code property

String get code

Implementation

static String get code => r'''
(function() {
'use strict';

const GALLERY_SELECTOR =
  '[data-arcane-gallery][data-arcane-gallery-draggable="true"]';
const ITEM_SELECTOR = '[data-arcane-draggable-item="true"]';
const HANDLE_SELECTOR = '[data-arcane-drag-handle="true"]';
const DRAG_THRESHOLD_PX = 6;
const CLICK_SUPPRESSION_MS = 500;
const INTERACTIVE_SELECTOR =
  'a[href],button,input,textarea,select,option,summary,[contenteditable="true"],' +
  '[role="button"],[role="link"],[tabindex]';
const offsetsByGallery = new WeakMap();
const offsetsByGalleryId = new Map();

function finiteNumber(value, fallback) {
  const parsed = Number.parseFloat(String(value ?? ''));
  return Number.isFinite(parsed) ? parsed : fallback;
}

function crossedThreshold(deltaX, deltaY) {
  return Math.hypot(deltaX, deltaY) >= DRAG_THRESHOLD_PX;
}

function clamp(value, minimum, maximum) {
  if (minimum > maximum) {
    return (minimum + maximum) / 2;
  }
  return Math.min(maximum, Math.max(minimum, value));
}

function clampOffset({
  originX,
  originY,
  deltaX,
  deltaY,
  itemRect,
  galleryRect,
  inset = 4,
}) {
  const minDeltaX = galleryRect.left + inset - itemRect.left;
  const maxDeltaX = galleryRect.right - inset - itemRect.right;
  const minDeltaY = galleryRect.top + inset - itemRect.top;
  const maxDeltaY = galleryRect.bottom - inset - itemRect.bottom;
  return {
    x: originX + clamp(deltaX, minDeltaX, maxDeltaX),
    y: originY + clamp(deltaY, minDeltaY, maxDeltaY),
  };
}

function offsetStoreFor(gallery) {
  const stableId = gallery?.dataset?.arcaneGalleryDragId;
  if (stableId) {
    if (!offsetsByGalleryId.has(stableId)) {
      offsetsByGalleryId.set(stableId, new Map());
    }
    return offsetsByGalleryId.get(stableId);
  }
  if (!offsetsByGallery.has(gallery)) {
    offsetsByGallery.set(gallery, new Map());
  }
  return offsetsByGallery.get(gallery);
}

function storedOffsetFor(item) {
  const gallery = item.closest(GALLERY_SELECTOR);
  const key = item.dataset.arcaneDragKey;
  if (!(gallery && key)) {
    return null;
  }
  return offsetStoreFor(gallery).get(key) ?? null;
}

function offsetFor(item) {
  const stored = storedOffsetFor(item);
  if (stored) {
    return { x: stored.x, y: stored.y };
  }
  return {
    x: finiteNumber(item.dataset.arcaneDragX, 0),
    y: finiteNumber(item.dataset.arcaneDragY, 0),
  };
}

function writeOffset(item, offset) {
  const x = Math.round(offset.x);
  const y = Math.round(offset.y);
  const xText = String(x);
  const yText = String(y);
  const xCss = `${x}px`;
  const yCss = `${y}px`;
  if (item.dataset.arcaneDragX !== xText) {
    item.dataset.arcaneDragX = xText;
  }
  if (item.dataset.arcaneDragY !== yText) {
    item.dataset.arcaneDragY = yText;
  }
  if (item.style.getPropertyValue('--arcane-drag-x') !== xCss) {
    item.style.setProperty('--arcane-drag-x', xCss);
  }
  if (item.style.getPropertyValue('--arcane-drag-y') !== yCss) {
    item.style.setProperty('--arcane-drag-y', yCss);
  }
  const gallery = item.closest(GALLERY_SELECTOR);
  const key = item.dataset.arcaneDragKey;
  if (gallery && key) {
    offsetStoreFor(gallery).set(key, { x, y });
  }
}

function dragInsetFor(gallery) {
  return Math.max(0, finiteNumber(gallery.dataset.arcaneDragInset, 4));
}

function keyboardStepFor(gallery) {
  return Math.max(
    1,
    finiteNumber(gallery.dataset.arcaneDragKeyboardStep, 16),
  );
}

function pointerDragIsAvailable() {
  return !window.matchMedia?.('(pointer: coarse)').matches;
}

function dragTargetFor(target) {
  if (!(target instanceof Element)) {
    return null;
  }
  const handle = target.closest(HANDLE_SELECTOR);
  const item = handle?.closest(ITEM_SELECTOR);
  const gallery = item?.closest(GALLERY_SELECTOR);
  if (!(handle && item && gallery)) {
    return null;
  }
  const interactive = target.closest(INTERACTIVE_SELECTOR);
  if (interactive && interactive !== item && interactive !== handle) {
    return null;
  }
  return { handle, item, gallery };
}

