From 1d2dfbf52c3734beb7e4752534803a1e52a02b47 Mon Sep 17 00:00:00 2001
From: Joshua Bell <inexorabletash@gmail.com>
Date: Sat, 23 Sep 2023 13:18:46 -0700
Subject: [PATCH] Add BITCUT and BITPASTE commands. Resolves #142

---
 language.html | 11 ++++++++++-
 logo.js       | 10 ++++++++++
 tests.js      |  2 ++
 turtle.js     | 17 +++++++++++++++++
 4 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/language.html b/language.html
index e8f34a9..5dabf14 100644
--- a/language.html
+++ b/language.html
@@ -826,9 +826,18 @@ <h4>6.6 Pen Queries</h4>
 
 <!--
 <h4>6.7 Saving and Loading Pictures</h4>
+-->
+<h4>6.7 Bitmap Operations</h4>
 <dl>
+  <dt><code>bitcut <var>width</var> <var>height</var></code>
+  <dd>Copy a bitmap, from the turtle's position <var>width</var> by <var>height</var> pixels.
+
+  <dt><code>bitpaste</code>
+  <dd>Paste the previously copied bitmap at the current turtle position.
+  <dd class=example>repeat 4 [ rt 90 fd 40 ] bitcut 50 50 pu fd 100 bitpaste</dd>
 </dl>
--->
+
+
 
 <h4>6.8 Mouse/Touch Queries</h4>
 <dl>
diff --git a/logo.js b/logo.js
index e17ecb1..243a6db 100644
--- a/logo.js
+++ b/logo.js
@@ -2428,6 +2428,16 @@ function LogoInterpreter(turtle, stream, savehook)
     return turtle.touches;
   });
 
+  // Extensions
+
+  def("bitcut", function(w, h) {
+    return turtle.copy(w, h);
+  });
+
+  def("bitpaste", function() {
+    return turtle.paste();
+  });
+
   //----------------------------------------------------------------------
   //
   // 7. Workspace Management
diff --git a/tests.js b/tests.js
index ed87bb4..e273d76 100644
--- a/tests.js
+++ b/tests.js
@@ -2026,8 +2026,10 @@ QUnit.test("Arity of Primitives", function(t) {
     ['bfs', [1, 1, 1]],
     ['bg', [0, 0, 0]],
     ['bitand', [0, 2, -1]],
+    ['bitcut', [2, 2, 2]],
     ['bitnot', [1, 1, 1]],
     ['bitor', [0, 2, -1]],
+    ['bitpaste', [0, 0, 0]],
     ['bitxor', [0, 2, -1]],
     ['bk', [1, 1, 1]],
     ['bl', [1, 1, 1]],
diff --git a/turtle.js b/turtle.js
index b95147c..40dc434 100644
--- a/turtle.js
+++ b/turtle.js
@@ -507,6 +507,23 @@
       this.pendown = state.pendown;
     }},
 
+    copy: {value: function(w, h) {
+      var x = this.width / 2 + this.x * this.sx;
+      var y = this.height / 2 - this.y * this.sy;
+      w *= this.sx;
+      h *= this.sy;
+      this._clipboard = this.canvas_ctx.getImageData(x, y, w, h);
+    }},
+
+    paste: {value: function() {
+      if (!this._clipboard)
+        return;
+
+      var x = this.width / 2 + this.x * this.sx;
+      var y = this.height / 2 - this.y * this.sy;
+      this.canvas_ctx.putImageData(this._clipboard, x, y);
+    }},
+
     // Properties
 
     pendown: {