From 124dbe9b93cfd8ab9cce52a82c367ca651f578e2 Mon Sep 17 00:00:00 2001
From: Robby Findler <robby@racket-lang.org>
Date: Wed, 17 Feb 2010 23:21:57 +0000
Subject: [PATCH] added empty-scene

svn: r18138
---
 collects/2htdp/image.ss                          |   1 +
 collects/2htdp/private/image-more.ss             |   5 +++++
 collects/2htdp/tests/test-image.ss               |   5 ++++-
 .../teachpack/2htdp/scribblings/image-toc.ss     |   1 +
 collects/teachpack/2htdp/scribblings/image.scrbl |  12 +++++++++++-
 .../2htdp/scribblings/img/216addb7809.png        | Bin 0 -> 306 bytes
 .../2htdp/scribblings/img/2bed4c99df8.png        | Bin 0 -> 1079 bytes
 7 files changed, 22 insertions(+), 2 deletions(-)
 create mode 100644 collects/teachpack/2htdp/scribblings/img/216addb7809.png
 create mode 100644 collects/teachpack/2htdp/scribblings/img/2bed4c99df8.png

diff --git a/collects/2htdp/image.ss b/collects/2htdp/image.ss
index fb81e88b3a..4c96dcc3c5 100644
--- a/collects/2htdp/image.ss
+++ b/collects/2htdp/image.ss
@@ -76,6 +76,7 @@ and they all have good sample contracts. (It is amazing what we can do with kids
          circle
          ellipse
          rectangle
+         empty-scene
          square
          rhombus
          regular-polygon
diff --git a/collects/2htdp/private/image-more.ss b/collects/2htdp/private/image-more.ss
index 5068aa47e4..48d1fb1360 100644
--- a/collects/2htdp/private/image-more.ss
+++ b/collects/2htdp/private/image-more.ss
@@ -654,6 +654,10 @@
   (check-mode/color-combination 'square 3 mode color)
   (make-a-polygon (rectangle-points side-length side-length) mode color))
 
+(define/chk (empty-scene width height)
+  (overlay (rectangle width height 'outline 'black)
+           (rectangle width height 'solid 'white)))
+
 (define/chk (rhombus side-length angle mode color)
   (check-mode/color-combination 'rhombus 3 mode color)
   (let* ([left-corner (make-polar side-length (+ (* pi 1/2) (/ (degrees->radians angle) 2)))]
@@ -956,6 +960,7 @@
          circle
          ellipse
          rectangle
+         empty-scene
          square
          rhombus
          
diff --git a/collects/2htdp/tests/test-image.ss b/collects/2htdp/tests/test-image.ss
index 604985cbbe..4b518e507c 100644
--- a/collects/2htdp/tests/test-image.ss
+++ b/collects/2htdp/tests/test-image.ss
@@ -630,7 +630,10 @@
        (make-bb 100 100 100)
        #f))
 
-
+(test (empty-scene 185 100)
+      =>
+      (overlay (rectangle 185 100 'outline 'black)
+               (rectangle 185 100 'solid 'white)))
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;
 ;;  testing normalization
diff --git a/collects/teachpack/2htdp/scribblings/image-toc.ss b/collects/teachpack/2htdp/scribblings/image-toc.ss
index 1bba743787..3813f89609 100644
--- a/collects/teachpack/2htdp/scribblings/image-toc.ss
+++ b/collects/teachpack/2htdp/scribblings/image-toc.ss
@@ -244,6 +244,7 @@
       (rectangle 48 48 "solid" "gray"))
     'image
     "126418b230e.png")
+   (list '(empty-scene 160 90) 'image "216addb7809.png")
    (list
     '(above/align
       "left"
diff --git a/collects/teachpack/2htdp/scribblings/image.scrbl b/collects/teachpack/2htdp/scribblings/image.scrbl
index 048a48f175..1ff710b855 100644
--- a/collects/teachpack/2htdp/scribblings/image.scrbl
+++ b/collects/teachpack/2htdp/scribblings/image.scrbl
@@ -621,11 +621,21 @@ Unlike @scheme[scene+curve], if the line passes outside of @scheme[image], the i
   
   }
 
-@section{Placing Images}
+@section{Placing Images & Scenes}
 
 Placing images into scenes is particularly useful when building worlds
 and universes using @scheme[2htdp/universe].
 
+@defproc[(empty-scene [width (and/c real? (not/c negative?))]
+                      [height (and/c real? (not/c negative?))])
+         image?]{
+
+Creates an empty scene, i.e., a rectangle with a black outline.
+
+@image-examples[(empty-scene 160 90)]
+                                                                 
+}
+
 @defproc[(place-image [image image?] [x real?] [y real?] [scene image?]) image?]{
 
  Places @scheme[image] onto @scheme[scene] with its center at the coordinates 
diff --git a/collects/teachpack/2htdp/scribblings/img/216addb7809.png b/collects/teachpack/2htdp/scribblings/img/216addb7809.png
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diff --git a/collects/teachpack/2htdp/scribblings/img/2bed4c99df8.png b/collects/teachpack/2htdp/scribblings/img/2bed4c99df8.png
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