gecko/browser/devtools/shared/LayoutHelpers.jsm

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ft=javascript 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/. */

const Cu = Components.utils;
const Ci = Components.interfaces;
const Cr = Components.results;

var EXPORTED_SYMBOLS = ["LayoutHelpers"];

LayoutHelpers = {

  /**
   * Compute the position and the dimensions for the visible portion
   * of a node, relativalely to the root window.
   *
   * @param nsIDOMNode aNode
   *        a DOM element to be highlighted
   */
  getDirtyRect: function LH_getDirectyRect(aNode) {
    let frameWin = aNode.ownerDocument.defaultView;
    let clientRect = aNode.getBoundingClientRect();

    // Go up in the tree of frames to determine the correct rectangle.
    // clientRect is read-only, we need to be able to change properties.
    rect = {top: clientRect.top,
            left: clientRect.left,
            width: clientRect.width,
            height: clientRect.height};

    // We iterate through all the parent windows.
    while (true) {

      // Does the selection overflow on the right of its window?
      let diffx = frameWin.innerWidth - (rect.left + rect.width);
      if (diffx < 0) {
        rect.width += diffx;
      }

      // Does the selection overflow on the bottom of its window?
      let diffy = frameWin.innerHeight - (rect.top + rect.height);
      if (diffy < 0) {
        rect.height += diffy;
      }

      // Does the selection overflow on the left of its window?
      if (rect.left < 0) {
        rect.width += rect.left;
        rect.left = 0;
      }

      // Does the selection overflow on the top of its window?
      if (rect.top < 0) {
        rect.height += rect.top;
        rect.top = 0;
      }

      // Selection has been clipped to fit in its own window.

      // Are we in the top-level window?
      if (frameWin.parent === frameWin || !frameWin.frameElement) {
        break;
      }

      // We are in an iframe.
      // We take into account the parent iframe position and its
      // offset (borders and padding).
      let frameRect = frameWin.frameElement.getBoundingClientRect();

      let [offsetTop, offsetLeft] =
        this.getIframeContentOffset(frameWin.frameElement);

      rect.top += frameRect.top + offsetTop;
      rect.left += frameRect.left + offsetLeft;

      frameWin = frameWin.parent;
    }

    return rect;
  },

  /**
   * Compute the absolute position and the dimensions of a node, relativalely
   * to the root window.
   *
   * @param nsIDOMNode aNode
   *        a DOM element to get the bounds for
   * @param nsIWindow aContentWindow
   *        the content window holding the node
   */
  getRect: function LH_getRect(aNode, aContentWindow) {
    let frameWin = aNode.ownerDocument.defaultView;
    let clientRect = aNode.getBoundingClientRect();

    // Go up in the tree of frames to determine the correct rectangle.
    // clientRect is read-only, we need to be able to change properties.
    rect = {top: clientRect.top + aContentWindow.pageYOffset,
            left: clientRect.left + aContentWindow.pageXOffset,
            width: clientRect.width,
            height: clientRect.height};

    // We iterate through all the parent windows.
    while (true) {

      // Are we in the top-level window?
      if (frameWin.parent === frameWin || !frameWin.frameElement) {
        break;
      }

      // We are in an iframe.
      // We take into account the parent iframe position and its
      // offset (borders and padding).
      let frameRect = frameWin.frameElement.getBoundingClientRect();

      let [offsetTop, offsetLeft] =
        this.getIframeContentOffset(frameWin.frameElement);

      rect.top += frameRect.top + offsetTop;
      rect.left += frameRect.left + offsetLeft;

      frameWin = frameWin.parent;
    }

    return rect;
  },

  /**
   * Returns iframe content offset (iframe border + padding).
   * Note: this function shouldn't need to exist, had the platform provided a
   * suitable API for determining the offset between the iframe's content and
   * its bounding client rect. Bug 626359 should provide us with such an API.
   *
   * @param aIframe
   *        The iframe.
   * @returns array [offsetTop, offsetLeft]
   *          offsetTop is the distance from the top of the iframe and the
   *            top of the content document.
   *          offsetLeft is the distance from the left of the iframe and the
   *            left of the content document.
   */
  getIframeContentOffset: function LH_getIframeContentOffset(aIframe) {
    let style = aIframe.contentWindow.getComputedStyle(aIframe, null);

    // In some cases, the computed style is null
    if (!style) {
      return [0, 0];
    }

    let paddingTop = parseInt(style.getPropertyValue("padding-top"));
    let paddingLeft = parseInt(style.getPropertyValue("padding-left"));

    let borderTop = parseInt(style.getPropertyValue("border-top-width"));
    let borderLeft = parseInt(style.getPropertyValue("border-left-width"));

    return [borderTop + paddingTop, borderLeft + paddingLeft];
  },

  /**
   * Apply the page zoom factor.
   */
  getZoomedRect: function LH_getZoomedRect(aWin, aRect) {
    // get page zoom factor, if any
    let zoom =
      aWin.QueryInterface(Components.interfaces.nsIInterfaceRequestor)
        .getInterface(Components.interfaces.nsIDOMWindowUtils)
        .screenPixelsPerCSSPixel;

