Preview pane error handling improvements

Files/ViewModels/PreviewPaneViewModel.cs

@@ -210,41 +210,57 @@ private async Task LoadPreviewControlAsync(CancellationToken token)
 
         private async Task<UIElement> LoadPreviewControlFromExtension(ListedItem item, Extension extension)
         {
-            try
-            {
-                UIElement control = null;
-                var file = await StorageFile.GetFileFromPathAsync(item.ItemPath);
-                string sharingToken = SharedStorageAccessManager.AddFile(file);
-                var result = await extension.Invoke(new ValueSet() { { "token", sharingToken } });
-
-                if (result.TryGetValue("preview", out object preview))
-                {
-                    control = XamlReader.Load(preview as string) as UIElement;
-                }
-
-                if (result.TryGetValue("details", out object details))
-                {
-                    var detailsList = JsonConvert.DeserializeObject<List<FileProperty>>(details as string);
-                    await BasePreviewModel.LoadDetailsOnly(item, detailsList);
-                }
+            UIElement control = null;
+            var file = await StorageFile.GetFileFromPathAsync(item.ItemPath);
+            string sharingToken = SharedStorageAccessManager.AddFile(file);
+            var result = await extension.Invoke(new ValueSet() { { "token", sharingToken } });
 
-                return control;
+            if (result.TryGetValue("preview", out object preview))
+            {
+                control = XamlReader.Load(preview as string) as UIElement;
             }
-            catch (Exception e)
+
+            if (result.TryGetValue("details", out object details))
             {
-                Debug.WriteLine(e.ToString());
+                var detailsList = JsonConvert.DeserializeObject<List<FileProperty>>(details as string);
+                await BasePreviewModel.LoadDetailsOnly(item, detailsList);
             }
-            return null;
+
+            return control;
         }
 
         private async void SelectedItemChanged()
         {
             loadCancellationTokenSource?.Cancel();
             if (SelectedItem != null && SelectedItems.Count == 1)
             {
-                DetailsListVisibility = Visibility.Visible;
-                loadCancellationTokenSource = new CancellationTokenSource();
-                await LoadPreviewControlAsync(loadCancellationTokenSource.Token);
+                try
+                {
+                    DetailsListVisibility = Visibility.Visible;
+                    loadCancellationTokenSource = new CancellationTokenSource();
+                    await LoadPreviewControlAsync(loadCancellationTokenSource.Token);
+                }
+                catch (Exception e)
+                {
+                    Debug.WriteLine(e);
+                    loadCancellationTokenSource?.Cancel();
+                    // If initial loading fails, attempt to load a basic preivew (thumbnail and details only)
+                    // If that fails, revert to no preview/details available
+                    try
+                    {
+                        var basicModel = new BasicPreviewViewModel(SelectedItem);
+                        await basicModel.LoadAsync();
+                        PreviewPaneContent = new BasicPreview(basicModel);
+                    }
+                    catch (Exception ex)
+                    {
+                        Debug.WriteLine(ex);
+                        PreviewPaneContent = null;
+                        DetailsListVisibility = Visibility.Collapsed;
+                        DetailsErrorText = "PreviewPaneDetailsNotAvailableText".GetLocalized();
+                        PreviewErrorText = "DetailsPanePreviewNotAvaliableText".GetLocalized();
+                    }
+                }
             }
             else if (SelectedItem != null)
             {

Files/ViewModels/Previews/BasePreviewModel.cs

@@ -4,7 +4,6 @@
 using Microsoft.Toolkit.Mvvm.ComponentModel;
 using System;
 using System.Collections.Generic;
-using System.Diagnostics;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
@@ -21,42 +20,32 @@ public BasePreviewModel(ListedItem item) : base()
             Item = item;
         }
 
-        public delegate void LoadedEventHandler(object sender, EventArgs e);
-
-        public event LoadedEventHandler LoadedEvent;
+        public ListedItem Item { get; internal set; }
 
         public List<FileProperty> DetailsFromPreview { get; set; }
-        public ListedItem Item { get; internal set; }
-        public CancellationTokenSource LoadCancelledTokenSource { get; } = new CancellationTokenSource();
 
-        public static async Task LoadDetailsOnly(ListedItem item, List<FileProperty> details = null)
-        {
-            var temp = new DetailsOnlyPreviewModel(item) { DetailsFromPreview = details };
-            await temp.LoadAsync();
-        }
+        /// <summary>
+        /// This is cancelled when the user has selected another file or closed the pane.
+        /// </summary>
+        public CancellationTokenSource LoadCancelledTokenSource { get; } = new CancellationTokenSource();
 
