TabPanel.cs source code in C# .NET

Source code for the .NET framework in C#

                        

Code:

/ Dotnetfx_Vista_SP2 / Dotnetfx_Vista_SP2 / 8.0.50727.4016 / DEVDIV / depot / DevDiv / releases / Orcas / QFE / wpf / src / Framework / System / Windows / Controls / Primitives / TabPanel.cs / 1 / TabPanel.cs

                            //---------------------------------------------------------------------------- 
//
// Copyright (C) Microsoft Corporation.  All rights reserved.
//
//--------------------------------------------------------------------------- 

using System; 
using MS.Internal; 
using MS.Utility;
using System.Collections; 
using System.ComponentModel;
using System.Diagnostics;
using System.Reflection;
using System.Windows.Threading; 
using System.Windows.Media;
using System.Windows.Input; 
 
namespace System.Windows.Controls.Primitives
{ 
    /// 
    /// TabPanel is a Panel designed to handle the intricacies of laying out the tab buttons in a TabControl.  Specically, it handles:
    /// Serving as an ItemsHost for TabItems within a TabControl
    /// Determining correct sizing and positioning for TabItems 
    /// Handling the logic associated with MultiRow scenarios, namely:
    /// Calculating row breaks in a collection of TabItems 
    /// Laying out TabItems in multiple rows based on those breaks 
    /// Performing specific layout for a selected item to indicate selection, namely:
    /// Bringing the selected tab to the front, or, in other words, making the selected tab appear to be in front of other tabs. 
    /// Increasing the size pre-layout size of a selected item (note that this is not a transform, but rather an increase in the size allotted to the element in which to perform layout).
    /// Bringing the selected tab to the front
    /// Exposing attached properties that allow TabItems to be styled based on their placement within the TabPanel.
    ///  
    public class TabPanel : Panel
    { 
        //------------------------------------------------------------------- 
        //
        //  Constructors 
        //
        //-------------------------------------------------------------------

        #region Constructors 

        ///  
        ///     Default DependencyObject constructor 
        /// 
        ///  
        ///     Automatic determination of current Dispatcher. Use alternative constructor
        ///     that accepts a Dispatcher for best performance.
        /// 
        public TabPanel() : base() 
        {
        } 
 
        static TabPanel()
        { 
            KeyboardNavigation.TabNavigationProperty.OverrideMetadata(typeof(TabPanel), new FrameworkPropertyMetadata(KeyboardNavigationMode.Once));
            KeyboardNavigation.DirectionalNavigationProperty.OverrideMetadata(typeof(TabPanel), new FrameworkPropertyMetadata(KeyboardNavigationMode.Cycle));
        }
 
        #endregion
 
        //-------------------------------------------------------------------- 
        //
        //  Public Methods 
        //
        //-------------------------------------------------------------------

        #region Public Methods 

        #endregion 
 
        //--------------------------------------------------------------------
        // 
        //  Protected Methods
        //
        //--------------------------------------------------------------------
 
        #region Protected Methods
 
        ///  
        /// Updates DesiredSize of the TabPanel.  Called by parent UIElement.  This is the first pass of layout.
        ///  
        /// 
        /// TabPanel
        /// 
        /// Constraint size is an "upper limit" that TabPanel should not exceed. 
        /// TabPanel' desired size.
        protected override Size MeasureOverride(Size constraint) 
        { 
            Size contentSize = new Size();
            Dock tabAlignment = TabStripPlacement; 

            _numRows = 1;
            _numHeaders = 0;
            _rowHeight = 0; 

                // For top and bottom placement the panel flow its children to calculate the number of rows and 
                // desired vertical size 
                if (tabAlignment == Dock.Top || tabAlignment == Dock.Bottom)
                { 
                    int numInCurrentRow = 0;
                    double currentRowWidth = 0;
                    double maxRowWidth = 0;
                    foreach (UIElement child in InternalChildren) 
                    {
                        if (child.Visibility == Visibility.Collapsed) 
                            continue; 

                        _numHeaders++; 

                        // Helper measures child, and deals with Min, Max, and base Width & Height properties.
                        // Helper returns the size a child needs to take up (DesiredSize or property specified size).
                        child.Measure(constraint); 
                        Size childSize = GetDesiredSizeWithoutMargin(child);
 
                        if (_rowHeight < childSize.Height) 
                            _rowHeight = childSize.Height;
 
                        if (currentRowWidth + childSize.Width > constraint.Width && numInCurrentRow > 0)
                        { // If child does not fit in the current row - create a new row
                            if (maxRowWidth < currentRowWidth)
                                maxRowWidth = currentRowWidth; 

