replace thumbs panel to support virtualization;

add option to disable most effects that affect performance;
fix decode pixel not being set correctly;
remember last view window position;
add opton for thumb change delay mutiplier;
other minor tweaks;

Author: Carl Chang

App.xaml

@@ -9,6 +9,7 @@
             <ResourceDictionary.MergedDictionaries>
                 <ResourceDictionary Source="UserControls/AppleStyleScrollBar.xaml"/>
                 <ResourceDictionary Source="UserControls/StylesAndAnimations.xaml"/>
+                <ResourceDictionary Source="UserControls/BorderlessWindow.xaml"/>
                 <ResourceDictionary Source="UserControls/Generic.xaml"/>
                 <!--<ResourceDictionary>
                     --><!--<FontFamily x:Key="FontAwesomeRegular">/ZipImageViewer;component/Resources/FontAwesome5FreeRegular400.otf#Font Awesome 5 Free Regular</FontFamily>

Helpers/Helpers.cs

@@ -219,10 +219,19 @@ public static BitmapSource GetImageSource(Stream stream, SizeInt decodeSize) {
             var bi = new BitmapImage();
             bi.BeginInit();
             bi.CacheOption = BitmapCacheOption.OnLoad;
-            if (frameSize.Width > frameSize.Height)
-                bi.DecodePixelHeight = decodeSize.Height;
-            else
-                bi.DecodePixelWidth = decodeSize.Width;
+            if (frameSize.Width > 0 && frameSize.Height > 0) {
+                var frameRatio = frameSize.Width / frameSize.Height;
+                if (decodeSize.Width > 0 && decodeSize.Height > 0) {
+                    if (frameRatio > (double)decodeSize.Width / decodeSize.Height)
+                        bi.DecodePixelHeight = decodeSize.Height;
+                    else
+                        bi.DecodePixelWidth = decodeSize.Width;
+                }
+                else if (decodeSize.Width == 0 && decodeSize.Height > 0)
+                    bi.DecodePixelHeight = decodeSize.Height;
+                else if (decodeSize.Height == 0 && decodeSize.Width > 0)
+                    bi.DecodePixelWidth = decodeSize.Width;
+            }
             bi.StreamSource = stream;
             bi.EndInit();
             bi.Freeze();
@@ -427,5 +436,30 @@ public static string CustomCmdArgsReplace(string input, ObjectInfo objInfo) {
             return input.Replace(@"%FileSystemPath%", objInfo.FileSystemPath);
         }
 
+
+        public static T GetVisualChild<T>(DependencyObject parent) where T : Visual {
+            T child = default;
+
+            int numVisuals = VisualTreeHelper.GetChildrenCount(parent);
+            for (int i = 0; i < numVisuals; i++) {
+                Visual v = (Visual)VisualTreeHelper.GetChild(parent, i);
+                child = v as T;
+                if (child == null) {
+                    child = GetVisualChild<T>(v);
+                }
+                if (child != null) {
+                    break;
+                }
+            }
+            return child;
+        }
+    }
+
+
+    public class VirtualizingWrapPanel : WpfToolkit.Controls.VirtualizingWrapPanel
+    {
+        public int TotalRowCount => rowCount;
+        public int RowItemCount => itemsPerRowCount;
+        public new int VisualChildrenCount => base.VisualChildrenCount;
     }
 }

Helpers/ObjectInfo.cs

@@ -136,4 +136,6 @@ public ObjectInfo(string fsPath, FileFlags flag = FileFlags.Unknown, ImageSource
             imageSources = sources;
         }
     }
+
+
 }

Helpers/Setting.cs

@@ -74,6 +74,16 @@ public static TransitionSpeed ViewerTransitionSpeed {
             }
         }
 
+        private static double thumbSwapDelayMultiplier = 1d;
+        public static double ThumbSwapDelayMultiplier {
+            get => thumbSwapDelayMultiplier;
+            set {
+                if (thumbSwapDelayMultiplier == value) return;
+                thumbSwapDelayMultiplier = value;
+                OnStaticPropertyChanged(nameof(ThumbSwapDelayMultiplier));
+            }
+        }
+
         private static double thumbDbSize = 2d;
         public static double ThumbDbSize {
             get => thumbDbSize;
@@ -104,6 +114,17 @@ public static string LastPath {
             }
         }
 
