Add graphics-context class for managing SDL2 resources

drawing.lisp

@@ -63,3 +63,25 @@
 
 (defun overlay (&rest drawings)
   (apply #'append drawings))
+
+(defclass graphics-context ()
+  (window
+   renderer
+   (width :initarg :width :initform 800)
+   (height :initarg :height :initform 600)))
+
+(defmethod initialize-instance :after ((ctx graphics-context) &key)
+  (with-slots (window renderer width height) ctx
+    (sdl2:init)
+    (setf window
+          (sdl2:create-window :title "Simulation"
+                              :w width :h height
+                              :flags '(:shown)))
+    (setf renderer
+          (sdl2:create-renderer window -1 '(:accelerated :presentvsync)))))
+
+(defmethod cleanup ((ctx graphics-context))
+  (with-slots (window renderer) ctx
+    (sdl2:destroy-renderer renderer)
+    (sdl2:destroy-window window)
+    (sdl2:quit)))