                            currentRowWidth = childSize.Width; 
                            numInCurrentRow = 1; 
                            _numRows++;
                        } 
                        else
                        {
                            currentRowWidth += childSize.Width;
                            numInCurrentRow++; 
                        }
                    } 
 
                    if (maxRowWidth < currentRowWidth)
                        maxRowWidth = currentRowWidth; 

                    contentSize.Height = _rowHeight * _numRows;

                    // If we don't have constraint or content wisth is smaller than constraint width then size to content 
                    if (double.IsInfinity(contentSize.Width) || DoubleUtil.IsNaN(contentSize.Width) || maxRowWidth < constraint.Width)
                        contentSize.Width = maxRowWidth; 
                    else 
                        contentSize.Width = constraint.Width;
                } 
                else if (tabAlignment == Dock.Left || tabAlignment == Dock.Right)
                {
                    foreach (UIElement child in InternalChildren)
                    { 
                        if (child.Visibility == Visibility.Collapsed)
                            continue; 
 
                        _numHeaders++;
 
                        // Helper measures child, and deals with Min, Max, and base Width & Height properties.
                        // Helper returns the size a child needs to take up (DesiredSize or property specified size).
                        child.Measure(constraint);
 
                        Size childSize = GetDesiredSizeWithoutMargin(child);
 
                        if (contentSize.Width < childSize.Width) 
                            contentSize.Width = childSize.Width;
 
                        contentSize.Height += childSize.Height;
                    }
                }
 
            // Returns our minimum size & sets DesiredSize.
            return contentSize; 
        } 

        ///  
        /// TabPanel arranges each of its children.
        /// 
        /// Size that TabPanel will assume to position children.
        protected override Size ArrangeOverride(Size arrangeSize) 
        {
            Dock tabAlignment = TabStripPlacement; 
            if (tabAlignment == Dock.Top || tabAlignment == Dock.Bottom) 
            {
                ArrangeHorizontal(arrangeSize); 
            }
            else if (tabAlignment == Dock.Left || tabAlignment == Dock.Right)
            {
                ArrangeVertical(arrangeSize); 
            }
            return arrangeSize; 
        } 

        ///  
        /// Override of .
        /// 
        /// Geometry to use as additional clip in case when element is larger then available space
        protected override Geometry GetLayoutClip(Size layoutSlotSize) 
        {
            return null; 
        } 

        #endregion Protected Methods 

        //-------------------------------------------------------------------
        //
        //  Private Methods 
        //
        //-------------------------------------------------------------------- 
 
        #region Private Methods
 
        private Size GetDesiredSizeWithoutMargin(UIElement element)
        {
            Thickness margin = (Thickness)element.GetValue(MarginProperty);
            Size desiredSizeWithoutMargin = new Size(); 
            desiredSizeWithoutMargin.Height = Math.Max(0d, element.DesiredSize.Height - margin.Top - margin.Bottom);
            desiredSizeWithoutMargin.Width = Math.Max(0d, element.DesiredSize.Width - margin.Left - margin.Right); 
            return desiredSizeWithoutMargin; 
        }
 
        private double[] GetHeadersSize()
        {
            double[] headerSize = new double[_numHeaders];
            int childIndex = 0; 
            foreach (UIElement child in InternalChildren)
            { 
                if (child.Visibility == Visibility.Collapsed) 
                    continue;
 
                Size childSize = GetDesiredSizeWithoutMargin(child);
                headerSize[childIndex] = childSize.Width;
                childIndex++;
            } 
            return headerSize;
        } 
 
        private void ArrangeHorizontal(Size arrangeSize)
        { 
            Dock tabAlignment = TabStripPlacement;
            bool isMultiRow = _numRows > 1;
            int activeRow = 0;
            int[] solution = new int[0]; 
            Vector childOffset = new Vector();
            double[] headerSize = GetHeadersSize(); 
 
            // If we have multirows, then calculate the best header distribution
            if (isMultiRow) 
            {
                solution = CalculateHeaderDistribution(arrangeSize.Width, headerSize);
                activeRow = GetActiveRow(solution);
 
                // TabPanel starts to layout children depend on activeRow which should be always on bottom (top)
                // The first row should start from Y = (_numRows - 1 - activeRow) * _rowHeight 
                if (tabAlignment == Dock.Top) 
                    childOffset.Y = (_numRows - 1 - activeRow) * _rowHeight;
 
                if (tabAlignment == Dock.Bottom && activeRow != 0)
                    childOffset.Y = (_numRows - activeRow) * _rowHeight;
            }
 
            int childIndex = 0;
            int separatorIndex = 0; 
            foreach (UIElement child in InternalChildren) 
            {
                if (child.Visibility == Visibility.Collapsed) 
                    continue;