    // adjust rect for zoom scaling
    let aRectScaled = {};
    for (let prop in aRect) {
      aRectScaled[prop] = aRect[prop] * zoom;
    }

    return aRectScaled;
  },


  /**
   * Find an element from the given coordinates. This method descends through
   * frames to find the element the user clicked inside frames.
   *
   * @param DOMDocument aDocument the document to look into.
   * @param integer aX
   * @param integer aY
   * @returns Node|null the element node found at the given coordinates.
   */
  getElementFromPoint: function LH_elementFromPoint(aDocument, aX, aY) {
    let node = aDocument.elementFromPoint(aX, aY);
    if (node && node.contentDocument) {
      if (node instanceof Ci.nsIDOMHTMLIFrameElement) {
        let rect = node.getBoundingClientRect();

        // Gap between the iframe and its content window.
        let [offsetTop, offsetLeft] = LayoutHelpers.getIframeContentOffset(node);

        aX -= rect.left + offsetLeft;
        aY -= rect.top + offsetTop;

        if (aX < 0 || aY < 0) {
          // Didn't reach the content document, still over the iframe.
          return node;
        }
      }
      if (node instanceof Ci.nsIDOMHTMLIFrameElement ||
          node instanceof Ci.nsIDOMHTMLFrameElement) {
        let subnode = this.getElementFromPoint(node.contentDocument, aX, aY);
        if (subnode) {
          node = subnode;
        }
      }
    }
    return node;
  },

  /**
   * Scroll the document so that the element "elem" appears in the viewport.
   *
   * @param Element elem the element that needs to appear in the viewport.
   * @param bool centered true if you want it centered, false if you want it to
   * appear on the top of the viewport. It is true by default, and that is
   * usually what you want.
   */
  scrollIntoViewIfNeeded:
  function LH_scrollIntoViewIfNeeded(elem, centered) {
    // We want to default to centering the element in the page,
    // so as to keep the context of the element.
    centered = centered === undefined? true: !!centered;

    let win = elem.ownerDocument.defaultView;
    let clientRect = elem.getBoundingClientRect();

    // The following are always from the {top, bottom, left, right}
    // of the viewport, to the {top, …} of the box.
    // Think of them as geometrical vectors, it helps.
    // The origin is at the top left.

    let topToBottom = clientRect.bottom;
    let bottomToTop = clientRect.top - win.innerHeight;
    let leftToRight = clientRect.right;
    let rightToLeft = clientRect.left - win.innerWidth;
    let xAllowed = true;  // We allow one translation on the x axis,
    let yAllowed = true;  // and one on the y axis.

    // Whatever `centered` is, the behavior is the same if the box is
    // (even partially) visible.

    if ((topToBottom > 0 || !centered) && topToBottom <= elem.offsetHeight) {
      win.scrollBy(0, topToBottom - elem.offsetHeight);
      yAllowed = false;
    } else
    if ((bottomToTop < 0 || !centered) && bottomToTop >= -elem.offsetHeight) {
      win.scrollBy(0, bottomToTop + elem.offsetHeight);
      yAllowed = false;
    }

    if ((leftToRight > 0 || !centered) && leftToRight <= elem.offsetWidth) {
      if (xAllowed) {
        win.scrollBy(leftToRight - elem.offsetWidth, 0);
        xAllowed = false;
      }
    } else
    if ((rightToLeft < 0 || !centered) && rightToLeft >= -elem.offsetWidth) {
      if (xAllowed) {
        win.scrollBy(rightToLeft + elem.offsetWidth, 0);
        xAllowed = false;
      }
    }

    // If we want it centered, and the box is completely hidden,
    // then we center it explicitly.

    if (centered) {

      if (yAllowed && (topToBottom <= 0 || bottomToTop >= 0)) {
        win.scroll(win.scrollX,
                   win.scrollY + clientRect.top
                   - (win.innerHeight - elem.offsetHeight) / 2);
      }

      if (xAllowed && (leftToRight <= 0 || rightToLeft <= 0)) {
        win.scroll(win.scrollX + clientRect.left
                   - (win.innerWidth - elem.offsetWidth) / 2,
                   win.scrollY);
      }
    }

    if (win.parent !== win) {
      // We are inside an iframe.
      LH_scrollIntoViewIfNeeded(win.frameElement, centered);
    }
  },

  /**
   * Check if a node and its document are still alive
   * and attached to the window.
   *
   * @param aNode
   */
  isNodeConnected: function LH_isNodeConnected(aNode)
  {
    try {
      let connected = (aNode.ownerDocument && aNode.ownerDocument.defaultView &&
                      !(aNode.compareDocumentPosition(aNode.ownerDocument.documentElement) &
                      aNode.DOCUMENT_POSITION_DISCONNECTED));
      return connected;
    } catch (e) {
      // "can't access dead object" error
      return false;
    }
  },
};