Rewrite the event loop to behave exactly like Scratch

include/scratchcpp/broadcast.h

@@ -13,12 +13,14 @@ class BroadcastPrivate;
 class LIBSCRATCHCPP_EXPORT Broadcast : public Entity
 {
     public:
-        Broadcast(const std::string &id, const std::string &name);
+        Broadcast(const std::string &id, const std::string &name, bool isBackdropBroadcast = false);
         Broadcast(const Broadcast &) = delete;
 
         const std::string &name() const;
         void setName(const std::string &newName);
 
+        bool isBackdropBroadcast() const;
+
     private:
         spimpl::unique_impl_ptr<BroadcastPrivate> impl;
 };

include/scratchcpp/iengine.h

@@ -56,11 +56,14 @@ class LIBSCRATCHCPP_EXPORT IEngine
         /*! Starts a script with the given top level block as the given Target (a sprite or the stage). */
         virtual VirtualMachine *startScript(std::shared_ptr<Block> topLevelBlock, Target *) = 0;
 
-        /*! Starts the script of the broadcast with the given index. */
-        virtual void broadcast(unsigned int index, VirtualMachine *sourceScript, bool wait = false) = 0;
+        /*! Starts the scripts of the broadcast with the given index. */
+        virtual void broadcast(unsigned int index) = 0;
 
-        /*! Starts the script of the given broadcast. */
-        virtual void broadcastByPtr(Broadcast *broadcast, VirtualMachine *sourceScript, bool wait = false) = 0;
+        /*! Starts the scripts of the given broadcast. */
+        virtual void broadcastByPtr(Broadcast *broadcast) = 0;
+
+        /*! Starts the "when backdrop switches to" scripts for the given backdrop broadcast. */
+        virtual void startBackdropScripts(Broadcast *broadcast) = 0;
 
         /*! Stops the given script. */
         virtual void stopScript(VirtualMachine *vm) = 0;
@@ -174,10 +177,10 @@ class LIBSCRATCHCPP_EXPORT IEngine
         virtual void setSpriteFencingEnabled(bool enable) = 0;
 
         /*! Returns true if there are any running script of the broadcast with the given index. */
-        virtual bool broadcastRunning(unsigned int index, VirtualMachine *sourceScript) = 0;
+        virtual bool broadcastRunning(unsigned int index) = 0;
 
         /*! Returns true if there are any running script of the given broadcast. */
-        virtual bool broadcastByPtrRunning(Broadcast *broadcast, VirtualMachine *sourceScript) = 0;
+        virtual bool broadcastByPtrRunning(Broadcast *broadcast) = 0;
 
         /*!
          * Call this from a block implementation to force a redraw (screen refresh).
@@ -242,14 +245,20 @@ class LIBSCRATCHCPP_EXPORT IEngine
         /*! Returns the index of the broadcast with the given ID. */
         virtual int findBroadcastById(const std::string &broadcastId) const = 0;
 
+        /*! Registers the "green flag" script. */
+        virtual void addGreenFlagScript(std::shared_ptr<Block> hatBlock) = 0;
+
         /*! Registers the broadcast script. */
-        virtual void addBroadcastScript(std::shared_ptr<Block> whenReceivedBlock, Broadcast *broadcast) = 0;
+        virtual void addBroadcastScript(std::shared_ptr<Block> whenReceivedBlock, int fieldId, Broadcast *broadcast) = 0;
+
+        /*! Registers the backdrop change script. */
+        virtual void addBackdropChangeScript(std::shared_ptr<Block> hatBlock, int fieldId) = 0;
 
         /* Registers the given "when I start as clone" script. */
         virtual void addCloneInitScript(std::shared_ptr<Block> hatBlock) = 0;
 
         /* Registers the given "when key pressed" script. */
-        virtual void addKeyPressScript(std::shared_ptr<Block> hatBlock, std::string keyName) = 0;
+        virtual void addKeyPressScript(std::shared_ptr<Block> hatBlock, int fieldId) = 0;
 