                Thickness margin = (Thickness)child.GetValue(MarginProperty);
                double leftOffset = margin.Left; 
                double rightOffset = margin.Right;
                double topOffset = margin.Top; 
                double bottomOffset = margin.Bottom; 

                bool lastHeaderInRow = isMultiRow && (separatorIndex < solution.Length && solution[separatorIndex] == childIndex || childIndex == _numHeaders - 1); 

                //Length left, top, right, bottom;
                Size cellSize = new Size(headerSize[childIndex], _rowHeight);
 
                // Align the last header in the row; If headers are not aligned directional nav would not work correctly
                if (lastHeaderInRow) 
                { 
                    cellSize.Width = arrangeSize.Width - childOffset.X;
                } 

                child.Arrange(new Rect(childOffset.X, childOffset.Y, cellSize.Width, cellSize.Height));

                Size childSize = cellSize; 
                childSize.Height = Math.Max(0d, childSize.Height - topOffset - bottomOffset);
                childSize.Width = Math.Max(0d, childSize.Width - leftOffset - rightOffset); 
 
                // Calculate the offset for the next child
                childOffset.X += cellSize.Width; 
                if (lastHeaderInRow)
                {
                    if ((separatorIndex == activeRow && tabAlignment == Dock.Top) ||
                        (separatorIndex == activeRow - 1 && tabAlignment == Dock.Bottom)) 
                        childOffset.Y = 0d;
                    else 
                        childOffset.Y += _rowHeight; 

                    childOffset.X = 0d; 
                    separatorIndex++;
                }

                childIndex++; 
            }
        } 
 
        private void ArrangeVertical(Size arrangeSize)
        { 
            double childOffsetY = 0d;
            foreach (UIElement child in InternalChildren)
            {
                if (child.Visibility != Visibility.Collapsed) 
                {
                    Size childSize = GetDesiredSizeWithoutMargin(child); 
                    child.Arrange(new Rect(0, childOffsetY, arrangeSize.Width, childSize.Height)); 

                    // Calculate the offset for the next child 
                    childOffsetY += childSize.Height;
                }
            }
        } 

        // Returns the row which contain the child with IsSelected==true 
        private int GetActiveRow(int[] solution) 
        {
            int activeRow = 0; 
            int childIndex = 0;
            if (solution.Length > 0)
            {
                foreach (UIElement child in InternalChildren) 
                {
                    if (child.Visibility == Visibility.Collapsed) 
                        continue; 

                    bool isActiveTab = (bool)child.GetValue(Selector.IsSelectedProperty); 

                    if (isActiveTab)
                    {
                        return activeRow; 
                    }
 
                    if (activeRow < solution.Length && solution[activeRow] == childIndex) 
                    {
                        activeRow++; 
                    }

                    childIndex++;
                } 
            }
 
            // If the is no selected element and aligment is Top  - then the active row is the last row 
            if (TabStripPlacement == Dock.Top)
            { 
                activeRow = _numRows - 1;
            }

            return activeRow; 
        }
 
        /*   TabPanel layout calculation: 

        After measure call we have: 
        rowWidthLimit - width of the TabPanel
        Header[0..n-1]  - headers
        headerWidth[0..n-1] - header width
 
        Calculated values:
        numSeparators                       - number of separators between numSeparators+1 rows 
        rowWidth[0..numSeparators]           - row width 
        rowHeaderCount[0..numSeparators]    - Row Count = number of headers on that row
        rowAverageGap[0..numSeparators]     - Average Gap for the row i = (rowWidth - rowWidth[i])/rowHeaderCount[i] 
        currentSolution[0..numSeparators-1] - separator currentSolution[i]=x means Header[x] and h[x+1] are separated with new line
        bestSolution[0..numSeparators-1]    - keep the last Best Solution
        bestSolutionRowAverageGap           - keep the last Best Solution Average Gap
 
        Between all separators distribution the best solution have minimum Average Gap -
        this is the amount of pixels added to the header (to justify) in the row 
 
        How does it work:
        First we flow the headers to calculate the number of necessary rows (numSeparators+1). 
        That means we need to insert numSeparators separators between n headers (numSeparators rowWidthLimit && numberOfHeadersInCurrentRow > 0) 
                { // if we cannot add next header - flow to next row 
                    // Store current row before we go to the next
                    rowWidth[currentRowIndex] = currentRowWidth; // Store the current row width 
                    rowHeaderCount[currentRowIndex] = numberOfHeadersInCurrentRow; // For each row we store the number os headers inside
                    currentAverageGap = Math.Max(0d, (rowWidthLimit - currentRowWidth) / numberOfHeadersInCurrentRow); // The amout of width that should be added to justify the header
                    rowAverageGap[currentRowIndex] = currentAverageGap;
                    currentSolution[currentRowIndex] = index - 1; // Separator points to the last header in the row 
                    if (bestSolutionMaxRowAverageGap < currentAverageGap) // Remember the maximum of all currentAverageGap
                        bestSolutionMaxRowAverageGap = currentAverageGap; 
 
