From 4b1370fc286db564e32a8e2e890061bc3ed413ac Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Wed, 10 Feb 2016 22:00:02 -0500
Subject: examples: Update everything to use deferred GL resource loading.

---
 examples/2048/2048.scm   | 245 +++++++++++++++++++++++++++++------------------
 examples/animation.scm   |  61 ++++++++----
 examples/common.scm      |   4 +-
 examples/font.scm        |  43 ++++-----
 examples/framebuffer.scm |  36 ++++---
 examples/life.scm        |  50 +++++-----
 examples/mines/mines.scm | 133 ++++++++++++++-----------
 examples/shapes.scm      |  56 +++++++----
 examples/simple.scm      |  23 ++---
 examples/tilemap.scm     |  52 +++++-----
 10 files changed, 410 insertions(+), 293 deletions(-)

(limited to 'examples')

diff --git a/examples/2048/2048.scm b/examples/2048/2048.scm
index e9eb16d..8d2ecf9 100755
--- a/examples/2048/2048.scm
+++ b/examples/2048/2048.scm
@@ -254,25 +254,26 @@
 (define-signal board
   (signal-map 2048-board 2048-state))
 
-(define-signal score-saver
-  (signal-tap (lambda (state)
-                (when (board-lose? (2048-board state))
-                  (save-best-score state)))
-              2048-state))
+(add-signal-hook! 2048-state
+  (lambda (state)
+    (when (board-lose? (2048-board state))
+      (save-best-score state))))
+
+(define-signal same-score?
+  (signal-let ((current 2048-state)
+               (prev (signal-delay 1 2048-state)))
+    (= (2048-score prev)
+       (2048-score current))))
 
 ;;;
 ;;; Rendering
 ;;;
 
-(init-window)
-(enable-fonts)
+(define (maybe-play-sample sample)
+  (and sample (play-sample sample)))
 
 (define background (rgb #xfaf8ef))
 
-(define tile-texture (load-texture "tile.png"))
-
-(define font (load-default-font 32))
-
 (define text-color-1 (rgb #x776e65))
 (define text-color-2 (rgb #xf9f6f2))
 
@@ -308,15 +309,12 @@
 (define (tile-text-color n)
   (assoc-ref (assoc-ref tile-properties n) 'text-color))
 
-(define tile-sprite
-  (make-sprite tile-texture #:anchor (vector2 0 0)))
-
-(define tile-label-cache
+(define (make-tile-label-cache font)
   (map (lambda (n)
          (cons n (make-label font (number->string n) #:anchor 'center)))
        '(2 4 8 16 32 64 128 256 512 1024 2048)))
 
-(define (render-tile x y n)
+(define (render-tile tile-texture tile-sprite tile-label-cache x y n)
   (let ((w (texture-width tile-texture))
         (h (texture-height tile-texture))
         (label (assoc-ref tile-label-cache n))
@@ -334,130 +332,191 @@
 
 (define window-width 640)
 (define window-height 480)
-(define board-width
-  (* board-size (texture-width tile-texture)))
-(define board-height
-  (* board-size (texture-height tile-texture)))
-(define center-pos
-  (vector2 (/ (- window-width board-width) 2) 8))
 
 (define (enumerate-board board)
   (enumerate (map (cut enumerate <>) board)))
 
-(define (render-board board)
+(define (render-board board tile-texture tile-sprite tile-label-cache)
   (list->renderer
    (append-map
     (match-lambda
      ((y (row ...))
       (map (match-lambda
             ((x n)
-             (render-tile x y n)))
+             (render-tile tile-texture tile-sprite tile-label-cache x y n)))
            row)))
     (enumerate-board board))))
 
-(define-signal tiles
-  (signal-map render-board board))
-
-(define play-again-font (load-default-font 16))
-
 (define (render-label font text anchor)
   (with-color black
     (render-sprite
      (make-label font text #:anchor anchor))))
 
-(define-signal status-message
-  (let ((play-again (render-label play-again-font
-                                  "Press N to play again"
-                                  'top-center))
-        (game-over  (render-label font "GAME OVER" 'bottom-center))
-        (you-win    (render-label font "YOU WIN!" 'bottom-center)))
-    (signal-map
-     (lambda (board)
-       (let ((message (cond
-                       ((board-lose? board) game-over)
-                       ((board-win? board) you-win)
-                       (else #f))))
-         (if message
-             (move (vector2 (/ board-width 2)
-                            (/ board-height 2))
-                   (render-begin message play-again))
-             render-nothing)))
-     board)))
-
-(define instruction-font (load-default-font 16))
-
 (define instruction-text
   "Use the arrow keys to join the numbers and get to the 2048 tile!")
 
