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/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (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.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is mozilla.org code.
 *
 * The Initial Developer of the Original Code is
 * Christopher Blizzard <blizzard@mozilla.org>.
 * Portions created by the Initial Developer are Copyright (C) 2002
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

#ifndef __nsBoundingMetrics_h
#define __nsBoundingMetrics_h

#include "nsCoord.h"

/* Struct used for accurate measurements of a string, in order to
 * allow precise positioning when processing MathML.  This is in its
 * own header file because some very-widely-included headers need it
 * but not the rest of nsFontMetrics, or vice versa.
 */

struct nsBoundingMetrics {

    ///////////
    // Metrics that _exactly_ enclose the text:

    // The character coordinate system is the one used on X Windows:
    // 1. The origin is located at the intersection of the baseline
    //    with the left of the character's cell.
    // 2. All horizontal bearings are oriented from left to right.
    // 2. All horizontal bearings are oriented from left to right.
    // 3. The ascent is oriented from bottom to top (being 0 at the orgin).
    // 4. The descent is oriented from top to bottom (being 0 at the origin).

    // Note that Win32/Mac/PostScript use a different convention for
    // the descent (all vertical measurements are oriented from bottom
    // to top on these palatforms). Make sure to flip the sign of the
    // descent on these platforms for cross-platform compatibility.

    // Any of the following member variables listed here can have
    // positive or negative value.

    nscoord leftBearing;
    /* The horizontal distance from the origin of the drawing
       operation to the left-most part of the drawn string. */

    nscoord rightBearing;
    /* The horizontal distance from the origin of the drawing
       operation to the right-most part of the drawn string.
       The _exact_ width of the string is therefore:
       rightBearing - leftBearing */

    nscoord ascent;
    /* The vertical distance from the origin of the drawing
       operation to the top-most part of the drawn string. */

    nscoord descent;
    /* The vertical distance from the origin of the drawing
       operation to the bottom-most part of the drawn string.
       The _exact_ height of the string is therefore:
       ascent + descent */

    nscoord width;
    /* The horizontal distance from the origin of the drawing
       operation to the correct origin for drawing another string
       to follow the current one. Depending on the font, this
       could be greater than or less than the right bearing. */

    nsBoundingMetrics() : leftBearing(0), rightBearing(0),
                          ascent(0), descent(0), width(0)
    {}

    void
    operator += (const nsBoundingMetrics& bm) {
        if (ascent + descent == 0 && rightBearing - leftBearing == 0) {
            ascent = bm.ascent;
            descent = bm.descent;
            leftBearing = width + bm.leftBearing;
            rightBearing = width + bm.rightBearing;
        }
        else {
            if (ascent < bm.ascent) ascent = bm.ascent;
            if (descent < bm.descent) descent = bm.descent;
            leftBearing = NS_MIN(leftBearing, width + bm.leftBearing);
            rightBearing = NS_MAX(rightBearing, width + bm.rightBearing);
        }
        width += bm.width;
    }
};

#endif // __nsBoundingMetrics_h