add ViewOffset to Photo for display

Photo.cs

@@ -102,6 +102,7 @@ public class Photo {
   public ushort Orientation = 1;
   public GpsInfo? Gps = null;
   public Rectangle CropRectangle = Rectangle.Empty;
+  public Vector2i ViewOffset = Vector2i.Zero;
 
   private static long touchCounter = 0;
   private Texture texture;

Program.cs

@@ -87,14 +87,22 @@ public class Transform {
 }
 
 public interface ITool {
-  ToolStatus HandleInput(KeyboardState input, MouseState mouse, Transform transform, Game game);
+  ToolStatus HandleInput(KeyboardState input, MouseState mouse, Transform transform, Game game, Photo photo);
   string Status();
   void Draw(UiGeometry geometry, Game game);
 }
 
 
 public class ViewTool : ITool {
-  public ToolStatus HandleInput(KeyboardState input, MouseState mouse, Transform transform, Game game) {
+  public ToolStatus HandleInput(KeyboardState input, MouseState mouse, Transform transform, Game game, Photo photo) {
+    Vector2i mousePosition = (Vector2i) mouse.Position;
+    if (mouse.IsButtonDown(MouseButton.Button1)) {
+      Vector2 delta = mouse.Delta;
+      Vector2i imageDelta = transform.ScreenToImageDelta((int) delta.X, (int) delta.Y);
+      photo.ViewOffset = Vector2i.Add(photo.ViewOffset, imageDelta);
+      Console.WriteLine("+++ " + photo.ViewOffset);
+    }
+
     return ToolStatus.Active;
   }
 
@@ -121,7 +129,7 @@ public class CropTool : ITool {
     mouseDragEnd = new(photo.CropRectangle.Right, photo.CropRectangle.Bottom);
   }
 
-  public ToolStatus HandleInput(KeyboardState input, MouseState mouse, Transform transform, Game game) {
+  public ToolStatus HandleInput(KeyboardState input, MouseState mouse, Transform transform, Game game, Photo photo) {
     Vector2i mousePosition = (Vector2i) mouse.Position;
     Vector2i imagePosition = transform.ScreenToImage(mousePosition);
 
@@ -585,6 +593,7 @@ public class Game : GameWindow {
     }
 
     if (input.IsKeyPressed(Keys.Q)) {
+      photos[photoIndex].ViewOffset = Vector2i.Zero;
       zoomLevel = 0f;
     }
 
@@ -620,7 +629,8 @@ public class Game : GameWindow {
     }
 
     // Delegate input to the active tool.
-    ToolStatus status = activeTool.HandleInput(KeyboardState, MouseState, transform, this);
+    ToolStatus status = activeTool.HandleInput(
+        KeyboardState, MouseState, transform, this, photos[photoIndex]);
 
     // Change back to the default tool if the active tool is done.
     if (status != ToolStatus.Active) {
@@ -798,7 +808,7 @@ public class Game : GameWindow {
     List<Task> tasks = new();
     foreach (Photo p in allPhotos) {
       tasks.Add(Task.Run( () => {
-        p.LoadThumbnailAsync(geometry.ThumbnailSize);
+        p.LoadThumbnailAsync(new Vector2i(256, 256));
         lock (numThumbnailsLoadedLock) {
           numThumbnailsLoaded++;
           toast.Set($"[{numThumbnailsLoaded}/{allPhotos.Count}] Loading thumbnails");
@@ -875,7 +885,10 @@ public class Game : GameWindow {
 
     Vector2i renderSize = (Vector2i) (((Vector2) active.Size) * scale);
     Vector2i center = (Vector2i) geometry.PhotoBox.Center;
-    Box2i photoBox = Util.MakeBox(center.X - renderSize.X / 2, center.Y - renderSize.Y / 2,
+    Vector2i offset = new((int) (activePhoto.ViewOffset.X * scale),
+                          (int) (activePhoto.ViewOffset.Y * scale));
+    Box2i photoBox = Util.MakeBox(center.X - renderSize.X / 2 + offset.X,
+                                  center.Y - renderSize.Y / 2 + offset.Y,
                                   renderSize.X, renderSize.Y);
     activeOffset = new(photoBox.Min.X, photoBox.Min.Y);
     transform = new Transform(activeScale, activeOffset, activePhoto.Size);