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//---------------------------------------------------------------------------
//
// <copyright file=GlyphInfoList.cs company=Microsoft>
// Copyright (C) Microsoft Corporation. All rights reserved.
// </copyright>
//
//
// Description: ThousandthOfEmRealDoubles class
//
// History:
// 1/13/2005: Garyyang 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
{
/// <summary>
/// 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.
/// </summary>
internal sealed class ThousandthOfEmRealDoubles : IList<double>
{
//----------------------------------
// Constructor
//----------------------------------
internal ThousandthOfEmRealDoubles(
double emSize,
int capacity
)
{
Debug.Assert(capacity >= 0);
_emSize = emSize;
InitArrays(capacity);
}
internal ThousandthOfEmRealDoubles(
double emSize,
IList<double> 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<double> GetEnumerator()
{
for (int i = 0; i < Count; i++)
{
yield return this[i];
}
}
System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
{
return ((IEnumerable<double>)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;
}
}
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