Canvas.cs source code in C# .NET

                        Code:
                         / DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / wcp / Framework / System / Windows / Controls / Canvas.cs / 1 / Canvas.cs
                        
                        
                            //---------------------------------------------------------------------------- 
//
// Copyright (C) Microsoft Corporation.  All rights reserved.
//
// File: Canvas.cs 
//
// Description: Contains the Canvas class. 
//              Spec at [....]/layout/Specs/Canvas.xml 
//
// History: 
//  06/02/2003 : [....]  - Added to WCP branch (was APEContainer.cs in old branch)
//
//---------------------------------------------------------------------------
 
using MS.Internal;
using MS.Utility; 
using System.ComponentModel; 

using System.Diagnostics; 
using System.Reflection;
using System.Windows.Threading;

using System.Windows.Media; 

 
using System; 

namespace System.Windows.Controls 
{
    /// 
    /// Canvas is used to place child UIElements at arbitrary positions or to draw children in multiple
    /// layers. 
    ///
    /// Child positions are computed from the Left, Top properties.  These properties do 
    /// not contribute to the size of the Canvas.  To position children in a way that affects the Canvas' size, 
    /// use the Margin properties.
    /// 
    /// The order that children are drawn (z-order) is determined exclusively by child order.
    /// 
    public class Canvas : Panel
    { 

        //------------------------------------------------------------------- 
        // 
        //  Constructors
        // 
        //-------------------------------------------------------------------

        #region Constructors
 
        /// 
        ///     Default DependencyObject constructor 
        ///  
        /// 
        ///     Automatic determination of current Dispatcher. Use alternative constructor 
        ///     that accepts a Dispatcher for best performance.
        /// 
        public Canvas() : base()
        { 
        }
 
        #endregion 

        //-------------------------------------------------------------------- 
        //
        //  Public Methods
        //
        //------------------------------------------------------------------- 

        #region Public Methods 
 
        /// 
        /// Reads the attached property Left from the given element. 
        /// 
        /// The element from which to read the Left attached property.
        /// The property's value.
        ///  
        [TypeConverter("System.Windows.LengthConverter, PresentationFramework, Version=" + Microsoft.Internal.BuildInfo.WCP_VERSION + ", Culture=neutral, PublicKeyToken=" + Microsoft.Internal.BuildInfo.WCP_PUBLIC_KEY_TOKEN + ", Custom=null")]
        [AttachedPropertyBrowsableForChildren()] 
        public static double GetLeft(UIElement element) 
        {
            if (element == null) { throw new ArgumentNullException("element"); } 
            return (double)element.GetValue(LeftProperty);
        }

        ///  
        /// Writes the attached property Left to the given element.
        ///  
        /// The element to which to write the Left attached property. 
        /// The length to set
        ///  
        public static void SetLeft(UIElement element, double length)
        {
            if (element == null) { throw new ArgumentNullException("element"); }
            element.SetValue(LeftProperty, length); 
        }
 
        ///  
        /// Reads the attached property Top from the given element.
        ///  
        /// The element from which to read the Top attached property.
        /// The property's value.
        /// 
        [TypeConverter("System.Windows.LengthConverter, PresentationFramework, Version=" + Microsoft.Internal.BuildInfo.WCP_VERSION + ", Culture=neutral, PublicKeyToken=" + Microsoft.Internal.BuildInfo.WCP_PUBLIC_KEY_TOKEN + ", Custom=null")] 
        [AttachedPropertyBrowsableForChildren()]
        public static double GetTop(UIElement element) 
        { 
            if (element == null) { throw new ArgumentNullException("element"); }
            return (double)element.GetValue(TopProperty); 
        }

        /// 
        /// Writes the attached property Top to the given element. 
        /// 
        /// The element to which to write the Top attached property. 
        /// The length to set 
        /// 
        public static void SetTop(UIElement element, double length) 
        {
            if (element == null) { throw new ArgumentNullException("element"); }
            element.SetValue(TopProperty, length);
        } 

