drupal/misc/tabledrag.js

// $Id$

/**
 * Drag and drop table rows with field manipulation.
 *
 * Using the drupal_add_tabledrag() function, any table with weights or parent
 * relationships may be made into draggable tables. Columns containing a field
 * may optionally be hidden, providing a better user experience.
 *
 * Created tableDrag instances may be modified with custom behaviors by
 * overriding the .onDrag, .onDrop, .row.onSwap, and .row.onIndent methods.
 * See blocks.js for an example of adding additional functionality to tableDrag.
 */
Drupal.behaviors.tableDrag = function(context) {
  for (var base in Drupal.settings.tableDrag) {
    if (!$('#' + base + '.tabledrag-processed', context).size()) {
      var tableSettings = Drupal.settings.tableDrag[base];

      $('#' + base).filter(':not(.tabledrag-processed)').each(function() {
        // Create the new tableDrag instance. Save in the Drupal variable
        // to allow other scripts access to the object.
        Drupal.tableDrag[base] = new Drupal.tableDrag(this, tableSettings);
      });

      $('#' + base).addClass('tabledrag-processed');
    }
  }
};

/**
 * Constructor for the tableDrag object. Provides table and field manipulation.
 *
 * @param table
 *   DOM object for the table to be made draggable.
 * @param tableSettings
 *   Settings for the table added via drupal_add_dragtable().
 */
Drupal.tableDrag = function(table, tableSettings) {
  var self = this;

  // Required object variables.
  this.table = table;
  this.tableSettings = tableSettings;
  this.dragObject = null; // Used to hold information about a current drag operation.
  this.rowObject = null; // Provides operations for row manipulation.
  this.oldRowElement = null; // Remember the previous element.
  this.oldY = 0; // Used to determine up or down direction from last mouse move.
  this.changed = false; // Whether anything in the entire table has changed.
  this.maxDepth = 0; // Maximum amount of allowed parenting.
  this.rtl = $(this.table).css('direction') == 'rtl' ? -1 : 1; // Direction of the table.

  // Configure the scroll settings.
  this.scrollSettings = { amount: 4, interval: 50, trigger: 70 };
  this.scrollInterval = null;
  this.scrollY = 0;
  this.windowHeight = 0;

  // Check this table's settings to see if there are parent relationships in
  // this table. For efficiency, large sections of code can be skipped if we
  // don't need to track horizontal movement and indentations.
  this.indentEnabled = false;
  for (group in tableSettings) {
    for (n in tableSettings[group]) {
      if (tableSettings[group][n]['relationship'] == 'parent') {
        this.indentEnabled = true;
      }
      if (tableSettings[group][n]['limit'] > 0) {
        this.maxDepth = tableSettings[group][n]['limit'];
      }
    }
  }
  if (this.indentEnabled) {
    this.oldX = 0;
    this.indentCount = 1; // Total width of indents, set in makeDraggable.
    // Find the width of indentations to measure mouse movements against.
    // Because the table doesn't need to start with any indentations, we
    // manually create an empty div, check it's width, then remove.
    var indent = $(Drupal.theme('tableDragIndentation')).appendTo('body');
    this.indentAmount = parseInt(indent.css('width'));
    indent.remove();
  }

  // Make each applicable row draggable.
  $('tr.draggable', table).each(function() { self.makeDraggable(this); });

  // Hide columns containing affected form elements.
  this.hideColumns();

  // Add mouse bindings to the document. The self variable is passed along
  // as event handlers do not have direct access to the tableDrag object.
  $(document).bind('mousemove', function(event) { self.dragRow(event, self); });
  $(document).bind('mouseup', function(event) { self.dropRow(event, self); });
};

/**
 * Hide the columns containing form elements according to the settings for
 * this tableDrag instance.
 */
Drupal.tableDrag.prototype.hideColumns = function() {
  for (var group in this.tableSettings) {
    // Find the first field in this group.
    for (var d in this.tableSettings[group]) {
      if ($('.' + this.tableSettings[group][d]['target'], this.table).size()) {
        var hidden = this.tableSettings[group][d]['hidden'];
        var field = $('.' + this.tableSettings[group][d]['target'] + ':first', this.table);
        var cell = field.parents('td:first, th:first');
        break;
      }
    }
    // Hide the column containing this field.
    if (hidden && cell[0] && cell.css('display') != 'none') {
      // Add 1 to our indexes. The nth-child selector is 1 based, not 0 based.
      var columnIndex = $('td', field.parents('tr:first')).index(cell.get(0)) + 1;
      var headerIndex = $('td:not(:hidden)', field.parents('tr:first')).index(cell.get(0)) + 1;
      $('tbody tr', this.table).each(function() {
        // Find and hide the cell in the table body.
        var cell = $('td:nth-child('+ columnIndex +')', this);
        if (cell.size()) {
          cell.css('display', 'none');
        }
        // We might be dealing with a row spanning the entire table.
        // Reduce the colspan on the first cell to prevent the cell from
        // overshooting the table.
        else {
          cell = $('td:first', this);
          cell.attr('colspan', cell.attr('colspan') - 1);
        }
      });
      $('thead tr', this.table).each(function() {
        // Remove table header cells entirely (Safari doesn't hide properly).
        var th = $('th:nth-child('+ headerIndex +')', this);
        if (th.size()) {
          th.remove();
        }
      });
    }
  }
};

