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-rw-r--r--Juick/Classes/DeferredLoadListBox.cs275
-rw-r--r--Juick/Classes/DeferredLoadListBoxItem.cs45
-rw-r--r--Juick/Classes/LowProfileImageLoader.cs294
3 files changed, 614 insertions, 0 deletions
diff --git a/Juick/Classes/DeferredLoadListBox.cs b/Juick/Classes/DeferredLoadListBox.cs
new file mode 100644
index 0000000..165a395
--- /dev/null
+++ b/Juick/Classes/DeferredLoadListBox.cs
@@ -0,0 +1,275 @@
+// Copyright (C) Microsoft Corporation. All Rights Reserved.
+// This code released under the terms of the Microsoft Public License
+// (Ms-PL, http://opensource.org/licenses/ms-pl.html).
+
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Controls.Primitives;
+using System.Windows.Data;
+using System.Windows.Media;
+
+namespace Juick.Classes
+{
+ /// <summary>
+ /// Implements a subclass of ListBox based on a StackPanel that defers the
+ /// loading of off-screen items until necessary in order to minimize impact
+ /// to the UI thread.
+ /// </summary>
+ public class DeferredLoadListBox : ListBox
+ {
+ private enum OverlapKind { Overlap, ChildAbove, ChildBelow };
+
+ private ScrollViewer _scrollViewer;
+ private ItemContainerGenerator _generator;
+ private bool _queuedUnmaskVisibleContent;
+ private bool _inOnApplyTemplate;
+
+ /// <summary>
+ /// Handles the application of the Control's Template.
+ /// </summary>
+ public override void OnApplyTemplate()
+ {
+ // Unhook from old Template elements
+ _inOnApplyTemplate = true;
+ ClearValue(VerticalOffsetShadowProperty);
+ _scrollViewer = null;
+ _generator = null;
+
+ // Apply new Template
+ base.OnApplyTemplate();
+
+ // Hook up to new Template elements
+ _scrollViewer = FindFirstChildOfType<ScrollViewer>(this);
+ if (null == _scrollViewer)
+ {
+ throw new NotSupportedException("Control Template must include a ScrollViewer (wrapping ItemsHost).");
+ }
+ _generator = ItemContainerGenerator;
+ SetBinding(VerticalOffsetShadowProperty, new Binding { Source = _scrollViewer, Path = new PropertyPath("VerticalOffset") });
+ _inOnApplyTemplate = false;
+ }
+
+ /// <summary>
+ /// Determines if the specified item is (or is eligible to be) its own item container.
+ /// </summary>
+ /// <param name="item">The specified item.</param>
+ /// <returns>true if the item is its own item container; otherwise, false.</returns>
+ protected override bool IsItemItsOwnContainerOverride(object item)
+ {
+ // Check container type
+ return item is DeferredLoadListBoxItem;
+ }
+
+ /// <summary>
+ /// Creates or identifies the element used to display a specified item.
+ /// </summary>
+ /// <returns>A DeferredLoadListBoxItem corresponding to a specified item.</returns>
+ protected override DependencyObject GetContainerForItemOverride()
+ {
+ // Create container (matches ListBox implementation)
+ var item = new DeferredLoadListBoxItem();
+ if (ItemContainerStyle != null)
+ {
+ item.Style = ItemContainerStyle;
+ }
+ return item;
+ }
+
+ /// <summary>
+ /// Prepares the specified element to display the specified item.
