1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/gfx/src/nsBoundingMetrics.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,87 @@
1.4 +/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
1.5 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.6 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.7 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.8 +
1.9 +#ifndef __nsBoundingMetrics_h
1.10 +#define __nsBoundingMetrics_h
1.11 +
1.12 +#include "nsCoord.h"
1.13 +#include <algorithm>
1.14 +
1.15 +/* Struct used for accurate measurements of a string, in order to
1.16 + * allow precise positioning when processing MathML. This is in its
1.17 + * own header file because some very-widely-included headers need it
1.18 + * but not the rest of nsFontMetrics, or vice versa.
1.19 + */
1.20 +
1.21 +struct nsBoundingMetrics {
1.22 +
1.23 + ///////////
1.24 + // Metrics that _exactly_ enclose the text:
1.25 +
1.26 + // The character coordinate system is the one used on X Windows:
1.27 + // 1. The origin is located at the intersection of the baseline
1.28 + // with the left of the character's cell.
1.29 + // 2. All horizontal bearings are oriented from left to right.
1.30 + // 2. All horizontal bearings are oriented from left to right.
1.31 + // 3. The ascent is oriented from bottom to top (being 0 at the orgin).
1.32 + // 4. The descent is oriented from top to bottom (being 0 at the origin).
1.33 +
1.34 + // Note that Win32/Mac/PostScript use a different convention for
1.35 + // the descent (all vertical measurements are oriented from bottom
1.36 + // to top on these palatforms). Make sure to flip the sign of the
1.37 + // descent on these platforms for cross-platform compatibility.
1.38 +
1.39 + // Any of the following member variables listed here can have
1.40 + // positive or negative value.
1.41 +
1.42 + nscoord leftBearing;
1.43 + /* The horizontal distance from the origin of the drawing
1.44 + operation to the left-most part of the drawn string. */
1.45 +
1.46 + nscoord rightBearing;
1.47 + /* The horizontal distance from the origin of the drawing
1.48 + operation to the right-most part of the drawn string.
1.49 + The _exact_ width of the string is therefore:
1.50 + rightBearing - leftBearing */
1.51 +
1.52 + nscoord ascent;
1.53 + /* The vertical distance from the origin of the drawing
1.54 + operation to the top-most part of the drawn string. */
1.55 +
1.56 + nscoord descent;
1.57 + /* The vertical distance from the origin of the drawing
1.58 + operation to the bottom-most part of the drawn string.
1.59 + The _exact_ height of the string is therefore:
1.60 + ascent + descent */
1.61 +
1.62 + nscoord width;
1.63 + /* The horizontal distance from the origin of the drawing
1.64 + operation to the correct origin for drawing another string
1.65 + to follow the current one. Depending on the font, this
1.66 + could be greater than or less than the right bearing. */
1.67 +
1.68 + nsBoundingMetrics() : leftBearing(0), rightBearing(0),
1.69 + ascent(0), descent(0), width(0)
1.70 + {}
1.71 +
1.72 + void
1.73 + operator += (const nsBoundingMetrics& bm) {
1.74 + if (ascent + descent == 0 && rightBearing - leftBearing == 0) {
1.75 + ascent = bm.ascent;
1.76 + descent = bm.descent;
1.77 + leftBearing = width + bm.leftBearing;
1.78 + rightBearing = width + bm.rightBearing;
1.79 + }
1.80 + else {
1.81 + if (ascent < bm.ascent) ascent = bm.ascent;
1.82 + if (descent < bm.descent) descent = bm.descent;
1.83 + leftBearing = std::min(leftBearing, width + bm.leftBearing);
1.84 + rightBearing = std::max(rightBearing, width + bm.rightBearing);
1.85 + }
1.86 + width += bm.width;
1.87 + }
1.88 +};
1.89 +
1.90 +#endif // __nsBoundingMetrics_h