                    // Iterate to next row
                    currentRowIndex++; 
                    currentRowWidth = headerWidth[index]; // Accumulate header widths on the same row
                    numberOfHeadersInCurrentRow = 1;
                }
                else 
                {
                    currentRowWidth += headerWidth[index]; // Accumulate header widths on the same row 
                    // Increase the number of headers only if they are not collapsed (width=0) 
                    if (headerWidth[index] != 0)
                        numberOfHeadersInCurrentRow++; 
                }
            }

            // If everithing fit in 1 row then exit (no separators needed) 
            if (currentRowIndex == 0)
                return new int[0]; 
 
            // Add the last row
            rowWidth[currentRowIndex] = currentRowWidth; 
            rowHeaderCount[currentRowIndex] = numberOfHeadersInCurrentRow;
            currentAverageGap = (rowWidthLimit - currentRowWidth) / numberOfHeadersInCurrentRow;
            rowAverageGap[currentRowIndex] = currentAverageGap;
            if (bestSolutionMaxRowAverageGap < currentAverageGap) 
                bestSolutionMaxRowAverageGap = currentAverageGap;
 
            currentSolution.CopyTo(bestSolution, 0); // Remember the first solution as initial bestSolution 
            rowAverageGap.CopyTo(bestSolutionRowAverageGap, 0); // bestSolutionRowAverageGap is used in ArrangeOverride to calculate header sizes
 
            // Search for the best solution
            // The exit condition if when we cannot move header to the next row
            while (true)
            { 
                // Find the row with maximum AverageGap
                int worstRowIndex = 0; // Keep the row index with maximum AverageGap 
                double maxAG = 0; 

                for (int i = 0; i < _numRows; i++) // for all rows 
                {
                    if (maxAG < rowAverageGap[i])
                    {
                        maxAG = rowAverageGap[i]; 
                        worstRowIndex = i;
                    } 
                } 

                // If we are on the first row - cannot move from previous 
                if (worstRowIndex == 0)
                    break;

                // From the row with maximum AverageGap we try to move a header from previous row 
                int moveToRow = worstRowIndex;
                int moveFromRow = moveToRow - 1; 
                int moveHeader = currentSolution[moveFromRow]; 
                double movedHeaderWidth = headerWidth[moveHeader];
 
                rowWidth[moveToRow] += movedHeaderWidth;

                // If the moved header cannot fit - exit. We have the best solution already.
                if (rowWidth[moveToRow] > rowWidthLimit) 
                    break;
 
                // If header is moved successfully to the worst row 
                // we update the arrays keeping the row state
                currentSolution[moveFromRow]--; 
                rowHeaderCount[moveToRow]++;
                rowWidth[moveFromRow] -= movedHeaderWidth;
                rowHeaderCount[moveFromRow]--;
                rowAverageGap[moveFromRow] = (rowWidthLimit - rowWidth[moveFromRow]) / rowHeaderCount[moveFromRow]; 
                rowAverageGap[moveToRow] = (rowWidthLimit - rowWidth[moveToRow]) / rowHeaderCount[moveToRow];
 
                // EvaluateSolution: 
                // If the current solution is better than bestSolution - keep it in bestSolution
                maxAG = 0; 
                for (int i = 0; i < _numRows; i++) // for all rows
                {
                    if (maxAG < rowAverageGap[i])
                    { 
                        maxAG = rowAverageGap[i];
                    } 
                } 

                if (maxAG < bestSolutionMaxRowAverageGap) 
                {
                    bestSolutionMaxRowAverageGap = maxAG;
                    currentSolution.CopyTo(bestSolution, 0);
                    rowAverageGap.CopyTo(bestSolutionRowAverageGap, 0); 
                }
            } 
 
            // Each header size should be increased so headers in the row stretch to fit the row
            currentRowIndex = 0; 
            for (int index = 0; index < numHeaders; index++)
            {
                headerWidth[index] += bestSolutionRowAverageGap[currentRowIndex];
                if (currentRowIndex < numSeparators && bestSolution[currentRowIndex] == index) 
                    currentRowIndex++;
            } 
            // Use the best solution bestSolution[0..numSeparators-1] to layout 
            return bestSolution;
        } 

        private Dock TabStripPlacement
        {
            get 
            {
                Dock placement = Dock.Top; 
                TabControl tc = TemplatedParent as TabControl; 
                if (tc != null)
                    placement = tc.TabStripPlacement; 
                return placement;
            }
        }
 
        #endregion
 
        //------------------------------------------------------------------- 
        //
        //  Private Data 
        //
        //-------------------------------------------------------------------