+ /// </summary>
+ /// <param name="element">The element used to display the specified item.</param>
+ /// <param name="item">The item to display.</param>
+ protected override void PrepareContainerForItemOverride(DependencyObject element, object item)
+ {
+ // Perform base class preparation
+ base.PrepareContainerForItemOverride(element, item);
+
+ // Mask the container's content
+ var container = (DeferredLoadListBoxItem)element;
+ if (!DesignerProperties.IsInDesignTool)
+ {
+ container.MaskContent();
+ }
+
+ // Queue a (single) pass to unmask newly visible content on the next tick
+ if (!_queuedUnmaskVisibleContent)
+ {
+ _queuedUnmaskVisibleContent = true;
+ Dispatcher.BeginInvoke(() =>
+ {
+ _queuedUnmaskVisibleContent = false;
+ UnmaskVisibleContent();
+ });
+ }
+ }
+
+ private static readonly DependencyProperty VerticalOffsetShadowProperty =
+ DependencyProperty.Register("VerticalOffsetShadow", typeof(double), typeof(DeferredLoadListBox), new PropertyMetadata(-1.0, OnVerticalOffsetShadowChanged));
+ private static void OnVerticalOffsetShadowChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
+ {
+ // Handle ScrollViewer VerticalOffset change by unmasking newly visible content
+ ((DeferredLoadListBox)o).UnmaskVisibleContent();
+ }
+
+ private void UnmaskVisibleContent()
+ {
+ // Capture variables
+ var count = Items.Count;
+
+ // Find index of any container within view using (1-indexed) binary search
+ var index = -1;
+ var l = 0;
+ var r = count + 1;
+ while (-1 == index)
+ {
+ var p = (r - l) / 2;
+ if (0 == p)
+ {
+ break;
+ }
+ p += l;
+ var c = (DeferredLoadListBoxItem)_generator.ContainerFromIndex(p - 1);
+ if (null == c)
+ {
+ if (_inOnApplyTemplate)
+ {
+ // Applying template; don't expect to have containers at this point
+ return;
+ }
+ // Should always be able to get the container
+ var presenter = FindFirstChildOfType<ItemsPresenter>(_scrollViewer);
+ var panel = (null == presenter) ? null : FindFirstChildOfType<Panel>(presenter);
+ if (panel is VirtualizingStackPanel)
+ {
+ throw new NotSupportedException("Must change ItemsPanel to be a StackPanel (via the ItemsPanel property).");
+ }
+ else
+ {
+ throw new NotSupportedException("Couldn't find container for item (ItemsPanel should be a StackPanel).");
+ }
+ }
+ switch (Overlap(_scrollViewer, c, 0))
+ {
+ case OverlapKind.Overlap:
+ index = p - 1;
+ break;
+ case OverlapKind.ChildAbove:
+ l = p;
+ break;
+ case OverlapKind.ChildBelow:
+ r = p;
+ break;
+ }
+ }
+
+ if (-1 != index)
+ {
+ // Unmask visible items below the current item
+ for (var i = index; i < count; i++)
+ {
+ if (!UnmaskItemContent(i))
+ {
+ break;
+ }
+ }
+
+ // Unmask visible items above the current item
+ for (var i = index - 1; 0 <= i; i--)
+ {
+ if (!UnmaskItemContent(i))
+ {
+ break;
+ }
+ }
+ }
+ }
+
+ private bool UnmaskItemContent(int index)
+ {
+ var container = (DeferredLoadListBoxItem)_generator.ContainerFromIndex(index);
+ if (null != container)
+ {
+ // Return quickly if not masked (but periodically check visibility anyway so we can stop once we're out of range)
+ if (!container.Masked && (0 != (index % 16)))
+ {
+ return true;
+ }
+ // Check necessary conditions
+ if (0 == container.ActualHeight)
+ {
+ // In some cases, ActualHeight will be 0 here, but can be "fixed" with an explicit call to UpdateLayout
+ container.UpdateLayout();
+ if (0 == container.ActualHeight)
+ {
+ throw new NotSupportedException("All containers must have a Height set (ex: via ItemContainerStyle), though the heights do not all need to be the same.");
+ }
+ }
+ // If container overlaps the "visible" area (i.e. on or near the screen), unmask it
+ if (OverlapKind.Overlap == Overlap(_scrollViewer, container, 2 * _scrollViewer.ActualHeight))
+ {
+ container.UnmaskContent();
+ return true;
+ }
+ }
+ return false;
+ }
+
+ private static bool Overlap(double startA, double endA, double startB, double endB)
+ {
+ return (((startA <= startB) && (startB <= endA)) ||
+ ((startB <= startA) && (startA <= endB)));
+ }
+
+ private static OverlapKind Overlap(ScrollViewer parent, FrameworkElement child, double padding)
+ {
+ // Get child transform relative to parent
+ //var transform = child.TransformToVisual(parent); // Unreliable on Windows Phone 7; throws ArgumentException sometimes
+ var layoutSlot = LayoutInformation.GetLayoutSlot(child);
+ var transform = new TranslateTransform { /*X = layoutSlot.Left - parent.HorizontalOffset,*/ Y = layoutSlot.Top - parent.VerticalOffset };
+ // Get child bounds relative to parent
+ var bounds = new Rect(transform.Transform(new Point()), transform.Transform(new Point(/*child.ActualWidth*/ 0, child.ActualHeight)));
+ // Return kind of overlap
+ if (Overlap(0 - padding, parent.ActualHeight + padding, bounds.Top, bounds.Bottom))
+ {
+ return OverlapKind.Overlap;
+ }
+ else if (bounds.Top < 0)
+ {
+ return OverlapKind.ChildAbove;
+ }
+ else
+ {
+ return OverlapKind.ChildBelow;
+ }
+ }
+
+ private static T FindFirstChildOfType<T>(DependencyObject root) where T : class
+ {
+ // Enqueue root node
+ var queue = new Queue<DependencyObject>();
+ queue.Enqueue(root);
+ while (0 < queue.Count)
+ {
+ // Dequeue next node and check its children
+ var current = queue.Dequeue();
+ for (var i = VisualTreeHelper.GetChildrenCount(current) - 1; 0 <= i; i--)
+ {
+ var child = VisualTreeHelper.GetChild(current, i);
+ var typedChild = child as T;
+ if (null != typedChild)
+ {
+ return typedChild;
+ }
+ // Enqueue child
+ queue.Enqueue(child);
+ }
+ }
+ // No children match
+ return null;
+ }
+ }
+}
diff --git a/Juick/Classes/DeferredLoadListBoxItem.cs b/Juick/Classes/DeferredLoadListBoxItem.cs
new file mode 100644
index 0000000..97bfc18
--- /dev/null
+++ b/Juick/Classes/DeferredLoadListBoxItem.cs
@@ -0,0 +1,45 @@
+// Copyright (C) Microsoft Corporation. All Rights Reserved.