-(define-signal instructions
-  (with-color text-color-1
-    (move (vector2 (/ board-width 2)
-                   (- window-height (vy center-pos)))
-          (render-sprite
-           (make-label instruction-font instruction-text
-                       #:anchor 'top-center)))))
-
-(define score-header-font (load-default-font 14))
-(define score-font (load-default-font 22))
-
 (define (score-label text score x)
   (let* ((duration 15)
          (position-tween (let* ((to (vector2 0 -32))
                                 (from (v- to (vector2 0 -8))))
                            (tween vlerp ease-linear from to duration)))
          (color-tween (tween color-lerp ease-linear
-                             transparent text-color-1 duration))
-         (header (make-label score-header-font text #:anchor 'top-center)))
-    (signal-let* ((score (signal-drop-repeats score))
+                             transparent text-color-1 duration)))
+    (signal-let* ((score-font score-font)
+                  (x x)
+                  (header (render-label-maybe score-header-font
+                                              text
+                                              'top-center))
+                  (score (signal-drop-repeats score))
                   (timer (signal-drop (lambda (t) (> t duration))
                                       0 (signal-since 1 score))))
-      (let ((score (make-label score-font (number->string score)
-                               #:anchor 'center)))
-        (move (vector2 x (- window-height 28))
-              (render-begin
-               (with-color text-color-1
-                 (render-sprite header))
-               (move (position-tween timer)
-                     (with-color (color-tween timer)
-                      (render-sprite score)))))))))
+      (if (and score-font header x)
+          (let ((score (make-label score-font (number->string score)
+                                   #:anchor 'center)))
+            (move (vector2 x (- window-height 28))
+                  (render-begin
+                   (with-color text-color-1 header)
+                   (move (position-tween timer)
+                         (with-color (color-tween timer)
+                           (render-sprite score))))))
+          render-nothing))))
+
+(define camera
+  (2d-camera #:area (make-rect 0 0 640 480) #:clear-color background))
+
+(define* (render-label-maybe font message anchor)
+  (signal-map-maybe (lambda (font)
+                      (render-label font message anchor))
+                    font))
+
+(define-signal tile-texture
+  (on-start (load-texture "tile.png")))
+
+(define-signal board-width
+  (signal-map-maybe (lambda (tile-texture)
+                      (* board-size (texture-width tile-texture)))
+                    tile-texture))
+
+(define-signal board-height
+  (signal-map-maybe (lambda (tile-texture)
+                      (* board-size (texture-height tile-texture)))
+                    tile-texture))
+
+(define-signal center-pos
+  (signal-map-maybe (lambda (board-width)
+                      (vector2 (/ (- window-width board-width) 2) 8))
+                    board-width))
+
+(define-signal score-unchanged-sound
+  (on-start (load-sample "../sounds/hit.wav")))
+
+(define-signal score-changed-sound
+  (on-start (load-sample "../sounds/jump.wav")))
+
+(define-signal sound-effect
+  (signal-map-maybe (cut if <> <> <>)
+                    same-score?
+                    score-unchanged-sound
+                    score-changed-sound))
+
+(define-signal font
+  (on-start (load-default-font 32)))
+
+(define-signal tile-sprite
+  (signal-map-maybe (cut make-sprite <> #:anchor (vector2 0 0))
+                    tile-texture))
+
+(define-signal tile-label-cache
+  (signal-map-maybe make-tile-label-cache font))
+
+(define-signal tiles
+  (signal-map-maybe render-board
+                    board
+                    tile-texture
+                    tile-sprite
+                    tile-label-cache))
+
+(define-signal instruction-font
+  (on-start (load-default-font 16)))
+
+(define-signal play-again-font
+  (on-start (load-default-font 16)))
+
+(define-signal score-header-font
+  (on-start (load-default-font 14)))
+
+(define-signal score-font
+  (on-start (load-default-font 22)))
+
+(define-signal status-message
+  (signal-let ((board board)
+               (play-again (render-label-maybe play-again-font
+                                               "Press N to play again"
+                                               'top-center))
+               (game-over  (render-label-maybe font "GAME OVER" 'bottom-center))
+               (you-win    (render-label-maybe font "YOU WIN!" 'bottom-center))
+               (board-width board-width)
+               (board-height board-height))
+    (let ((message (cond
+                    ((board-lose? board) game-over)
+                    ((board-win? board) you-win)
+                    (else #f))))
+      (if message
+          (move (vector2 (/ board-width 2)
+                         (/ board-height 2))
+                (render-begin message play-again))
+          render-nothing))))
 