        #region Private data 

        private int _numRows = 1;       // Nubmer of row calculated in measure and used in arrange 
        private int _numHeaders = 0;    // Number of headers excluding the collapsed items 
        private double _rowHeight = 0;  // Maximum of all headers height
 
        #endregion
    }
}

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

using System; 
using MS.Internal; 
using MS.Utility;
using System.Collections; 
using System.ComponentModel;
using System.Diagnostics;
using System.Reflection;
using System.Windows.Threading; 
using System.Windows.Media;
using System.Windows.Input; 
 
namespace System.Windows.Controls.Primitives
{ 
    /// 
    /// TabPanel is a Panel designed to handle the intricacies of laying out the tab buttons in a TabControl.  Specically, it handles:
    /// Serving as an ItemsHost for TabItems within a TabControl
    /// Determining correct sizing and positioning for TabItems 
    /// Handling the logic associated with MultiRow scenarios, namely:
    /// Calculating row breaks in a collection of TabItems 
    /// Laying out TabItems in multiple rows based on those breaks 
    /// Performing specific layout for a selected item to indicate selection, namely:
    /// Bringing the selected tab to the front, or, in other words, making the selected tab appear to be in front of other tabs. 
    /// Increasing the size pre-layout size of a selected item (note that this is not a transform, but rather an increase in the size allotted to the element in which to perform layout).
    /// Bringing the selected tab to the front
    /// Exposing attached properties that allow TabItems to be styled based on their placement within the TabPanel.
    ///  
    public class TabPanel : Panel
    { 
        //------------------------------------------------------------------- 
        //
        //  Constructors 
        //
        //-------------------------------------------------------------------

        #region Constructors 

        ///  
        ///     Default DependencyObject constructor 
        /// 
        ///  
        ///     Automatic determination of current Dispatcher. Use alternative constructor
        ///     that accepts a Dispatcher for best performance.
        /// 
        public TabPanel() : base() 
        {
        } 
 
        static TabPanel()
        { 
            KeyboardNavigation.TabNavigationProperty.OverrideMetadata(typeof(TabPanel), new FrameworkPropertyMetadata(KeyboardNavigationMode.Once));
            KeyboardNavigation.DirectionalNavigationProperty.OverrideMetadata(typeof(TabPanel), new FrameworkPropertyMetadata(KeyboardNavigationMode.Cycle));
        }
 
        #endregion
 
        //-------------------------------------------------------------------- 
        //
        //  Public Methods 
        //
        //-------------------------------------------------------------------

        #region Public Methods 

        #endregion 
 
        //--------------------------------------------------------------------
        // 
        //  Protected Methods
        //
        //--------------------------------------------------------------------
 
        #region Protected Methods
 
        ///  
        /// Updates DesiredSize of the TabPanel.  Called by parent UIElement.  This is the first pass of layout.
        ///  
        /// 
        /// TabPanel
        /// 
        /// Constraint size is an "upper limit" that TabPanel should not exceed. 
        /// TabPanel' desired size.
        protected override Size MeasureOverride(Size constraint) 
        { 
            Size contentSize = new Size();
            Dock tabAlignment = TabStripPlacement; 

            _numRows = 1;
            _numHeaders = 0;
            _rowHeight = 0; 

                // For top and bottom placement the panel flow its children to calculate the number of rows and 
                // desired vertical size 
                if (tabAlignment == Dock.Top || tabAlignment == Dock.Bottom)
                { 
                    int numInCurrentRow = 0;
                    double currentRowWidth = 0;
                    double maxRowWidth = 0;
                    foreach (UIElement child in InternalChildren) 
                    {
                        if (child.Visibility == Visibility.Collapsed) 
                            continue; 

                        _numHeaders++; 

                        // Helper measures child, and deals with Min, Max, and base Width & Height properties.
                        // Helper returns the size a child needs to take up (DesiredSize or property specified size).
                        child.Measure(constraint); 
                        Size childSize = GetDesiredSizeWithoutMargin(child);
 
                        if (_rowHeight < childSize.Height) 
                            _rowHeight = childSize.Height;
 
                        if (currentRowWidth + childSize.Width > constraint.Width && numInCurrentRow > 0)
                        { // If child does not fit in the current row - create a new row
                            if (maxRowWidth < currentRowWidth)
                                maxRowWidth = currentRowWidth; 

                            currentRowWidth = childSize.Width; 
                            numInCurrentRow = 1; 
                            _numRows++;
                        } 
                        else
                        {
                            currentRowWidth += childSize.Width;
                            numInCurrentRow++; 
                        }
                    } 
 
                    if (maxRowWidth < currentRowWidth)
                        maxRowWidth = currentRowWidth; 

                    contentSize.Height = _rowHeight * _numRows;