/**
 * Find the target used within a particular row and group.
 */
Drupal.tableDrag.prototype.rowSettings = function(group, row) {
  var field = $('.' + group, row);
  for (delta in this.tableSettings[group]) {
    var targetClass = this.tableSettings[group][delta]['target'];
    if (field.is('.' + targetClass)) {
      // Return a copy of the row settings.
      var rowSettings = new Object();
      for (var n in this.tableSettings[group][delta]) {
        rowSettings[n] = this.tableSettings[group][delta][n];
      }
      return rowSettings;
    }
  }
};

/**
 * Take an item and add event handlers to make it become draggable.
 */
Drupal.tableDrag.prototype.makeDraggable = function(item) {
  var self = this;

  // Create the handle.
  var handle = $('<a href="#" class="tabledrag-handle"><div class="handle">&nbsp;</div></a>').attr('title', Drupal.t('Drag to re-order'));
  // Insert the handle after indentations (if any).
  if ($('td:first .indentation:last', item).after(handle).size()) {
    // Update the total width of indentation in this entire table.
    self.indentCount = Math.max($('.indentation', item).size(), self.indentCount);
  }
  else {
    $('td:first', item).prepend(handle);
  }

  // Add hover action for the handle.
  handle.hover(function() {
    self.dragObject == null ? $(this).addClass('tabledrag-handle-hover') : null;
  }, function() {
    self.dragObject == null ? $(this).removeClass('tabledrag-handle-hover') : null;
  });

  // Add the mousedown action for the handle.
  handle.mousedown(function(event) {
    // Create a new dragObject recording the event information.
    self.dragObject = new Object();
    self.dragObject.initMouseOffset = self.getMouseOffset(item, event);
    self.dragObject.initMouseCoords = self.mouseCoords(event);
    if (self.indentEnabled) {
      self.dragObject.indentMousePos = self.dragObject.initMouseCoords;
    }

    // If there's a lingering row object from the keyboard, remove its focus.
    if (self.rowObject) {
      $('a.tabledrag-handle', self.rowObject.element).blur();
    }

    // Create a new rowObject for manipulation of this row.
    self.rowObject = new self.row(item, 'mouse', self.indentEnabled, self.maxDepth, true);

    // Save the position of the table.
    self.table.topY = self.getPosition(self.table).y;
    self.table.bottomY = self.table.topY + self.table.offsetHeight;

    // Add classes to the handle and row.
    $(this).addClass('tabledrag-handle-hover');
    $(item).addClass('drag');

    // Set the document to use the move cursor during drag.
    $('body').addClass('drag');
    if (self.oldRowElement) {
      $(self.oldRowElement).removeClass('drag-previous');
    }

    // Hack for IE6 that flickers uncontrollably if select lists are moved.
    if (navigator.userAgent.indexOf('MSIE 6.') != -1) {
      $('select', this.table).css('display', 'none');
    }

    // Hack for Konqueror, prevent the blur handler from firing.
    // Konqueror always gives links focus, even after returning false on mousedown.
    self.safeBlur = false;

    // Call optional placeholder function.
    self.onDrag();
    return false;
  });

  // Prevent the anchor tag from jumping us to the top of the page.
  handle.click(function() {
    return false;
  });

  // Similar to the hover event, add a class when the handle is focused.
  handle.focus(function() {
    $(this).addClass('tabledrag-handle-hover');
    self.safeBlur = true;
  });

  // Remove the handle class on blur and fire the same function as a mouseup.
  handle.blur(function(event) {
    $(this).removeClass('tabledrag-handle-hover');
    if (self.rowObject && self.safeBlur) {
      self.dropRow(event, self);
    }
  });