-        public virtual async Task LoadAsync()
+        /// <summary>
+        /// Override this if the preview control needs to handle the unloaded event.
+        /// </summary>
+        /// <param name="sender"></param>
+        /// <param name="e"></param>
+        public virtual void PreviewControlBase_Unloaded(object sender, RoutedEventArgs e)
         {
-            // Files can be corrupt, in use, and stuff
-            try
-            {
-                var detailsFull = new List<FileProperty>();
-                Item.ItemFile ??= await StorageFile.GetFileFromPathAsync(Item.ItemPath);
-                DetailsFromPreview = await LoadPreviewAndDetails();
-                RaiseLoadedEvent();
-                var props = await GetSystemFileProperties();
-
-                DetailsFromPreview?.ForEach(i => detailsFull.Add(i));
-                props?.ForEach(i => detailsFull.Add(i));
-
-                Item.FileDetails = new System.Collections.ObjectModel.ObservableCollection<FileProperty>(detailsFull);
-            }
-            catch (Exception e)
-            {
-                Debug.WriteLine(e);
-            }
+            LoadCancelledTokenSource.Cancel();
         }
 
+        /// <summary>
+        /// Override this and place the code to load the file preview here.
+        /// You can return details that may have been obtained while loading the preview (eg. word count).
+        /// This details will be displayed *before* the system file properties.
+        /// If there are none, return an empty list.
+        /// </summary>
+        /// <returns>A list of details</returns>
         public async virtual Task<List<FileProperty>> LoadPreviewAndDetails()
         {
             var (IconData, OverlayData, IsCustom) = await FileThumbnailHelper.LoadIconOverlayAsync(Item.ItemPath, 400);
@@ -75,17 +64,6 @@ public async virtual Task<List<FileProperty>> LoadPreviewAndDetails()
             return new List<FileProperty>();
         }
 
-        public virtual void PreviewControlBase_Unloaded(object sender, RoutedEventArgs e)
-        {
-            LoadCancelledTokenSource.Cancel();
-        }
-
-        protected virtual void RaiseLoadedEvent()
-        {
-            // Raise the event in a thread-safe manner using the ?. operator.
-            LoadedEvent?.Invoke(this, new EventArgs());
-        }
-
         private async Task<List<FileProperty>> GetSystemFileProperties()
         {
             if (Item.IsShortcutItem)
@@ -100,6 +78,42 @@ private async Task<List<FileProperty>> GetSystemFileProperties()
             return list.Where(i => i.Value != null).ToList();
         }
 
+        /// <summary>
+        /// Call this function when you are ready to load the preview and details.
+        /// Override if you need custom loading code.
+        /// </summary>
+        /// <returns>The task to run</returns>
+        public virtual async Task LoadAsync()
+        {
+            var detailsFull = new List<FileProperty>();
+            Item.ItemFile ??= await StorageFile.GetFileFromPathAsync(Item.ItemPath);
+            DetailsFromPreview = await LoadPreviewAndDetails();
+            RaiseLoadedEvent();
+            var props = await GetSystemFileProperties();
+
+            // Add the details from the preview function, then the system file properties
+            DetailsFromPreview?.ForEach(i => detailsFull.Add(i));
+            props?.ForEach(i => detailsFull.Add(i));
+
+            Item.FileDetails = new System.Collections.ObjectModel.ObservableCollection<FileProperty>(detailsFull);
+        }
+
+        public event LoadedEventHandler LoadedEvent;
+
+        public delegate void LoadedEventHandler(object sender, EventArgs e);
+
+        protected virtual void RaiseLoadedEvent()
+        {
+            // Raise the event in a thread-safe manner using the ?. operator.
+            LoadedEvent?.Invoke(this, new EventArgs());
+        }
+
+        public static async Task LoadDetailsOnly(ListedItem item, List<FileProperty> details = null)
+        {
+            var temp = new DetailsOnlyPreviewModel(item) { DetailsFromPreview = details };
+            await temp.LoadAsync();
+        }
+
         internal class DetailsOnlyPreviewModel : BasePreviewModel
         {
             public DetailsOnlyPreviewModel(ListedItem item) : base(item)

Files/ViewModels/Previews/FolderPreviewViewModel.cs

@@ -22,13 +22,7 @@ public FolderPreviewViewModel(ListedItem item)
 
         public async Task LoadAsync()
         {
-            try
-            {
-                await LoadPreviewAndDetailsAsync();
-            }
-            catch (Exception)
-            {
-            }
+            await LoadPreviewAndDetailsAsync();
         }
 
         private async Task LoadPreviewAndDetailsAsync()

Files/ViewModels/Previews/HtmlPreviewViewModel.cs

@@ -30,14 +30,7 @@ public string TextValue
 
         public async override Task<List<FileProperty>> LoadPreviewAndDetails()
         {
-            try
-            {
-                TextValue = await FileIO.ReadTextAsync(Item.ItemFile);
-            }
-            catch (Exception e)
-            {
-                Debug.WriteLine(e);
-            }
+            TextValue = await FileIO.ReadTextAsync(Item.ItemFile);
             return new List<FileProperty>();
         }
     }