                    // If we don't have constraint or content wisth is smaller than constraint width then size to content 
                    if (double.IsInfinity(contentSize.Width) || DoubleUtil.IsNaN(contentSize.Width) || maxRowWidth < constraint.Width)
                        contentSize.Width = maxRowWidth; 
                    else 
                        contentSize.Width = constraint.Width;
                } 
                else if (tabAlignment == Dock.Left || tabAlignment == Dock.Right)
                {
                    foreach (UIElement child in InternalChildren)
                    { 
                        if (child.Visibility == Visibility.Collapsed)
                            continue; 
 
                        _numHeaders++;
 
                        // Helper measures child, and deals with Min, Max, and base Width & Height properties.
                        // Helper returns the size a child needs to take up (DesiredSize or property specified size).
                        child.Measure(constraint);
 
                        Size childSize = GetDesiredSizeWithoutMargin(child);
 
                        if (contentSize.Width < childSize.Width) 
                            contentSize.Width = childSize.Width;
 
                        contentSize.Height += childSize.Height;
                    }
                }
 
            // Returns our minimum size & sets DesiredSize.
            return contentSize; 
        } 

        ///  
        /// TabPanel arranges each of its children.
        /// 
        /// Size that TabPanel will assume to position children.
        protected override Size ArrangeOverride(Size arrangeSize) 
        {
            Dock tabAlignment = TabStripPlacement; 
            if (tabAlignment == Dock.Top || tabAlignment == Dock.Bottom) 
            {
                ArrangeHorizontal(arrangeSize); 
            }
            else if (tabAlignment == Dock.Left || tabAlignment == Dock.Right)
            {
                ArrangeVertical(arrangeSize); 
            }
            return arrangeSize; 
        } 

        ///  
        /// Override of .
        /// 
        /// Geometry to use as additional clip in case when element is larger then available space
        protected override Geometry GetLayoutClip(Size layoutSlotSize) 
        {
            return null; 
        } 

        #endregion Protected Methods 

        //-------------------------------------------------------------------
        //
        //  Private Methods 
        //
        //-------------------------------------------------------------------- 
 
        #region Private Methods
 
        private Size GetDesiredSizeWithoutMargin(UIElement element)
        {
            Thickness margin = (Thickness)element.GetValue(MarginProperty);
            Size desiredSizeWithoutMargin = new Size(); 
            desiredSizeWithoutMargin.Height = Math.Max(0d, element.DesiredSize.Height - margin.Top - margin.Bottom);
            desiredSizeWithoutMargin.Width = Math.Max(0d, element.DesiredSize.Width - margin.Left - margin.Right); 
            return desiredSizeWithoutMargin; 
        }
 
        private double[] GetHeadersSize()
        {
            double[] headerSize = new double[_numHeaders];
            int childIndex = 0; 
            foreach (UIElement child in InternalChildren)
            { 
                if (child.Visibility == Visibility.Collapsed) 
                    continue;
 
                Size childSize = GetDesiredSizeWithoutMargin(child);
                headerSize[childIndex] = childSize.Width;
                childIndex++;
            } 
            return headerSize;
        } 
 
        private void ArrangeHorizontal(Size arrangeSize)
        { 
            Dock tabAlignment = TabStripPlacement;
            bool isMultiRow = _numRows > 1;
            int activeRow = 0;
            int[] solution = new int[0]; 
            Vector childOffset = new Vector();
            double[] headerSize = GetHeadersSize(); 
 
            // If we have multirows, then calculate the best header distribution
            if (isMultiRow) 
            {
                solution = CalculateHeaderDistribution(arrangeSize.Width, headerSize);
                activeRow = GetActiveRow(solution);
 
                // TabPanel starts to layout children depend on activeRow which should be always on bottom (top)
                // The first row should start from Y = (_numRows - 1 - activeRow) * _rowHeight 
                if (tabAlignment == Dock.Top) 
                    childOffset.Y = (_numRows - 1 - activeRow) * _rowHeight;
 
                if (tabAlignment == Dock.Bottom && activeRow != 0)
                    childOffset.Y = (_numRows - activeRow) * _rowHeight;
            }
 
            int childIndex = 0;
            int separatorIndex = 0; 
            foreach (UIElement child in InternalChildren) 
            {
                if (child.Visibility == Visibility.Collapsed) 
                    continue;

                Thickness margin = (Thickness)child.GetValue(MarginProperty);
                double leftOffset = margin.Left; 
                double rightOffset = margin.Right;
                double topOffset = margin.Top; 
                double bottomOffset = margin.Bottom; 

                bool lastHeaderInRow = isMultiRow && (separatorIndex < solution.Length && solution[separatorIndex] == childIndex || childIndex == _numHeaders - 1); 

