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+;;; guile-2d
+;;; Copyright (C) 2013 David Thompson <dthompson2@worcester.edu>
+;;;
+;;; Guile-2d is free software: you can redistribute it and/or modify it
+;;; under the terms of the GNU Lesser General Public License as
+;;; published by the Free Software Foundation, either version 3 of the
+;;; License, or (at your option) any later version.
+;;;
+;;; Guile-2d is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+;;; Lesser General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU Lesser General Public
+;;; License along with this program.  If not, see
+;;; <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+;;
+;; Keyboard signals.
+;;
+;;; Code:
+
+(define-module (2d keyboard)
+  #:use-module ((sdl sdl) #:prefix SDL:)
+  #:use-module (2d game)
+  #:use-module (2d signals)
+  #:use-module (2d vector2)
+  #:export (key-last-down
+            key-last-up
+            key-down?
+            key-directions
+            key-arrows
+            key-wasd))
+
+(define key-last-down (make-signal))
+(define key-last-up (make-signal))
+
+(define (key-down? key)
+  "Create a signal for the state of KEY. Value is #t when key is
+pressed and #f otherwise."
+  (make-signal
+   #:filter (lambda (value old from)
+              (eq? value key))
+   #:transformer (lambda (value old from)
+                   (if (eq? from key-last-down) #t #f))
+   #:connectors (list key-last-down key-last-up)))
+
+(define (key-directions up down left right)
+  (signal-lift4 (lambda (up? down? left? right?)
+                  (vector2 (+ (if left? -1 0)
+                              (if right? 1 0))
+                           (+ (if up? -1 0)
+                              (if down? 1 0))))
+                (key-down? up)
+                (key-down? down)
+                (key-down? left)
+                (key-down? right)))
+
+(define key-arrows (key-directions 'up 'down 'left 'right))
+(define key-wasd (key-directions 'w 's 'a 'd))
+
+(register-event-handler
+ 'key-down
+ (lambda (e)
+   (signal-set! key-last-down (SDL:event:key:keysym:sym e))))
+
+(register-event-handler
+ 'key-up
+ (lambda (e)
+   (signal-set! key-last-up (SDL:event:key:keysym:sym e))))