 (define-signal score
-  (score-label "SCORE" (signal-map 2048-score 2048-state) (/ board-width 4)))
+  (score-label "SCORE"
+               (signal-map 2048-score 2048-state)
+               (signal-map-maybe (cut / <> 4) board-width)))
 
 (define-signal best-score
-  (score-label "BEST" (signal-map 2048-best-score 2048-state)
-               (- board-width (/ board-width 4))))
+  (score-label "BEST"
+               (signal-map 2048-best-score 2048-state)
+               (signal-map-maybe (lambda (width)
+                                   (- width (/ width 4)))
+                                 board-width)))
 
-(define-signal 2048-view
-  (signal-let ((instructions instructions)
-               (tiles tiles)
-               (score score)
-               (best-score best-score)
-               (status-message status-message))
-    (move center-pos
-          (render-begin
-           instructions
-           tiles
-           score
-           best-score
-           status-message))))
+(define-signal instructions
+  (signal-map-maybe (lambda (board-width center-pos instruction-font)
+                      (with-color text-color-1
+                        (move (vector2 (/ board-width 2)
+                                       (- window-height (vy center-pos)))
+                              (render-sprite
+                               (make-label instruction-font instruction-text
+                                           #:anchor 'top-center)))))
+                    board-width
+                    center-pos
+                    instruction-font))
 
-(define camera
-  (2d-camera #:area (make-rect 0 0 640 480) #:clear-color background))
+(define-signal 2048-view
+  (signal-map-maybe (lambda (center . renderers)
+                      (move center (list->renderer renderers)))
+                    center-pos
+                    instructions
+                    tiles
+                    score
+                    best-score
+                    status-message))
 
 (define-signal 2048-scene
   (signal-let ((view 2048-view))
-    (with-camera camera view)))
+    (with-camera camera (or view render-nothing))))
 
 ;;;
 ;;; Initialization
 ;;;
 
-(start-sly-repl)
+;; (start-sly-repl)
 
+(add-signal-hook! sound-effect maybe-play-sample)
 (add-hook! window-close-hook stop-game-loop)
 
 (with-window (make-window #:title "2048")
+  (enable-fonts)
+  (enable-audio)
   (run-game-loop 2048-scene))
 
 ;;; Local Variables:
diff --git a/examples/animation.scm b/examples/animation.scm
index 8aaff2e..6afbf34 100644
--- a/examples/animation.scm
+++ b/examples/animation.scm
@@ -15,12 +15,14 @@
 ;;; along with this program.  If not, see
 ;;; <http://www.gnu.org/licenses/>.
 
-(use-modules (sly utils)
+(use-modules (srfi srfi-43)
+             (sly utils)
              (sly game)
              (sly window)
              (sly signal)
              (sly math)
              (sly math rect)
+             ((sly math transform) #:prefix t:)
              (sly math tween)
              (sly math vector)
              (sly render)
@@ -33,31 +35,54 @@
 (define sprite* (memoize make-sprite))
 (define move* (memoize move))
 
-(define walk-cycle
-  (let ((tiles (load-tileset "images/princess.png" 64 64)))
-    (list->vector
-     (map (lambda (id)
-            (sprite* (tileset-ref tiles id)))
-          '(19 20 21 22 23 24 25 26)))))
+(define (make-walk-cycle tiles)
+  (list->vector
+   (map (lambda (id)
+          (sprite* (tileset-ref tiles id)))
+        '(19 20 21 22 23 24 25 26))))
 
 (define position-tween
   (tween vlerp (compose ease-linear ease-loop)
-         (vector2 480 240) (vector2 160 240) 120))
+         (vector2 640 240) (vector2 0 240) 90))
 
-(define frame-tween
-  (let* ((frame-count (vector-length walk-cycle))
-         (frame-rate (/ 60 frame-count)))
-    (tween (compose floor lerp) (compose ease-linear ease-loop)
-           0 frame-count (* frame-count frame-rate))))
+(define (make-frame-tween walk-cycle)
+  (if (vector-empty? walk-cycle)
+      (const 0)
+      (let* ((frame-count (vector-length walk-cycle))
+             (frame-rate (/ 60 frame-count)))
+        (tween (compose floor lerp) (compose ease-linear ease-loop)
+               0 frame-count (* frame-count frame-rate)))))
 
 (define camera (2d-camera #:area (make-rect 0 0 640 480)))
 
