TextParagraphCache.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Core / CSharp / System / Windows / Media / textformatting / TextParagraphCache.cs / 1305600 / TextParagraphCache.cs
                        
                        
                            //------------------------------------------------------------------------ 
//
//  Microsoft Windows Client Platform
//  Copyright (C) Microsoft Corporation
// 
//  File:      TextParagraphCache.cs
// 
//  Contents:  Cache object of paragraph content used to improve performance 
//             of optimal paragraph formatting
// 
//  Spec:      http://team/sites/Avalon/Specs/Text%20Formatting%20API.doc
//
//  Created:   2-4-2005 Worachai Chaoweeraprasit (Wchao)
// 
//-----------------------------------------------------------------------
 
using System; 
using System.Runtime.InteropServices;
using System.Diagnostics; 
using System.Collections.Generic;
using System.Security;
using System.Windows;
using System.Windows.Media; 

using MS.Internal; 
using MS.Internal.TextFormatting; 
using MS.Internal.PresentationCore;
using SR = MS.Internal.PresentationCore.SR; 
using SRID = MS.Internal.PresentationCore.SRID;


namespace System.Windows.Media.TextFormatting 
{
    ///  
    /// Text formatter caches all potential breakpoints within a paragraph in this cache object 
    /// during FormatParagraphContent call. This object is to be managed by text layout client.
    /// The use of this cache is to improve performance of line construction in optimal paragraph 
    /// line formatting.
    /// 
#if OPTIMALBREAK_API
    public sealed class TextParagraphCache : IDisposable 
#else
    [FriendAccessAllowed] 
    internal sealed class TextParagraphCache : IDisposable 
#endif
    { 
        private FullTextState                       _fullText;                  // full text state of the whole paragraph
        private SecurityCriticalDataForSet  _ploparabreak;              // unmanaged LS resource for parabreak session
        private int                                 _finiteFormatWidth;         // finite formatting ideal width
        private bool                                _penalizedAsJustified;      // flag indicating whether the paragraph should be penalized as fully-justified one 

 
        ///  
        /// Construct a paragraph cache to be used during optimal paragraph formatting
        ///  
        /// 
        /// Critical - as this calls the setter for _ploparabreak.Value which is type SecurityCriticalDataForSet.
        /// Safe - as it doesn't set security critical data to a random value passed in but rather to a value returned
        ///        by a safe function TextFormatterContext.CreateParaBreakingSession(). 
        /// 
        [SecurityCritical, SecurityTreatAsSafe] 
        internal TextParagraphCache( 
            FormatSettings      settings,
            int                 firstCharIndex, 
            int                 paragraphWidth
            )
        {
            Invariant.Assert(settings != null); 

            // create full text 
            _finiteFormatWidth = settings.GetFiniteFormatWidth(paragraphWidth); 
            _fullText = FullTextState.Create(settings, firstCharIndex, _finiteFormatWidth);
 
            // acquiring LS context
            TextFormatterContext context = settings.Formatter.AcquireContext(_fullText, IntPtr.Zero);

            _fullText.SetTabs(context); 

            IntPtr ploparabreakValue = IntPtr.Zero; 
 
            LsErr lserr = context.CreateParaBreakingSession(
                firstCharIndex, 
                _finiteFormatWidth,
                // breakrec is not needed before the first cp of para cache
                // since we handle Bidi break ourselves.
                IntPtr.Zero, 
                ref ploparabreakValue,
                ref _penalizedAsJustified 
                ); 

            // get the exception in context before it is released 
            Exception callbackException = context.CallbackException;

            // release the context
            context.Release(); 

            if(lserr != LsErr.None) 
            { 
                GC.SuppressFinalize(this);
                if(callbackException != null) 
                {
                    // rethrow exception thrown in callbacks
                    throw new InvalidOperationException(SR.Get(SRID.CreateParaBreakingSessionFailure, lserr), callbackException);
                } 
                else
                { 
                    // throw with LS error codes 
                    TextFormatterContext.ThrowExceptionFromLsError(SR.Get(SRID.CreateParaBreakingSessionFailure, lserr), lserr);
                } 
            }