  // Add arrow-key support to the handle.
  handle.keydown(function(event) {
    // If a rowObject doesn't yet exist and this isn't the tab key.
    if (event.keyCode != 9 && !self.rowObject) {
      self.rowObject = new self.row(item, 'keyboard', self.indentEnabled, self.maxDepth, true);
    }

    var keyChange = false;
    switch (event.keyCode) {
      case 37: // Left arrow.
      case 63234: // Safari left arrow.
        keyChange = true;
        self.rowObject.indent(-1 * self.rtl);
        break;
      case 38: // Up arrow.
      case 63232: // Safari up arrow.
        var previousRow = $(self.rowObject.element).prev('tr').get(0);
        while (previousRow && $(previousRow).is(':hidden')) {
          previousRow = $(previousRow).prev('tr').get(0);
        }
        if (previousRow) {
          self.safeBlur = false; // Do not allow the onBlur cleanup.
          self.rowObject.direction = 'up';
          keyChange = true;
          if (self.rowObject.isValidSwap(previousRow, 0)) {
            self.rowObject.swap('before', previousRow);
            window.scrollBy(0, -parseInt(item.offsetHeight));
          }
          else if (self.table.tBodies[0].rows[0] != previousRow || $(previousRow).is('.draggable')) {
            self.rowObject.swap('before', previousRow);
            self.rowObject.indent(-1);
            window.scrollBy(0, -parseInt(item.offsetHeight));
          }
          handle.get(0).focus(); // Regain focus after the DOM manipulation.
        }
        break;
      case 39: // Right arrow.
      case 63235: // Safari right arrow.
        keyChange = true;
        self.rowObject.indent(1 * self.rtl);
        break;
      case 40: // Down arrow.
      case 63233: // Safari down arrow.
        var nextRow = $(self.rowObject.group).filter(':last').next('tr').get(0);
        while (nextRow && $(nextRow).is(':hidden')) {
          nextRow = $(nextRow).next('tr').get(0);
        }
        if (nextRow) {
          self.safeBlur = false; // Do not allow the onBlur cleanup.
          self.rowObject.direction = 'down';
          keyChange = true;
          if (self.rowObject.isValidSwap(nextRow, 0)) {
            self.rowObject.swap('after', nextRow);
          }
          else {
            self.rowObject.swap('after', nextRow);
            self.rowObject.indent(-1);
          }
          handle.get(0).focus(); // Regain focus after the DOM manipulation.
          window.scrollBy(0, parseInt(item.offsetHeight));
        }
        break;
    }

    if (self.rowObject && self.rowObject.changed == true) {
      $(item).addClass('drag');
      if (self.oldRowElement) {
        $(self.oldRowElement).removeClass('drag-previous');
      }
      self.oldRowElement = item;
      self.restripeTable();
      self.onDrag();
    }

    // Returning false if we have an arrow key to prevent scrolling.
    if (keyChange) {
      return false;
    }
  });

  // Compatibility addition, return false on keypress to prevent unwanted scrolling.
  // IE and Safari will supress scrolling on keydown, but all other browsers
  // need to return false on keypress. http://www.quirksmode.org/js/keys.html
  handle.keypress(function(event) {
    switch (event.keyCode) {
      case 37: // Left arrow.
      case 38: // Up arrow.
      case 39: // Right arrow.
      case 40: // Down arrow.
        return false;
    }
  });
};

/**
 * Mousemove event handler, bound to document.
 */
Drupal.tableDrag.prototype.dragRow = function(event, self) {
  if (self.dragObject) {
    self.currentMouseCoords = self.mouseCoords(event);

    var y = self.currentMouseCoords.y - self.dragObject.initMouseOffset.y;
    var x = self.currentMouseCoords.x - self.dragObject.initMouseOffset.x;

    // Check for row swapping and vertical scrolling.
    if (y != self.oldY) {
      self.rowObject.direction = y > self.oldY ? 'down' : 'up';
      self.oldY = y; // Update the old value.

      // Check if the window should be scrolled (and how fast).
      var scrollAmount = self.checkScroll(self.currentMouseCoords.y);
      // Stop any current scrolling.
      clearInterval(self.scrollInterval);
      // Continue scrolling if the mouse has moved in the scroll direction.
      if (scrollAmount > 0 && self.rowObject.direction == 'down' || scrollAmount < 0 && self.rowObject.direction == 'up') {
        self.setScroll(scrollAmount);
      }

      // If we have a valid target, perform the swap and restripe the table.
      var currentRow = self.findDropTargetRow(x, y);
      if (currentRow) {
        if (self.rowObject.direction == 'down') {
          self.rowObject.swap('after', currentRow, self);
        }
        else {
          self.rowObject.swap('before', currentRow, self);
        }
        self.restripeTable();
      }
    }

