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+title: Live Asset Reloading with guile-2d
+date: 2014-05-04 22:00:00
+tags: foss, gnu, guile, scheme, gamedev, wsu
+summary: Automatically reload modified assets while developing guile-2d progams
+---
+
+Guile-2d provides a dynamic environment in which a developer can build
+a game incrementally as it runs via the Guile REPL.  It’s nice to be
+able to hot-swap code and have the running game reflect the changes
+made, but what about the game data files?  If an image file or other
+game asset is modified, it would be nice if the game engine took
+notice and reloaded it automatically.  This is what guile-2d’s live
+asset reloading feature does.
+
+The new `(2d live-reload)` module provides the `live-reload`
+procedure.  `live-reload` takes a procedure like `load-texture` and
+returns a new procedure that adds the live reload magic.  The new
+procedure returns assets wrapped in a signal, a time-varying value.  A
+coroutine is started that periodically checks if the asset file has
+been modified, and if so, reloads the asset and propagates it via the
+signal.  Game objects that depend on the asset will be regenerated
+immediately.
+
+Here’s some example code:
+
+```scheme
+(define load-texture/live
+  (live-reload load-texture))
+
+(define-signal texture
+  (load-texture/live "images/p1_front.png"))
+
+(define-signal sprite
+  (signal-map
+   (lambda (texture)
+     (make-sprite texture
+                  #:position (vector2 320 240)))
+   texture))
+```
+
+`load-texture/live` loads textures and reloads them when they change
+on disk.  Every time the texture is reloaded, the sprite is
+regenerated using the new texture.
+
+Here’s a screencast to see live reloading in action:
+
+   <video src="http://media.dthompson.us/mgoblin_media/media_entries/10/Screencast_from_05-04-2014_053639_PM.medium.webm"
+          style="width:640px;height:360px;" controls>
+   </video>
+
+Guile-2d is ever-so-slowly approaching a 0.2 release.  Stay tuned!