+(define (move/interpolate new old renderer)
+  (lambda (gfx)
+    (graphics-model-view-excursion gfx
+      (lambda (gfx)
+        (let ((v (vlerp old new (graphics-alpha gfx))))
+          (graphics-model-view-mul! gfx (t:translate v))
+          (renderer gfx))))))
+
+(define (render time walk-cycle frame-tween)
+  (let* ((frame (vector-ref walk-cycle (frame-tween time))))
+    (with-camera camera
+      (move/interpolate (position-tween time)
+                        (position-tween (1- time))
+                        (render-sprite frame)))))
+
+(define-signal walk-cycle
+  (signal-map-maybe make-walk-cycle
+                    (on-start (load-tileset "images/princess.png" 64 64))))
+
+(define-signal time (signal-timer))
+
+(define-signal frame-tween
+  (signal-map-maybe make-frame-tween walk-cycle))
+
 (define-signal scene
-  (signal-let ((time (signal-timer)))
-    (let* ((frame (vector-ref walk-cycle (frame-tween time))))
-      (with-camera camera
-        (move* (position-tween time)
-               (render-sprite frame))))))
+  (signal-map (lambda (render)
+                (or render render-nothing))
+              (signal-map-maybe render time walk-cycle frame-tween)))
 
 (with-window (make-window #:title "Animation")
   (run-game-loop scene))
diff --git a/examples/common.scm b/examples/common.scm
index 915c5fa..0c54447 100644
--- a/examples/common.scm
+++ b/examples/common.scm
@@ -18,8 +18,6 @@
 (use-modules (sly)
              (sly fps))
 
-(sly-init)
-
 (add-hook! key-press-hook (lambda (key)
                             (when (eq? key 'escape)
                               (stop-game-loop))))
@@ -31,4 +29,4 @@
    (format #t "FPS: ~d\n" (signal-ref fps)))
  60)
 
-(start-sly-repl)
+;; (start-sly-repl)
diff --git a/examples/font.scm b/examples/font.scm
index 64d32e0..f5b4a0d 100644
--- a/examples/font.scm
+++ b/examples/font.scm
@@ -19,6 +19,7 @@
              (sly fps)
              (sly signal)
              (sly window)
+             (sly math rect)
              (sly math vector)
              (sly render)
              (sly render camera)
@@ -30,36 +31,34 @@
 
 (load "common.scm")
 
-(define font (load-default-font 18))
-
 (define camera (2d-camera #:area (make-rect 0 0 640 480)))
 
-(define-signal render-message
-  (move (vector2 320 240)
-        (render-sprite
-         (make-label font "The quick brown fox jumped over the lazy dog."
-                     #:anchor 'center))))
-
-(define-signal render-fps
-  (signal-let ((fps fps))
-    (let ((text (format #f "FPS: ~d" fps)))
-      (move (vector2 0 480)
-            (render-sprite (make-label font text))))))
+(define (render-messages font fps pos)
+  (render-begin
+   (move (vector2 320 240)
+         (render-sprite
+          (make-label font "The quick brown fox jumped over the lazy dog."
+                      #:anchor 'center)))
+   (let ((text (format #f "FPS: ~d" fps)))
+     (move (vector2 0 480)
+           (render-sprite (make-label font text))))
+   (let ((text (format #f "Mouse: (~d, ~d)" (vx pos) (vy pos))))
+     (move (vector2 0 460)
+           (render-sprite (make-label font text))))))
 
-(define-signal render-mouse
-  (signal-let ((pos (signal-throttle 10 mouse-position)))
-    (let ((text (format #f "Mouse: (~d, ~d)" (vx pos) (vy pos))))
-      (move (vector2 0 460)
-            (render-sprite (make-label font text))))))
+(define-signal font (on-start (load-default-font 18)))
 
 (define-signal scene
-  (signal-let ((message render-message)
-               (fps render-fps)
-               (mouse render-mouse))
+  (signal-let ((fps fps)
+               (mouse-position (signal-throttle 10 mouse-position))
+               (font font))
     (with-camera camera
-      (render-begin message fps mouse))))
+      (if font
+          (render-messages font fps mouse-position)
+          render-nothing))))
 
 (with-window (make-window #:title "Fonts")
+  (enable-fonts)
   (run-game-loop scene))
 
 ;;; Local Variables:
diff --git a/examples/framebuffer.scm b/examples/framebuffer.scm
index 894cbc3..50c65e8 100644
--- a/examples/framebuffer.scm
+++ b/examples/framebuffer.scm
@@ -31,30 +31,36 @@
 
 (load "common.scm")
 
-(define framebuffer
-  (make-framebuffer 320 240))
-
 (define inner-camera
   (2d-camera #:area (make-rect 0 0 320 240)))
 
 (define outer-camera
   (2d-camera #:area (make-rect 0 0 640 480)))
 
-(define inner-sprite
-  (load-sprite "images/p1_front.png"))
+(define-signal framebuffer
+  (on-start (make-framebuffer 320 240)))
+
+(define-signal outer-sprite
+  (signal-map-maybe (lambda (framebuffer)
+                      (make-sprite (framebuffer-texture framebuffer)
+                                   #:anchor 'bottom-left))
+                    framebuffer))
 
