Allow draw after clear

src/canvas.js

@@ -142,7 +142,6 @@ class Canvas {
     /** @type {(image: import('./image-metadata').ImageMetadata) => import('./image-metadata').ImageMetadata} */
     this._imageAdjuster = itself;
     this._outline = outline || Classic;
-    this._drawn = false;
   }
 
   _initialize() {
@@ -154,6 +153,7 @@ class Canvas {
     this.templates = {};
     /** @type {import('./vector').Vector} */
     this._figurePadding = null;
+    this._drawn = false;
   }
 
   /**

test/canvas-spec.js

@@ -41,6 +41,21 @@ describe("Canvas", () => {
     assert.deepEqual(canvas.puzzle.head.centralAnchor, {x: 50, y: 50});
   })
 
+  it("can not draw a canvas twice", () => {
+    const canvas = new Canvas('canvas', {
+      width: 800, height: 800,
+      painter: painter
+    })
+
+    canvas.sketchPiece({
+      structure: {right: Tab, down: Tab, left: Slot},
+      metadata: {}
+    });
+
+    canvas.draw();
+    assert.throws(() => canvas.draw());
+  })
+
   it("can create a single-piece puzzle with size overriden ", () => {
     const canvas = new Canvas('canvas', {
       width: 800, height: 800,
@@ -265,10 +280,12 @@ describe("Canvas", () => {
     canvas.draw();
     canvas.clear();
 
+    assert.equal(canvas._drawn, false);
     assert.equal(canvas._painter, painter);
     assert.equal(canvas._puzzle, null);
     assert.equal(canvas.puzzle.pieces.length, 0);
     assert.deepEqual(canvas.figures, {});
+    assert.doesNotThrow(() => canvas.draw());
   })
 
   it("can sketch a whole puzzle", () => {