Easier scrolling while dragging in sortable

src/back/routes/common/sortable/sortable.css

@@ -1,3 +1,28 @@
+@keyframes sortable-enter {
+	from {
+		transform: scale(0);
+	}
+
+	to {
+		transform: scale(1);
+	}
+}
+.sortable-wrapper {
+	.edge-detector {
+		height: 30px;
+		position: fixed;
+		left: 0;
+		width: 100%;
+		display: none;
+		z-index: 2;
+	}
+
+	&:has(.is-dragged) {
+		.edge-detector {
+			display: block;
+		}
+	}
+
 	.sortable {
 		display: grid;
 		grid-template-columns: 1fr;
@@ -6,6 +31,9 @@
 
 		.sortable__element {
 			height: var(--element-height);
+			grid-column: 1/2;
+			grid-row: calc((var(--index) + 1) * 3 + 1) / calc((var(--index) + 1) * 3 + 3);
+
 			background-color: white;
 			box-sizing: border-box;
 			min-width: 400px;
@@ -16,8 +44,8 @@
 			justify-content: center;
 			cursor: move;
 			user-select: none;
-		grid-column: 1/2;
-		grid-row: calc((var(--index) + 1) * 3 + 1) / calc((var(--index) + 1) * 3 + 3);
+
+			animation: sortable-enter 100ms;
 
 			&.is-dragged {
 				opacity: 0.2;
@@ -26,8 +54,8 @@
 
 		.sortable__hole {
 			grid-column: 1/2;
-		opacity: 0.5;
 			z-index: 1;
+			/* background-color: red; */
 			pointer-events: none;
 			grid-row: calc((var(--index) + 1) * 3 + 2) / calc((var(--index) + 1) * 3 + 5);
 
@@ -45,7 +73,8 @@
 		.sortable__spacer {
 			grid-column: 1/2;
 			grid-row: calc((var(--index) + 1) * 3 + 3) / calc((var(--index) + 1) * 3 + 4);
-		transition: all 100ms;
+			transition: all 200ms;
 			height: 8px;
 		}
 	}
+}

src/back/routes/common/sortable/sortable.stimulus.ts

@@ -1,5 +1,11 @@
 import { Controller } from "stimulus";
 
+async function sleep(time: number) {
+	return new Promise((resolve) => {
+		setTimeout(resolve, time);
+	});
+}
+
 export default class Sortable extends Controller {
 	dragged_element: HTMLDivElement | null = null;
 
@@ -79,7 +85,7 @@ export default class Sortable extends Controller {
 	connect() {
 		this.element.querySelectorAll(".sortable__element").forEach((element) => {
 			element.addEventListener("dragstart", (e: DragEvent) => {
-				event.dataTransfer.effectAllowed = "move";
+				e.dataTransfer.effectAllowed = "move";
 				const target = e.target as HTMLDivElement;
 				this.dragged_element = target;
 				setTimeout(() => {
@@ -94,6 +100,32 @@ export default class Sortable extends Controller {
 				target.classList.remove("is-dragged");
 			});
 		});
+		this.element
+			.querySelectorAll(".edge-detector")
+			.forEach((detector: HTMLDivElement) => {
+				let is_hovered = false;
+				detector.addEventListener("dragenter", async (e) => {
+					e.preventDefault();
+					const target = e.target as HTMLDivElement;
+					const step = parseInt(target.getAttribute("data-step"));
+					is_hovered = true;
+					while (is_hovered && this.dragged_element) {
+						window.scrollTo(window.scrollX, window.scrollY + step);
+						await sleep(16);
+					}
+				});
+
+				detector.addEventListener("dragover ", (e) => {
+					// necessary for drag events;
+					e.preventDefault();
+				});
+
+				detector.addEventListener("dragleave", (e) => {
+					const target = e.target as HTMLDivElement;
+					e.preventDefault();
+					is_hovered = false;
+				});
+			});
 		this.element
 			.querySelectorAll(".sortable__hole")
 			.forEach((dropElement: HTMLDivElement) =>

src/back/routes/common/sortable/sortable.tsx

@@ -2,7 +2,7 @@ import { TempstreamJSX } from "tempstream";
 
 export function sortable({ items }: { items: JSX.Element[] }) {
 	return (
-		<div>
+		<div class="sortable-wrapper">
 			<div
 				data-controller="sortable"
 				class="sortable"
@@ -10,6 +10,8 @@ export function sortable({ items }: { items: JSX.Element[] }) {
 					items.length * 2
 				}, minmax(8px, min-content))`}
 			>
+				<div class="edge-detector" style="top: 0" data-step="-10"></div>
+				<div class="edge-detector" style="bottom: 0" data-step="10"></div>
 				<div class="sortable__hole" data-index="-1" style="--index: -1"></div>
 				<div class="sortable__spacer" data-index="-1" style="--index: -1"></div>
 				{items.map((item, index) => (

src/back/routes/demos/sortable.page.tsx

@@ -16,9 +16,22 @@ export default new (class SortableDemoPage extends Page {
 		return html(
 			ctx,
 			"SortableDemo",
-			sortable({
-				items: ["One", "Two", "Three", "Four", "Five"].map((e) => <div>{e}</div>),
-			})
+			<div>
+				<h2>Short list</h2>
+				{sortable({
+					items: ["One", "Two", "Three", "Four", "Five"].map((e) => (
+						<div>{e}</div>
+					)),
+				})}
+
+				<h2>Long list</h2>
+				{sortable({
+					items: "a"
+						.repeat(100)
+						.split("")
+						.map((_, index) => <div>{index}</div>),
+				})}
+			</div>
 		);
 	}
 })();