keep around more loaded images

Program.cs

@@ -438,9 +438,11 @@ public class UiGeometry {
   public UiGeometry(Vector2i windowSize, int starSize) {
     WindowSize = windowSize;
 
-    int numThumbnails = 15;
+    int numThumbnails = WindowSize.Y / 100;
     int thumbnailHeight = WindowSize.Y / numThumbnails;
     int thumbnailWidth = (int) 1.0 * thumbnailHeight * activeCamera.Resolution.X / activeCamera.Resolution.Y;
+
+    Console.WriteLine($"thumbnail size: {thumbnailWidth} x {thumbnailHeight}");
     for (int i = 0; i < numThumbnails; i++) {
       Box2i box = Util.MakeBox(WindowSize.X - thumbnailWidth, i * thumbnailHeight, thumbnailWidth, thumbnailHeight);
       ThumbnailBoxes.Add(box);
@@ -815,7 +817,7 @@ public class Game : GameWindow {
     // Unload images that haven't been touched in a while.
     // FIXME: keep around thumbnail-sized textures?
     lock (loadedImagesLock) {
-      while (loadedImages.Count > 60) {
+      while (loadedImages.Count > 100) {
         long earliestTime = long.MaxValue;
         Photo? earliest = null;
         foreach (Photo photo in loadedImages) {
@@ -825,7 +827,7 @@ public class Game : GameWindow {
           }
         }
         if (earliest != null) {
-          // Console.WriteLine($"loadedImages.Count: {loadedImages.Count}, evicting {earliest.Filename} @ {earliestTime}");
+          Console.WriteLine($"loadedImages.Count: {loadedImages.Count}, evicting {earliest.Filename} @ {earliestTime}");
           // TODO: we have to free textures on the GL thread, but could we do that async'ly to keep the UI responsive?
           earliest.Unload();
           loadedImages.Remove(earliest);