Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Core / CSharp / System / Windows / Media / MatrixStack.cs / 1305600 / MatrixStack.cs
//------------------------------------------------------------------------------ // Microsoft Avalon // Copyright (c) Microsoft Corporation, 2001 // // File: MatrixStack.cs //----------------------------------------------------------------------------- using System; using System.Diagnostics; using System.Collections; using MS.Internal; using System.Security; using System.Security.Permissions; namespace System.Windows.Media { ///MatrixStack class implementation internal class MatrixStack { private Matrix[] _items; private int _size; #if DEBUG private static readonly int s_initialSize = 4; #else private static readonly int s_initialSize = 40; // sizeof(Matrix) * 40 = 2240 bytes. Must be > 4 #endif private static readonly int s_growFactor = 2; private static readonly int s_shrinkFactor = s_growFactor + 1; // The following members are used to lazily manage the memory allocated by the stack. private int _highWaterMark; private int _observeCount; private static readonly int s_trimCount = 10; public MatrixStack() { _items = new Matrix[s_initialSize]; } ////// Ensures that there is space for at least one more element. /// private void EnsureCapacity() { // If we reached the capacity of the _items array we need to increase // the size. We use an exponential growth to keep Push in average O(1). if (_size == _items.Length) { Matrix[] newItems = new Matrix[s_growFactor * _size]; Array.Copy(_items, newItems, _size); _items = newItems; } } ////// Push new matrix on the stack. /// /// The new matrix to be pushed /// Iff true, the matrix is multiplied with the current /// top matrix on the stack and then pushed on the stack. If false the matrix /// is pushed as is on top of the stack. public void Push(ref Matrix matrix, bool combine) { EnsureCapacity(); if (combine && (_size > 0)) { // Combine means that we push the product of the top matrix and the new // one on the stack. Note that there isn't a top-matrix if the stack is empty. // In this case the top-matrix is assumed to be identity. See else case. _items[_size] = matrix; // _items[_size] = _items[_size] * _items[_size-1]; MatrixUtil.MultiplyMatrix(ref _items[_size], ref _items[_size - 1]); } else { // If the stack is empty or we are not combining, we just assign the matrix passed // in to the next free slot in the array. _items[_size] = matrix; } _size++; // For memory optimization purposes we track the max usage of the stack here. // See the optimze method for more details about this. _highWaterMark = Math.Max(_highWaterMark, _size); } ////// Pushes a transformation on the stack. The transformation is multiplied with the top element /// on the stack and then pushed on the stack. /// /// 2D transformation. /// The combine argument indicates if the transform should be pushed multiplied with the /// current top transform or as is. ////// The code duplication between Push(ref Matrix, bool) and Push(Transform, bool) is not ideal. /// However, we did see a performance gain by optimizing the Push(Transform, bool) method /// minimizing the copies of data. /// public void Push(Transform transform, bool combine) { EnsureCapacity(); if (combine && (_size > 0)) { // Combine means that we push the product of the top matrix and transform // on the stack. Note that there isn't a top-matrix if the stack is empty. // In this case the top-matrix is assumed to be identity. See else case. // _items[_size] is the new top of the stack, _items[_size - 1] is the // previous top. transform.MultiplyValueByMatrix(ref _items[_size], ref _items[_size - 1]); } else { // If we don't combine or if the stack is empty. _items[_size] = transform.Value; } _size++; // For memory optimization purposes we track the max usage of the stack here. // See the optimze method for more details about this. _highWaterMark = Math.Max(_highWaterMark, _size); } ////// Pushes the offset on the stack. If the combine flag is true, the offset is applied to the top element before /// it is pushed onto the stack. /// public void Push(Vector offset, bool combine) { EnsureCapacity(); if (combine && (_size > 0)) { // In combine mode copy the top element, but only if the stack is not empty. _items[_size] = _items[_size-1]; } else { // If combine is false, initialize the new top stack element with the identity // matrix. _items[_size] = Matrix.Identity; } // Apply the offset to the new top element. MatrixUtil.PrependOffset(ref _items[_size], offset.X, offset.Y); _size++; // For memory optimization purposes we track the max usage of the stack here. // See the optimze method for more details about this. _highWaterMark = Math.Max(_highWaterMark, _size); } ////// Pops the top stack element from the stack. /// public void Pop() { Debug.Assert(!IsEmpty); #if DEBUG _items[_size-1] = new Matrix(); #endif _size--; } ////// Peek returns the matrix on the top of the stack. /// public Matrix Peek() { Debug.Assert(!IsEmpty); return _items[_size-1]; } ////// This is true iff the stack is empty. /// public bool IsEmpty { get { return _size == 0; } } ////// Instead of allocating and releasing memory continuously while pushing on /// and popping off the stack, we call the optimize method after each frame /// to readjust the internal stack capacity. /// public void Optimize() { Debug.Assert(_size == 0); // The stack must be empty before this is called. Debug.Assert(_highWaterMark <= _items.Length); // After s_trimCount calls to this method we check the past usage of the stack. if (_observeCount == s_trimCount) { int newSize = Math.Max(_highWaterMark, s_initialSize); if (newSize * (s_shrinkFactor) <= _items.Length) { // If the water mark is less or equal to capacity divided by the shrink // factor, then we shrink the stack. Usually the shrink factor is greater // than the grow factor. This avoids an oscillation of shrinking and growing // the stack if the high water mark goes only slightly up and down. // Note that we don't need to copy the array because the stack is empty. _items = new Matrix[newSize]; } _highWaterMark = 0; _observeCount = 0; } else { // Keep incrementing our observe count _observeCount++; } } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007. // Copyright (c) Microsoft Corporation. All rights reserved.
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