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259 lines
8.3 KiB
C
259 lines
8.3 KiB
C
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* ***** BEGIN LICENSE BLOCK *****
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* Version: MPL 1.1/GPL 2.0/LGPL 2.1
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*
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* The contents of this file are subject to the Mozilla Public License Version
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* 1.1 (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS IS" basis,
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* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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* for the specific language governing rights and limitations under the
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* License.
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*
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* The Original Code is mozilla.org code.
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*
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* The Initial Developer of the Original Code is
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* Netscape Communications Corporation.
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* Portions created by the Initial Developer are Copyright (C) 1998
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* the Initial Developer. All Rights Reserved.
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*
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* Contributor(s):
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*
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* Alternatively, the contents of this file may be used under the terms of
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* either of the GNU General Public License Version 2 or later (the "GPL"),
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* or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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* in which case the provisions of the GPL or the LGPL are applicable instead
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* of those above. If you wish to allow use of your version of this file only
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* under the terms of either the GPL or the LGPL, and not to allow others to
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* use your version of this file under the terms of the MPL, indicate your
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* decision by deleting the provisions above and replace them with the notice
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* and other provisions required by the GPL or the LGPL. If you do not delete
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* the provisions above, a recipient may use your version of this file under
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* the terms of any one of the MPL, the GPL or the LGPL.
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*
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* ***** END LICENSE BLOCK ***** */
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#ifndef NSCOORD_H
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#define NSCOORD_H
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#include <math.h>
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#include "nsDebug.h"
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/*
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* Basic type used for the geometry classes.
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*
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* Normally all coordinates are maintained in the twips coordinate
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* space. A twip is 1/20th of a point, and there are 72 points per
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* inch. However, nscoords do appear in pixel space and other
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* coordinate spaces.
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*
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* Twips are used because they are a device-independent unit of measure. See
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* header file nsUnitConversion.h for many useful macros to convert between
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* different units of measure.
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*/
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// This controls whether we're using integers or floats for coordinates. We
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// want to eventually use floats. If you change this, you need to manually
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// change the definition of nscoord in gfx/idl/gfxtypes.idl.
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//#define NS_COORD_IS_FLOAT
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inline float NS_IEEEPositiveInfinity() {
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union { PRUint32 mPRUint32; float mFloat; } pun;
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pun.mPRUint32 = 0x7F800000;
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return pun.mFloat;
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}
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inline PRBool NS_IEEEIsNan(float aF) {
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union { PRUint32 mBits; float mFloat; } pun;
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pun.mFloat = aF;
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return (pun.mBits & 0x7F800000) == 0x7F800000 &&
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(pun.mBits & 0x007FFFFF) != 0;
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}
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#ifdef NS_COORD_IS_FLOAT
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typedef float nscoord;
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#define nscoord_MAX NS_IEEEPositiveInfinity()
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#else
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typedef PRInt32 nscoord;
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#define nscoord_MAX nscoord(1 << 30)
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#endif
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#define nscoord_MIN (-nscoord_MAX)
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inline void VERIFY_COORD(nscoord aCoord) {
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#ifdef NS_COORD_IS_FLOAT
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NS_ASSERTION(floorf(aCoord) == aCoord,
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"Coords cannot have fractions");
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#endif
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}
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inline nscoord NSCoordMultiply(nscoord aCoord, float aVal) {
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VERIFY_COORD(aCoord);
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#ifdef NS_COORD_IS_FLOAT
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return floorf(aCoord*aVal);
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#else
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return (PRInt32)(aCoord*aVal);
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#endif
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}
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inline nscoord NSCoordMultiply(nscoord aCoord, PRInt32 aVal) {
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VERIFY_COORD(aCoord);
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return aCoord*aVal;
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}
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inline nscoord NSCoordDivide(nscoord aCoord, float aVal) {
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VERIFY_COORD(aCoord);
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#ifdef NS_COORD_IS_FLOAT
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return floorf(aCoord/aVal);
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#else
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return (PRInt32)(aCoord/aVal);
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#endif
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}
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inline nscoord NSCoordDivide(nscoord aCoord, PRInt32 aVal) {
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VERIFY_COORD(aCoord);
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#ifdef NS_COORD_IS_FLOAT
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return floorf(aCoord/aVal);
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#else
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return aCoord/aVal;
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#endif
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}
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/**
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* Returns a + b, capping the sum to nscoord_MAX.
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*
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* This function assumes that neither argument is nscoord_MIN.
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*
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* Note: If/when we start using floats for nscoords, this function won't be as
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* necessary. Normal float addition correctly handles adding with infinity,
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* assuming we aren't adding nscoord_MIN. (-infinity)
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*/
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inline nscoord
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NSCoordSaturatingAdd(nscoord a, nscoord b)
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{
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VERIFY_COORD(a);
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VERIFY_COORD(b);
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NS_ASSERTION(a != nscoord_MIN && b != nscoord_MIN,
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"NSCoordSaturatingAdd got nscoord_MIN as argument");
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#ifdef NS_COORD_IS_FLOAT
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// Float math correctly handles a+b, given that neither is -infinity.
