Straw-man implementation of targets/sprites/clones

src/engine/execute.js

@@ -7,6 +7,7 @@ var Thread = require('./thread');
  */
 var execute = function (sequencer, thread) {
     var runtime = sequencer.runtime;
+    var target = runtime.targetForThread(thread);
 
     // Current block to execute is the one on the top of the stack.
     var currentBlockId = thread.peekStack();
@@ -29,13 +30,13 @@ var execute = function (sequencer, thread) {
     var argValues = {};
 
     // Add all fields on this block to the argValues.
-    var fields = runtime.blocks.getFields(currentBlockId);
+    var fields = target.blocks.getFields(currentBlockId);
     for (var fieldName in fields) {
         argValues[fieldName] = fields[fieldName].value;
     }
 
     // Recursively evaluate input blocks.
-    var inputs = runtime.blocks.getInputs(currentBlockId);
+    var inputs = target.blocks.getInputs(currentBlockId);
     for (var inputName in inputs) {
         var input = inputs[inputName];
         var inputBlockId = input.block;

src/engine/runtime.js

@@ -10,19 +10,19 @@ var defaultBlockPackages = {
 };
 
 /**
- * Manages blocks, stacks, and the sequencer.
- * @param {!Blocks} blocks Blocks instance for this runtime.
+ * Manages targets, stacks, and the sequencer.
+ * @param {!Array.<Target>} targets List of targets for this runtime.
  */
-function Runtime (blocks) {
+function Runtime (targets) {
     // Bind event emitter
     EventEmitter.call(this);
 
     // State for the runtime
 
     /**
-     * Block management and storage
+     * Target management and storage.
      */
-    this.blocks = blocks;
+    this.targets = targets;
 
     /**
      * A list of threads that are currently running in the VM.
@@ -163,32 +163,13 @@ Runtime.prototype.greenFlag = function () {
         this._removeThread(this.threads[i]);
     }
     // Add all top stacks with green flag
-    var stacks = this.blocks.getStacks();
-    for (var j = 0; j < stacks.length; j++) {
-        var topBlock = stacks[j];
-        if (this.blocks.getBlock(topBlock).opcode === 'event_whenflagclicked') {
-            this._pushThread(stacks[j]);
-        }
-    }
-};
-
-/**
- * Distance sensor hack
- */
-Runtime.prototype.startDistanceSensors = function () {
-    // Add all top stacks with distance sensor
-    var stacks = this.blocks.getStacks();
-    for (var j = 0; j < stacks.length; j++) {
-        var topBlock = stacks[j];
-        if (this.blocks.getBlock(topBlock).opcode ===
-            'wedo_whendistanceclose') {
-            var alreadyRunning = false;
-            for (var k = 0; k < this.threads.length; k++) {
-                if (this.threads[k].topBlock === topBlock) {
-                    alreadyRunning = true;
-                }
-            }
-            if (!alreadyRunning) {
+    for (var t = 0; t < this.targets.length; t++) {
+        var target = this.targets[t];
+        var stacks = target.blocks.getStacks();
+        for (var j = 0; j < stacks.length; j++) {
+            var topBlock = stacks[j];
+            if (target.blocks.getBlock(topBlock).opcode ===
+                'event_whenflagclicked') {
                 this._pushThread(stacks[j]);
             }
         }
@@ -228,9 +209,6 @@ Runtime.prototype._step = function () {
  * @param {boolean} isGlowing True to turn on glow; false to turn off.
  */
 Runtime.prototype.glowBlock = function (blockId, isGlowing) {
-    if (!this.blocks.getBlock(blockId)) {
-        return;
-    }
     if (isGlowing) {
         this.emit(Runtime.BLOCK_GLOW_ON, blockId);
     } else {
@@ -238,6 +216,23 @@ Runtime.prototype.glowBlock = function (blockId, isGlowing) {
     }
 };
 
+/**
+ * Return the Target for a particular thread.
+ * @param {!Thread} thread Thread to determine target for.
+ * @return {?Target} Target object, if one exists.
+ */
+Runtime.prototype.targetForThread = function (thread) {
+    // @todo This is a messy solution,
+    // but prevents having circular data references.
+    // Have a map or some other way to associate target with threads.
+    for (var t = 0; t < this.targets.length; t++) {
+        var target = this.targets[t];
+        if (target.blocks.getBlock(thread.topBlock)) {
+            return target;
+        }
+    }
+};
+
 /**
  * setInterval implementation that works in a WebWorker or not.
  * @param {?Function} fcn Function to call.

