/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsISupports.idl"

typedef short TextBoundaryType;

interface nsIAccessible;
interface nsIAccessibleText;
interface nsIAccessibleTraversalRule;
interface nsIAccessiblePivotObserver;

/**
 * The pivot interface encapsulates a reference to a single place in an accessible
 * subtree. The pivot is a point or a range in the accessible tree. This interface
 * provides traversal methods to move the pivot to next/prev state that complies 
 * to a given rule.
 */
[scriptable, uuid(15ff23de-879e-47ea-b536-6532466108c5)]
interface nsIAccessiblePivot : nsISupports
{
  const TextBoundaryType CHAR_BOUNDARY = 0;
  const TextBoundaryType WORD_BOUNDARY = 1;
  const TextBoundaryType LINE_BOUNDARY = 2;
  const TextBoundaryType ATTRIBUTE_RANGE_BOUNDARY = 3;

  /**
   * The accessible the pivot is currently pointed at.
   */
  attribute nsIAccessible position;

  /**
   * The root of the subtree in which the pivot traverses.
   */
  readonly attribute nsIAccessible root;

  /**
   * The start offset of the text range the pivot points at, otherwise -1.
   */
  readonly attribute long startOffset;

  /**
   * The end offset of the text range the pivot points at, otherwise -1.
   */
  readonly attribute long endOffset;

  /**
   * Set the pivot's text range in a text accessible.
   *
   * @param aTextAccessible [in] the text accessible that contains the desired
   *                        range.
   * @param aStartOffset    [in] the start offset to set.
   * @param aEndOffset      [in] the end offset to set.
   * @throws NS_ERROR_INVALID_ARG when the offset exceeds the accessible's
   *   character count.
   */
  void setTextRange(in nsIAccessibleText aTextAccessible,
                    in long aStartOffset, in long aEndOffset);

  /**
   * Move pivot to next object, from current position or given anchor,
   * complying to given traversal rule.
   *
   * @param aRule         [in] traversal rule to use.
   * @param aAnchor       [in] accessible to start search from, if not provided,
   *                           current position will be used.
   * @param aIncludeStart [in] include anchor accessible in search.
   * @return true on success, false if there are no new nodes to traverse to.
   */
  [optional_argc] boolean moveNext(in nsIAccessibleTraversalRule aRule,
                                   [optional] in nsIAccessible aAnchor,
                                   [optional] in boolean aIncludeStart);

  /**
   * Move pivot to previous object, from current position or given anchor,
   * complying to given traversal rule.
   *
   * @param aRule         [in] traversal rule to use.
   * @param aAnchor       [in] accessible to start search from, if not provided,
   *                           current position will be used.
   * @param aIncludeStart [in] include anchor accessible in search.
   * @return true on success, false if there are no new nodes to traverse to.
   */
  [optional_argc] boolean movePrevious(in nsIAccessibleTraversalRule aRule,
                                       [optional] in nsIAccessible aAnchor,
                                       [optional] in boolean aIncludeStart);

  /**
   * Move pivot to first object in subtree complying to given traversal rule.
   *
   * @param aRule [in] traversal rule to use.
   * @return true on success, false if there are no new nodes to traverse to.
   */
  boolean moveFirst(in nsIAccessibleTraversalRule aRule);

  /**
   * Move pivot to last object in subtree complying to given traversal rule.
   *
   * @param aRule [in] traversal rule to use.
   * @return true on success, false if there are no new nodes to traverse to.
   */
  boolean moveLast(in nsIAccessibleTraversalRule aRule);

  /**
   * Move pivot to next text range.
   *
   * @param aBoundary [in] type of boundary for next text range, character, word,
   *                  etc.
   * @return true on success, false if there are is no more text.
   */
  boolean moveNextByText(in TextBoundaryType aBoundary);
  
  /**
   * Move pivot to previous text range.
   *
   * @param aBoundary [in] type of boundary for previous text range, character,
   *                  word, etc.
   * @return true on success, false if there are is no more text.
   */
  boolean movePreviousByText(in TextBoundaryType aBoundary);

  /**
   * Add an observer for pivot changes.
   *
   * @param aObserver [in] the observer object to be notified of pivot changes.
   */
  void addObserver(in nsIAccessiblePivotObserver aObserver);

  /**
   * Remove an observer for pivot changes.
   *
   * @param aObserver [in] the observer object to remove from being notified.
   */
  void removeObserver(in nsIAccessiblePivotObserver aObserver);
};

/**
 * An observer interface for pivot changes.
 */
[scriptable, uuid(b6508c5e-c081-467d-835c-613eedf9ee9b)]
interface nsIAccessiblePivotObserver : nsISupports
{
  /**
   * Called when the pivot changes.
   *
   * @param aPivot         [in] the pivot that has changed.
   * @param aOldAccessible [in] the old pivot position before the change, or null.
   * @param aOldStart      [in] the old start offset, or -1.
   * @param aOldEnd        [in] the old end offset, or -1.
   */
  void onPivotChanged(in nsIAccessiblePivot aPivot,
                      in nsIAccessible aOldAccessible,
                      in long aOldStart, in long aOldEnd);
};

[scriptable, uuid(307d98b6-dba9-49cf-ba17-ef8b053044eb)]
interface nsIAccessibleTraversalRule : nsISupports
{
  /* Ignore this accessible object */
  const unsigned short FILTER_IGNORE = 0x0;
  /* Accept this accessible object */
  const unsigned short FILTER_MATCH = 0x1;
  /* Don't traverse accessibles children */
  const unsigned short FILTER_IGNORE_SUBTREE = 0x2;

  /* Pre-filters */
  const unsigned long PREFILTER_INVISIBLE     = 0x00000001;
  const unsigned long PREFILTER_OFFSCREEN     = 0x00000002;
  const unsigned long PREFILTER_NOT_FOCUSABLE = 0x00000004;

  /**
   * Pre-filter bitfield to filter out obviously ignorable nodes and lighten
   * the load on match().
   */
  readonly attribute unsigned long preFilter;

  /**
   * Retrieve a list of roles that the traversal rule should test for. Any node
   * with a role not in this list will automatically be ignored. An empty list
   * will match all roles. It should be assumed that this method is called once
   * at the start of a traversal, so changing the method's return result after
   * that would have no affect.
   *
   * @param aRoles [out] an array of the roles to match.
   * @param aCount [out] the length of the array.
   */
  void getMatchRoles([array, size_is(aCount)]out unsigned long aRoles,
                     [retval]out unsigned long aCount);

  /**
   * Determines if a given accessible is to be accepted in our traversal rule
   *
   * @param aAccessible [in] accessible to examine.
   * @return a bitfield of FILTER_MATCH and FILTER_IGNORE_SUBTREE.
   */
  unsigned short match(in nsIAccessible aAccessible);
};