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return a + b;
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#else
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if (a == nscoord_MAX || b == nscoord_MAX) {
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// infinity + anything = anything + infinity = infinity
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return nscoord_MAX;
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} else {
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// a + b = a + b
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NS_ASSERTION(a < nscoord_MAX && b < nscoord_MAX,
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"Doing nscoord addition with values > nscoord_MAX");
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NS_ASSERTION((PRInt64)a + (PRInt64)b > (PRInt64)nscoord_MIN,
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"nscoord addition will reach or pass nscoord_MIN");
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// This one's only a warning because the PR_MIN below means that
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// we'll handle this case correctly.
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NS_WARN_IF_FALSE((PRInt64)a + (PRInt64)b < (PRInt64)nscoord_MAX,
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"nscoord addition capped to nscoord_MAX");
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// Cap the result, just in case we're dealing with numbers near nscoord_MAX
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return PR_MIN(nscoord_MAX, a + b);
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}
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#endif
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}
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/**
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* Returns a - b, gracefully handling cases involving nscoord_MAX.
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* This function assumes that neither argument is nscoord_MIN.
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*
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* The behavior is as follows:
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*
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* a) infinity - infinity -> infMinusInfResult
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* b) N - infinity -> 0 (unexpected -- triggers NOTREACHED)
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* c) infinity - N -> infinity
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* d) N1 - N2 -> N1 - N2
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*
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* Note: For float nscoords, cases (c) and (d) are handled by normal float
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* math. We still need to explicitly specify the behavior for cases (a)
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* and (b), though. (Under normal float math, those cases would return NaN
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* and -infinity, respectively.)
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*/
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inline nscoord
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NSCoordSaturatingSubtract(nscoord a, nscoord b,
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nscoord infMinusInfResult)
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{
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VERIFY_COORD(a);
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VERIFY_COORD(b);
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NS_ASSERTION(a != nscoord_MIN && b != nscoord_MIN,
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"NSCoordSaturatingSubtract got nscoord_MIN as argument");
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if (b == nscoord_MAX) {
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if (a == nscoord_MAX) {
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// case (a)
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return infMinusInfResult;
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} else {
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// case (b)
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NS_NOTREACHED("Attempted to subtract [n - nscoord_MAX]");
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return 0;
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}
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} else {
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#ifdef NS_COORD_IS_FLOAT
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// case (c) and (d) for floats. (float math handles both)
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return a - b;
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#else
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if (a == nscoord_MAX) {
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// case (c) for integers
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return nscoord_MAX;
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} else {
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// case (d) for integers
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NS_ASSERTION(a < nscoord_MAX && b < nscoord_MAX,
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"Doing nscoord subtraction with values > nscoord_MAX");
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NS_ASSERTION((PRInt64)a - (PRInt64)b > (PRInt64)nscoord_MIN,
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"nscoord subtraction will reach or pass nscoord_MIN");
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// This one's only a warning because the PR_MIN below means that
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// we'll handle this case correctly.
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NS_WARN_IF_FALSE((PRInt64)a - (PRInt64)b < (PRInt64)nscoord_MAX,
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"nscoord subtraction capped to nscoord_MAX");
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// Cap the result, in case we're dealing with numbers near nscoord_MAX
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return PR_MIN(nscoord_MAX, a - b);
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}
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}
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#endif
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}
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/**
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* Convert an nscoord to a PRInt32. This *does not* do rounding because
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* coords are never fractional. They can be out of range, so this does
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* clamp out of bounds coord values to PR_INT32_MIN and PR_INT32_MAX.
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*/
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inline PRInt32 NSCoordToInt(nscoord aCoord) {
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VERIFY_COORD(aCoord);
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#ifdef NS_COORD_IS_FLOAT
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NS_ASSERTION(!NS_IEEEIsNan(aCoord), "NaN encountered in int conversion");
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if (aCoord < -2147483648.0f) {
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// -2147483648 is the smallest 32-bit signed integer that can be
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// exactly represented as a float
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return PR_INT32_MIN;
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} else if (aCoord > 2147483520.0f) {
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// 2147483520 is the largest 32-bit signed integer that can be
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// exactly represented as an IEEE float
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return PR_INT32_MAX;
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} else {
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return (PRInt32)aCoord;
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}
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#else
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return aCoord;
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#endif
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}
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inline float NSCoordToFloat(nscoord aCoord) {
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VERIFY_COORD(aCoord);
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#ifdef NS_COORD_IS_FLOAT
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NS_ASSERTION(!NS_IEEEIsNan(aCoord), "NaN encountered in float conversion");
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#endif
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return (float)aCoord;
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}
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#endif /* NSCOORD_H */
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