MarginCollapsingState.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Framework / MS / Internal / PtsHost / MarginCollapsingState.cs / 1305600 / MarginCollapsingState.cs
                        

                        
                            //---------------------------------------------------------------------------- 
//
// Copyright (C) Microsoft Corporation.  All rights reserved.
//
// File: MarginCollapsingState.cs 
//
// Description: Provides paragraph level margin collapsing support. 
// 
// History:
//  05/05/2003 : [....] - moving from Avalon branch. 
//
//---------------------------------------------------------------------------

using System; 

namespace MS.Internal.PtsHost 
{ 
    // ---------------------------------------------------------------------
    // MarginCollapsingState class provides paragraph level margin collapsing 
    // support.
    //
    // Adjoining vertical margins of two paragraphs collapse. The resulting
    // margin width is the maximum of the adjoining margin widths. In the case 
    // of negative margins, the absolute maximum of the negative adjoining
    // margins is deducted from the maximum of the positive adjoining margins. 
    // If there are no positive margins, the absolute maximum of the negative 
    // adjoining margins is deducted from zero.
    // --------------------------------------------------------------------- 
    internal sealed class MarginCollapsingState : UnmanagedHandle
    {
        // ------------------------------------------------------------------
        // Create new margin collapsing state and collapse margins if necessary. 
        // If no collapsing happens, retrieve margin from old collapsing state.
        // This margin value should be used to advance pen. 
        // ----------------------------------------------------------------- 
        internal static void CollapseTopMargin(
            PtsContext ptsContext,              // Current PTS Context. 
            MbpInfo mbp,                        // MBP information for element entering the scope
            MarginCollapsingState mcsCurrent,   // current margin collapsing state (adjacent to the new one).
            out MarginCollapsingState mcsNew,   // margin collapsing state for element entering the scope
            out int margin)                     // collapsed margin value 
        {
            margin = 0; 
            mcsNew = null; 

            // Create new margin collapsing info 
            mcsNew = new MarginCollapsingState(ptsContext, mbp.MarginTop);
            // collapse margins, if current margin collapsing exists
            if (mcsCurrent != null)
            { 
                mcsNew.Collapse(mcsCurrent);
            } 
 
            // If border or paddind is specified:
            // (1) get collapsed margin value 
            // (2) set new mcs to null, because we don't have one anymore
            if (mbp.BPTop != 0)
            {
                margin = mcsNew.Margin; 
                mcsNew.Dispose();
                mcsNew = null; 
            } 
            else if (mcsCurrent == null && DoubleUtil.IsZero(mbp.Margin.Top))
            { 
                // No need to create new margin collapsing info
                mcsNew.Dispose();
                mcsNew = null;
            } 
        }
 
        // ------------------------------------------------------------------ 
        // Update current margin collapsing state and collapse margins if
        // necessary. If no collapsing happens, retrieve margin from previous 
        // collapsing state. This margin value should be used to advance pen.
        // ------------------------------------------------------------------
        internal static void CollapseBottomMargin(
            PtsContext ptsContext,              // Current PTS Context. 
            MbpInfo mbp,                        // MBP information for element leaving the scope
            MarginCollapsingState mcsCurrent,   // current margin collapsing state (adjacent to the new one). 
            out MarginCollapsingState mcsNew,   // margin collapsing state for element leaving the scope 
            out int margin)                     // collapsed margin value
        { 
            margin = 0;
            mcsNew = null;

            // Create new margin collapsing state, if necessary 
            if (!DoubleUtil.IsZero(mbp.Margin.Bottom))
            { 
                mcsNew = new MarginCollapsingState(ptsContext, mbp.MarginBottom); 
            }
 
            // If the current margin collapsing state does not exist, we are done.
            // Otherwise, get current border and padding and decide if to collapse margin.
            if (mcsCurrent != null)
            { 
                if (mbp.BPBottom != 0)
                { 
                    // No collapsing happens, get margin value 
                    margin = mcsCurrent.Margin;
                } 
                else
                {
                    // Collapse margins
                    if (mcsNew == null) 
                    {
                        mcsNew = new MarginCollapsingState(ptsContext, 0); 
                    } 
                    mcsNew.Collapse(mcsCurrent);
                } 
            }
        }

        // ----------------------------------------------------------------- 
        // Constructor.
        // 
        //      ptsContext - Current PTS context. 
        //      margin - margin value
        // ------------------------------------------------------------------ 
        internal MarginCollapsingState(PtsContext ptsContext, int margin) : base(ptsContext)
        {
            _maxPositive = (margin >= 0) ? margin : 0;
            _minNegative = (margin <  0) ? margin : 0; 
        }
 
        // ----------------------------------------------------------------- 
        // Constructor. Make identical copy of the margin collapsing state.
        // 
        //      mcs - margin collapsing state to copy
        // -----------------------------------------------------------------
        private MarginCollapsingState(MarginCollapsingState mcs) : base(mcs.PtsContext)
        { 
            _maxPositive = mcs._maxPositive;
            _minNegative = mcs._minNegative; 
        } 

        // ----------------------------------------------------------------- 
        // Make identical copy of the margin collapsing state.
        //
        // Returns: identical copy of margin collapsing state.
        // ------------------------------------------------------------------ 
        internal MarginCollapsingState Clone()
        { 
            return new MarginCollapsingState(this); 
        }
 
        // -----------------------------------------------------------------
        // Compare margin collapsing state with another one.
        //
        //      mcs - another margin collapsing state 
        //
        // Returns: 'true' if both are the same. 
        // ------------------------------------------------------------------ 
        internal bool IsEqual(MarginCollapsingState mcs)
        { 
            return (_maxPositive == mcs._maxPositive && _minNegative == mcs._minNegative);
        }

        // ------------------------------------------------------------------ 
        // The resulting margin width is the maximum of the adjoining margin
        // widths. In the case of negative margins, the absolute maximum of 
        // the negative adjoining margins is deducted from the maximum of 
        // the positive adjoining margins. If there are no positive margins,
        // the absolute maximum of the negative adjoining margins is deducted 
        // from zero.
        //
        //      mcs - margin collapsing state to collapse with
        // ----------------------------------------------------------------- 
        internal void Collapse(MarginCollapsingState mcs)
        { 
            _maxPositive = Math.Max(_maxPositive, mcs._maxPositive); 
            _minNegative = Math.Min(_minNegative, mcs._minNegative);
        } 

        // ------------------------------------------------------------------
        // The resulting margin width is the maximum of the adjoining margin
        // widths. In the case of negative margins, the absolute maximum of 
        // the negative adjoining margins is deducted from the maximum of
        // the positive adjoining margins. If there are no positive margins, 
        // the absolute maximum of the negative adjoining margins is deducted 
        // from zero.
        // 
        //      margin - margin value to collapse with
        // -----------------------------------------------------------------
        //internal void Collapse(int margin)
        //{ 
        //    _maxPositive = Math.Max(_maxPositive, margin);
        //    _minNegative = Math.Min(_minNegative, margin); 
        //} 

        // ----------------------------------------------------------------- 
        // Actual margin value.
        // -----------------------------------------------------------------
        internal int Margin { get { return _maxPositive + _minNegative; } }
 
        // ------------------------------------------------------------------
        // Maximum positive and minimum negative value for margin. 
        // ----------------------------------------------------------------- 
        private int _maxPositive;
        private int _minNegative; 
    }
}

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

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