         /*! Returns the list of targets. */
         virtual const std::vector<std::shared_ptr<Target>> &targets() const = 0;

include/scratchcpp/script.h

@@ -12,6 +12,7 @@ namespace libscratchcpp
 {
 
 class Target;
+class Block;
 class IEngine;
 class Value;
 class VirtualMachine;
@@ -23,10 +24,11 @@ class ScriptPrivate;
 class LIBSCRATCHCPP_EXPORT Script
 {
     public:
-        Script(Target *target, IEngine *engine);
+        Script(Target *target, std::shared_ptr<Block> topBlock, IEngine *engine);
         Script(const Script &) = delete;
 
         Target *target() const;
+        std::shared_ptr<Block> topBlock() const;
 
         unsigned int *bytecode() const;
         const std::vector<unsigned int> &bytecodeVector() const;

include/scratchcpp/virtualmachine.h

@@ -128,6 +128,7 @@ class LIBSCRATCHCPP_EXPORT VirtualMachine
         void replaceReturnValue(const Value &v, unsigned int offset);
 
         void run();
+        void kill();
         void reset();
         void moveToLastCheckpoint();
 

src/blocks/eventblocks.cpp

@@ -21,7 +21,7 @@ std::string EventBlocks::name() const
 void EventBlocks::registerBlocks(IEngine *engine)
 {
     // Blocks
-    engine->addHatBlock(this, "event_whenflagclicked");
+    engine->addCompileFunction(this, "event_whenflagclicked", &compileWhenFlagClicked);
     engine->addCompileFunction(this, "event_broadcast", &compileBroadcast);
     engine->addCompileFunction(this, "event_broadcastandwait", &compileBroadcastAndWait);
     engine->addCompileFunction(this, "event_whenbroadcastreceived", &compileWhenBroadcastReceived);
@@ -37,6 +37,11 @@ void EventBlocks::registerBlocks(IEngine *engine)
     engine->addField(this, "KEY_OPTION", KEY_OPTION);
 }
 
+void EventBlocks::compileWhenFlagClicked(Compiler *compiler)
+{
+    compiler->engine()->addGreenFlagScript(compiler->block());
+}
+
 void EventBlocks::compileBroadcast(Compiler *compiler)
 {
     auto input = compiler->input(BROADCAST_INPUT);
@@ -72,60 +77,54 @@ void EventBlocks::compileWhenBroadcastReceived(Compiler *compiler)
 {
     auto broadcast = std::static_pointer_cast<Broadcast>(compiler->field(BROADCAST_OPTION)->valuePtr());
 
-    compiler->engine()->addBroadcastScript(compiler->block(), broadcast.get());
+    compiler->engine()->addBroadcastScript(compiler->block(), BROADCAST_OPTION, broadcast.get());
 }
 
 void EventBlocks::compileWhenBackdropSwitchesTo(Compiler *compiler)
 {
-    if (Stage *stage = compiler->engine()->stage()) {
-        std::string backdropName = compiler->field(BACKDROP)->value().toString();
-        int index = stage->findCostume(backdropName);
-
-        if (index != -1)
-            compiler->engine()->addBroadcastScript(compiler->block(), stage->costumeAt(index)->broadcast());
-    }
+    compiler->engine()->addBackdropChangeScript(compiler->block(), BACKDROP);
 }
 
 void EventBlocks::compileWhenKeyPressed(Compiler *compiler)
 {
     // NOTE: Field values don't have to be registered because keys are referenced by their names
-    compiler->engine()->addKeyPressScript(compiler->block(), compiler->field(KEY_OPTION)->value().toString());
+    compiler->engine()->addKeyPressScript(compiler->block(), KEY_OPTION);
 }
 
 unsigned int EventBlocks::broadcast(VirtualMachine *vm)
 {
-    vm->engine()->broadcast(vm->engine()->findBroadcast(vm->getInput(0, 1)->toString()), vm);
+    vm->engine()->broadcast(vm->engine()->findBroadcast(vm->getInput(0, 1)->toString()));
     return 1;
 }
 
