useGridCell.ts

/*
 * Copyright 2020 Adobe. All rights reserved.
 * This file is licensed to you under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License. You may obtain a copy
 * of the License at http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under
 * the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR REPRESENTATIONS
 * OF ANY KIND, either express or implied. See the License for the specific language
 * governing permissions and limitations under the License.
 */

import {DOMAttributes, FocusableElement, Key, RefObject} from '@react-types/shared';
import {focusSafely, isFocusVisible} from '@react-aria/interactions';
import {getActiveElement, getScrollParent, isFocusWithin, mergeProps, nodeContains, scrollIntoViewport} from '@react-aria/utils';
import {getFocusableTreeWalker} from '@react-aria/focus';
import {GridCollection, GridNode} from '@react-types/grid';
import {gridMap} from './utils';
import {GridState} from '@react-stately/grid';
import {KeyboardEvent as ReactKeyboardEvent, useRef} from 'react';
import {useLocale} from '@react-aria/i18n';
import {useSelectableItem} from '@react-aria/selection';

export interface GridCellProps {
  /** An object representing the grid cell. Contains all the relevant information that makes up the grid cell. */
  node: GridNode<unknown>,
  /** Whether the grid cell is contained in a virtual scroller. */
  isVirtualized?: boolean,
  /** Whether the cell or its first focusable child element should be focused when the grid cell is focused. */
  focusMode?: 'child' | 'cell',
  /** Whether selection should occur on press up instead of press down. */
  shouldSelectOnPressUp?: boolean,
  /** Indicates how many columns the data cell spans. */
  colSpan?: number,
  /**
   * Handler that is called when a user performs an action on the cell.
   * Please use onCellAction at the collection level instead.
   * @deprecated
   **/
  onAction?: () => void
}

export interface GridCellAria {
  /** Props for the grid cell element. */
  gridCellProps: DOMAttributes,
  /** Whether the cell is currently in a pressed state. */
  isPressed: boolean
}

/**
 * Provides the behavior and accessibility implementation for a cell in a grid.
 * @param props - Props for the cell.
 * @param state - State of the parent grid, as returned by `useGridState`.
 */
export function useGridCell<T, C extends GridCollection<T>>(props: GridCellProps, state: GridState<T, C>, ref: RefObject<FocusableElement | null>): GridCellAria {
  let {
    node,
    isVirtualized,
    focusMode = 'child',
    shouldSelectOnPressUp,
    onAction
  } = props;

  let {direction} = useLocale();
  let {keyboardDelegate, actions: {onCellAction}} = gridMap.get(state)!;

  // We need to track the key of the item at the time it was last focused so that we force
  // focus to go to the item when the DOM node is reused for a different item in a virtualizer.
  let keyWhenFocused = useRef<Key | null>(null);

  // Handles focusing the cell. If there is a focusable child,
  // it is focused, otherwise the cell itself is focused.
  let focus = () => {
    if (ref.current) {
      let treeWalker = getFocusableTreeWalker(ref.current);
      if (focusMode === 'child') {
        // If focus is already on a focusable child within the cell, early return so we don't shift focus
        if (isFocusWithin(ref.current) && ref.current !== getActiveElement()) {
          return;
        }

        let focusable = state.selectionManager.childFocusStrategy === 'last'
          ? last(treeWalker)
          : treeWalker.firstChild() as FocusableElement;
        if (focusable) {
          focusSafely(focusable);
          return;
        }
      }

      if (
        (keyWhenFocused.current != null && node.key !== keyWhenFocused.current) ||
        !isFocusWithin(ref.current)
      ) {
        focusSafely(ref.current);
      }
    }
  };

  let {itemProps, isPressed} = useSelectableItem({
    selectionManager: state.selectionManager,
    key: node.key,
    ref,
    isVirtualized,
    focus,
    shouldSelectOnPressUp,
    onAction: onCellAction ? () => onCellAction(node.key) : onAction,
    isDisabled: state.collection.size === 0
  });

  let onKeyDownCapture = (e: ReactKeyboardEvent) => {
    let activeElement = getActiveElement();
    if (!nodeContains(e.currentTarget, e.target as Element) || state.isKeyboardNavigationDisabled || !ref.current || !activeElement) {
      return;
    }

    let walker = getFocusableTreeWalker(ref.current);
    walker.currentNode = activeElement;

    switch (e.key) {
      case 'ArrowLeft': {
        // Find the next focusable element within the cell.
        let focusable: FocusableElement | null = direction === 'rtl'
          ? walker.nextNode() as FocusableElement
          : walker.previousNode() as FocusableElement;

        // Don't focus the cell itself if focusMode is "child"
        if (focusMode === 'child' && focusable === ref.current) {
          focusable = null;
        }

        e.preventDefault();
        e.stopPropagation();
        if (focusable) {
          focusSafely(focusable);
          scrollIntoViewport(focusable, {containingElement: getScrollParent(ref.current)});
        } else {
          // If there is no next focusable child, then move to the next cell to the left of this one.
          // This will be handled by useSelectableCollection. However, if there is no cell to the left
          // of this one, only one column, and the grid doesn't focus rows, then the next key will be the
          // same as this one. In that case we need to handle focusing either the cell or the first/last
          // child, depending on the focus mode.
          let prev = keyboardDelegate.getKeyLeftOf?.(node.key);
          if (prev !== node.key) {
            // We prevent the capturing event from reaching children of the cell, e.g. pickers.
            // We want arrow keys to navigate to the next cell instead. We need to re-dispatch
            // the event from a higher parent so it still bubbles and gets handled by useSelectableCollection.
            ref.current.parentElement?.dispatchEvent(
              new KeyboardEvent(e.nativeEvent.type, e.nativeEvent)
            );
            break;
          }

