From 7db1719c3afa83b8fb6ad629c4ce558135240a7a Mon Sep 17 00:00:00 2001
From: George Oliver <georgeolivergo@gmail.com>
Date: Tue, 30 Jun 2020 20:39:35 -0700
Subject: [PATCH] added bounds and walkable test in move action simplified
 vector-ref'ing

---
 janus0x1.scm | 37 +++++++++++++++++++++++--------------
 1 file changed, 23 insertions(+), 14 deletions(-)

diff --git a/janus0x1.scm b/janus0x1.scm
index bdcedc3..b5404b9 100644
--- a/janus0x1.scm
+++ b/janus0x1.scm
@@ -78,7 +78,8 @@
 
 (vector-for-each
  (lambda (x) (tile-walkable?-set! x #f) (tile-clear?-set! x #f))
- (subvector world 96 128))
+ (subvector world 30 33))
+;;;;
 
 ;; output views
 (define-record view glyph)
@@ -99,6 +100,11 @@
   (make-view (glyphs #x0023)))
 ;;;;
 
+(define (in-bounds? x y)
+  (and (<= 0 x) (<= 0 y) (>= (sub1 ww) x) (>= (sub1 wh) y)))
+
+(define (walkable? x y)
+  (tile-walkable? (vector-ref world (pos->idx x y))))
 
 ;; actions
 (define (move thing dir)
@@ -106,10 +112,15 @@
 	(y (thing-y thing))
 	(dirs '((#:up 0 -16) (#:down 0 16) (#:left -16 0) (#:right 16 0)))
 	(dx (second (assoc dir dirs)))
-	(dy (third (assoc dir dirs))))	
-    (thing-x-set! thing (+ x dx))
-    (thing-y-set! thing (+ y dy))))
+	(dy (third (assoc dir dirs)))
+	(nx (+ x dx))
+	(ny (+ y dy)))
+    (when (and (in-bounds? nx ny) (walkable? nx ny))
+      (begin
+	(thing-x-set! thing nx)
+	(thing-y-set! thing ny)))))
 ;;;;
+
 	       
 ;; event handler
 (define (handle-event event exit-main!)
@@ -138,8 +149,8 @@
 ;; y will go from 0 to 380 by 20s (based on screen height divided by 16).
 ;; add x and y to get i.
 
-(define (pos->screen-rect x y)
-  (vector-ref screen-rects (+ (/ x 16) (* (/ wh 16) (/ y 16)))))
+(define (pos->idx x y)
+  (+ (/ x 16) (* (/ wh 16) (/ y 16))))
 
 ;; given an index i, how to find the (x y) where the tile is?
 ;; take (304, 0) which is index 19.
@@ -150,24 +161,22 @@
 (define (idx->pos i)
   (values (* 16 (modulo i (/ ww 16))) (* 16 (quotient i (/ wh 16)))))
 
-(define (idx->screen-rect i)
-  (vector-ref screen-rects i))
-
 (define (draw-world! xs)
   (let loop ((xs xs)
 	     (i 0))
     (cond ((tile-walkable? (vector-ref xs i))
-	   (sdl2:blit-surface! (view-glyph tile-space-view) #f w-surf (idx->screen-rect i)))
+	   (sdl2:blit-surface! (view-glyph tile-space-view) #f w-surf (vector-ref screen-rects i)))
 	  ((not (tile-walkable? (vector-ref xs i)))
-	   (sdl2:blit-surface! (view-glyph tile-wall-view) #f w-surf (idx->screen-rect i))))
+	   (sdl2:blit-surface! (view-glyph tile-wall-view) #f w-surf (vector-ref screen-rects i))))
     (when (> (sub1 (vector-length xs)) i) (loop xs (add1 i)))))
 
-
 (define (redraw!)
   (sdl2:fill-rect! w-surf #f black)
   (draw-world! world)
-  (sdl2:blit-surface! (view-glyph player-view) #f w-surf (pos->screen-rect (thing-x player) (thing-y player)))
-  (sdl2:blit-surface! (view-glyph npc-view) #f w-surf (pos->screen-rect (thing-x npc) (thing-y npc)))  
+  (sdl2:blit-surface!
+   (view-glyph player-view) #f w-surf (vector-ref screen-rects (pos->idx (thing-x player) (thing-y player))))
+  (sdl2:blit-surface!
+   (view-glyph npc-view) #f w-surf (vector-ref screen-rects (pos->idx (thing-x npc) (thing-y npc))))  
   (sdl2:update-window-surface! window))
 ;;;;