Method setupContainerDragHandlers

src/bases/TaskListView.ts:1237–1322

* Container-level drag event delegation. * Handles dragenter/dragover/drop/dragleave on the itemsContainer so it * works with both normal and virtual-scrolling rendering. * * IMPORTANT: Both dragenter and dragover must call e.preventDefault() to * tell the browser this container accepts dr

()

	 * the cursor is between cards or over the dragged card itself.
	 */
	private setupContainerDragHandlers(): void {
		if (!this.itemsContainer) return;

		// dragenter: required by the HTML5 DnD spec alongside dragover to
		// indicate this container is a valid drop zone.
		this.itemsContainer.addEventListener("dragenter", (e: DragEvent) => {
			if (!this.draggedTaskPath) return;
			e.preventDefault();
			if (e.dataTransfer) e.dataTransfer.dropEffect = "move";
		});

		this.itemsContainer.addEventListener("dragover", (e: DragEvent) => {
			if (!this.draggedTaskPath) return;

			// Always accept – must be unconditional so the browser keeps
			// the drop zone active even when the cursor is between cards.
			e.preventDefault();
			if (e.dataTransfer) e.dataTransfer.dropEffect = "move";

			// Throttle visual updates via rAF
			this.pendingDragClientY = e.clientY;
			if (!this.dragOverRafId) {
				this.dragOverRafId = window.requestAnimationFrame(() => {
					this.dragOverRafId = 0;

					const clientY = this.pendingDragClientY;
					this.pendingDragClientY = null;
					if (clientY === null) return;

					this.updateResolvedInsertionSlot(clientY);
				});
			}
		});

		this.itemsContainer.addEventListener("dragleave", (e: DragEvent) => {
			// Only clear if leaving the container entirely (not moving between children)
			const related = e.relatedTarget as HTMLElement | null;
			if (!related || !this.itemsContainer?.contains(related)) {
				this.clearDropIndicators();
			}
		});

		this.itemsContainer.addEventListener("drop", (e: DragEvent) => {
			void (async () => {
				e.preventDefault();
				if (!this.draggedTaskPath) return;

				if (!this.flushPendingInsertionSlot(e.clientY) && this.currentInsertionIndex < 0)
					return;

				const draggedPath = this.draggedTaskPath;
				const sourceGroupKey = this.dragGroupKey;
				const targetGroupKey = this.currentInsertionGroupKey;
				const targetVisiblePaths = this.getVisibleSortScopePathsForDrag(targetGroupKey);
				const insertionSegmentIndex = this.currentInsertionSegmentIndex;
				const insertionIndex = this.currentInsertionIndex;
				const dropTarget =
					insertionSegmentIndex >= 0 && insertionIndex >= 0