function keyboardTargetFor(target) {
  if (!(target instanceof Element)) {
    return null;
  }
  const item = target.closest(ITEM_SELECTOR);
  const gallery = item?.closest(GALLERY_SELECTOR);
  if (!(item && gallery)) {
    return null;
  }
  const interactive = target.closest(INTERACTIVE_SELECTOR);
  if (interactive && interactive !== item) {
    return null;
  }
  return { item, gallery };
}

function createAnnouncer() {
  const existing = document.querySelector('.arcane-gallery-drag-announcer');
  if (existing) {
    return existing;
  }
  const announcer = document.createElement('div');
  announcer.className = 'arcane-gallery-drag-announcer';
  announcer.setAttribute('role', 'status');
  announcer.setAttribute('aria-live', 'polite');
  announcer.setAttribute('aria-atomic', 'true');
  document.body.appendChild(announcer);
  return announcer;
}

function announce(message) {
  const announcer = createAnnouncer();
  announcer.textContent = '';
  window.setTimeout(() => {
    announcer.textContent = message;
  }, 0);
}

function restoreOffsets(gallery) {
  if (!gallery?.matches?.(GALLERY_SELECTOR)) {
    return;
  }
  const store = offsetStoreFor(gallery);
  gallery.querySelectorAll(ITEM_SELECTOR).forEach((item) => {
    const key = item.dataset.arcaneDragKey;
    const stored = key ? store.get(key) : null;
    if (stored) {
      writeOffset(item, stored);
    }
  });
}

function reclampGallery(gallery) {
  if (
    !gallery?.matches?.(GALLERY_SELECTOR) ||
    gallery.clientWidth <= 0 ||
    gallery.clientHeight <= 0
  ) {
    return;
  }
  const galleryRect = gallery.getBoundingClientRect();
  const inset = dragInsetFor(gallery);
  gallery.querySelectorAll(ITEM_SELECTOR).forEach((item) => {
    const origin = offsetFor(item);
    const next = clampOffset({
      originX: origin.x,
      originY: origin.y,
      deltaX: 0,
      deltaY: 0,
      itemRect: item.getBoundingClientRect(),
      galleryRect,
      inset,
    });
    if (next.x !== origin.x || next.y !== origin.y) {
      writeOffset(item, next);
    }
  });
}

if (typeof window === 'undefined') {
  return;
}

window.ArcaneGalleryDrag = {
  crossedThreshold,
  clampOffset,
  refresh: () => {
    if (typeof document !== 'undefined') {
      document.querySelectorAll(GALLERY_SELECTOR).forEach(observeGallery);
    }
  },
};

if (typeof document === 'undefined') {
  return;
}

let active = null;
let suppressedClick = null;
let zOrder = 10;
const restoreScheduled = new WeakSet();

const resizeObserver = 'ResizeObserver' in window
  ? new ResizeObserver((entries) => {
      for (const entry of entries) {
        reclampGallery(entry.target);
      }
    })
  : null;

function scheduleRestore(gallery) {
  if (!gallery || restoreScheduled.has(gallery)) {
    return;
  }
  restoreScheduled.add(gallery);
  window.requestAnimationFrame(() => {
    restoreScheduled.delete(gallery);
    restoreOffsets(gallery);
    reclampGallery(gallery);
  });
}

function observeGallery(gallery) {
  if (!gallery) {
    return;
  }
  if (gallery.dataset.arcaneDragObserved !== 'true') {
    gallery.dataset.arcaneDragObserved = 'true';
    resizeObserver?.observe(gallery);
  }
  scheduleRestore(gallery);
}

function refreshAll() {
  document.querySelectorAll(GALLERY_SELECTOR).forEach(observeGallery);
}

function finishDrag(pointerId, cancelled = false) {
  if (!active || pointerId !== active.pointerId) {
    return;
  }
  const current = active;
  active = null;
  const { item, gallery, dragging, origin } = current;
  if (cancelled && dragging) {
    writeOffset(item, origin);
  }
  try {
    if (item.hasPointerCapture(pointerId)) {
      item.releasePointerCapture(pointerId);
    }
  } catch (_) {
    // Browsers can release pointer capture automatically.
  }
  item.classList.remove('is-arcane-gallery-dragging');
  gallery.classList.remove('is-arcane-gallery-drag-active');
  if (dragging && !cancelled) {
    suppressedClick = {
      item,
      until: performance.now() + CLICK_SUPPRESSION_MS,
    };
    announce(
      'Item repositioned. Use Shift and the arrow keys to fine tune it.',
    );
  }
  if (gallery.dataset.packing === 'true') {
    window.ArcaneGallery?.observe?.(gallery);
  }
}