    // Similar to row swapping, handle indentations.
    if (self.indentEnabled && x != self.oldX) {
      self.oldX = x;
      var xDiff = self.currentMouseCoords.x - self.dragObject.indentMousePos.x;
      // Set the number of indentations the mouse has been moved left or right.
      var indentDiff = parseInt(xDiff / self.indentAmount * self.rtl);
      // Limit the indentation to no less than the left edge of the table and no
      // more than the total amount of indentation in the table.
      indentDiff = indentDiff > 0 ? Math.min(indentDiff, self.indentCount - self.rowObject.indents + 1) : Math.max(indentDiff, -self.rowObject.indents);
      if (indentDiff != 0) {
        // Indent the row with our estimated diff, which may be further
        // restricted according to the rows around this row.
        var indentChange = self.rowObject.indent(indentDiff);

        // Update table and mouse indentations.
        self.dragObject.indentMousePos.x += self.indentAmount * indentChange * self.rtl;
        self.indentCount = Math.max(self.indentCount, self.rowObject.indents);
      }
    }

    return false;
  }
};

/**
 * Mouseup event handler, bound to document.
 * Blur event handler, bound to drag handle for keyboard support.
 */
Drupal.tableDrag.prototype.dropRow = function(event, self) {
  // Drop row functionality shared between mouseup and blur events.
  if (self.rowObject != null) {
    var droppedRow = self.rowObject.element;
    // The row is already in the right place so we just release it.
    if (self.rowObject.changed == true) {
      // Update the fields in the dropped row.
      self.updateFields(droppedRow);

      // If a setting exists for affecting the entire group, update all the
      // fields in the entire dragged group.
      for (var group in self.tableSettings) {
        var rowSettings = self.rowSettings(group, droppedRow);
        if (rowSettings.relationship == 'group') {
          for (n in self.rowObject.children) {
            self.updateField(self.rowObject.children[n], group);
          }
        }
      }

      self.rowObject.markChanged();
      if (self.changed == false) {
        $(Drupal.theme('tableDragChangedWarning')).insertAfter(self.table).hide().fadeIn('slow');
        self.changed = true;
      }
    }

    if (self.indentEnabled) {
      self.rowObject.removeIndentClasses();
    }
    if (self.oldRowElement) {
      $(self.oldRowElement).removeClass('drag-previous');
    }
    $(droppedRow).removeClass('drag').addClass('drag-previous');
    self.oldRowElement = droppedRow;
    self.onDrop();
    self.rowObject = null;
  }

  // Functionality specific only to mouseup event.
  if (self.dragObject != null) {
    $('.tabledrag-handle', droppedRow).removeClass('tabledrag-handle-hover');

    self.dragObject = null;
    $('body').removeClass('drag');
    clearInterval(self.scrollInterval);

    // Hack for IE6 that flickers uncontrollably if select lists are moved.
    if (navigator.userAgent.indexOf('MSIE 6.') != -1) {
      $('select', this.table).css('display', 'block');
    }
  }
};

/**
 * Get the position of an element by adding up parent offsets in the DOM tree.
 */
Drupal.tableDrag.prototype.getPosition = function(element){
  var left = 0;
  var top  = 0;
  // Because Safari doesn't report offsetHeight on table rows, but does on table
  // cells, grab the firstChild of the row and use that instead.
  // http://jacob.peargrove.com/blog/2006/technical/table-row-offsettop-bug-in-safari
  if (element.offsetHeight == 0) {
    element = element.firstChild; // a table cell
  }

  while (element.offsetParent){
    left   += element.offsetLeft;
    top    += element.offsetTop;
    element = element.offsetParent;
  }

  left += element.offsetLeft;
  top  += element.offsetTop;

  return {x:left, y:top};
};

/**
 * Get the mouse coordinates from the event (allowing for browser differences).
 */
Drupal.tableDrag.prototype.mouseCoords = function(event){
  if (event.pageX || event.pageY) {
    return {x:event.pageX, y:event.pageY};
  }
  return {
    x:event.clientX + document.body.scrollLeft - document.body.clientLeft,
    y:event.clientY + document.body.scrollTop  - document.body.clientTop
  };
};

/**
 * Given a target element and a mouse event, get the mouse offset from that
 * element. To do this we need the element's position and the mouse position.
 */
Drupal.tableDrag.prototype.getMouseOffset = function(target, event) {
  var docPos   = this.getPosition(target);
  var mousePos = this.mouseCoords(event);
  return {x:mousePos.x - docPos.x, y:mousePos.y - docPos.y};
};

