gecko/browser/base/content/newtab/drag.js

#ifdef 0
/* 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/. */
#endif

/**
 * This singleton implements site dragging functionality.
 */
let gDrag = {
  /**
   * The site offset to the drag start point.
   */
  _offsetX: null,
  _offsetY: null,

  /**
   * The site that is dragged.
   */
  _draggedSite: null,
  get draggedSite() this._draggedSite,

  /**
   * The cell width/height at the point the drag started.
   */
  _cellWidth: null,
  _cellHeight: null,
  get cellWidth() this._cellWidth,
  get cellHeight() this._cellHeight,

  /**
   * Start a new drag operation.
   * @param aSite The site that's being dragged.
   * @param aEvent The 'dragstart' event.
   */
  start: function Drag_start(aSite, aEvent) {
    this._draggedSite = aSite;

    // Prevent moz-transform for left, top.
    aSite.node.setAttribute("dragged", "true");

    // Make sure the dragged site is floating above the grid.
    aSite.node.setAttribute("ontop", "true");

    this._setDragData(aSite, aEvent);

    // Store the cursor offset.
    let node = aSite.node;
    let rect = node.getBoundingClientRect();
    this._offsetX = aEvent.clientX - rect.left;
    this._offsetY = aEvent.clientY - rect.top;

    // Store the cell dimensions.
    let cellNode = aSite.cell.node;
    this._cellWidth = cellNode.offsetWidth;
    this._cellHeight = cellNode.offsetHeight;

    gTransformation.freezeSitePosition(aSite);
  },

  /**
   * Handles the 'drag' event.
   * @param aSite The site that's being dragged.
   * @param aEvent The 'drag' event.
   */
  drag: function Drag_drag(aSite, aEvent) {
    // Get the viewport size.
    let {clientWidth, clientHeight} = document.documentElement;

    // We'll want a padding of 5px.
    let border = 5;

    // Enforce minimum constraints to keep the drag image inside the window.
    let left = Math.max(scrollX + aEvent.clientX - this._offsetX, border);
    let top = Math.max(scrollY + aEvent.clientY - this._offsetY, border);

    // Enforce maximum constraints to keep the drag image inside the window.
    left = Math.min(left, scrollX + clientWidth - this.cellWidth - border);
    top = Math.min(top, scrollY + clientHeight - this.cellHeight - border);

    // Update the drag image's position.
    gTransformation.setSitePosition(aSite, {left: left, top: top});
  },

  /**
   * Ends the current drag operation.
   * @param aSite The site that's being dragged.
   * @param aEvent The 'dragend' event.
   */
  end: function Drag_end(aSite, aEvent) {
    aSite.node.removeAttribute("dragged");

    // Slide the dragged site back into its cell (may be the old or the new cell).
    gTransformation.slideSiteTo(aSite, aSite.cell, {
      unfreeze: true,
      callback: function () aSite.node.removeAttribute("ontop")
    });

    this._draggedSite = null;
  },

  /**
   * Checks whether we're responsible for a given drag event.
   * @param aEvent The drag event to check.
   * @return Whether we should handle this drag and drop operation.
   */
  isValid: function Drag_isValid(aEvent) {
    let dt = aEvent.dataTransfer;
    return dt && dt.types.contains("text/x-moz-url");
  },

  /**
   * Initializes the drag data for the current drag operation.
   * @param aSite The site that's being dragged.
   * @param aEvent The 'dragstart' event.
   */
  _setDragData: function Drag_setDragData(aSite, aEvent) {
    let {url, title} = aSite;

    let dt = aEvent.dataTransfer;
    dt.mozCursor = "default";
    dt.effectAllowed = "move";
    dt.setData("text/plain", url);
    dt.setData("text/uri-list", url);
    dt.setData("text/x-moz-url", url + "\n" + title);
    dt.setData("text/html", "<a href=\"" + url + "\">" + url + "</a>");

    // Create and use an empty drag element. We don't want to use the default
    // drag image with its default opacity.
    let dragElement = document.createElementNS(HTML_NAMESPACE, "div");
    dragElement.classList.add("drag-element");
    let body = document.getElementById("body");
    body.appendChild(dragElement);
    dt.setDragImage(dragElement, 0, 0);

    // After the 'dragstart' event has been processed we can remove the
    // temporary drag element from the DOM.
    setTimeout(function () body.removeChild(dragElement), 0);
  }
};