-(define outer-sprite
-  (make-sprite (framebuffer-texture framebuffer)
-               #:anchor 'bottom-left))
+(define-signal player-sprite
+  (on-start (load-sprite "images/p1_front.png")))
 
 (define-signal scene
-  (render-begin
-   (with-framebuffer framebuffer
-     (with-camera inner-camera
-       (move (vector2 160 120)
-             (render-sprite inner-sprite))))
-   (with-camera outer-camera
-     (scale 2 (render-sprite outer-sprite)))))
+  (signal-let ((framebuffer framebuffer)
+               (outer-sprite outer-sprite)
+               (inner-sprite player-sprite))
+    (if (and framebuffer outer-sprite inner-sprite)
+        (render-begin
+         (with-framebuffer framebuffer
+           (with-camera inner-camera
+             (move (vector2 160 120) (render-sprite inner-sprite))))
+         (with-camera outer-camera
+           (scale 2 (render-sprite outer-sprite))))
+        render-nothing)))
 
 (with-window (make-window #:title "Simple Sprite Demo")
   (run-game-loop scene))
diff --git a/examples/life.scm b/examples/life.scm
index 763e5d4..4e747ec 100644
--- a/examples/life.scm
+++ b/examples/life.scm
@@ -68,17 +68,17 @@
 (define tile-size 32)
 (define window-res (vector2 448 480))
 
-(define tileset
-  (load-tileset "mines/images/tiles.png" 32 32))
+(define-signal tileset
+  (on-start (load-tileset "mines/images/tiles.png" 32 32)))
 
-(define alive-texture
+(define (alive-texture tileset)
   (tileset-ref tileset 12))
 
-(define empty-texture
+(define (empty-texture tileset)
   (tileset-ref tileset 13))
 
-(define batch
-  (make-sprite-batch (expt 14 2)))
+(define-signal batch
+  (on-start (make-sprite-batch (expt 14 2))))
 
 ;;;
 ;;; State
@@ -296,23 +296,27 @@ If there is no neighbor on an edge, the board wraps around"
 ;; Model of the tile grid
 (define-signal tiles-view
   (signal-let ((board board)
-               (board-size board-size))
-    (lambda (gfx)
-      (with-sprite-batch batch gfx
-        (enumerate-each
-         (lambda (row y)
-           (enumerate-each
-            (lambda (alive? x)
-              (let ((rect (rect-move sprite-rect
-                                     (tile-pos y x board-size tile-size))))
-                (sprite-batch-add! batch
-                                   gfx
-                                   (if alive?
-                                       alive-texture
-                                       empty-texture)
-                                   rect)))
-            (vlist->list row)))
-         (vlist->list board))))))
+               (board-size board-size)
+               (batch batch)
+               (tileset tileset))
+    (if tileset
+        (lambda (gfx)
+          (with-sprite-batch batch gfx
+            (enumerate-each
+             (lambda (row y)
+               (enumerate-each
+                (lambda (alive? x)
+                  (let ((rect (rect-move sprite-rect
+                                         (tile-pos y x board-size tile-size))))
+                    (sprite-batch-add! batch
+                                       gfx
+                                       (if alive?
+                                           (alive-texture tileset)
+                                           (empty-texture tileset))
+                                       rect)))
+                (vlist->list row)))
+             (vlist->list board))))
+        render-nothing)))
 
 (define-signal camera
   (signal-let ((running? simulation-running?))
diff --git a/examples/mines/mines.scm b/examples/mines/mines.scm
index 502d780..0b93473 100644
--- a/examples/mines/mines.scm
+++ b/examples/mines/mines.scm
@@ -289,17 +289,7 @@
 ;;; View
 ;;;
 
-(init-window)
-(enable-fonts)
-
-(define font (load-default-font))
-
-;; Minefield is 8x8, and there are 2 layers of tile graphics.
-(define batch (make-sprite-batch (* 8 8 2)))
-
-(define tileset (load-tileset "images/tiles.png" 32 32))
-
-(define tiles
+(define (make-tiles tileset)
   (map (match-lambda
          ((key . tile-index)
           (cons key (tileset-ref tileset tile-index))))
@@ -318,66 +308,92 @@
          (tile-up . 13)
          (tile-down . 12))))
 
-(define (tile-ref key)
+(define (tile-ref tiles key)
   (assoc-ref tiles key))
 
