransform);
-
-    if (updatedShape && shape?.equals(updatedShape)) {
-      return shape;
-    }
-
-    this.shape = updatedShape;
-
-    return updatedShape;
-  }
+  public accessor element: Element | undefined;
 
-  internal: {
-    element: Signal<Element | undefined>;
-  };
+  public refreshShape: () => Shape | undefined;
 }