Files/ViewModels/Previews/ImagePreviewViewModel.cs

@@ -31,27 +31,20 @@ public ImageSource ImageSource
 
         public override async Task<List<FileProperty>> LoadPreviewAndDetails()
         {
-            try
-            {
-                FileRandomAccessStream stream = (FileRandomAccessStream)await Item.ItemFile.OpenAsync(FileAccessMode.Read);
+            FileRandomAccessStream stream = (FileRandomAccessStream)await Item.ItemFile.OpenAsync(FileAccessMode.Read);
 
-                // svg files require a different type of source
-                if (!Item.ItemPath.EndsWith(".svg"))
-                {
-                    var bitmap = new BitmapImage();
-                    ImageSource = bitmap;
-                    await bitmap.SetSourceAsync(stream);
-                }
-                else
-                {
-                    var bitmap = new SvgImageSource();
-                    ImageSource = bitmap;
-                    await bitmap.SetSourceAsync(stream);
-                }
+            // svg files require a different type of source
+            if (!Item.ItemPath.EndsWith(".svg"))
+            {
+                var bitmap = new BitmapImage();
+                ImageSource = bitmap;
+                await bitmap.SetSourceAsync(stream);
             }
-            catch (Exception e)
+            else
             {
-                Debug.WriteLine(e);
+                var bitmap = new SvgImageSource();
+                ImageSource = bitmap;
+                await bitmap.SetSourceAsync(stream);
             }
 
             return new List<FileProperty>();

Files/ViewModels/Previews/MarkdownPreviewViewModel.cs

@@ -28,16 +28,9 @@ public string TextValue
 
         public override async Task<List<FileProperty>> LoadPreviewAndDetails()
         {
-            try
-            {
-                var text = await FileIO.ReadTextAsync(Item.ItemFile);
-                var displayText = text.Length < Constants.PreviewPane.TextCharacterLimit ? text : text.Remove(Constants.PreviewPane.TextCharacterLimit);
-                TextValue = displayText;
-            }
-            catch (Exception e)
-            {
-                Debug.WriteLine(e);
-            }
+            var text = await FileIO.ReadTextAsync(Item.ItemFile);
+            var displayText = text.Length < Constants.PreviewPane.TextCharacterLimit ? text : text.Remove(Constants.PreviewPane.TextCharacterLimit);
+            TextValue = displayText;
 
             return new List<FileProperty>();
         }

Files/ViewModels/Previews/PDFPreviewViewModel.cs

@@ -3,6 +3,7 @@
 using System;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
+using System.Diagnostics;
 using System.Threading.Tasks;
 using Windows.Data.Pdf;
 using Windows.Storage.Streams;
@@ -35,20 +36,34 @@ public Visibility LoadingBarVisibility
         public async override Task<List<FileProperty>> LoadPreviewAndDetails()
         {
             var pdf = await PdfDocument.LoadFromFileAsync(Item.ItemFile);
-            var details = new List<FileProperty>();
-
-            LoadPagesAsync(pdf);
-            // Add the number of pages to the details
-            details.Add(new FileProperty()
+            TryLoadPagesAsync(pdf);
+            var details = new List<FileProperty>
             {
-                NameResource = "PropertyPageCount",
-                Value = pdf.PageCount,
-            });
+
+                // Add the number of pages to the details
+                new FileProperty()
+                {
+                    NameResource = "PropertyPageCount",
+                    Value = pdf.PageCount,
+                }
+            };
 
             return details;
         }
 
-        private async void LoadPagesAsync(PdfDocument pdf)
+        public async void TryLoadPagesAsync(PdfDocument pdf)
+        {
+            try
+            {
+                await LoadPagesAsync(pdf);
+            }
+            catch (Exception e)
+            {
+                Debug.WriteLine(e);
+            }
+        }
+
+        private async Task LoadPagesAsync(PdfDocument pdf)
         {
             // This fixes an issue where loading an absurdly large PDF would take to much RAM
             // and eventually cause a crash

Files/ViewModels/Previews/RichTextPreviewViewModel.cs

@@ -22,15 +22,7 @@ public RichTextPreviewViewModel(ListedItem item) : base(item)
 
         public async override Task<List<FileProperty>> LoadPreviewAndDetails()
         {
-            try
-            {
-                Stream = await Item.ItemFile.OpenReadAsync();
-            }
-            catch (Exception e)
-            {
-                Debug.WriteLine(e);
-            }
-
+            Stream = await Item.ItemFile.OpenReadAsync();
             return new List<FileProperty>();
         }
     }