-(define (tile-base tile)
-  (tile-ref
-   (if (tile-shown? tile)
-       'tile-down
-       'tile-up)))
-
-(define (tile-overlay tile)
-  (and=> (cond
-          ((tile-shown-mine? tile) 'exploded)
-          ((tile-flagged-mine? tile) 'flag)
-          ((tile-flagged-maybe? tile) 'maybe)
-          ((and (tile-shown-not-mine? tile)
-                (tile-neighboring-mines? tile))
-           (tile-mine-count tile))
-          (else #f))
-         tile-ref))
+(define (tile-base tiles tile)
+  (tile-ref tiles
+            (if (tile-shown? tile)
+                'tile-down
+                'tile-up)))
+
+(define (tile-overlay tiles tile)
+  (let ((type (cond
+               ((tile-shown-mine? tile) 'exploded)
+               ((tile-flagged-mine? tile) 'flag)
+               ((tile-flagged-maybe? tile) 'maybe)
+               ((and (tile-shown-not-mine? tile)
+                     (tile-neighboring-mines? tile))
+                (tile-mine-count tile))
+               (else #f))))
+    (tile-ref tiles type)))
 
 (define tile-rect (make-rect 0 0 32 32))
 
-(define-signal board-view
-  (signal-let ((board board))
-    (lambda (gfx)
-      (with-sprite-batch batch gfx
-        (enumerate-each
-         (lambda (row y)
-           (enumerate-each
-            (lambda (tile x)
-              (let ((rect (rect-move tile-rect
-                                     (* x tile-size)
-                                     (* y tile-size)))
-                    (base-tex (tile-base tile))
-                    (overlay-tex (tile-overlay tile)))
-                (sprite-batch-add! batch gfx base-tex rect)
-                (when overlay-tex
-                  (sprite-batch-add! batch gfx overlay-tex rect))))
-            row))
-         board)))))
-
-(define (render-message message)
+(define (render-board board tiles batch)
+  (lambda (gfx)
+    (with-sprite-batch batch gfx
+      (enumerate-each
+       (lambda (row y)
+         (enumerate-each
+          (lambda (tile x)
+            (let ((rect (rect-move tile-rect
+                                   (* x tile-size)
+                                   (* y tile-size)))
+                  (base-tex (tile-base tiles tile))
+                  (overlay-tex (tile-overlay tiles tile)))
+              (sprite-batch-add! batch gfx base-tex rect)
+              (when overlay-tex
+                (sprite-batch-add! batch gfx overlay-tex rect))))
+          row))
+       board))))
+
+(define (render-message font message)
   (move (vector2 (/ (vx resolution) 2)
                  (- (vy resolution) 64))
         (render-sprite
          (make-label font message #:anchor 'center))))
 
-(define-signal status-message
-  (let ((game-over (render-message "GAME OVER - Press N to play again"))
-        (you-win   (render-message "YOU WIN! - Press N to play again")))
-    (signal-let ((board board))
-      (cond
-       ((board-lose? board) game-over)
-       ((board-win? board) you-win)
-       (else render-nothing)))))
+(define (render-message-maybe message)
+  (signal-map-maybe (lambda (font)
+                      (render-message font message))
+                    font))
 
 (define camera
   (2d-camera #:area (make-rect (vector2 0 0) resolution)
              #:clear-color tango-dark-plum))
 
+(define-signal font
+  (on-start (load-default-font)))
+
+;; Minefield is 8x8, and there are 2 layers of tile graphics.
+(define-signal batch
+  (on-start (make-sprite-batch (* 8 8 2))))
+
+(define-signal tileset
+  (on-start (load-tileset "images/tiles.png" 32 32)))
+
+(define-signal tiles
+  (signal-map-maybe make-tiles tileset))
+
+(define-signal board-view
+  (signal-map-maybe render-board board tiles batch))
+
+(define-signal status-message
+  (signal-let ((game-over (render-message-maybe
+                           "GAME OVER - Press N to play again"))
+               (you-win   (render-message-maybe
+                           "YOU WIN! - Press N to play again"))
+               (board board))
+    (cond
+     ((not (or game-over you-win)) ; assets not loaded
+      render-nothing)
+     ((board-lose? board)
+      game-over)
+     ((board-win? board)
+      you-win)
+     (else render-nothing))))
+
 (define-signal scene
   (signal-let ((view   board-view)
                (status status-message)
@@ -385,17 +401,18 @@
     (with-camera camera
       (render-begin
        status
-       (move center view)))))
+       (move center (or view render-nothing))))))
 
 ;;;
 ;;; Initialization
 ;;;
 
-(start-sly-repl)
+;;(start-sly-repl)
 
 (add-hook! window-close-hook stop-game-loop)
 
 (with-window (make-window #:title "Mines" #:resolution resolution)
+  (enable-fonts)
   (run-game-loop scene))
 
 ;;; Local Variables:
diff --git a/examples/shapes.scm b/examples/shapes.scm
index abaf371..1c20219 100644
--- a/examples/shapes.scm
+++ b/examples/shapes.scm
@@ -15,7 +15,8 @@
 ;;; along with this program.  If not, see
 ;;; <http://www.gnu.org/licenses/>.
 
