allow user to drag around the crop box

Program.cs

@@ -50,7 +50,7 @@ public class CameraInfo {
 }
 
 
-public enum ToolState {
+public enum ToolStatus {
   Active,
   Done,
   Canceled
@@ -58,15 +58,15 @@ public enum ToolState {
 
 
 public interface ITool {
-  ToolState HandleInput(UiGeometry geometry, KeyboardState input, MouseState mouse, Game game);
+  ToolStatus HandleInput(KeyboardState input, MouseState mouse, Game game);
   string Status();
   void Draw(UiGeometry geometry, Game game);
 }
 
 
 public class ViewTool : ITool {
-  public ToolState HandleInput(UiGeometry geometry, KeyboardState input, MouseState mouse, Game game) {
-    return ToolState.Active;
+  public ToolStatus HandleInput(KeyboardState input, MouseState mouse, Game game) {
+    return ToolStatus.Active;
   }
 
   public string Status() {
@@ -81,59 +81,82 @@ public class ViewTool : ITool {
 // FIXME: remove unneeded dependencies on "Game" or at least refactor them a bit.
 public class CropTool : ITool {
 
-  Photo activePhoto;
+  Photo photo;
   Vector2i mouseDragStart;
   Vector2i mouseDragEnd;
+  bool dragging;
   string status = "";
 
   public CropTool(Photo photo) {
-    activePhoto = photo;
+    this.photo = photo;
+    mouseDragStart = new(photo.CropRectangle.Left, photo.CropRectangle.Top);
+    mouseDragEnd = new(photo.CropRectangle.Right, photo.CropRectangle.Bottom);
   }
 
-  public ToolState HandleInput(UiGeometry geometry, KeyboardState input, MouseState mouse, Game game) {
+  public ToolStatus HandleInput(KeyboardState input, MouseState mouse, Game game) {
     Vector2i mousePosition = (Vector2i) mouse.Position;
     Vector2i imagePosition = game.ScreenToImage(mousePosition);
 
     if (mouse.IsButtonPressed(MouseButton.Button1)) {
-      if (geometry.PhotoBox.ContainsInclusive(mousePosition)) {
+      dragging = photo.CropRectangle.Contains(imagePosition.X, imagePosition.Y);
+    }
+
+    if (!dragging) {
+      if (mouse.IsButtonPressed(MouseButton.Button1)) {
         mouseDragStart = imagePosition;
       }
-    }
-
-    if (mouse.IsButtonDown(MouseButton.Button1)) {
-      if (geometry.PhotoBox.ContainsInclusive(mousePosition)) {
+      if (mouse.IsButtonDown(MouseButton.Button1)) {
         mouseDragEnd = imagePosition;
       }
+
+      var (left, right, top, bottom) = GetCrop();
+      if (left != right && top != bottom) {
+        photo.CropRectangle = Rectangle.FromLTRB(left, top, right, bottom);
+      } else {
+        photo.CropRectangle = Rectangle.Empty;
+      }
+    } else {
+      if (mouse.IsButtonDown(MouseButton.Button1)) {
+        Vector2 delta = mouse.Delta;
+        Vector2i imageDelta = game.ScreenToImageDelta((int) delta.X, (int) delta.Y);
+        photo.CropRectangle.Offset(imageDelta.X, imageDelta.Y);
+        if (photo.CropRectangle.Left < 0) {
+          photo.CropRectangle.Offset(-photo.CropRectangle.Left, 0);
+        }
+        if (photo.CropRectangle.Right > photo.Size.X) {
+          int overshoot = photo.CropRectangle.Right - photo.Size.X;
+          photo.CropRectangle.Offset(-overshoot, 0);
+        }
+        if (photo.CropRectangle.Top < 0) {
+          photo.CropRectangle.Offset(0, -photo.CropRectangle.Top);
+        }
+        if (photo.CropRectangle.Bottom > photo.Size.Y) {
+          int overshoot = photo.CropRectangle.Bottom - photo.Size.Y;
+          photo.CropRectangle.Offset(0, -overshoot);
+        }
+      }
     }
 
-    var (left, right, top, bottom) = GetCrop();
-    Vector2i size = new(right - left, bottom - top);
-
-    status = $"({left}, {top}) {size.X}x{size.Y}";
-
-    Rectangle crop = Rectangle.Empty;
-    if (size.X > 0 && size.Y > 0) {
-      crop = Rectangle.FromLTRB(left, top, right, bottom);
-    }
-    activePhoto.CropRectangle = crop;
+    Rectangle r = photo.CropRectangle;
+    status = $"({r.Left}, {r.Top}, {r.Right}, {r.Bottom}) {r.Width}x{r.Height}";
 
     if (input.IsKeyPressed(Keys.Enter)) {
-      return ToolState.Done;
+      return ToolStatus.Done;
     }
 
     if (input.IsKeyPressed(Keys.Escape)) {
-      activePhoto.CropRectangle = Rectangle.Empty;
-      return ToolState.Canceled;
+      photo.CropRectangle = Rectangle.Empty;
+      return ToolStatus.Canceled;
     }
 
-    return ToolState.Active;
+    return ToolStatus.Active;
   }
 
   // left, right, top, bottom
   (int, int, int, int) GetCrop() {
     // FIXME: this expects the start point in the top left and the end point
     // in the bottom right; some sign flipping needs to occur to make anchors
-    // in other direction work well.
+    // in other directions work well.
     Vector2i start = mouseDragStart;
     Vector2i end = mouseDragEnd;
     // FIXME: choose the aspect ratio based on the original image aspect ratio.
@@ -551,10 +574,10 @@ public class Game : GameWindow {
     }
 
     // Delegate input to the active tool.
-    ToolState state = activeTool.HandleInput(geometry, KeyboardState, MouseState, this);
+    ToolStatus status = activeTool.HandleInput(KeyboardState, MouseState, this);
 
     // Change back to the default tool if the active tool is done.
-    if (state != ToolState.Active) {
+    if (status != ToolStatus.Active) {
       activeTool = viewTool;
     }
   }
@@ -823,10 +846,14 @@ public class Game : GameWindow {
     }
   }
 
+  public Vector2i ScreenToImageDelta(int x, int y) {
+    return new((int) (x / activeScale), (int) (y / activeScale));
+  }
+
   public Vector2i ScreenToImage(int x, int y) {
     int rx = (int) ((x - activeOffset.X) / activeScale);
-    rx = Math.Clamp(rx, 0, photos[photoIndex].Size.X);
     int ry = (int) ((y - activeOffset.Y) / activeScale);
+    rx = Math.Clamp(rx, 0, photos[photoIndex].Size.X);
     ry = Math.Clamp(ry, 0, photos[photoIndex].Size.Y);
     return new(rx, ry);
   }