michael@0: /* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #ifndef __nsBoundingMetrics_h
michael@0: #define __nsBoundingMetrics_h
michael@0: 
michael@0: #include "nsCoord.h"
michael@0: #include <algorithm>
michael@0: 
michael@0: /* Struct used for accurate measurements of a string, in order to
michael@0:  * allow precise positioning when processing MathML.  This is in its
michael@0:  * own header file because some very-widely-included headers need it
michael@0:  * but not the rest of nsFontMetrics, or vice versa.
michael@0:  */
michael@0: 
michael@0: struct nsBoundingMetrics {
michael@0: 
michael@0:     ///////////
michael@0:     // Metrics that _exactly_ enclose the text:
michael@0: 
michael@0:     // The character coordinate system is the one used on X Windows:
michael@0:     // 1. The origin is located at the intersection of the baseline
michael@0:     //    with the left of the character's cell.
michael@0:     // 2. All horizontal bearings are oriented from left to right.
michael@0:     // 2. All horizontal bearings are oriented from left to right.
michael@0:     // 3. The ascent is oriented from bottom to top (being 0 at the orgin).
michael@0:     // 4. The descent is oriented from top to bottom (being 0 at the origin).
michael@0: 
michael@0:     // Note that Win32/Mac/PostScript use a different convention for
michael@0:     // the descent (all vertical measurements are oriented from bottom
michael@0:     // to top on these palatforms). Make sure to flip the sign of the
michael@0:     // descent on these platforms for cross-platform compatibility.
michael@0: 
michael@0:     // Any of the following member variables listed here can have
michael@0:     // positive or negative value.
michael@0: 
michael@0:     nscoord leftBearing;
michael@0:     /* The horizontal distance from the origin of the drawing
michael@0:        operation to the left-most part of the drawn string. */
michael@0: 
michael@0:     nscoord rightBearing;
michael@0:     /* The horizontal distance from the origin of the drawing
michael@0:        operation to the right-most part of the drawn string.
michael@0:        The _exact_ width of the string is therefore:
michael@0:        rightBearing - leftBearing */
michael@0: 
michael@0:     nscoord ascent;
michael@0:     /* The vertical distance from the origin of the drawing
michael@0:        operation to the top-most part of the drawn string. */
michael@0: 
michael@0:     nscoord descent;
michael@0:     /* The vertical distance from the origin of the drawing
michael@0:        operation to the bottom-most part of the drawn string.
michael@0:        The _exact_ height of the string is therefore:
michael@0:        ascent + descent */
michael@0: 
michael@0:     nscoord width;
michael@0:     /* The horizontal distance from the origin of the drawing
michael@0:        operation to the correct origin for drawing another string
michael@0:        to follow the current one. Depending on the font, this
michael@0:        could be greater than or less than the right bearing. */
michael@0: 
michael@0:     nsBoundingMetrics() : leftBearing(0), rightBearing(0),
michael@0:                           ascent(0), descent(0), width(0)
michael@0:     {}
michael@0: 
michael@0:     void
michael@0:     operator += (const nsBoundingMetrics& bm) {
michael@0:         if (ascent + descent == 0 && rightBearing - leftBearing == 0) {
michael@0:             ascent = bm.ascent;
michael@0:             descent = bm.descent;
michael@0:             leftBearing = width + bm.leftBearing;
michael@0:             rightBearing = width + bm.rightBearing;
michael@0:         }
michael@0:         else {
michael@0:             if (ascent < bm.ascent) ascent = bm.ascent;
michael@0:             if (descent < bm.descent) descent = bm.descent;
michael@0:             leftBearing = std::min(leftBearing, width + bm.leftBearing);
michael@0:             rightBearing = std::max(rightBearing, width + bm.rightBearing);
michael@0:         }
michael@0:         width += bm.width;
michael@0:     }
michael@0: };
michael@0: 
michael@0: #endif // __nsBoundingMetrics_h