                //Length left, top, right, bottom;
                Size cellSize = new Size(headerSize[childIndex], _rowHeight);
 
                // Align the last header in the row; If headers are not aligned directional nav would not work correctly
                if (lastHeaderInRow) 
                { 
                    cellSize.Width = arrangeSize.Width - childOffset.X;
                } 

                child.Arrange(new Rect(childOffset.X, childOffset.Y, cellSize.Width, cellSize.Height));

                Size childSize = cellSize; 
                childSize.Height = Math.Max(0d, childSize.Height - topOffset - bottomOffset);
                childSize.Width = Math.Max(0d, childSize.Width - leftOffset - rightOffset); 
 
                // Calculate the offset for the next child
                childOffset.X += cellSize.Width; 
                if (lastHeaderInRow)
                {
                    if ((separatorIndex == activeRow && tabAlignment == Dock.Top) ||
                        (separatorIndex == activeRow - 1 && tabAlignment == Dock.Bottom)) 
                        childOffset.Y = 0d;
                    else 
                        childOffset.Y += _rowHeight; 

                    childOffset.X = 0d; 
                    separatorIndex++;
                }

                childIndex++; 
            }
        } 
 
        private void ArrangeVertical(Size arrangeSize)
        { 
            double childOffsetY = 0d;
            foreach (UIElement child in InternalChildren)
            {
                if (child.Visibility != Visibility.Collapsed) 
                {
                    Size childSize = GetDesiredSizeWithoutMargin(child); 
                    child.Arrange(new Rect(0, childOffsetY, arrangeSize.Width, childSize.Height)); 

                    // Calculate the offset for the next child 
                    childOffsetY += childSize.Height;
                }
            }
        } 

        // Returns the row which contain the child with IsSelected==true 
        private int GetActiveRow(int[] solution) 
        {
            int activeRow = 0; 
            int childIndex = 0;
            if (solution.Length > 0)
            {
                foreach (UIElement child in InternalChildren) 
                {
                    if (child.Visibility == Visibility.Collapsed) 
                        continue; 

                    bool isActiveTab = (bool)child.GetValue(Selector.IsSelectedProperty); 

                    if (isActiveTab)
                    {
                        return activeRow; 
                    }
 
                    if (activeRow < solution.Length && solution[activeRow] == childIndex) 
                    {
                        activeRow++; 
                    }

                    childIndex++;
                } 
            }
 
            // If the is no selected element and aligment is Top  - then the active row is the last row 
            if (TabStripPlacement == Dock.Top)
            { 
                activeRow = _numRows - 1;
            }

            return activeRow; 
        }
 
        /*   TabPanel layout calculation: 

        After measure call we have: 
        rowWidthLimit - width of the TabPanel
        Header[0..n-1]  - headers
        headerWidth[0..n-1] - header width
 
        Calculated values:
        numSeparators                       - number of separators between numSeparators+1 rows 
        rowWidth[0..numSeparators]           - row width 
        rowHeaderCount[0..numSeparators]    - Row Count = number of headers on that row
        rowAverageGap[0..numSeparators]     - Average Gap for the row i = (rowWidth - rowWidth[i])/rowHeaderCount[i] 
        currentSolution[0..numSeparators-1] - separator currentSolution[i]=x means Header[x] and h[x+1] are separated with new line
        bestSolution[0..numSeparators-1]    - keep the last Best Solution
        bestSolutionRowAverageGap           - keep the last Best Solution Average Gap
 
        Between all separators distribution the best solution have minimum Average Gap -
        this is the amount of pixels added to the header (to justify) in the row 
 
        How does it work:
        First we flow the headers to calculate the number of necessary rows (numSeparators+1). 
        That means we need to insert numSeparators separators between n headers (numSeparators rowWidthLimit && numberOfHeadersInCurrentRow > 0) 
                { // if we cannot add next header - flow to next row 
                    // Store current row before we go to the next
                    rowWidth[currentRowIndex] = currentRowWidth; // Store the current row width 
                    rowHeaderCount[currentRowIndex] = numberOfHeadersInCurrentRow; // For each row we store the number os headers inside
                    currentAverageGap = Math.Max(0d, (rowWidthLimit - currentRowWidth) / numberOfHeadersInCurrentRow); // The amout of width that should be added to justify the header
                    rowAverageGap[currentRowIndex] = currentAverageGap;
                    currentSolution[currentRowIndex] = index - 1; // Separator points to the last header in the row 
                    if (bestSolutionMaxRowAverageGap < currentAverageGap) // Remember the maximum of all currentAverageGap
                        bestSolutionMaxRowAverageGap = currentAverageGap; 
 