/**
 * Find the row the mouse is currently over. This row is then taken and swapped
 * with the one being dragged.
 *
 * @param x
 *   The x coordinate of the mouse on the page (not the screen).
 * @param y
 *   The y coordinate of the mouse on the page (not the screen).
 */
Drupal.tableDrag.prototype.findDropTargetRow = function(x, y) {
  var rows = this.table.tBodies[0].rows;
  for (var n=0; n<rows.length; n++) {
    var row = rows[n];
    var indentDiff = 0;
    // Safari fix see Drupal.tableDrag.prototype.getPosition()
    if (row.offsetHeight == 0) {
      var rowY = this.getPosition(row.firstChild).y;
      var rowHeight = parseInt(row.firstChild.offsetHeight)/2;
    }
    // Other browsers.
    else {
      var rowY = this.getPosition(row).y;
      var rowHeight = parseInt(row.offsetHeight)/2;
    }

    // Because we always insert before, we need to offset the height a bit.
    if ((y > (rowY - rowHeight)) && (y < (rowY + rowHeight))) {
      if (this.indentEnabled) {
        // Check that this row is not a child of the row being dragged.
        for (n in this.rowObject.group) {
          if (this.rowObject.group[n] == row) {
            return null;
          }
        }
        // Check that moving this row will not cause invalid relationships.
        var xDiff = this.currentMouseCoords.x - this.dragObject.initMouseCoords.x;
        indentDiff = parseInt(xDiff / this.indentAmount);
      }

      if (!this.rowObject.isValidSwap(row, indentDiff)) {
        return null;
      }

      // We've may have found the row the mouse just passed over, but it doesn't
      // take into account hidden rows. Skip backwards until we find a draggable
      // row.
      while ($(row).is(':hidden') && $(row).prev('tr').is(':hidden')) {
        row = $(row).prev('tr').get(0);
      }
      return row;
    }
  }
  return null;
};

/**
 * After the row is dropped, update the table fields according to the settings
 * set for this table.
 *
 * @param changedRow
 *   DOM object for the row that was just dropped.
 */
Drupal.tableDrag.prototype.updateFields = function(changedRow) {
  for (var group in this.tableSettings) {
    // Each group may have a different setting for relationship, so we find
    // the source rows for each seperately.
    this.updateField(changedRow, group);
  }
};

/**
 * After the row is dropped, update a single table field according to specific
 * settings.
 *
 * @param changedRow
 *   DOM object for the row that was just dropped.
 * @param group
 *   The settings group on which field updates will occur.
 */
Drupal.tableDrag.prototype.updateField = function(changedRow, group) {
  var rowSettings = this.rowSettings(group, changedRow);

  // Set the row as it's own target.
  if (rowSettings.relationship == 'self' || rowSettings.relationship == 'group') {
    var sourceRow = changedRow;
  }
  // Siblings are easy, check previous and next rows.
  else if (rowSettings.relationship == 'sibling') {
    var previousRow = $(changedRow).prev('tr').get(0);
    var nextRow = $(changedRow).next('tr').get(0);
    var sourceRow = changedRow;
    if ($(previousRow).is('.draggable') && $('.' + group, previousRow).length) {
      if (this.indentEnabled) {
        if ($('.indentations', previousRow).size() == $('.indentations', changedRow)) {
          sourceRow = previousRow;
        }
      }
      else {
        sourceRow = previousRow;
      }
    }
    else if ($(nextRow).is('.draggable') && $('.' + group, nextRow).length) {
      if (this.indentEnabled) {
        if ($('.indentations', nextRow).size() == $('.indentations', changedRow)) {
          sourceRow = nextRow;
        }
      }
      else {
        sourceRow = nextRow;
      }
    }
  }
  // Parents, look up the tree until we find a field not in this group.
  // Go up as many parents as indentations in the changed row.
  else if (rowSettings.relationship == 'parent') {
    var previousRow = $(changedRow).prev('tr');
    while (previousRow.length && $('.indentation', previousRow).length >= this.rowObject.indents) {
      previousRow = previousRow.prev('tr');
    }
    // If we found a row.
    if (previousRow.length) {
      sourceRow = previousRow[0];
    }
    // Otherwise we went all the way to the left of the table without finding
    // a parent, meaning this item has been placed at the root level.
    else {
      // Use the first row in the table as source, because it's garanteed to
      // be at the root level. Find the first item, then compare this row
      // against it as a sibling.
      sourceRow = $('tr.draggable:first').get(0);
      if (sourceRow == this.rowObject.element) {
        sourceRow = $(this.rowObject.group[this.rowObject.group.length - 1]).next('tr.draggable').get(0);
      }
      var useSibling = true;
    }
  }

