Implement counter blocks

src/blocks/scratch3_control.js

@@ -7,6 +7,12 @@ class Scratch3ControlBlocks {
          * @type {Runtime}
          */
         this.runtime = runtime;
+
+        /**
+         * The "counter" block value. For compatibility with 2.0.
+         * @type {number}
+         */
+        this._counter = 0;
     }
 
     /**
@@ -25,7 +31,10 @@ class Scratch3ControlBlocks {
             control_if_else: this.ifElse,
             control_stop: this.stop,
             control_create_clone_of: this.createClone,
-            control_delete_this_clone: this.deleteClone
+            control_delete_this_clone: this.deleteClone,
+            control_get_counter: this.getCounter,
+            control_incr_counter: this.incrCounter,
+            control_clear_counter: this.clearCounter
         };
     }
 
@@ -146,6 +155,18 @@ class Scratch3ControlBlocks {
         this.runtime.disposeTarget(util.target);
         this.runtime.stopForTarget(util.target);
     }
+
+    getCounter () {
+        return this._counter;
+    }
+
+    clearCounter () {
+        this._counter = 0;
+    }
+
+    incrCounter () {
+        this._counter++;
+    }
 }
 
 module.exports = Scratch3ControlBlocks;

src/serialization/sb2_specmap.js

@@ -815,6 +815,21 @@ const specMap = {
         argMap: [
         ]
     },
+    'COUNT': {
+        opcode: 'control_get_counter',
+        argMap: [
+        ]
+    },
+    'INCR_COUNT': {
+        opcode: 'control_incr_counter',
+        argMap: [
+        ]
+    },
+    'CLR_COUNT': {
+        opcode: 'control_clear_counter',
+        argMap: [
+        ]
+    },
     'touching:': {
         opcode: 'sensing_touchingobject',
         argMap: [

test/unit/blocks_control.js

@@ -169,3 +169,20 @@ test('stop', t => {
     t.strictEqual(state.stopThisScript, 1);
     t.end();
 });
+
+test('counter, incrCounter, clearCounter', t => {
+    const rt = new Runtime();
+    const c = new Control(rt);
+
+    // Default value
+    t.strictEqual(c.getCounter(), 0);
+
+    c.incrCounter();
+    c.incrCounter();
+    t.strictEqual(c.getCounter(), 2);
+
+    c.clearCounter();
+    t.strictEqual(c.getCounter(), 0);
+
+    t.end();
+});