-(use-modules (sly game)
+(use-modules (srfi srfi-26)
+             (sly game)
              (sly window)
              (sly utils)
              (sly signal)
@@ -31,45 +32,58 @@
 
 (load "common.scm")
 
-(define crate-texture
-  (load-texture "images/crate.png"))
+(define-signal crate-texture
+  (on-start (load-texture "images/crate.png")))
 
-(define sky-background
-  (load-sprite "images/country-sky.png"))
+(define-signal sky-background
+  (on-start (load-sprite "images/country-sky.png")))
 
-(define forest-background
-  (load-sprite "images/country-trees.png"))
+(define-signal forest-background
+  (on-start (load-sprite "images/country-trees.png")))
 
-(define background
+(define (make-background sky forest)
   (scale 1/10
          (move (vector3 0 0 -10)
                (render-begin
-                (render-sprite sky-background)
-                (render-sprite forest-background)))))
+                (render-sprite sky)
+                (render-sprite forest)))))
 
-(define unit-cube
-  (make-cube 1 #:texture crate-texture))
+(define-signal background
+  (signal-map-maybe make-background
+                    sky-background
+                    forest-background))
 
-(define cubes
+(define-signal unit-cube
+  (signal-map-maybe (cut make-cube 1 #:texture <>)
+                    crate-texture))
+
+(define (make-cubes unit-cube)
   (move (vector3 0 0 -3)
         (render-begin
          (move (vector3 2 0 0) unit-cube)
          unit-cube
          (move (vector3 -2 0 0) unit-cube))))
 
+(define-signal cubes
+  (signal-map-maybe make-cubes unit-cube))
+
 (define camera
   (3d-camera #:area (make-rect 0 0 640 480)))
 
 (define-signal scene
   (signal-let ((rotation (signal-map (lambda (x) (/ x 48))
-                                     (signal-timer))))
-    (with-camera camera
-      (render-begin
-       background
-       ;; Spinnin' cubes!
-       (with-depth-test #t
-         (rotate-x (* rotation 2)
-                   (rotate-y rotation cubes)))))))
+                                     (signal-timer)))
+               (background background)
+               (cubes cubes))
+    (if (and background cubes)
+        (with-camera camera
+          (render-begin
+           background
+           ;; Spinnin' cubes!
+           (with-depth-test #t
+             (rotate-x (* rotation 2)
+                       (rotate-y rotation cubes)))))
+        render-nothing)))
 
 (with-window (make-window #:title "Shapes!")
   (run-game-loop scene))
diff --git a/examples/simple.scm b/examples/simple.scm
index 0f3760b..f1882b7 100644
--- a/examples/simple.scm
+++ b/examples/simple.scm
@@ -15,27 +15,16 @@
 ;;; along with this program.  If not, see
 ;;; <http://www.gnu.org/licenses/>.
 
-(use-modules (sly game)
-             (sly window)
-             (sly utils)
-             (sly signal)
-             (sly math rect)
-             (sly math vector)
-             (sly render)
-             (sly render camera)
-             (sly render color)
-             (sly render shader)
-             (sly render sprite)
-             (sly render texture))
+(use-modules (sly))
 
 (load "common.scm")
 
-(define sprite (load-sprite "images/p1_front.png"))
-
 (define-signal scene
-  (with-camera (2d-camera #:area (make-rect 0 0 640 480))
-    (move (vector2 320 240)
-          (render-sprite sprite))))
+  (signal-let ((sprite (on-start (load-sprite "images/p1_front.png")
+                                 null-sprite)))
+    (with-camera (2d-camera #:area (make-rect 0 0 640 480))
+      (move (vector2 320 240)
+            (render-sprite sprite)))))
 
 (with-window (make-window #:title "Simple Sprite Demo")
   (run-game-loop scene))
diff --git a/examples/tilemap.scm b/examples/tilemap.scm
index 2e6bdf9..430e6a0 100644
--- a/examples/tilemap.scm
+++ b/examples/tilemap.scm
@@ -47,13 +47,13 @@
 ;; loading. Just a hardcoded tile map that demonstrates the
 ;; split-texture procedure.
 