  // Because we may have moved the row from one category to another,
  // take a look at our sibling and borrow its sources and targets.
  this.copyDragClasses(sourceRow, changedRow, group);
  rowSettings = this.rowSettings(group, changedRow);

  // In the case that we're looking for a parent, but the row is at the top
  // of the tree, copy our sibling's values.
  if (useSibling) {
    rowSettings.relationship = 'sibling';
    rowSettings.source = rowSettings.target;
  }

  var targetClass = '.' + rowSettings.target;
  var targetElement = $(targetClass, changedRow).get(0);

  // Check if a target element exists in this row.
  if (targetElement) {
    var sourceClass = '.' + rowSettings.source;
    var sourceElement = $(sourceClass, sourceRow).get(0);
    switch (rowSettings.action) {
      case 'depth':
        // Get the depth of the target row.
        targetElement.value = $('.indentation', $(sourceElement).parents('tr:first')).size();
        break;
      case 'match':
        // Update the value.
        targetElement.value = sourceElement.value;
        break;
      case 'order':
        var siblings = this.rowObject.findSiblings(rowSettings);
        if ($(targetElement).is('select')) {
          // Get a list of acceptable values.
          var values = new Array();
          $('option', targetElement).each(function() {
            values.push(this.value);
          });
          // Populate the values in the siblings.
          $(targetClass, siblings).each(function() {
            this.value = values.shift();
          });
        }
        else {
          // Assume a numeric input field.
          var weight = parseInt($(targetClass, siblings[0]).val()) || 0;
          $(targetClass, siblings).each(function() {
            this.value = weight;
            weight++;
          });
        }
        break;
    }
  }
};

/**
 * Copy all special tableDrag classes from one row's form elements to a
 * different one, removing any special classes that the destination row
 * may have had.
 */
Drupal.tableDrag.prototype.copyDragClasses = function(sourceRow, targetRow, group) {
  var sourceElement = $('.' + group, sourceRow);
  var targetElement = $('.' + group, targetRow);
  if (sourceElement.length && targetElement.length) {
    targetElement[0].className = sourceElement[0].className;
  }
};

Drupal.tableDrag.prototype.checkScroll = function(cursorY) {
  var de  = document.documentElement;
  var b  = document.body;

  var windowHeight = this.windowHeight = window.innerHeight || (de.clientHeight && de.clientWidth != 0 ? de.clientHeight : b.offsetHeight);
  var scrollY = this.scrollY = (document.all ? (!de.scrollTop ? b.scrollTop : de.scrollTop) : (window.pageYOffset ? window.pageYOffset : window.scrollY));
  var trigger = this.scrollSettings.trigger;
  var delta = 0;

  // Return a scroll speed relative to the edge of the screen.
  if (cursorY - scrollY > windowHeight - trigger) {
    delta = trigger / (windowHeight + scrollY - cursorY);
    delta = (delta > 0 && delta < trigger) ? delta : trigger;
    return delta * this.scrollSettings.amount;
  }
  else if (cursorY - scrollY < trigger) {
    delta = trigger / (cursorY - scrollY);
    delta = (delta > 0 && delta < trigger) ? delta : trigger;
    return -delta * this.scrollSettings.amount;
  }
};

Drupal.tableDrag.prototype.setScroll = function(scrollAmount) {
  var self = this;

  this.scrollInterval = setInterval(function() {
    // Update the scroll values stored in the object.
    self.checkScroll(self.currentMouseCoords.y);
    var aboveTable = self.scrollY > self.table.topY;
    var belowTable = self.scrollY + self.windowHeight < self.table.bottomY;
    if (scrollAmount > 0 && belowTable || scrollAmount < 0 && aboveTable) {
      window.scrollBy(0, scrollAmount);
    }
  }, this.scrollSettings.interval);
};

Drupal.tableDrag.prototype.restripeTable = function() {
  // :even and :odd are reversed because jquery counts from 0 and
  // we count from 1, so we're out of sync.
  $('tr.draggable', this.table)
    .filter(':odd').filter('.odd')
      .removeClass('odd').addClass('even')
    .end().end()
    .filter(':even').filter('.even')
      .removeClass('even').addClass('odd');
};

/**
 * Stub function. Allows a custom handler when a row begins dragging.
 */
Drupal.tableDrag.prototype.onDrag = function() {
  return null;
};

/**
 * Stub function. Allows a custom handler when a row is dropped.
 */
Drupal.tableDrag.prototype.onDrop = function() {
  return null;
};