        ///  
        /// Reads the attached property Right from the given element. 
        /// 
        /// The element from which to read the Right attached property. 
        /// The property's Length value.
        /// 
        [TypeConverter("System.Windows.LengthConverter, PresentationFramework, Version=" + Microsoft.Internal.BuildInfo.WCP_VERSION + ", Culture=neutral, PublicKeyToken=" + Microsoft.Internal.BuildInfo.WCP_PUBLIC_KEY_TOKEN + ", Custom=null")]
        [AttachedPropertyBrowsableForChildren()] 
        public static double GetRight(UIElement element)
        { 
            if (element == null) { throw new ArgumentNullException("element"); } 
            return (double)element.GetValue(RightProperty);
        } 

        /// 
        /// Writes the attached property Right to the given element.
        ///  
        /// The element to which to write the Right attached property.
        /// The Length to set 
        ///  
        public static void SetRight(UIElement element, double length)
        { 
            if (element == null) { throw new ArgumentNullException("element"); }
            element.SetValue(RightProperty, length);
        }
 
        /// 
        /// Reads the attached property Bottom from the given element. 
        ///  
        /// The element from which to read the Bottom attached property.
        /// The property's Length value. 
        /// 
        [TypeConverter("System.Windows.LengthConverter, PresentationFramework, Version=" + Microsoft.Internal.BuildInfo.WCP_VERSION + ", Culture=neutral, PublicKeyToken=" + Microsoft.Internal.BuildInfo.WCP_PUBLIC_KEY_TOKEN + ", Custom=null")]
        [AttachedPropertyBrowsableForChildren()]
        public static double GetBottom(UIElement element) 
        {
            if (element == null) { throw new ArgumentNullException("element"); } 
            return (double)element.GetValue(BottomProperty); 
        }
 
        /// 
        /// Writes the attached property Bottom to the given element.
        /// 
        /// The element to which to write the Bottom attached property. 
        /// The Length to set
        ///  
        public static void SetBottom(UIElement element, double length) 
        {
            if (element == null) { throw new ArgumentNullException("element"); } 
            element.SetValue(BottomProperty, length);
        }

 

        #endregion 
 
        //--------------------------------------------------------------------
        // 
        //  Public Properties + Dependency Properties's
        //
        //--------------------------------------------------------------------
 
        #region Public Properties
 
        //having this invalidate callback allows to host UIElements in Canvas and still 
        //receive invalidations when Left/Top/Bottom/Right properties change -
        //registering the attached properties with AffectsParentArrange flag would be a mistake 
        //because those flags only work for FrameworkElements
        private static void OnPositioningChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            UIElement uie = d as UIElement; 
            if(uie != null)
            { 
                Canvas p = VisualTreeHelper.GetParent(uie) as Canvas; 
                if(p != null)
                    p.InvalidateArrange(); 
            }
         }

        ///  
        /// This is the dependency property registered for the Canvas' Left attached property.
        /// 
        /// The Left property is read by a Canvas on its children to determine where to position them. 
        /// The child's offset from this property does not have an effect on the Canvas' own size.
        /// Conflict between the Left and Right properties is resolved in favor of Left. 
        /// 
        public static readonly DependencyProperty LeftProperty
            = DependencyProperty.RegisterAttached("Left", typeof(double), typeof(Canvas),
                    new FrameworkPropertyMetadata(Double.NaN, new PropertyChangedCallback(OnPositioningChanged)), 
                    new ValidateValueCallback(System.Windows.Shapes.Shape.IsDoubleFiniteOrNaN));
 
        ///  
        /// This is the dependency property registered for the Canvas' Top attached property.
        /// 
        /// The Top property is read by a Canvas on its children to determine where to position them.
        /// The child's offset from this property does not have an effect on the Canvas' own size.
        /// 
        public static readonly DependencyProperty TopProperty 
            = DependencyProperty.RegisterAttached("Top", typeof(double), typeof(Canvas),
                    new FrameworkPropertyMetadata(Double.NaN, new PropertyChangedCallback(OnPositioningChanged)), 
                    new ValidateValueCallback(System.Windows.Shapes.Shape.IsDoubleFiniteOrNaN)); 

