render: Add separate projection and model-view matrix stacks.

Just like the Opengl 2.x days! ;)

* sly/render.scm (graphics-transform, graphics-transform-mul!,
  graphics-transform-identity!): Delete.
  (graphics-model-view-transform, graphics-model-view-mul!,
   graphics-model-view-identity!, graphics-projection-transform,
   graphics-projection-mul!, graphics-projection-identity!): New
   procedures.
   (with-model-view-excursion, with-projection-excursion): New syntax.
   (call-with-transform-excursion): Move matrix copying out of the "in
   guard."
   (draw-scene): Use new matrix stacks.

1 files changed, 31 insertions, 13 deletions

diff --git a/sly/render.scm b/sly/render.scm
index c1d19e3..6ff7bb9 100644
--- a/sly/render.scm
+++ b/sly/render.scm
@@ -54,11 +54,15 @@
             set-graphics-framebuffer!
             graphics-viewport
             set-graphics-viewport!
-            graphics-transform
-            graphics-transform-mul!
-            graphics-transform-identity!
+            graphics-model-view-transform
+            graphics-model-view-mul!
+            graphics-model-view-identity!
+            with-model-view-excursion
+            graphics-projection-transform
+            graphics-projection-mul!
+            graphics-projection-identity!
+            with-projection-excursion
             with-graphics
-            with-transform-excursion
             with-graphics-excursion))
 
 ;;;
@@ -84,9 +88,10 @@
 (define (call-with-transform-excursion stack thunk)
   (let ((t (q-pop! stack)))
     (dynamic-wind
+      (const #t)
       (lambda ()
-        (copy-transform! t (q-front stack)))
-      thunk
+        (copy-transform! t (q-front stack))
+        (thunk))
       (lambda ()
         (q-push! stack t)))))
 
@@ -180,20 +185,33 @@
     body ...
     (graphics-reset! gfx)))
 
-(define (graphics-transform gfx)
+(define (graphics-model-view-transform gfx)
   (q-front (graphics-model-view gfx)))
 
-(define (graphics-transform-mul! gfx t)
+(define (graphics-model-view-mul! gfx t)
   (stack-transform-mul! (graphics-model-view gfx) t))
 
-(define (graphics-transform-identity! gfx)
+(define (graphics-model-view-identity! gfx)
   (stack-transform-identity! (graphics-model-view gfx)))
 
-;; emacs: (put 'with-transform-excursion 'scheme-indent-function 1)
-(define-syntax-rule (with-transform-excursion gfx body ...)
+;; emacs: (put 'with-model-view-excursion 'scheme-indent-function 1)
+(define-syntax-rule (with-model-view-excursion gfx body ...)
   (call-with-transform-excursion (graphics-model-view gfx)
-                                 (lambda ()
-                                   body ...)))
+    (lambda () body ...)))
+
+(define (graphics-projection-transform gfx)
+  (q-front (graphics-projection gfx)))
+
+(define (graphics-projection-mul! gfx t)
+  (stack-transform-mul! (graphics-projection gfx) t))
+
+(define (graphics-projection-identity! gfx)
+  (stack-transform-identity! (graphics-projection gfx)))
+
+;; emacs: (put 'with-projection-excursion 'scheme-indent-function 1)
+(define-syntax-rule (with-projection-excursion gfx body ...)
+  (call-with-transform-excursion (graphics-projection gfx)
+    (lambda () body ...)))
 
 (define-syntax-rule (with-graphics-excursion gfx body ...)
   (match gfx