+        private static bool liteMode = false;
+        public static bool LiteMode {
+            get => liteMode;
+            set {
+                if (liteMode == value) return;
+                liteMode = value;
+                OnStaticPropertyChanged(nameof(LiteMode));
+            }
+        }
+
+
         private static ObservableCollection<ObservableObj> customCommands;
         public static ObservableCollection<ObservableObj> CustomCommands {
             get => customCommands;
@@ -147,14 +168,16 @@ public static void LoadConfigFromFile(string path = "config.ini") {
             //parse config file
             var iniData = new FileIniDataParser().ReadFile(path, System.Text.Encoding.UTF8);
 
-            SevenZipDllPath =       ParseConfig(iniData, nameof(SevenZipDllPath),       SevenZipDllPath);
-            ThumbDbDir =            ParseConfig(iniData, nameof(ThumbDbDir),            ThumbDbDir);
-            ThumbnailSize =         ParseConfig(iniData, nameof(ThumbnailSize),         ThumbnailSize);
-            ThumbDbSize =           ParseConfig(iniData, nameof(ThumbDbSize),           ThumbDbSize);
-            ViewerTransition =      ParseConfig(iniData, nameof(ViewerTransition),      ViewerTransition);
-            ViewerTransitionSpeed = ParseConfig(iniData, nameof(ViewerTransitionSpeed), ViewerTransitionSpeed);
-            LastWindowSize =        ParseConfig(iniData, nameof(LastWindowSize),        LastWindowSize);
-            LastPath =              ParseConfig(iniData, nameof(LastPath),              LastPath);
+            SevenZipDllPath =          ParseConfig(iniData, nameof(SevenZipDllPath),       SevenZipDllPath);
+            ThumbDbDir =               ParseConfig(iniData, nameof(ThumbDbDir),            ThumbDbDir);
+            ThumbnailSize =            ParseConfig(iniData, nameof(ThumbnailSize),         ThumbnailSize);
+            ThumbSwapDelayMultiplier = ParseConfig(iniData, nameof(ThumbSwapDelayMultiplier), ThumbSwapDelayMultiplier);
+            ThumbDbSize =              ParseConfig(iniData, nameof(ThumbDbSize),           ThumbDbSize);
+            ViewerTransition =         ParseConfig(iniData, nameof(ViewerTransition),      ViewerTransition);
+            ViewerTransitionSpeed =    ParseConfig(iniData, nameof(ViewerTransitionSpeed), ViewerTransitionSpeed);
+            LastWindowSize =           ParseConfig(iniData, nameof(LastWindowSize),        LastWindowSize);
+            LastPath =                 ParseConfig(iniData, nameof(LastPath),              LastPath);
+            LiteMode =                 ParseConfig(iniData, nameof(LiteMode),              LiteMode);
 
             //parse custom commands
             CustomCommands = new ObservableCollection<ObservableObj>();
@@ -189,6 +212,9 @@ private static T ParseConfig<T>(IniData iniData, string key, T defaultVal) {
                 case string _:
                     result = value;
                     break;
+                case bool _:
+                    result = bool.Parse(value);
+                    break;
                 case SizeInt _:
                 case ObservablePair<int, int> _:
                     int iW, iH;
@@ -250,11 +276,13 @@ [App Config]
 {nameof(SevenZipDllPath)}={SevenZipDllPath}
 {nameof(ThumbDbDir)}={ThumbDbDir}
 {nameof(ThumbnailSize)}={ThumbnailSize.Item1}x{ThumbnailSize.Item2}
+{nameof(ThumbSwapDelayMultiplier)}={ThumbSwapDelayMultiplier}
 {nameof(ThumbDbSize)}={ThumbDbSize}
 {nameof(ViewerTransition)}={ViewerTransition}
 {nameof(ViewerTransitionSpeed)}={ViewerTransitionSpeed}
 {nameof(LastWindowSize)}={LastWindowSize.Width}x{LastWindowSize.Height}
 {nameof(LastPath)}={LastPath}
+{nameof(LiteMode)}={LiteMode}
 
 [Custom Commands]
 {(CustomCommands?.Count > 0 ?