Added drag functionality to update precendence for sort condition

mathesar_ui/src/components/sortable/README.md

@@ -0,0 +1,66 @@
+# Sortable
+
+> **Note**
+>
+> We'd like to move this code into its own package at some point, which is why it has no imports.
+
+This is a set of Svelte actions which make it easy to add drag-and-drop sorting to UI elements.
+
+## Usage
+
+1. Apply the `sortableContainer` action to the container element which contains the items you want to sort. This action takes two arguments:
+
+   - `getItems` — a function which returns the items to be sorted
+   - `onSort` — a function which is called when the user drops an item, with the new sorted items as its argument. Use this to update your data.
+
+1. Apply the `sortableItem` action to each item you want to be sortable.
+
+   These items must be descendants of the `sortableContainer` element.
+
+1. Apply the `sortableTrigger` action to the element which the user should drag to sort the item.
+
+   This element can be the same as the `sortableItem` element or a descendant of it.
+
+```svelte
+<script>
+  import { sortableContainer, sortableItem, sortableTrigger } from 'sortable';
+</script>
+
+<div
+  use:sortableContainer={{
+    getItems: () => items,
+    onSort: (newItems) => { items = newItems; }
+  }}
+>
+  {#each items as item}
+    <div use:sortableItem>
+      <div use:sortableTrigger>(trigger UI here)</div>
+      (more complex per-item UI here)
+    </div>
+  {/each}
+</div>
+
+<style lang="scss">
+  @import '/src/components/sortable/sortable.css';
+</style>
+```
+
+## Features
+
+- ✅ Actions-only API — no components and easy to style to your liking
+- ✅ Sortable trigger is defined separately from the sortable item, making drag handles possible within more complex UIs
+- ✅ Touch support
+- ✅ Animated transitions while sorting
+- ✅ Sort preview is done in pure CSS without manipulating the DOM before the sort is confirmed
+- ✅ No dependencies
+
+## Current limitations
+
+(Improvements welcome!)
+
+- Vertical sorting only
+- No support for nested sorting containers
+- Data cannot be updated in realtime while the user is dragging an item — updates are only applied when the user drops the item
+- No transitions after the user drops an item
+- Touch support is restricted to one touch at a time
+- The browser must support [pointer events](https://caniuse.com/pointer)

mathesar_ui/src/components/sortable/sortable.css

@@ -0,0 +1,21 @@
+[data-sortable-container] {
+  isolation: isolate;
+}
+
+[data-sortable-container].is-sorting [data-sortable-item]:not(.is-dragging) {
+  transition: transform 0.2s ease-in-out;
+}
+
+[data-sortable-item].is-dragging {
+  position: relative;
+  z-index: 1;
+}
+
+[data-sortable-trigger] {
+  cursor: grab;
+  touch-action: none;
+}
+
+[data-sortable-item].is-dragging [data-sortable-trigger] {
+  cursor: grabbing;
+}