-(define (build-map tile-indices)
+(define (build-map tileset tile-indices)
   (list->vlist*
    (map (lambda (row)
           (map (cut tileset-ref tileset <>) row))
         tile-indices)))
 
-(define (random-map width height)
+(define (random-map tileset width height)
   (let ((n (vector-length (tileset-tiles tileset))))
     (list->vlist*
      (list-tabulate
@@ -66,39 +66,45 @@
 
 (define tile-width 32)
 (define tile-height 32)
-(define tileset
-  (load-tileset "images/tiles.png" tile-width tile-height))
 
 (define map-width 20)
 (define map-height 15)
 (define map-tiles
-  (build-map
-   '((65 65 65 65 65 65 65 65 65 224 194 225 194 192 209 210 65 65 65 65)
-     (65 65 65 65 65 65 65 65 208 193 225 194 176 241 177 192 210 65 65 65)
-     (65 65 65 65 65 65 65 65 224 225 194 194 226 65 240 177 192 210 65 65)
-     (65 65 65 65 65 65 65 65 224 225 225 176 242 65 65 240 177 226 65 65)
-     (65 65 65 65 65 65 65 208 193 225 225 226 65 65 65 65 224 226 65 65)
-     (65 65 65 65 65 65 208 193 194 225 225 226 65 65 65 208 193 226 65 65)
-     (65 65 65 65 208 209 193 194 194 225 194 192 209 209 209 193 176 242 65 65)
-     (65 65 65 65 224 194 194 194 225 176 241 241 177 225 225 194 192 209 209 209)
-     (65 65 65 65 240 177 225 225 176 242 65 65 240 241 241 177 225 225 194 225)
-     (65 65 65 208 209 193 225 176 242 65 65 65 65 65 65 240 241 241 241 241)
-     (65 65 208 193 225 225 176 242 65 65 65 65 65 65 65 65 65 65 65 65)
-     (65 208 193 225 176 241 242 65 65 65 65 65 65 65 65 65 65 65 65 65)
-     (208 193 225 176 242 65 65 65 65 65 65 65 65 65 65 65 65 65 65 65)
-     (193 225 225 226 65 65 65 65 65 65 65 65 65 65 65 65 65 65 65 65)
-     (225 225 176 242 65 65 65 65 65 65 65 65 65 65 65 65 65 65 65 65))))
+  '((65 65 65 65 65 65 65 65 65 224 194 225 194 192 209 210 65 65 65 65)
+    (65 65 65 65 65 65 65 65 208 193 225 194 176 241 177 192 210 65 65 65)
+    (65 65 65 65 65 65 65 65 224 225 194 194 226 65 240 177 192 210 65 65)
+    (65 65 65 65 65 65 65 65 224 225 225 176 242 65 65 240 177 226 65 65)
+    (65 65 65 65 65 65 65 208 193 225 225 226 65 65 65 65 224 226 65 65)
+    (65 65 65 65 65 65 208 193 194 225 225 226 65 65 65 208 193 226 65 65)
+    (65 65 65 65 208 209 193 194 194 225 194 192 209 209 209 193 176 242 65 65)
+    (65 65 65 65 224 194 194 194 225 176 241 241 177 225 225 194 192 209 209 209)
+    (65 65 65 65 240 177 225 225 176 242 65 65 240 241 241 177 225 225 194 225)
+    (65 65 65 208 209 193 225 176 242 65 65 65 65 65 65 240 241 241 241 241)
+    (65 65 208 193 225 225 176 242 65 65 65 65 65 65 65 65 65 65 65 65)
+    (65 208 193 225 176 241 242 65 65 65 65 65 65 65 65 65 65 65 65 65)
+    (208 193 225 176 242 65 65 65 65 65 65 65 65 65 65 65 65 65 65 65)
+    (193 225 225 226 65 65 65 65 65 65 65 65 65 65 65 65 65 65 65 65)
+    (225 225 176 242 65 65 65 65 65 65 65 65 65 65 65 65 65 65 65 65)))
 
-(define render
+(define (render tiles)
   (move (v- (vector2 320 240)
             (v* (vector2 tile-width tile-height)
                 (vector2 10 15/2)))
-        (list->renderer (compile-tile-layer map-tiles 32 32))))
+        (list->renderer
+         (compile-tile-layer (build-map tiles map-tiles) 32 32))))
 
 (define camera (2d-camera #:area (make-rect 0 0 640 480)))
 
+(define-signal tileset
+  (on-start
+   (load-tileset "images/tiles.png" tile-width tile-height)))
+
 (define-signal scene
-  (with-camera camera render))
+  (signal-let ((tileset tileset))
+    (if tileset
+        (with-camera camera
+          (render tileset))
+        render-nothing)))
 
 (with-window (make-window #:title "Tilemap")
   (run-game-loop scene))
-- 
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