/**
 * Constructor to make a new object to manipulate a table row.
 *
 * @param tableRow
 *   The DOM element for the table row we will be manipulating.
 * @param method
 *   The method in which this row is being moved. Either 'keyboard' or 'mouse'.
 * @param indentEnabled
 *   Whether the containing table uses indentations. Used for optimizations.
 * @param maxDepth
 *   The maximum amount of indentations this row may contain.
 * @param addClasses
 *   Whether we want to add classes to this row to indicate child relationships.
 */
Drupal.tableDrag.prototype.row = function(tableRow, method, indentEnabled, maxDepth, addClasses) {
  this.element = tableRow;
  this.method = method;
  this.group = new Array(tableRow);
  this.groupDepth = $('.indentation', tableRow).size();
  this.changed = false;
  this.table = $(tableRow).parents('table:first').get(0);
  this.indentEnabled = indentEnabled;
  this.maxDepth = maxDepth;
  this.direction = ''; // Direction the row is being moved.

  if (this.indentEnabled) {
    this.indents = $('.indentation', tableRow).size();
    this.children = this.findChildren(addClasses);
    this.group = $.merge(this.group, this.children);
    // Find the depth of this entire group.
    for (var n = 0; n < this.group.length; n++) {
      this.groupDepth = Math.max($('.indentation', this.group[n]).size(), this.groupDepth);
    }
  }
};

/**
 * Find all children of rowObject by indentation.
 *
 * @param addClasses
 *   Whether we want to add classes to this row to indicate child relationships.
 */
Drupal.tableDrag.prototype.row.prototype.findChildren = function(addClasses) {
  var parentIndentation = this.indents;
  var currentRow = $(this.element, this.table).next('tr.draggable');
  var rows = new Array();
  var child = 0;
  while (currentRow.length) {
    var rowIndentation = $('.indentation', currentRow).length;
    // A greater indentation indicates this is a child.
    if (rowIndentation > parentIndentation) {
      child++;
      rows.push(currentRow[0]);
      if (addClasses) {
        $('.indentation', currentRow).each(function(indentNum) {
          if (child == 1 && (indentNum == parentIndentation)) {
            $(this).addClass('tree-child-first');
          }
          if (indentNum == parentIndentation) {
            $(this).addClass('tree-child');
          }
          else if (indentNum > parentIndentation) {
            $(this).addClass('tree-child-horizontal');
          }
        });
      }
    }
    else {
      break;
    }
    currentRow = currentRow.next('tr.draggable');
  }
  if (addClasses && rows.length) {
    $('.indentation:nth-child(' + (parentIndentation + 1) + ')', rows[rows.length - 1]).addClass('tree-child-last');
  }
  return rows;
};

/**
 * Ensure that two rows are allowed to be swapped. Returns false if swapping
 * will cause invalid parent relationships.
 *
 * @param row
 *   The row being considered for swapping.
 * @param indentDiff
 *   A horizontal difference in indendations.
 */
Drupal.tableDrag.prototype.row.prototype.isValidSwap = function(row, indentDiff) {
  if (this.indentEnabled) {
    var rowIndents = $('.indentation', row).size();
    var prevIndents = $('.indentation', $(row).prev('tr')).size();
    var nextIndents = $('.indentation', $(row).next('tr')).size();

    if (
      (this.direction == 'down') && (
        // Prevent being able to drag a row downward with 2 indentations from a parent.
        this.indents > rowIndents + 1 ||
        // Prevent orphaning children when dragging into a parent.
        this.indents < nextIndents - indentDiff
      ) ||
      (this.direction == 'up') && (
        // Prevent being able to drag a row upward with 2 indentations from a parent.
        this.indents < rowIndents ||
        // Prevent orphaning children when dragging between a child and parent.
        this.indents > prevIndents + 1 - indentDiff
      )
    ) {
      return false;
    }
  }

  // Restriction special cases for the first row in the table.
  if (this.table.tBodies[0].rows[0] == row) {
    // Do not let the first row contain indentations
    // or let an un-draggable first row have anything put before it.
    if ((this.indents + indentDiff) > 0 || $(row).is(':not(.draggable)')) {
      return false;
    }
  }

  return true;
};

/**
 * Perform the swap between two rows.
 *
 * @param position
 *   Whether the swap will occur 'before' or 'after' the given row.
 * @param row
 *   DOM element what will be swapped with the row group.
 */
Drupal.tableDrag.prototype.row.prototype.swap = function(position, row) {
  $(row)[position](this.group);
  this.changed = true;
  this.onSwap(row);
};