document.addEventListener(
  'pointerdown',
  (event) => {
    if (
      active ||
      !pointerDragIsAvailable() ||
      event.button !== 0 ||
      event.isPrimary === false ||
      event.altKey ||
      event.ctrlKey ||
      event.metaKey ||
      event.shiftKey
    ) {
      return;
    }
    const target = dragTargetFor(event.target);
    if (!target) {
      return;
    }
    const origin = offsetFor(target.item);
    target.item.setAttribute('draggable', 'false');
    target.item.style.zIndex = String(++zOrder);
    active = {
      ...target,
      pointerId: event.pointerId,
      startX: event.clientX,
      startY: event.clientY,
      startRect: target.item.getBoundingClientRect(),
      galleryRect: target.gallery.getBoundingClientRect(),
      origin,
      dragging: false,
    };
    try {
      target.item.setPointerCapture(event.pointerId);
    } catch (_) {
      // Dragging still works while the pointer remains over the document.
    }
  },
  true,
);

document.addEventListener(
  'pointermove',
  (event) => {
    if (!active || event.pointerId !== active.pointerId) {
      return;
    }
    const deltaX = event.clientX - active.startX;
    const deltaY = event.clientY - active.startY;
    if (!active.dragging) {
      if (!crossedThreshold(deltaX, deltaY)) {
        return;
      }
      active.dragging = true;
      active.item.classList.add('is-arcane-gallery-dragging');
      active.gallery.classList.add('is-arcane-gallery-drag-active');
    }
    event.preventDefault();
    writeOffset(
      active.item,
      clampOffset({
        originX: active.origin.x,
        originY: active.origin.y,
        deltaX,
        deltaY,
        itemRect: active.startRect,
        galleryRect: active.galleryRect,
        inset: dragInsetFor(active.gallery),
      }),
    );
  },
  true,
);

document.addEventListener(
  'pointerup',
  (event) => finishDrag(event.pointerId),
  true,
);
document.addEventListener(
  'pointercancel',
  (event) => finishDrag(event.pointerId, true),
  true,
);
document.addEventListener(
  'lostpointercapture',
  (event) => {
    if (
      active &&
      event.pointerId === active.pointerId &&
      event.target === active.item
    ) {
      finishDrag(event.pointerId, true);
    }
  },
  true,
);

document.addEventListener(
  'click',
  (event) => {
    if (!suppressedClick) {
      return;
    }
    if (performance.now() > suppressedClick.until) {
      suppressedClick = null;
      return;
    }
    if (event.composedPath().includes(suppressedClick.item)) {
      event.preventDefault();
      event.stopImmediatePropagation();
      suppressedClick = null;
    }
  },
  true,
);

document.addEventListener(
  'keydown',
  (event) => {
    if (active && event.key === 'Escape') {
      writeOffset(active.item, active.origin);
      finishDrag(active.pointerId, true);
      event.preventDefault();
      return;
    }
    if (!event.shiftKey || !event.key.startsWith('Arrow')) {
      return;
    }
    const target = keyboardTargetFor(event.target);
    if (!target) {
      return;
    }
    const step = keyboardStepFor(target.gallery);
    const direction = {
      ArrowLeft: [-step, 0],
      ArrowRight: [step, 0],
      ArrowUp: [0, -step],
      ArrowDown: [0, step],
    }[event.key];
    if (!direction) {
      return;
    }
    event.preventDefault();
    const origin = offsetFor(target.item);
    const next = clampOffset({
      originX: origin.x,
      originY: origin.y,
      deltaX: direction[0],
      deltaY: direction[1],
      itemRect: target.item.getBoundingClientRect(),
      galleryRect: target.gallery.getBoundingClientRect(),
      inset: dragInsetFor(target.gallery),
    });
    if (
      Math.round(next.x) === Math.round(origin.x) &&
      Math.round(next.y) === Math.round(origin.y)
    ) {
      announce('Item is already at the edge of the gallery.');
      return;
    }
    writeOffset(target.item, next);
    target.item.style.zIndex = String(++zOrder);
    announce(`Item moved ${event.key.replace('Arrow', '').toLowerCase()}.`);
  },
  true,
);

const mutationObserver = 'MutationObserver' in window
  ? new MutationObserver((mutations) => {
      for (const mutation of mutations) {
        if (mutation.type === 'attributes') {
          const gallery = mutation.target.closest?.(GALLERY_SELECTOR);
          if (gallery) {
            observeGallery(gallery);
          }
          continue;
        }
        for (const node of mutation.addedNodes) {
          if (!node || node.nodeType !== 1) {
            continue;
          }
          if (node.matches?.(GALLERY_SELECTOR)) {
            observeGallery(node);
          }
          node.querySelectorAll?.(GALLERY_SELECTOR).forEach(observeGallery);
        }
      }
    })
  : null;

function start() {
  refreshAll();
  mutationObserver?.observe(document.documentElement || document.body, {
    childList: true,
    subtree: true,
    attributes: true,
    attributeFilter: [
      'style',
      'data-arcane-drag-x',
      'data-arcane-drag-y',
    ],
  });
}

if (document.readyState === 'loading') {
  document.addEventListener('DOMContentLoaded', start, { once: true });
} else {
  start();
}
})();
''';