        ///  
        /// This is the dependency property registered for the Canvas' Right attached property.
        ///
        /// The Right property is read by a Canvas on its children to determine where to position them.
        /// The child's offset from this property does not have an effect on the Canvas' own size. 
        /// Conflict between the Left and Right properties is resolved in favor of Left.
        ///  
        public static readonly DependencyProperty RightProperty 
            = DependencyProperty.RegisterAttached("Right", typeof(double), typeof(Canvas),
                    new FrameworkPropertyMetadata(Double.NaN, new PropertyChangedCallback(OnPositioningChanged)), 
                    new ValidateValueCallback(System.Windows.Shapes.Shape.IsDoubleFiniteOrNaN));

        /// 
        /// This is the dependency property registered for the Canvas' Bottom attached property. 
        ///
        /// The Bottom property is read by a Canvas on its children to determine where to position them. 
        /// The child's offset from this property does not have an effect on the Canvas' own size. 
        /// 
        public static readonly DependencyProperty BottomProperty 
            = DependencyProperty.RegisterAttached("Bottom", typeof(double), typeof(Canvas),
                    new FrameworkPropertyMetadata(Double.NaN, new PropertyChangedCallback(OnPositioningChanged)),
                    new ValidateValueCallback(System.Windows.Shapes.Shape.IsDoubleFiniteOrNaN));
 
        #endregion
 
        //------------------------------------------------------------------- 
        //
        //  Protected Methods 
        //
        //--------------------------------------------------------------------

        #region Protected Methods 

        ///  
        /// Updates DesiredSize of the Canvas.  Called by parent UIElement.  This is the first pass of layout. 
        /// 
        /// Constraint size is an "upper limit" that Canvas should not exceed. 
        /// Canvas' desired size.
        protected override Size MeasureOverride(Size constraint)
        {
            Size childConstraint = new Size(Double.PositiveInfinity, Double.PositiveInfinity); 

            foreach (UIElement child in InternalChildren) 
            { 
                if (child == null) { continue; }
                child.Measure(childConstraint); 
            }

            return new Size();
        } 

        ///  
        /// Canvas computes a position for each of its children taking into account their margin and 
        /// attached Canvas properties: Top, Left.
        /// 
        /// Canvas will also arrange each of its children.
        /// 
        /// Size that Canvas will assume to position children.
        protected override Size ArrangeOverride(Size arrangeSize) 
        {
            //Canvas arranges children at their DesiredSize. 
            //This means that Margin on children is actually respected and added 
            //to the size of layout partition for a child.
            //Therefore, is Margin is 10 and Left is 20, the child's ink will start at 30. 

            foreach (UIElement child in InternalChildren)
            {
                if (child == null) { continue; } 

                double x = 0; 
                double y = 0; 

 
                //Compute offset of the child:
                //If Left is specified, then Right is ignored
                //If Left is not specified, then Right is used
                //If both are not there, then 0 
                double left = GetLeft(child);
                if(!DoubleUtil.IsNaN(left)) 
                { 
                    x = left;
                } 
                else
                {
                    double right = GetRight(child);
 
                    if(!DoubleUtil.IsNaN(right))
                    { 
                        x = arrangeSize.Width - child.DesiredSize.Width - right; 
                    }
                } 

                double top = GetTop(child);
                if(!DoubleUtil.IsNaN(top))
                { 
                    y = top;
                } 
                else 
                {
                    double bottom = GetBottom(child); 

                    if(!DoubleUtil.IsNaN(bottom))
                    {
                        y = arrangeSize.Height - child.DesiredSize.Height - bottom; 
                    }
                } 
 
                child.Arrange(new Rect(new Point(x, y), child.DesiredSize));
            } 
            return arrangeSize;
        }

        ///  
        /// Override of .
        ///  
        /// Geometry to use as additional clip if LayoutConstrained=true 
        protected override Geometry GetLayoutClip(Size layoutSlotSize)
        { 
            //Canvas only clips to bounds if ClipToBounds is set,
            //  no automatic clipping
            if(ClipToBounds)
                return new RectangleGeometry(new Rect(RenderSize)); 
            else
                return null; 
        } 

        // 
        //  This property
        //  1. Finds the correct initial size for the _effectiveValues store on the current DependencyObject
        //  2. This is a performance optimization
        // 
        internal override int EffectiveValuesInitialSize
        { 
            get { return 9; } 
        }
 
        #endregion Protected Methods
    }
}
 

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