+// This code released under the terms of the Microsoft Public License
+// (Ms-PL, http://opensource.org/licenses/ms-pl.html).
+
+using System.Windows;
+using System.Windows.Controls;
+
+namespace Juick.Classes
+{
+ /// <summary>
+ /// Implements a subclass of ListBoxItem that is used in conjunction with
+ /// the DeferredLoadListBox to defer the loading of off-screen items.
+ /// </summary>
+ public class DeferredLoadListBoxItem : ListBoxItem
+ {
+ private object _maskedContent;
+ private DataTemplate _maskedContentTemplate;
+
+ internal bool Masked { get; set; }
+
+ internal void MaskContent()
+ {
+ if (!Masked)
+ {
+ _maskedContent = Content;
+ _maskedContentTemplate = ContentTemplate;
+ Content = null;
+ ContentTemplate = null;
+ Masked = true;
+ }
+ }
+
+ internal void UnmaskContent()
+ {
+ if (Masked)
+ {
+ ContentTemplate = _maskedContentTemplate;
+ Content = _maskedContent;
+ _maskedContentTemplate = null;
+ _maskedContent = null;
+ Masked = false;
+ }
+ }
+ }
+}
diff --git a/Juick/Classes/LowProfileImageLoader.cs b/Juick/Classes/LowProfileImageLoader.cs
new file mode 100644
index 0000000..d1eb3da
--- /dev/null
+++ b/Juick/Classes/LowProfileImageLoader.cs
@@ -0,0 +1,294 @@
+// Copyright (C) Microsoft Corporation. All Rights Reserved.
+// This code released under the terms of the Microsoft Public License
+// (Ms-PL, http://opensource.org/licenses/ms-pl.html).
+
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Diagnostics.CodeAnalysis;
+using System.IO;
+using System.Net;
+using System.Threading;
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Media.Imaging;
+
+namespace Juick.Classes
+{
+ /// <summary>
+ /// Provides access to the Image.UriSource attached property which allows
+ /// Images to be loaded by Windows Phone with less impact to the UI thread.
+ /// </summary>
+ public static class LowProfileImageLoader
+ {
+ private const int WorkItemQuantum = 5;
+ private static readonly Thread _thread = new Thread(WorkerThreadProc);
+ private static readonly Queue<PendingRequest> _pendingRequests = new Queue<PendingRequest>();
+ private static readonly Queue<IAsyncResult> _pendingResponses = new Queue<IAsyncResult>();
+ private static readonly object _syncBlock = new object();
+ private static bool _exiting;
+
+ /// <summary>
+ /// Gets the value of the Uri to use for providing the contents of the Image's Source property.
+ /// </summary>
+ /// <param name="obj">Image needing its Source property set.</param>
+ /// <returns>Uri to use for providing the contents of the Source property.</returns>
+ [SuppressMessage("Microsoft.Design", "CA1011:ConsiderPassingBaseTypesAsParameters", Justification = "UriSource is applicable only to Image elements.")]
+ public static Uri GetUriSource(Image obj)
+ {
+ if (null == obj)
+ {
+ throw new ArgumentNullException("obj");
+ }
+ return (Uri)obj.GetValue(UriSourceProperty);
+ }
+
+ /// <summary>
+ /// Sets the value of the Uri to use for providing the contents of the Image's Source property.
