render: Reimplement rendering engine using functional combinators.

Warning: This is a huge commit.

I completely gutted the old scene graph and replaced it with a somewhat
monadic rendering combinator module instead.  The interface remains
purely functional, but replaces the <model> data type with procedures in
the rendering monad instead.  This opens the door for
rendering *anything*, not just meshes.  Now I can implement particle
systems and other non-static things.

1 files changed, 22 insertions, 12 deletions

diff --git a/examples/joystick.scm b/examples/joystick.scm
index a191de5..661b18e 100644
--- a/examples/joystick.scm
+++ b/examples/joystick.scm
@@ -1,5 +1,6 @@
 ;;; Sly
 ;;; Copyright (C) 2014 Jordan Russell <jordan.likes.curry@gmail.com>
+;;; Copyright (C) 2015 David Thompson <davet@gnu.org>
 ;;;
 ;;; This program is free software: you can redistribute it and/or
 ;;; modify it under the terms of the GNU General Public License as
@@ -17,21 +18,21 @@
 
 ;;; Commentary:
 ;;
-;; Joystick example code
+;; Joystick example code.
 ;;
 ;;; Code:
 
 (use-modules (sly game)
              (sly signal)
              (sly window)
+             (sly math rect)
              (sly math vector)
              (sly input joystick)
+             (sly render)
              (sly render camera)
-             (sly render model)
              (sly render sprite)
              (sly render texture)
-             (sly render font)
-             (sly render scene))
+             (sly render font))
 
 (load "common.scm")
 
@@ -42,7 +43,10 @@
 
 (define resolution (vector2 640 480))
 
-(define player (load-sprite "images/p1_front.png"))
+(define player-texture
+  (load-texture "images/p1_front.png"))
+
+(define player (make-sprite player-texture))
 
 (define-signal player-position
   (signal-fold v+ (vector2 320 240)
@@ -56,7 +60,8 @@
 
 (define-signal caption
   (signal-map (lambda (text)
-                (model-move (vector2 -76 -90) (label font text)))
+                (move (vector2 -76 -90)
+                      (render-sprite (make-label font text))))
               (signal-merge
                (make-signal "Press a button")
                (button-caption-signal "Hello there" 0)
@@ -64,15 +69,20 @@
                (button-caption-signal "This is the other caption" 2)
                (button-caption-signal "This is the other other caption" 3))))
 
-(define-signal model
-  (signal-map (lambda (position caption)
-                (model-move position (model-group player caption)))
-              player-position caption))
+(define-signal view
+  (signal-let ((position player-position)
+               (caption caption))
+    (move position
+          (render-begin
+           (render-sprite player)
+           caption))))
 
-(define camera (orthographic-camera (vx resolution) (vy resolution)))
+(define camera
+  (2d-camera #:area (make-rect (vector2 0 0) resolution)))
 
 (define-signal scene
-  (signal-map (lambda (model) (make-scene camera model)) model))
+  (signal-let ((view view))
+    (with-camera camera view)))
 
 (add-hook! joystick-axis-hook
            (lambda (which axis value)