mathesar_ui/src/components/sortable/sortable.ts

@@ -0,0 +1,266 @@
+const CONTAINER_ATTR = 'data-sortable-container';
+const ITEM_ATTR = 'data-sortable-item';
+const TRIGGER_ATTR = 'data-sortable-trigger';
+const DRAGGING_CLASS = 'is-dragging';
+const SORTING_CLASS = 'is-sorting';
+
+function clamp(value: number, min: number, max: number) {
+  return Math.min(Math.max(value, min), max);
+}
+
+interface Controller<Item> {
+  isSorting: boolean;
+  getItems: () => Item[];
+  onSort: (newItems: Item[]) => void;
+}
+
+interface ContainerElement<Item> extends HTMLElement {
+  sortableController: Controller<Item>;
+}
+
+function getItemFromTrigger(element: HTMLElement): HTMLElement | undefined {
+  if (element.hasAttribute(ITEM_ATTR)) return element;
+  return (element.closest(`[${ITEM_ATTR}]`) ?? undefined) as
+    | HTMLElement
+    | undefined;
+}
+
+function getContainerFromTrigger<Item>(
+  element: HTMLElement,
+): ContainerElement<Item> | undefined {
+  return (element.closest(`[${CONTAINER_ATTR}]`) ?? undefined) as
+    | ContainerElement<Item>
+    | undefined;
+}
+
+function preventDefault(e: Event) {
+  e.preventDefault();
+}
+
+function midpoint(rect: DOMRect) {
+  return rect.top + rect.height / 2;
+}
+
+function setTransform(element: HTMLElement, value: number) {
+  if (value === 0) element.style.removeProperty('transform');
+  element.style.setProperty('transform', `translateY(${value}px)`);
+}
+
+function analyze(container: HTMLElement, draggingItem: HTMLElement) {
+  const containerRect = container.getBoundingClientRect();
+  const items = container.querySelectorAll<HTMLElement>(`[${ITEM_ATTR}]`);
+  const itemIndexes = [...Array(items.length).keys()];
+  const rects = [...items].map((i) => i.getBoundingClientRect());
+  const draggingItemIndex = [...items].indexOf(draggingItem);
+  const draggingItemRect = rects[draggingItemIndex];
+  return {
+    items,
+    draggingItemIndex,
+    draggingItemHeight: draggingItemRect.height,
+    draggingItemMarginTop: rects[draggingItemIndex - 1]
+      ? draggingItemRect.top - rects[draggingItemIndex - 1].bottom
+      : 0,
+    draggingItemMarginBottom: rects[draggingItemIndex + 1]
+      ? rects[draggingItemIndex + 1].top - draggingItemRect.bottom
+      : 0,
+    /** The most extreme negative drag change possible for the item */
+    minDelta: containerRect.top - draggingItemRect.top,
+    /** The most extreme positive drag change possible for the item */
+    maxDelta: containerRect.bottom - draggingItemRect.bottom,
+    /**
+     * An array of lower bounds which describe the possible destination
+     * positions to which the dragging item can be moved. For each entry in this
+     * array, the index indicates the destination index, and the value indicates
+     * the minimum possible drag delta required to move the dragging item to
+     * that destination. Adjacent entries in this array can be used to validate
+     * a potential destination index, given the drag delta.
+     *
+     * The bounds are computed such that the leading edge of the dragging item
+     * must be moved to the midpoint of the destination item in order for the
+     * destination to be valid.
+     */
+    destinationsLowerBounds: itemIndexes.map((i) => {
+      if (i === 0) return -Infinity;
+      if (i <= draggingItemIndex) {
+        return midpoint(rects[i - 1]) - draggingItemRect.top;
+      }
+      return midpoint(rects[i]) - draggingItemRect.bottom;
+    }),
+  };
+}
+type Analysis = ReturnType<typeof analyze>;
+
+/**
+ * Walks through destinations from a best-guess starting point to efficiently
+ * find a matching destination.
+ *
+ * In theory we could make this function much simpler by searching through
+ * destinations using `findIndex` or similar, which would obviate the need to
+ * supply a `destinationToTry`. But, given that the new destination will almost
+ * always be adjacent to the old destination, we can make this much more
+ * efficient using a walking search. Efficiency is important because this is
+ * called on every pointer move event.
+ */
+function getDestination(
+  delta: number,
+  destinationToTry: number,
+  destinationsLowerBounds: number[],
+  /**
+   * The direction we're moving with our walking search. 0 indicates we haven't
+   * started walking yet.
+   */
+  searchDirection: -1 | 0 | 1 = 0,
+): number {
+  const target = destinationToTry + searchDirection;
+
+  // Test if lower bounds are met
+  if (searchDirection === -1 || searchDirection === 0) {
+    const lowerBound = destinationsLowerBounds[target];
+    if (delta < lowerBound) {
+      // Continue searching lower destinations
+      return getDestination(delta, target, destinationsLowerBounds, -1);
+    }
+  }
+
+  // Test if upper bounds are met
+  if (searchDirection === 1 || searchDirection === 0) {
+    const upperBound = destinationsLowerBounds[target + 1] ?? Infinity;
+    if (delta > upperBound) {
+      // Continue searching higher destinations
+      return getDestination(delta, target, destinationsLowerBounds, 1);
+    }
+  }
+
+  return target;
+}
+
+function getItemShift(
