multiple columns of thumbnails

Program.cs

@@ -237,7 +237,6 @@ public class UiGeometry {
   public static Vector2i MIN_WINDOW_SIZE = new(1024, 768);
 
   public readonly Vector2i WindowSize;
-  public readonly Vector2i ThumbnailSize;
   public readonly Box2i ThumbnailBox;
   public readonly List<Box2i> ThumbnailBoxes = new();
   public readonly List<Box2i> StarBoxes = new();
@@ -249,24 +248,26 @@ public class UiGeometry {
   public UiGeometry(Vector2i windowSize, int starSize) {
     WindowSize = windowSize;
 
-    int numThumbnails = Math.Max(WindowSize.Y / 100, 1);
-    int thumbnailHeight = WindowSize.Y / numThumbnails;
+    int numThumbnailsPerColumn = Math.Max(WindowSize.Y / 100, 1);
+    int thumbnailHeight = WindowSize.Y / numThumbnailsPerColumn;
     int thumbnailWidth = (int) (1.0 * thumbnailHeight * CameraInfo.AspectRatio);
-    ThumbnailSize = new(thumbnailWidth, thumbnailHeight);
 
     Console.WriteLine($"thumbnail size: {thumbnailWidth}x{thumbnailHeight}");
-    for (int i = 0; i < numThumbnails; i++) {
-      Box2i box = Util.MakeBox(WindowSize.X - thumbnailWidth, i * thumbnailHeight,
-                               thumbnailWidth, thumbnailHeight);
-      ThumbnailBoxes.Add(box);
+    int thumbnailColumns = 3;
+    for (int j = thumbnailColumns; j > 0; j--) {
+      for (int i = 0; i < numThumbnailsPerColumn; i++) {
+        Box2i box = Util.MakeBox(WindowSize.X - thumbnailWidth * j, i * thumbnailHeight,
+                                 thumbnailWidth, thumbnailHeight);
+        ThumbnailBoxes.Add(box);
+      }
     }
 
     int statusBoxHeight = 40;
     int statusBoxPadding = 4;
     PhotoBox = new Box2i(
-        0, 0, WindowSize.X - thumbnailWidth, WindowSize.Y - statusBoxHeight - statusBoxPadding);
+        0, 0, WindowSize.X - thumbnailWidth * thumbnailColumns, WindowSize.Y - statusBoxHeight - statusBoxPadding);
     StatusBox = new Box2i(
-        0, WindowSize.Y - statusBoxHeight, WindowSize.X - thumbnailWidth, WindowSize.Y);
+        0, WindowSize.Y - statusBoxHeight, WindowSize.X - thumbnailWidth * thumbnailColumns, WindowSize.Y);
     ThumbnailBox = new Box2i(
         ThumbnailBoxes[0].Min.X, ThumbnailBoxes[0].Min.Y, WindowSize.X, WindowSize.Y);