+ /// </summary>
+ /// <param name="obj">Image needing its Source property set.</param>
+ /// <param name="value">Uri to use for providing the contents of the Source property.</param>
+ [SuppressMessage("Microsoft.Design", "CA1011:ConsiderPassingBaseTypesAsParameters", Justification = "UriSource is applicable only to Image elements.")]
+ public static void SetUriSource(Image obj, Uri value)
+ {
+ if (null == obj)
+ {
+ throw new ArgumentNullException("obj");
+ }
+ obj.SetValue(UriSourceProperty, value);
+ }
+
+ /// <summary>
+ /// Identifies the UriSource attached DependencyProperty.
+ /// </summary>
+ public static readonly DependencyProperty UriSourceProperty = DependencyProperty.RegisterAttached(
+ "UriSource", typeof(Uri), typeof(LowProfileImageLoader), new PropertyMetadata(OnUriSourceChanged));
+
+ /// <summary>
+ /// Gets or sets a value indicating whether low-profile image loading is enabled.
+ /// </summary>
+ public static bool IsEnabled { get; set; }
+
+ [SuppressMessage("Microsoft.Performance", "CA1810:InitializeReferenceTypeStaticFieldsInline", Justification = "Static constructor performs additional tasks.")]
+ static LowProfileImageLoader()
+ {
+ // Start worker thread
+ _thread.Start();
+ Application.Current.Exit += new EventHandler(HandleApplicationExit);
+ IsEnabled = true;
+ }
+
+ private static void HandleApplicationExit(object sender, EventArgs e)
+ {
+ // Tell worker thread to exit
+ _exiting = true;
+ if (Monitor.TryEnter(_syncBlock, 100))
+ {
+ Monitor.Pulse(_syncBlock);
+ Monitor.Exit(_syncBlock);
+ }
+ }
+
+ [SuppressMessage("Microsoft.Design", "CA1031:DoNotCatchGeneralExceptionTypes", Justification = "Relevant exceptions don't have a common base class.")]
+ [SuppressMessage("Microsoft.Maintainability", "CA1502:AvoidExcessiveComplexity", Justification = "Linear flow is easy to understand.")]
+ private static void WorkerThreadProc(object unused)
+ {
+ Random rand = new Random();
+ var pendingRequests = new List<PendingRequest>();
+ var pendingResponses = new Queue<IAsyncResult>();
+ while (!_exiting)
+ {
+ lock (_syncBlock)
+ {
+ // Wait for more work if there's nothing left to do
+ if ((0 == _pendingRequests.Count) && (0 == _pendingResponses.Count) && (0 == pendingRequests.Count) && (0 == pendingResponses.Count))
+ {
+ Monitor.Wait(_syncBlock);
+ if (_exiting)
+ {
+ return;
+ }
+ }
+ // Copy work items to private collections
+ while (0 < _pendingRequests.Count)
+ {
+ var pendingRequest = _pendingRequests.Dequeue();
+ // Search for another pending request for the same Image element
+ for (var i = 0; i < pendingRequests.Count; i++)
+ {
+ if (pendingRequests[i].Image == pendingRequest.Image)
+ {
+ // Found one; replace it
+ pendingRequests[i] = pendingRequest;
+ pendingRequest = null;
+ break;
+ }
+ }
+ if (null != pendingRequest)
+ {
+ // Unique request; add it
+ pendingRequests.Add(pendingRequest);
+ }
+ }
+ while (0 < _pendingResponses.Count)
+ {
+ pendingResponses.Enqueue(_pendingResponses.Dequeue());
+ }
+ }
+ Queue<PendingCompletion> pendingCompletions = new Queue<PendingCompletion>();
+ // Process pending requests
+ var count = pendingRequests.Count;
+ for (var i = 0; (0 < count) && (i < WorkItemQuantum); i++)
+ {
+ // Choose a random item to behave reasonably at both extremes (FIFO/FILO)
+ var index = rand.Next(count);
+ var pendingRequest = pendingRequests[index];
+ pendingRequests[index] = pendingRequests[count - 1];
+ pendingRequests.RemoveAt(count - 1);
+ count--;
+ if (pendingRequest.Uri.IsAbsoluteUri)
+ {
+ // Download from network
+ var webRequest = HttpWebRequest.CreateHttp(pendingRequest.Uri);
+ webRequest.AllowReadStreamBuffering = true; // Don't want to block this thread or the UI thread on network access
+ webRequest.BeginGetResponse(HandleGetResponseResult, new ResponseState(webRequest, pendingRequest.Image, pendingRequest.Uri));
