LowProfileImageLoader

8 files changed, 632 insertions, 13 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;
+            }
+        }
+    }
+}
diff --git a/Juick/Juick.csproj b/Juick/Juick.csproj
index 1ae974a..d467f85 100644
--- a/Juick/Juick.csproj
+++ b/Juick/Juick.csproj
@@ -71,9 +71,12 @@
     </Compile>

     <Compile Include="Classes\AccountManager.cs" />

     <Compile Include="Classes\BindingChangedEventArgs.cs" />

+    <Compile Include="Classes\DeferredLoadListBox.cs" />

+    <Compile Include="Classes\DeferredLoadListBoxItem.cs" />

     <Compile Include="Classes\DelegateCommand.cs" />

     <Compile Include="Classes\DependencyPropertyListener.cs" />

     <Compile Include="Classes\ExpressionHelper.cs" />

+    <Compile Include="Classes\LowProfileImageLoader.cs" />

     <Compile Include="Classes\ScrollViewerMonitor.cs" />

     <Compile Include="Classes\TileHelper.cs" />

     <Compile Include="Controls\HyperLinkRichTextBox.cs" />

diff --git a/Juick/MainPage.xaml b/Juick/MainPage.xaml
index ded6d33..dfa0c4f 100644
--- a/Juick/MainPage.xaml
+++ b/Juick/MainPage.xaml
@@ -67,7 +67,7 @@
                                                         <RowDefinition Height="Auto" />

                                                         <RowDefinition Height="Auto" />

                                                     </Grid.RowDefinitions>

-                                                    <Image Source="{Binding UserAvatar}" Grid.Row="0" Grid.Column="0" Margin="3" />

+                                                    <Image bindings:LowProfileImageLoader.UriSource="{Binding AvatarUri}" Grid.Row="0" Grid.Column="0" Margin="3" />

                                                     <TextBlock Text="{Binding Username}" Grid.Row="0" Grid.Column="1"

                      Margin="5,0,5,5" VerticalAlignment="Top"

                      HorizontalAlignment="Left"

@@ -122,7 +122,7 @@
                                                         <RowDefinition Height="Auto" />

                                                         <RowDefinition Height="Auto" />

                                                     </Grid.RowDefinitions>

-                                                    <Image Source="{Binding UserAvatar}" Grid.Row="0" Grid.Column="0" Margin="3" />

+                                                    <Image bindings:LowProfileImageLoader.UriSource="{Binding AvatarUri}" Grid.Row="0" Grid.Column="0" Margin="3" />

                                                     <TextBlock Text="{Binding Username}" Grid.Row="0" Grid.Column="1"

                      Margin="5,0,5,5" VerticalAlignment="Top"

                      HorizontalAlignment="Left"

diff --git a/Juick/ThreadView.xaml b/Juick/ThreadView.xaml
index ebfd166..c83fed0 100644
--- a/Juick/ThreadView.xaml
+++ b/Juick/ThreadView.xaml
@@ -6,7 +6,7 @@
     xmlns:shell="clr-namespace:Microsoft.Phone.Shell;assembly=Microsoft.Phone"

     xmlns:d="http://schemas.microsoft.com/expression/blend/2008"

     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"

-    xmlns:controls="clr-namespace:Juick.Controls"

+    xmlns:controls="clr-namespace:Juick.Controls" xmlns:bindings="clr-namespace:Juick.Classes"

     FontFamily="{StaticResource PhoneFontFamilyNormal}"

     FontSize="{StaticResource PhoneFontSizeNormal}"

     Foreground="{StaticResource PhoneForegroundBrush}"

@@ -48,7 +48,7 @@
                                     <RowDefinition Height="Auto" />

                                     <!-- RowDefinition Height="Auto" / -->

                                 </Grid.RowDefinitions>

-                                <Image Source="{Binding UserAvatar}" Grid.Row="0" Grid.Column="0" Margin="3" />

+                                <Image bindings:LowProfileImageLoader.UriSource="{Binding AvatarUri}" Grid.Row="0" Grid.Column="0" Margin="3" />

                                 <TextBlock Text="{Binding Username}" Grid.Row="0" Grid.Column="1"

                                        Margin="5,0,5,5" VerticalAlignment="Top"

                                        HorizontalAlignment="Left"

diff --git a/Juick/ViewModels/MessageListViewModelBase.cs b/Juick/ViewModels/MessageListViewModelBase.cs
index 60c0a94..f49ef4f 100644
--- a/Juick/ViewModels/MessageListViewModelBase.cs
+++ b/Juick/ViewModels/MessageListViewModelBase.cs
@@ -91,10 +91,12 @@ namespace Juick.ViewModels
             foreach (var post in response.Data)

             {

                 var status = string.Format("Posted on: {0}, replies: {1}", post.Timestamp, post.Replies);

-                var item = new MessageViewModel(post) { Status = status };

+                var item = new MessageViewModel(post)

+                               {

+                                   Status = status,

+                                   AvatarUri = new Uri(string.Format("http://i.juick.com/as/{0}.png", post.User.Uid), UriKind.Absolute)

+                               };

                 Items.Add(item);

-                var imageUri = new Uri(string.Format("http://i.juick.com/as/{0}.png", post.User.Uid), UriKind.Absolute);

-                item.UserAvatar = new BitmapImage { UriSource = imageUri };

                 if (post.Photo != null)

                 {

                     item.Attachment = new BitmapImage { UriSource = new Uri(post.Photo.Small, UriKind.Absolute) };

diff --git a/Juick/ViewModels/MessageViewModel.cs b/Juick/ViewModels/MessageViewModel.cs
index 6a53669..08cdcaa 100644
--- a/Juick/ViewModels/MessageViewModel.cs
+++ b/Juick/ViewModels/MessageViewModel.cs
@@ -88,16 +88,16 @@ namespace Juick.ViewModels
             }

         }

 

-        private BitmapImage _avatar;

-        public BitmapImage UserAvatar

+        private Uri _avatarUri;

+        public Uri AvatarUri

         {

-            get { return _avatar; }

+            get { return _avatarUri; }

             set

             {

-                if (value != _avatar)

+                if (value != _avatarUri)

                 {

-                    _avatar = value;

-                    NotifyPropertyChanged("UserAvatar");

+                    _avatarUri = value;

+                    NotifyPropertyChanged("AvatarUri");

                 }

             }

         }