Code:
/ DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / wcp / Framework / System / Windows / Controls / ItemsPresenter.cs / 2 / ItemsPresenter.cs
//---------------------------------------------------------------------------- // //// Copyright (C) Microsoft Corporation. All rights reserved. // // // Description: ItemsPresenter object - site of the panel for layout of groups or items. // // Specs: [....]/connecteddata/M5%20General%20Docs/Data%20Styling.mht // //--------------------------------------------------------------------------- using System; using System.Collections; using System.Diagnostics; using System.Windows.Media; using MS.Internal; using MS.Internal.Data; // WeakRefKey namespace System.Windows.Controls { ////// An ItemsPresenter marks the site (in a style) of the panel that controls /// layout of groups or items. /// [Localizability(LocalizationCategory.NeverLocalize)] public class ItemsPresenter : FrameworkElement { //----------------------------------------------------- // // Public Methods // //----------------------------------------------------- ////// Called when the Template's tree is about to be generated /// internal override void OnPreApplyTemplate() { base.OnPreApplyTemplate(); AttachToOwner(); } ////// This is the virtual that sub-classes must override if they wish to get /// notified that the template tree has been created. /// public override void OnApplyTemplate() { // verify that the template produced a panel with no children Panel panel = GetVisualChild(0) as Panel; if (panel == null || VisualTreeHelper.GetChildrenCount(panel) > 0) throw new InvalidOperationException(SR.Get(SRID.ItemsPanelNotSingleNode)); base.OnApplyTemplate(); } //------------------------------------------------------ // // Protected Methods // //----------------------------------------------------- ////// Override of /// Constraint size is an "upper limit" that the return value should not exceed. ///. /// The ItemsPresenter's desired size. protected override Size MeasureOverride(Size constraint) { return Helper.MeasureElementWithSingleChild(this, constraint); } ////// Override of /// Size the ItemsPresenter will assume. protected override Size ArrangeOverride(Size arrangeSize) { return Helper.ArrangeElementWithSingleChild(this, arrangeSize); } //------------------------------------------------------ // // Internal Properties // //------------------------------------------------------ internal ItemsControl Owner { get { return _owner; } } internal ItemContainerGenerator Generator { get { return _generator; } } // Internal Helper so the FrameworkElement could see this property internal override FrameworkTemplate TemplateInternal { get { return Template; } } // Internal Helper so the FrameworkElement could see the template cache internal override FrameworkTemplate TemplateCache { get { return _templateCache; } set { _templateCache = (ItemsPanelTemplate)value; } } ///. /// /// TemplateProperty /// internal static readonly DependencyProperty TemplateProperty = DependencyProperty.Register( "Template", typeof(ItemsPanelTemplate), typeof(ItemsPresenter), new FrameworkPropertyMetadata( (ItemsPanelTemplate) null, // default value FrameworkPropertyMetadataOptions.AffectsMeasure, new PropertyChangedCallback(OnTemplateChanged))); ////// Template Property /// private ItemsPanelTemplate Template { get { return _templateCache; } set { SetValue(TemplateProperty, value); } } // Internal helper so FrameworkElement could see call the template changed virtual internal override void OnTemplateChangedInternal(FrameworkTemplate oldTemplate, FrameworkTemplate newTemplate) { OnTemplateChanged((ItemsPanelTemplate)oldTemplate, (ItemsPanelTemplate)newTemplate); } // Property invalidation callback invoked when TemplateProperty is invalidated private static void OnTemplateChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) { ItemsPresenter ip = (ItemsPresenter) d; StyleHelper.UpdateTemplateCache(ip, (FrameworkTemplate) e.OldValue, (FrameworkTemplate) e.NewValue, TemplateProperty); } ////// Template has changed /// ////// When a Template changes, the VisualTree is removed. The new Template's /// VisualTree will be created when ApplyTemplate is called /// /// The old Template /// The new Template protected virtual void OnTemplateChanged(ItemsPanelTemplate oldTemplate, ItemsPanelTemplate newTemplate) { } //----------------------------------------------------- // // Internal Methods // //------------------------------------------------------ internal static ItemsPresenter FromPanel(Panel panel) { if (panel == null) return null; return panel.TemplatedParent as ItemsPresenter; } internal static ItemsPresenter FromGroupItem(GroupItem groupItem) { if (groupItem == null) return null; Visual parent = VisualTreeHelper.GetParent(groupItem) as Visual; if (parent == null) return null; return VisualTreeHelper.GetParent(parent) as ItemsPresenter; } internal override void OnAncestorChanged() { if (TemplatedParent == null) { UseGenerator(null); ClearPanel(); } base.OnAncestorChanged(); } //----------------------------------------------------- // // Private Methods // //----------------------------------------------------- // initialize (called during measure, from ApplyTemplate) void AttachToOwner() { ItemsControl owner = this.TemplatedParent as ItemsControl; ItemContainerGenerator generator; if (owner != null) { // top-level presenter - get information from ItemsControl generator = owner.ItemContainerGenerator; } else { // subgroup presenter - get information from GroupItem GroupItem parentGI = this.TemplatedParent as GroupItem; ItemsPresenter parentIP = FromGroupItem(parentGI); if (parentIP != null) owner = parentIP.Owner; generator = (parentGI != null) ? parentGI.Generator : null; } _owner = owner; UseGenerator(generator); // create the panel, based either on ItemsControl.ItemsPanel or GroupStyle.Panel GroupStyle groupStyle = (_generator != null) ? _generator.GroupStyle : null; Template = (groupStyle != null) ? groupStyle.Panel : (_owner != null) ? _owner.ItemsPanel : null; } void UseGenerator(ItemContainerGenerator generator) { if (generator == _generator) return; if (_generator != null) _generator.PanelChanged -= new EventHandler(OnPanelChanged); _generator = generator; if (_generator != null) _generator.PanelChanged += new EventHandler(OnPanelChanged); } private void OnPanelChanged(object sender, EventArgs e) { // something has changed that affects the ItemsPresenter. // Re-measure. This will recalculate everything from scratch. InvalidateMeasure(); // If the parent is a ScrollViewer and the ItemsPanel property has // changed, the ScrollViewer/ScrollContentPresenter might need to // choose a different style. Give it a chance to do this by // invalidating its Content property. ScrollViewer parent = Parent as ScrollViewer; if (parent != null) { // call GetValueCore to get this value from the Style/Template parent.InvalidateProperty(ScrollViewer.ContentProperty); } } // workaround, pending bug 953483. The panel is // being removed from the tree, so it should release // its resources (chiefly - stop listening for generator's // ItemsChanged event). Until there's a mechanism for // this, just mark the panel as a non-ItemsHost, so // that the next time it gets ItemsChanged it will // stop listening. (See also bug 942265) private void ClearPanel() { Panel oldPanel = (this.VisualChildrenCount > 0) ? this.GetVisualChild(0) as Panel : null; Type type = null; if( Template != null ) { // Get the type of the template content's root // Is this a FEF-based template? if( Template.VisualTree != null ) { type = Template.VisualTree.Type; } // Or, is it a (non-empty) Baml-based template? else if( !Template.OptimizedTemplateContent.IsEmpty ) { type = Template.OptimizedTemplateContent.RootType; } } if (oldPanel != null && oldPanel.GetType() == type) { oldPanel.IsItemsHost = false; } } //----------------------------------------------------- // // Private Fields // //------------------------------------------------------ ItemsControl _owner; ItemContainerGenerator _generator; ItemsPanelTemplate _templateCache; } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007. // Copyright (c) Microsoft Corporation. All rights reserved.
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