src/engine/sequencer.js

@@ -106,7 +106,7 @@ Sequencer.prototype.stepToSubstack = function (thread, substackNum) {
         substackNum = 1;
     }
     var currentBlockId = thread.peekStack();
-    var substackId = this.runtime.blocks.getSubstack(
+    var substackId = this.runtime.targetForThread(thread).blocks.getSubstack(
         currentBlockId,
         substackNum
     );
@@ -153,7 +153,8 @@ Sequencer.prototype.proceedThread = function (thread) {
     // Pop from the stack - finished this level of execution.
     thread.popStack();
     // Push next connected block, if there is one.
-    var nextBlockId = this.runtime.blocks.getNextBlock(currentBlockId);
+    var nextBlockId = (this.runtime.targetForThread(thread).
+        blocks.getNextBlock(currentBlockId));
     if (nextBlockId) {
         thread.pushStack(nextBlockId);
     }

src/engine/target.js

@@ -0,0 +1,20 @@
+var Blocks = require('./blocks');
+
+/**
+ * @fileoverview
+ * A Target is an abstract "code-running" object for the Scratch VM.
+ * Examples include sprites/clones or potentially physical-world devices.
+ */
+
+/**
+ * @param {?Blocks} blocks Blocks instance for the blocks owned by this target.
+ * @constructor
+ */
+function Target (blocks) {
+    if (!blocks) {
+        blocks = new Blocks(this);
+    }
+    this.blocks = blocks;
+}
+
+module.exports = Target;

src/index.js

@@ -1,7 +1,7 @@
 var EventEmitter = require('events');
 var util = require('util');
 
-var Blocks = require('./engine/blocks');
+var Sprite = require('./sprites/sprite');
 var Runtime = require('./engine/runtime');
 
 /**
@@ -21,18 +21,22 @@ function VirtualMachine () {
     // Bind event emitter and runtime to VM instance
     // @todo Post message (Web Worker) polyfill
     EventEmitter.call(instance);
-    instance.blocks = new Blocks();
-    instance.runtime = new Runtime(instance.blocks);
+    // @todo support multiple targets/sprites.
+    // This is just a demo/example.
+    var exampleSprite = new Sprite();
+    var exampleTargets = [exampleSprite.clones[0]];
+    instance.exampleSprite = exampleSprite;
+    instance.runtime = new Runtime(exampleTargets);
 
     /**
      * Event listeners for scratch-blocks.
      */
     instance.blockListener = (
-        instance.blocks.generateBlockListener(false, instance.runtime)
+        exampleSprite.blocks.generateBlockListener(false, instance.runtime)
     );
 
     instance.flyoutBlockListener = (
-        instance.blocks.generateBlockListener(true, instance.runtime)
+        exampleSprite.blocks.generateBlockListener(true, instance.runtime)
     );
 
     // Runtime emits are passed along as VM emits.
@@ -81,7 +85,7 @@ VirtualMachine.prototype.stopAll = function () {
  */
 VirtualMachine.prototype.getPlaygroundData = function () {
     this.emit('playgroundData', {
-        blocks: this.blocks,
+        blocks: this.exampleSprite.blocks,
         threads: this.runtime.threads
     });
 };
@@ -114,7 +118,7 @@ if (ENV_WORKER) {
         case 'getPlaygroundData':
             self.postMessage({
                 method: 'playgroundData',
-                blocks: self.vmInstance.blocks,
+                blocks: self.vmInstance.exampleSprite.blocks,
                 threads: self.vmInstance.runtime.threads
             });
             break;

src/sprites/clone.js

@@ -0,0 +1,16 @@
+var util = require('util');
+var Target = require('../engine/target');
+
+function Clone(spriteBlocks) {
+    Target.call(this, spriteBlocks);
+}
+util.inherits(Clone, Target);
+
+// Clone-level properties
+Clone.prototype.x = 0;
+
+Clone.prototype.y = 0;
+
+Clone.prototype.direction = 90;
+
+module.exports = Clone;

src/sprites/sprite.js

@@ -0,0 +1,17 @@
+var Clone = require('./clone');
+var Blocks = require('../engine/blocks');
+
+function Sprite (blocks) {
+    // Sprites have: shared blocks, shared costumes, shared variables, etc.
+    if (!blocks) {
+        // Shared set of blocks for all clones.
+        blocks = new Blocks();
+    }
+    this.blocks = blocks;
+    this.clones = [];
+
+    // Initial single clone with the shared blocks.
+    this.clones.push(new Clone(this.blocks));
+}
+
+module.exports = Sprite;