                    // Iterate to next row
                    currentRowIndex++; 
                    currentRowWidth = headerWidth[index]; // Accumulate header widths on the same row
                    numberOfHeadersInCurrentRow = 1;
                }
                else 
                {
                    currentRowWidth += headerWidth[index]; // Accumulate header widths on the same row 
                    // Increase the number of headers only if they are not collapsed (width=0) 
                    if (headerWidth[index] != 0)
                        numberOfHeadersInCurrentRow++; 
                }
            }

            // If everithing fit in 1 row then exit (no separators needed) 
            if (currentRowIndex == 0)
                return new int[0]; 
 
            // Add the last row
            rowWidth[currentRowIndex] = currentRowWidth; 
            rowHeaderCount[currentRowIndex] = numberOfHeadersInCurrentRow;
            currentAverageGap = (rowWidthLimit - currentRowWidth) / numberOfHeadersInCurrentRow;
            rowAverageGap[currentRowIndex] = currentAverageGap;
            if (bestSolutionMaxRowAverageGap < currentAverageGap) 
                bestSolutionMaxRowAverageGap = currentAverageGap;
 
            currentSolution.CopyTo(bestSolution, 0); // Remember the first solution as initial bestSolution 
            rowAverageGap.CopyTo(bestSolutionRowAverageGap, 0); // bestSolutionRowAverageGap is used in ArrangeOverride to calculate header sizes
 
            // Search for the best solution
            // The exit condition if when we cannot move header to the next row
            while (true)
            { 
                // Find the row with maximum AverageGap
                int worstRowIndex = 0; // Keep the row index with maximum AverageGap 
                double maxAG = 0; 

                for (int i = 0; i < _numRows; i++) // for all rows 
                {
                    if (maxAG < rowAverageGap[i])
                    {
                        maxAG = rowAverageGap[i]; 
                        worstRowIndex = i;
                    } 
                } 

                // If we are on the first row - cannot move from previous 
                if (worstRowIndex == 0)
                    break;

                // From the row with maximum AverageGap we try to move a header from previous row 
                int moveToRow = worstRowIndex;
                int moveFromRow = moveToRow - 1; 
                int moveHeader = currentSolution[moveFromRow]; 
                double movedHeaderWidth = headerWidth[moveHeader];
 
                rowWidth[moveToRow] += movedHeaderWidth;

                // If the moved header cannot fit - exit. We have the best solution already.
                if (rowWidth[moveToRow] > rowWidthLimit) 
                    break;
 
                // If header is moved successfully to the worst row 
                // we update the arrays keeping the row state
                currentSolution[moveFromRow]--; 
                rowHeaderCount[moveToRow]++;
                rowWidth[moveFromRow] -= movedHeaderWidth;
                rowHeaderCount[moveFromRow]--;
                rowAverageGap[moveFromRow] = (rowWidthLimit - rowWidth[moveFromRow]) / rowHeaderCount[moveFromRow]; 
                rowAverageGap[moveToRow] = (rowWidthLimit - rowWidth[moveToRow]) / rowHeaderCount[moveToRow];
 
                // EvaluateSolution: 
                // If the current solution is better than bestSolution - keep it in bestSolution
                maxAG = 0; 
                for (int i = 0; i < _numRows; i++) // for all rows
                {
                    if (maxAG < rowAverageGap[i])
                    { 
                        maxAG = rowAverageGap[i];
                    } 
                } 

                if (maxAG < bestSolutionMaxRowAverageGap) 
                {
                    bestSolutionMaxRowAverageGap = maxAG;
                    currentSolution.CopyTo(bestSolution, 0);
                    rowAverageGap.CopyTo(bestSolutionRowAverageGap, 0); 
                }
            } 
 
            // Each header size should be increased so headers in the row stretch to fit the row
            currentRowIndex = 0; 
            for (int index = 0; index < numHeaders; index++)
            {
                headerWidth[index] += bestSolutionRowAverageGap[currentRowIndex];
                if (currentRowIndex < numSeparators && bestSolution[currentRowIndex] == index) 
                    currentRowIndex++;
            } 
            // Use the best solution bestSolution[0..numSeparators-1] to layout 
            return bestSolution;
        } 

        private Dock TabStripPlacement
        {
            get 
            {
                Dock placement = Dock.Top; 
                TabControl tc = TemplatedParent as TabControl; 
                if (tc != null)
                    placement = tc.TabStripPlacement; 
                return placement;
            }
        }
 
        #endregion
 
        //------------------------------------------------------------------- 
        //
        //  Private Data 
        //
        //-------------------------------------------------------------------

        #region Private data 

        private int _numRows = 1;       // Nubmer of row calculated in measure and used in arrange 
        private int _numHeaders = 0;    // Number of headers excluding the collapsed items 
        private double _rowHeight = 0;  // Maximum of all headers height
 
        #endregion
    }
}

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

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