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/ DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / wcp / Core / MS / Internal / TextFormatting / ThousandthOfEmRealDoubles.cs / 1 / ThousandthOfEmRealDoubles.cs
//---------------------------------------------------------------------------- // //// Copyright (C) Microsoft Corporation. All rights reserved. // // // // Description: ThousandthOfEmRealDoubles class // // History: // 1/13/2005: [....] Created the file // //--------------------------------------------------------------------------- using System; using System.Diagnostics; using System.Collections.Generic; using System.Windows; using SR=MS.Internal.PresentationCore.SR; using SRID=MS.Internal.PresentationCore.SRID; namespace MS.Internal.TextFormatting { ////// This is a fixed-size implementation of IList<double>. It is aimed to reduce the double values storage /// while providing enough precision for glyph run operations. Current usage pattern suggests that there is no /// need to support resizing functionality (i.e. Add(), Insert(), Remove(), RemoveAt()). /// /// For each double being stored, it will try to scale the value to 16-bit integer expressed in 1/1000th of /// the given Em size. The scale will only be done if the precision remains no less than 1/2000th of an inch. /// /// There are two scenarios where the given double value can not be scaled to 16-bit integer: /// o The given Em size is so big such that 1/1000th of it is not precise enough. /// o The given double value is so big such that the scaled value cannot be fit into a short. /// /// If either of these cases happens (expected to happen rarely), this array implementation will fall back to store all /// values as double. /// internal sealed class ThousandthOfEmRealDoubles : IList{ //---------------------------------- // Constructor //---------------------------------- internal ThousandthOfEmRealDoubles( double emSize, int capacity ) { Debug.Assert(capacity >= 0); _emSize = emSize; InitArrays(capacity); } internal ThousandthOfEmRealDoubles( double emSize, IList realValues ) { Debug.Assert(realValues != null); _emSize = emSize; InitArrays(realValues.Count); // do the setting for (int i = 0; i < Count; i++) { this[i] = realValues[i]; } } //------------------------------------- // Internal properties //------------------------------------- public int Count { get { if (_shortList != null) { return _shortList.Length; } else { return _doubleList.Length; } } } public bool IsReadOnly { get { return false; } } public double this[int index] { get { // Let underlying array do boundary check if (_shortList != null) { return ThousandthOfEmToReal(_shortList[index]); } else { return _doubleList[index]; } } set { // Let underlying array do boundary check if (_shortList != null) { short sValue; if (RealToThousandthOfEm(value, out sValue)) { _shortList[index] = sValue; } else { // The input double can't be scaled. We will // fall back to use double[] now _doubleList = new double[_shortList.Length]; for (int i = 0; i < _shortList.Length; i++) { _doubleList[i] = ThousandthOfEmToReal(_shortList[i]); } _doubleList[index] = value; // set the current value _shortList = null; // deprecate the short array from now on } } else { _doubleList[index] = value; // we are using double array } } } //------------------------------------ // internal methods //------------------------------------ public int IndexOf(double item) { // linear search for (int i = 0; i < Count; i++) { if (this[i] == item) { return i; } } return -1; } public void Clear() { // zero the stored values if (_shortList != null) { for (int i = 0; i < _shortList.Length; i++) { _shortList[i] = 0; } } else { for (int i = 0; i < _doubleList.Length; i++) { _doubleList[i] = 0; } } } public bool Contains(double item) { return IndexOf(item) >= 0; } public void CopyTo(double[] array, int arrayIndex) { // parameter validations if (array == null) { throw new ArgumentNullException("array"); } if (array.Rank != 1) { throw new ArgumentException( SR.Get(SRID.Collection_CopyTo_ArrayCannotBeMultidimensional), "array"); } if (arrayIndex < 0) { throw new ArgumentOutOfRangeException("arrayIndex"); } if (arrayIndex >= array.Length) { throw new ArgumentException( SR.Get( SRID.Collection_CopyTo_IndexGreaterThanOrEqualToArrayLength, "arrayIndex", "array"), "arrayIndex"); } if ((array.Length - Count - arrayIndex) < 0) { throw new ArgumentException( SR.Get( SRID.Collection_CopyTo_NumberOfElementsExceedsArrayLength, "arrayIndex", "array")); } // do the copying here for (int i = 0; i < Count; i++) { array[arrayIndex + i] = this[i]; } } public IEnumerator GetEnumerator() { for (int i = 0; i < Count; i++) { yield return this[i]; } } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return ((IEnumerable )this).GetEnumerator(); } public void Add(double value) { // not supported, same as double[] throw new NotSupportedException(SR.Get(SRID.CollectionIsFixedSize)); } public void Insert(int index, double item) { // not supported, same as double[] throw new NotSupportedException(SR.Get(SRID.CollectionIsFixedSize)); } public bool Remove(double item) { // not supported, same as double[] throw new NotSupportedException(SR.Get(SRID.CollectionIsFixedSize)); } public void RemoveAt(int index) { // not supported, same as double[] throw new NotSupportedException(SR.Get(SRID.CollectionIsFixedSize)); } //--------------------------------------------- // Private methods //--------------------------------------------- private void InitArrays(int capacity) { if (_emSize > CutOffEmSize) { // use double storage when emsize is too big _doubleList = new double[capacity]; } else { // store value as scaled short. _shortList = new short[capacity]; } } private bool RealToThousandthOfEm(double value, out short thousandthOfEm) { double scaled = (value / _emSize) * ToThousandthOfEm; if (scaled > short.MaxValue || scaled < short.MinValue) { // value too big to fit into a short thousandthOfEm = 0; return false; } else { // round to nearest short thousandthOfEm = (short) Math.Round(scaled); return true; } } private double ThousandthOfEmToReal(short thousandthOfEm) { return ((double)thousandthOfEm) * ToReal * _emSize; } //---------------------------------------- // Private members //---------------------------------------- private short[] _shortList; // scaled short values private double[] _doubleList; // fall-back double list, is null for most cases private double _emSize; // em size to scaled with // Default scaling is 1/1000 emsize. private const double ToThousandthOfEm = 1000.0; private const double ToReal = 1.0 / ToThousandthOfEm; // To achieve precsion of no less than 1/2000 of an inch, font Em size must be no greater than 48. // i.e. 48px is 1/2 inch. 1000th of Em size at 48px is 1/2000 inch. private const double CutOffEmSize = 48; } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007. // Copyright (c) Microsoft Corporation. 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