          if (focusMode === 'cell' && direction === 'rtl') {
            focusSafely(ref.current);
            scrollIntoViewport(ref.current, {containingElement: getScrollParent(ref.current)});
          } else {
            walker.currentNode = ref.current;
            focusable = direction === 'rtl'
              ? walker.firstChild() as FocusableElement
              : last(walker);
            if (focusable) {
              focusSafely(focusable);
              scrollIntoViewport(focusable, {containingElement: getScrollParent(ref.current)});
            }
          }
        }
        break;
      }
      case 'ArrowRight': {
        let focusable: FocusableElement | null = direction === 'rtl'
          ? walker.previousNode() as FocusableElement
          : walker.nextNode() as FocusableElement;

        if (focusMode === 'child' && focusable === ref.current) {
          focusable = null;
        }

        e.preventDefault();
        e.stopPropagation();
        if (focusable) {
          focusSafely(focusable);
          scrollIntoViewport(focusable, {containingElement: getScrollParent(ref.current)});
        } else {
          let next = keyboardDelegate.getKeyRightOf?.(node.key);
          if (next !== node.key) {
            // We prevent the capturing event from reaching children of the cell, e.g. pickers.
            // We want arrow keys to navigate to the next cell instead. We need to re-dispatch
            // the event from a higher parent so it still bubbles and gets handled by useSelectableCollection.
            ref.current.parentElement?.dispatchEvent(
              new KeyboardEvent(e.nativeEvent.type, e.nativeEvent)
            );
            break;
          }

          if (focusMode === 'cell' && direction === 'ltr') {
            focusSafely(ref.current);
            scrollIntoViewport(ref.current, {containingElement: getScrollParent(ref.current)});
          } else {
            walker.currentNode = ref.current;
            focusable = direction === 'rtl'
              ? last(walker)
              : walker.firstChild() as FocusableElement;
            if (focusable) {
              focusSafely(focusable);
              scrollIntoViewport(focusable, {containingElement: getScrollParent(ref.current)});
            }
          }
        }
        break;
      }
      case 'ArrowUp':
      case 'ArrowDown':
        // Prevent this event from reaching cell children, e.g. menu buttons. We want arrow keys to navigate
        // to the cell above/below instead. We need to re-dispatch the event from a higher parent so it still
        // bubbles and gets handled by useSelectableCollection.
        if (!e.altKey && nodeContains(ref.current, e.target as Element)) {
          e.stopPropagation();
          e.preventDefault();
          ref.current.parentElement?.dispatchEvent(
            new KeyboardEvent(e.nativeEvent.type, e.nativeEvent)
          );
        }
        break;
    }
  };

  // Grid cells can have focusable elements inside them. In this case, focus should
  // be marshalled to that element rather than focusing the cell itself.
  let onFocus = (e) => {
    keyWhenFocused.current = node.key;
    if (e.target !== ref.current) {
      // useSelectableItem only handles setting the focused key when
      // the focused element is the gridcell itself. We also want to
      // set the focused key when a child element receives focus.
      // If focus is currently visible (e.g. the user is navigating with the keyboard),
      // then skip this. We want to restore focus to the previously focused row/cell
      // in that case since the table should act like a single tab stop.
      if (!isFocusVisible()) {
        state.selectionManager.setFocusedKey(node.key);
      }
      return;
    }

    // If the cell itself is focused, wait a frame so that focus finishes propagatating
    // up to the tree, and move focus to a focusable child if possible.
    requestAnimationFrame(() => {
      if (focusMode === 'child' && getActiveElement() === ref.current) {
        focus();
      }
    });
  };

  let gridCellProps: DOMAttributes = mergeProps(itemProps, {
    role: 'gridcell',
    onKeyDownCapture,
    'aria-colspan': node.colSpan,
    'aria-colindex': node.colIndex != null ? node.colIndex + 1 : undefined, // aria-colindex is 1-based
    colSpan: isVirtualized ? undefined : node.colSpan,
    onFocus
  });

  if (isVirtualized) {
    gridCellProps['aria-colindex'] = (node.colIndex ?? node.index) + 1; // aria-colindex is 1-based
  }

  // When pressing with a pointer and cell selection is not enabled, usePress will be applied to the
  // row rather than the cell. However, when the row is draggable, usePress cannot preventDefault
  // on pointer down, so the browser will try to focus the cell which has a tabIndex applied.
  // To avoid this, remove the tabIndex from the cell briefly on pointer down.
  if (shouldSelectOnPressUp && gridCellProps.tabIndex != null && gridCellProps.onPointerDown == null) {
    gridCellProps.onPointerDown = (e) => {
      let el = e.currentTarget;
      let tabindex = el.getAttribute('tabindex');
      el.removeAttribute('tabindex');
      requestAnimationFrame(() => {
        if (tabindex != null) {
          el.setAttribute('tabindex', tabindex);
        }
      });
    };
  }

  return {
    gridCellProps,
    isPressed
  };
}

function last(walker: TreeWalker) {
  let next: FocusableElement | null = null;
  let last: FocusableElement | null = null;
  do {
    last = walker.lastChild() as FocusableElement | null;
    if (last) {
      next = last;
    }
  } while (last);
  return next;
}