+  itemIndex: number,
+  analysis: Analysis,
+  destination: number,
+): number {
+  const {
+    draggingItemIndex,
+    draggingItemHeight,
+    draggingItemMarginBottom,
+    draggingItemMarginTop,
+  } = analysis;
+  if (itemIndex >= destination && itemIndex < draggingItemIndex) {
+    // We are shifting the item down
+    return draggingItemHeight + draggingItemMarginTop;
+  }
+  if (itemIndex <= destination && itemIndex > draggingItemIndex) {
+    // We are shifting the item up
+    return -1 * (draggingItemHeight + draggingItemMarginBottom);
+  }
+  return 0;
+}
+
+/** A Svelte action for the element containing all sortable items */
+export function sortableContainer<Item>(
+  node: HTMLElement,
+  options: {
+    getItems: () => Item[];
+    onSort: (newItems: Item[]) => void;
+  },
+) {
+  node.setAttribute(CONTAINER_ATTR, '');
+  const containerElement = node as ContainerElement<Item>;
+  containerElement.sortableController = {
+    isSorting: false,
+    getItems: options.getItems,
+    onSort: options.onSort,
+  };
+  return {};
+}
+
+/** A Svelte action for each sortable item */
+export function sortableItem(itemElement: Element) {
+  itemElement.setAttribute(ITEM_ATTR, '');
+  return {};
+}
+
+/** A Svelte action for the drag trigger element within each sortable item */
+export function sortableTrigger(triggerElement: HTMLElement) {
+  let containerElement: ContainerElement<unknown>;
+  let itemElement: HTMLElement;
+  let initialY: number;
+  let destination: number;
+  let analysis: Analysis;
+
+  function arrange() {
+    for (const [itemIndex, item] of analysis.items.entries()) {
+      if (itemIndex === analysis.draggingItemIndex) continue;
+      setTransform(item, getItemShift(itemIndex, analysis, destination));
+    }
+  }
+
+  function handlePointerMove(event: PointerEvent) {
+    const rawDelta = event.clientY - initialY;
+    const clampedDelta = clamp(rawDelta, analysis.minDelta, analysis.maxDelta);
+    setTransform(itemElement, clampedDelta);
+    const newDestination = getDestination(
+      clampedDelta,
+      destination,
+      analysis.destinationsLowerBounds,
+    );
+    if (newDestination !== destination) {
+      destination = newDestination;
+      arrange();
+    }
+  }
+
+  function handlePointerUp(event: PointerEvent) {
+    triggerElement.removeEventListener('pointermove', handlePointerMove);
+    triggerElement.removeEventListener('pointerup', handlePointerUp);
+    triggerElement.removeEventListener('pointercancel', handlePointerUp);
+    window.removeEventListener('selectstart', preventDefault);
+    triggerElement.releasePointerCapture(event.pointerId);
+    containerElement.classList.remove(SORTING_CLASS);
+    itemElement.classList.remove(DRAGGING_CLASS);
+    const controller = containerElement.sortableController;
+    controller.isSorting = false;
+
+    for (const item of analysis.items) {
+      setTransform(item, 0);
+    }
+
+    if (analysis.draggingItemIndex !== destination) {
+      const items = [...controller.getItems()];
+      const draggedItem = items.splice(analysis.draggingItemIndex, 1)[0];
+      items.splice(destination, 0, draggedItem);
+      void controller.onSort(items);
+    }
+  }
+
+  function handlePointerDown(event: PointerEvent) {
+    const item = getItemFromTrigger(triggerElement);
+    if (!item) return;
+    itemElement = item;
+    const container = getContainerFromTrigger(triggerElement);
+    if (!container) return;
+    containerElement = container;
+    containerElement.classList.add(SORTING_CLASS);
+    const controller = containerElement.sortableController;
+    if (controller.isSorting) return; // To prevent multi-touch
+    controller.isSorting = true;
+    itemElement.classList.add(DRAGGING_CLASS);
+    analysis = analyze(containerElement, itemElement);
+    destination = analysis.draggingItemIndex;
+    initialY = event.clientY;
+    triggerElement.setPointerCapture(event.pointerId);
+    triggerElement.addEventListener('pointermove', handlePointerMove);
+    triggerElement.addEventListener('pointerup', handlePointerUp);
+    triggerElement.addEventListener('pointercancel', handlePointerUp);
+    window.addEventListener('selectstart', preventDefault);
+  }
+
+  triggerElement.setAttribute(TRIGGER_ATTR, '');
+  triggerElement.addEventListener('pointerdown', handlePointerDown);
+  triggerElement.addEventListener('contextmenu', preventDefault);
+  return {
+    destroy() {
+      triggerElement.removeEventListener('pointerdown', handlePointerDown);
+    },
+  };
+}

mathesar_ui/src/icons/index.ts

@@ -71,6 +71,7 @@ import {
   faShareFromSquare,
   faXmark,
   faExternalLink,
+  faGrip,
 } from '@fortawesome/free-solid-svg-icons';
 import type { IconProps } from '@mathesar-component-library/types';
 import {
@@ -142,6 +143,7 @@ export const iconShare: IconProps = { data: faShareFromSquare };
 export const iconRecreate: IconProps = { data: faRedo };
 export const iconDisable: IconProps = { data: faXmark };
 export const iconOpenLinkInNewTab = { data: faExternalLink };
+export const iconGrip = { data: faGrip };
 
 // THINGS
 //