// Licensed to the .NET Foundation under one or more agreements. // The .NET Foundation licenses this file to you under the MIT license. // See the LICENSE file in the project root for more information. using System; using System.Collections; using System.Collections.Generic; using System.Windows.Automation.Provider; using System.Windows.Controls; using System.Windows.Controls.Primitives; namespace System.Windows.Automation.Peers { /// <summary> /// AutomationPeer for DataGridColumnHeadersPresenter /// </summary> public sealed class DataGridColumnHeadersPresenterAutomationPeer : ItemsControlAutomationPeer, IItemContainerProvider { #region Constructors /// <summary> /// AutomationPeer for DataGridColumnHeadersPresenter /// </summary> /// <param name="owner">DataGridColumnHeadersPresenter</param> public DataGridColumnHeadersPresenterAutomationPeer(DataGridColumnHeadersPresenter owner) : base(owner) { } #endregion #region AutomationPeer Overrides /// <summary> /// Gets the control type for the element that is associated with the UI Automation peer. /// </summary> /// <returns>The control type.</returns> protected override AutomationControlType GetAutomationControlTypeCore() { return AutomationControlType.Header; } /// <summary> /// Called by GetClassName that gets a human readable name that, in addition to AutomationControlType, /// differentiates the control represented by this AutomationPeer. /// </summary> /// <returns>The string that contains the name.</returns> protected override string GetClassNameCore() { return Owner.GetType().Name; } ///<summary> /// Creates Children peers. /// /// GetChildrenCore and FindItemByProperty are almost straight copies of the /// ItemControlAutomationPeer code; however since DataGridColumHeaderPresenter /// returns the Column.Header's as the items some specialized code was needed to /// create and store peers. ///</summary> protected override List<AutomationPeer> GetChildrenCore() { List<AutomationPeer> children = null; ItemPeersStorage<ItemAutomationPeer> oldChildren = ItemPeers; //cache the old ones for possible reuse ItemPeers = new ItemPeersStorage<ItemAutomationPeer>(); ItemsControl owner = (ItemsControl)Owner; if (OwningDataGrid?.Columns.Count > 0) { IList childItems = null; Panel itemHost = owner.ItemsHost; // To avoid the situation on legacy systems which may not have new unmanaged core. this check with old unmanaged core // ensures the older behavior as ItemContainer pattern won't be available. if (IsVirtualized) { if (itemHost == null) return null; childItems = itemHost.Children; } else { childItems = OwningDataGrid.Columns; } children = new List<AutomationPeer>(childItems.Count); foreach (object item in childItems) { DataGridColumn dataItem; if (item is DataGridColumnHeader) { dataItem = ((DataGridColumnHeader) item).Column; } else { dataItem = item as DataGridColumn; } // try to reuse old peer if it exists either in Current AT or in WeakRefStorage of Peers being sent to Client ItemAutomationPeer peer = oldChildren[dataItem]; if (peer == null) { peer = GetPeerFromWeakRefStorage(dataItem); // As cached peer is getting used it must be invalidated. if (peer != null) { peer.AncestorsInvalid = false; peer.ChildrenValid = false; } } // If the peer is null or dataItem.Header has changed, create a new peer. object dataItemHeader = dataItem == null ? null : dataItem.Header; if (peer == null || !ItemsControl.EqualsEx(peer.Item, dataItemHeader)) { peer = CreateItemAutomationPeer(dataItem); } // perform hookup so the events sourced from wrapper peer are fired as if from the data item if (peer != null) { AutomationPeer wrapperPeer = peer.GetWrapperPeer(); if (wrapperPeer != null) { wrapperPeer.EventsSource = peer; } } // protection from indistinguishable items - for example, 2 strings with same value // this scenario does not work in ItemsControl however is not checked for. if (peer != null && ItemPeers[dataItem] == null) { children.Add(peer); ItemPeers[dataItem] = peer; } } return children; } return null; } ///<summary> /// Find Childrend Peers based on Automation Properties. /// Used to enable virtualization with automation. /// /// GetChildrenCore and FindItemByProperty are almost straight copies of the /// ItemControlAutomationPeer code; however since DataGridColumHeaderPresenter /// returns the Column.Header's as the items some specialized code was needed to /// create and store peers. ///</summary> IRawElementProviderSimple IItemContainerProvider.FindItemByProperty(IRawElementProviderSimple startAfter, int propertyId, object value) { ResetChildrenCache(); // Checks if propertyId is valid else throws ArgumentException to notify it as invalid argument is being passed if (propertyId != 0) { if (!IsPropertySupportedByControlForFindItem(propertyId)) { throw new ArgumentException(SR.PropertyNotSupported); } } ItemsControl owner = (ItemsControl)Owner; IList items = null; if (owner != null) items = OwningDataGrid.Columns; if (items != null && items.Count > 0) { DataGridColumnHeaderItemAutomationPeer startAfterItem = null; if (startAfter != null) { // get the peer corresponding to this provider startAfterItem = PeerFromProvider(startAfter) as DataGridColumnHeaderItemAutomationPeer; if (startAfterItem == null) return null; } // startIndex refers to the index of the item just after startAfterItem int startIndex = 0; if (startAfterItem != null) { if (startAfterItem.Item == null) { throw new InvalidOperationException(SR.InavalidStartItem); } // To find the index of the column items collection which occurs // immidiately after startAfterItem.Item startIndex = items.IndexOf(startAfterItem.Column) + 1; if (startIndex == 0 || startIndex == items.Count) return null; } if (propertyId == 0) { for (int i = startIndex; i < items.Count; i++) { // This is to handle the case of when dataItems are just plain strings and have duplicates, // only the first occurence of duplicate Items will be returned. It has also been used couple more times below. if (items.IndexOf(items[i]) != i) continue; return (ProviderFromPeer(FindOrCreateItemAutomationPeer(items[i]))); } } ItemAutomationPeer currentItemPeer; object currentValue = null; for (int i = startIndex; i < items.Count; i++) { currentItemPeer = FindOrCreateItemAutomationPeer(items[i]); if (currentItemPeer == null) continue; try { currentValue = GetSupportedPropertyValue(currentItemPeer, propertyId); } catch (Exception ex) { if (ex is ElementNotAvailableException) continue; } if (value == null || currentValue == null) { // Accept null as value corresponding to the property if it finds an item with null as the value of corresponding property else ignore. if (currentValue == null && value == null && items.IndexOf(items[i]) == i) return (ProviderFromPeer(currentItemPeer)); else continue; } // Match is found within the specified criterion of search if (value.Equals(currentValue) && items.IndexOf(items[i]) == i) return (ProviderFromPeer(currentItemPeer)); } } return null; } // AutomationControlType.Header must return IsContentElement false. // See http://msdn.microsoft.com/en-us/library/ms753110.aspx protected override bool IsContentElementCore() { return false; } protected override ItemAutomationPeer CreateItemAutomationPeer(object column) { DataGridColumn dataGridColumn = column as DataGridColumn; if (column != null) { // Pass in the column and the Header in so that ItemsContainerGenerator will give a container // when ItemAutomationPeer.GetWrapper is called. return new DataGridColumnHeaderItemAutomationPeer(dataGridColumn.Header, dataGridColumn, this) as ItemAutomationPeer; } return null; } #endregion #region Private Methods private DataGrid OwningDataGrid { get { return ((DataGridColumnHeadersPresenter)Owner).ParentDataGrid; } } #endregion } } |