/**
 * Indent a row within the legal bounds of the table.
 *
 * @param indentDiff
 *   The number of indentations the row group should receive, can be negative or
 *   positive.
 */
Drupal.tableDrag.prototype.row.prototype.indent = function(indentDiff) {
  if (indentDiff > 0) {
    var prevRow = $(this.group).filter(':first').prev('tr').get(0);
    if (prevRow) {
      var prevIndent = $('.indentation', $(this.group).filter(':first').prev('tr')).size();
      indentDiff = Math.min(prevIndent - this.indents + 1, indentDiff);
    }
    else {
      indentDiff = 0; // First row may not contain indents.
    }
  }
  else {
    var nextIndent = $('.indentation', $(this.group).filter(':last').next('tr')).size();
    indentDiff = Math.max(nextIndent - this.indents, indentDiff);
  }

  // Never allow indentation greater the set limit.
  if (this.maxDepth && indentDiff + this.groupDepth > this.maxDepth) {
    indentDiff = 0;
  }

  for (var n = 1; n <= Math.abs(indentDiff); n++) {
    // Add or remove indentations.
    if (indentDiff < 0) {
      $('.indentation:first', this.group).remove();
      this.indents--;
    }
    else {
      $('td:first', this.group).prepend(Drupal.theme('tableDragIndentation'));
      this.indents++;
    }
  }
  if (indentDiff) {
    this.changed = true;
  }

  // Update indentation for this row.
  this.groupDepth += indentDiff;
  this.onIndent();

  return indentDiff;
};

/**
 * Find all siblings for a row, either according to its subgroup or indentation.
 * Note that the passed in row is included in the list of siblings.
 *
 * @param settings
 *   The field settings we're using to identify what constitutes a sibling.
 */
Drupal.tableDrag.prototype.row.prototype.findSiblings = function(rowSettings) {
  var siblings = new Array();
  var directions = new Array('prev', 'next');
  var rowIndentation = this.indents;
  for (var d in directions) {
    var checkRow = $(this.element)[directions[d]]();
    while (checkRow.length) {
      // Check that the sibling contains a similar target field.
      if ($('.' + rowSettings.target, checkRow)) {
        // Either add immediately if this is a flat table, or check to ensure
        // that this row has the same level of indentaiton.
        if (this.indentEnabled) {
          var checkRowIndentation = $('.indentation', checkRow).length
        }

        if (!(this.indentEnabled) || (checkRowIndentation == rowIndentation)) {
          siblings.push(checkRow[0]);
        }
        else if (checkRowIndentation < rowIndentation) {
          // No need to keep looking for siblings when we get to a parent.
          break;
        }
      }
      else {
        break;
      }
      checkRow = $(checkRow)[directions[d]]();
    }
    // Since siblings are added in reverse order for previous, reverse the
    // completed list of previous siblings. Add the current row and continue.
    if (directions[d] == 'prev') {
      siblings.reverse();
      siblings.push(this.element);
    }
  }
  return siblings;
};

/**
 * Remove indentation helper classes from the current row group.
 */
Drupal.tableDrag.prototype.row.prototype.removeIndentClasses = function() {
  for (n in this.children) {
    $('.indentation', this.children[n])
      .removeClass('tree-child')
      .removeClass('tree-child-first')
      .removeClass('tree-child-last')
      .removeClass('tree-child-horizontal');
  }
};

/**
 * Add an asterisk or other marker to the changed row.
 */
Drupal.tableDrag.prototype.row.prototype.markChanged = function() {
  var marker = Drupal.theme('tableDragChangedMarker');
  var cell = $('td:first', this.element);
  if ($('span.tabledrag-changed', cell).length == 0) {
    cell.append(marker);
  }
};

/**
 * Stub function. Allows a custom handler when a row is indented.
 */
Drupal.tableDrag.prototype.row.prototype.onIndent = function() {
  return null;
};

/**
 * Stub function. Allows a custom handler when a row is swapped.
 */
Drupal.tableDrag.prototype.row.prototype.onSwap = function(swappedRow) {
  return null;
};

Drupal.theme.prototype.tableDragChangedMarker = function () {
  return '<span class="warning tabledrag-changed">*</span>';
};

Drupal.theme.prototype.tableDragIndentation = function () {
  return '<div class="indentation">&nbsp;</div>';
};

Drupal.theme.prototype.tableDragChangedWarning = function () {
  return '<div class="warning">' + Drupal.theme('tableDragChangedMarker') + ' ' + Drupal.t("Changes made in this table will not be saved until the form is submitted.") + '</div>';
};