            _ploparabreak.Value = ploparabreakValue;
 
            // keep context alive till here
            GC.KeepAlive(context); 
        } 

 
        /// 
        /// Finalizing paragraph content cache
        /// 
        ~TextParagraphCache() 
        {
            Dispose(false); 
        } 

 
        /// 
        /// Disposing paragraph content cache
        /// 
        public void Dispose() 
        {
            Dispose(true); 
            GC.SuppressFinalize(this); 
        }
 


        /// 
        /// Client to format all feasible breakpoints for a line started at the specified character position. 
        /// The number of breakpoints returned is restricted by penalty restr
        ///  
        ///  
        /// This method is provided for direct access of PTS during optimal paragraph process. The breakpoint
        /// restriction handle is passed as part of the parameter to PTS callback pfnFormatLineVariants. The 
        /// value comes from earlier steps in PTS code to compute the accumulated penalty of the entire paragraph
        /// using 'best-fit' algorithm.
        /// 
        internal IList FormatBreakpoints( 
            int                             firstCharIndex,
            TextLineBreak                   previousLineBreak, 
            IntPtr                          breakpointRestrictionHandle, 
            double                          maxLineWidth,
            out int                         bestFitIndex 
            )
        {
            // format all potential breakpoints starting from the specified firstCharIndex.
            // The number of breakpoints returned is restricted by penaltyRestriction. 
            return FullTextBreakpoint.CreateMultiple(
                this, 
                firstCharIndex, 
                VerifyMaxLineWidth(maxLineWidth),
                previousLineBreak, 
                breakpointRestrictionHandle,
                out bestFitIndex
                );
        } 

 
        ///  
        /// Releasing LS unmanaged resource on paragraph content
        ///  
        /// 
        /// Critical - as this sets critical data _ploparabreak
        /// Safe - as it does not set critical data thru incoming parameter
        ///  
        [SecurityCritical, SecurityTreatAsSafe]
        private void Dispose(bool disposing) 
        { 
            if(_ploparabreak.Value != IntPtr.Zero)
            { 
                UnsafeNativeMethods.LoDisposeParaBreakingSession(_ploparabreak.Value, !disposing);

                _ploparabreak.Value = IntPtr.Zero;
                GC.KeepAlive(this); 
            }
        } 
 
        /// 
        /// Verify that the input line format width is within the maximum ideal value 
        /// 
        private int VerifyMaxLineWidth(double maxLineWidth)
        {
            if (DoubleUtil.IsNaN(maxLineWidth)) 
                throw new ArgumentOutOfRangeException("maxLineWidth", SR.Get(SRID.ParameterValueCannotBeNaN));
 
            if (maxLineWidth == 0 || double.IsPositiveInfinity(maxLineWidth)) 
            {
                // consider 0 or positive infinity as maximum ideal width 
                return Constants.IdealInfiniteWidth;
            }

            if (    maxLineWidth < 0 
                ||  maxLineWidth > Constants.RealInfiniteWidth)
            { 
                throw new ArgumentOutOfRangeException("maxLineWidth", SR.Get(SRID.ParameterMustBeBetween, 0, Constants.RealInfiniteWidth)); 
            }
 
            // convert real value to ideal value
            return TextFormatterImp.RealToIdeal(maxLineWidth);

        } 

        ///  
        /// Full text state of the paragraph 
        /// 
        internal FullTextState FullText 
        {
            get { return _fullText; }
        }
 
        /// 
        /// Unmanaged LS parabreak session object 
        ///  
        internal SecurityCriticalDataForSet Ploparabreak
        { 
            get { return _ploparabreak; }
        }
    }
} 


// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
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