 unsigned int EventBlocks::broadcastByIndex(VirtualMachine *vm)
 {
-    vm->engine()->broadcast(vm->getInput(0, 1)->toLong(), vm);
+    vm->engine()->broadcast(vm->getInput(0, 1)->toLong());
     return 1;
 }
 
 unsigned int EventBlocks::broadcastAndWait(VirtualMachine *vm)
 {
-    vm->engine()->broadcast(vm->engine()->findBroadcast(vm->getInput(0, 1)->toString()), vm, true);
+    vm->engine()->broadcast(vm->engine()->findBroadcast(vm->getInput(0, 1)->toString()));
     return 1;
 }
 
 unsigned int EventBlocks::broadcastByIndexAndWait(VirtualMachine *vm)
 {
-    vm->engine()->broadcast(vm->getInput(0, 1)->toLong(), vm, true);
+    vm->engine()->broadcast(vm->getInput(0, 1)->toLong());
     return 1;
 }
 
 unsigned int EventBlocks::checkBroadcast(VirtualMachine *vm)
 {
-    if (vm->engine()->broadcastRunning(vm->engine()->findBroadcast(vm->getInput(0, 1)->toString()), vm))
+    if (vm->engine()->broadcastRunning(vm->engine()->findBroadcast(vm->getInput(0, 1)->toString())))
         vm->stop(true, true, true);
     return 1;
 }
 
 unsigned int EventBlocks::checkBroadcastByIndex(VirtualMachine *vm)
 {
-    if (vm->engine()->broadcastRunning(vm->getInput(0, 1)->toLong(), vm))
+    if (vm->engine()->broadcastRunning(vm->getInput(0, 1)->toLong()))
         vm->stop(true, true, true);
     return 1;
 }

src/blocks/eventblocks.h

@@ -30,6 +30,7 @@ class EventBlocks : public IBlockSection
 
         void registerBlocks(IEngine *engine) override;
 
+        static void compileWhenFlagClicked(Compiler *compiler);
         static void compileBroadcast(Compiler *compiler);
         static void compileBroadcastAndWait(Compiler *compiler);
         static void compileWhenBroadcastReceived(Compiler *compiler);

src/blocks/looksblocks.cpp

@@ -388,6 +388,7 @@ void LooksBlocks::compileSwitchBackdropToAndWait(Compiler *compiler)
         compiler->addFunctionCall(&switchBackdropToAndWait);
     }
 
+    compiler->addFunctionCall(&backdropNumber);
     compiler->addFunctionCall(&checkBackdropScripts);
 }
 
@@ -750,7 +751,7 @@ void LooksBlocks::startBackdropScripts(VirtualMachine *vm, bool wait)
 {
     if (Stage *stage = vm->engine()->stage()) {
         if (stage->costumes().size() > 0)
-            vm->engine()->broadcastByPtr(stage->currentCostume()->broadcast(), vm, wait);
+            vm->engine()->startBackdropScripts(stage->currentCostume()->broadcast());
     }
 }
 
@@ -894,11 +895,14 @@ unsigned int LooksBlocks::randomBackdropAndWait(VirtualMachine *vm)
 unsigned int LooksBlocks::checkBackdropScripts(VirtualMachine *vm)
 {
     if (Stage *stage = vm->engine()->stage()) {
-        if ((stage->costumes().size() > 0) && vm->engine()->broadcastByPtrRunning(stage->currentCostume()->broadcast(), vm))
+        long index = vm->getInput(0, 1)->toLong() - 1;
+        assert(stage->costumes().size() == 0 || index >= 0);
+
+        if ((stage->costumes().size() > 0) && vm->engine()->broadcastByPtrRunning(stage->costumeAt(index)->broadcast()))
             vm->stop(true, true, true);
     }
 
-    return 0;
+    return 1;
 }
 
 unsigned int LooksBlocks::goToFront(VirtualMachine *vm)