+ }
+ else
+ {
+ // Load from application (must have "Build Action"="Content")
+ var originalUriString = pendingRequest.Uri.OriginalString;
+ // Trim leading '/' to avoid problems
+ var resourceStreamUri = originalUriString.StartsWith("/", StringComparison.Ordinal) ? new Uri(originalUriString.TrimStart('/'), UriKind.Relative) : pendingRequest.Uri;
+ // Enqueue resource stream for completion
+ var streamResourceInfo = Application.GetResourceStream(resourceStreamUri);
+ if (null != streamResourceInfo)
+ {
+ pendingCompletions.Enqueue(new PendingCompletion(pendingRequest.Image, pendingRequest.Uri, streamResourceInfo.Stream));
+ }
+ }
+ // Yield to UI thread
+ Thread.Sleep(1);
+ }
+ // Process pending responses
+ for (var i = 0; (0 < pendingResponses.Count) && (i < WorkItemQuantum); i++)
+ {
+ var pendingResponse = pendingResponses.Dequeue();
+ var responseState = (ResponseState)pendingResponse.AsyncState;
+ try
+ {
+ var response = responseState.WebRequest.EndGetResponse(pendingResponse);
+ pendingCompletions.Enqueue(new PendingCompletion(responseState.Image, responseState.Uri, response.GetResponseStream()));
+ }
+ catch (WebException)
+ {
+ // Ignore web exceptions (ex: not found)
+ }
+ // Yield to UI thread
+ Thread.Sleep(1);
+ }
+ // Process pending completions
+ if (0 < pendingCompletions.Count)
+ {
+ // Get the Dispatcher and process everything that needs to happen on the UI thread in one batch
+ Deployment.Current.Dispatcher.BeginInvoke(() =>
+ {
+ while (0 < pendingCompletions.Count)
+ {
+ // Decode the image and set the source
+ var pendingCompletion = pendingCompletions.Dequeue();
+ if (GetUriSource(pendingCompletion.Image) == pendingCompletion.Uri)
+ {
+ var bitmap = new BitmapImage();
+ try
+ {
+ bitmap.SetSource(pendingCompletion.Stream);
+ }
+ catch
+ {
+ // Ignore image decode exceptions (ex: invalid image)
+ }
+ pendingCompletion.Image.Source = bitmap;
+ }
+ else
+ {
+ // Uri mis-match; do nothing
+ }
+ // Dispose of response stream
+ pendingCompletion.Stream.Dispose();
+ }
+ });
+ }
+ }
+ }
+
+ private static void OnUriSourceChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
+ {
+ var image = (Image)o;
+ var uri = (Uri)e.NewValue;
+
+ if (!IsEnabled || DesignerProperties.IsInDesignTool)
+ {
+ // Avoid handing off to the worker thread (can cause problems for design tools)
+ image.Source = new BitmapImage(uri);
+ }
+ else
+ {
+ // Clear-out the current image because it's now stale (helps when used with virtualization)
+ image.Source = null;
+ lock (_syncBlock)
+ {
+ // Enqueue the request
+ _pendingRequests.Enqueue(new PendingRequest(image, uri));
+ Monitor.Pulse(_syncBlock);
+ }
+ }
+ }
+
+ private static void HandleGetResponseResult(IAsyncResult result)
+ {
+ lock (_syncBlock)
+ {
+ // Enqueue the response
+ _pendingResponses.Enqueue(result);
+ Monitor.Pulse(_syncBlock);
+ }
+ }
+
+ private class PendingRequest
+ {
+ public Image Image { get; private set; }
+ public Uri Uri { get; private set; }
+ public PendingRequest(Image image, Uri uri)
+ {
+ Image = image;
+ Uri = uri;
+ }
+ }
+
+ private class ResponseState
+ {
+ public WebRequest WebRequest { get; private set; }
+ public Image Image { get; private set; }
+ public Uri Uri { get; private set; }
+ public ResponseState(WebRequest webRequest, Image image, Uri uri)
+ {
+ WebRequest = webRequest;
+ Image = image;
+ Uri = uri;
+ }
+ }
+
+ private class PendingCompletion
+ {
+ public Image Image { get; private set; }
+ public Uri Uri { get; private set; }
+ public Stream Stream { get; private set; }
+ public PendingCompletion(Image image, Uri uri, Stream stream)
+ {
+ Image = image;
+ Uri = uri;
+ Stream = stream;
+ }
+ }
+ }
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-27 06:04:21 +0000