Fix #563: Refactor broadcasts using promise API

include/scratchcpp/iengine.h

@@ -61,13 +61,13 @@ class LIBSCRATCHCPP_EXPORT IEngine
         virtual VirtualMachine *startScript(std::shared_ptr<Block> topLevelBlock, Target *) = 0;
 
         /*! Starts the scripts of the broadcast with the given index. */
-        virtual void broadcast(int index) = 0;
+        virtual void broadcast(int index, VirtualMachine *sender) = 0;
 
         /*! Starts the scripts of the given broadcast. */
-        virtual void broadcastByPtr(Broadcast *broadcast) = 0;
+        virtual void broadcastByPtr(Broadcast *broadcast, VirtualMachine *sender) = 0;
 
         /*! Starts the "when backdrop switches to" scripts for the given backdrop broadcast. */
-        virtual void startBackdropScripts(Broadcast *broadcast) = 0;
+        virtual void startBackdropScripts(Broadcast *broadcast, VirtualMachine *sender) = 0;
 
         /*! Stops the given script. */
         virtual void stopScript(VirtualMachine *vm) = 0;

src/blocks/eventblocks.cpp

@@ -96,43 +96,14 @@ void EventBlocks::compileWhenStageClicked(Compiler *compiler)
 
 void EventBlocks::compileBroadcast(Compiler *compiler)
 {
-    auto input = compiler->input(BROADCAST_INPUT);
-
-    if (input->type() != Input::Type::ObscuredShadow) {
-        std::vector<int> broadcasts = compiler->engine()->findBroadcasts(input->primaryValue()->value().toString());
-
-        for (int index : broadcasts) {
-            compiler->addConstValue(index);
-            compiler->addFunctionCall(&broadcastByIndex);
-        }
-    } else {
-        compiler->addInput(input);
-        compiler->addFunctionCall(&broadcast);
-    }
+    compiler->addInput(BROADCAST_INPUT);
+    compiler->addFunctionCall(&broadcast);
 }
 
 void EventBlocks::compileBroadcastAndWait(Compiler *compiler)
 {
-    auto input = compiler->input(BROADCAST_INPUT);
-
-    if (input->type() != Input::Type::ObscuredShadow) {
-        std::vector<int> broadcasts = compiler->engine()->findBroadcasts(input->primaryValue()->value().toString());
-
-        for (int index : broadcasts) {
-            compiler->addConstValue(index);
-            compiler->addFunctionCall(&broadcastByIndexAndWait);
-        }
-
-        for (int index : broadcasts) {
-            compiler->addConstValue(index);
-            compiler->addFunctionCall(&checkBroadcastByIndex);
-        }
-    } else {
-        compiler->addInput(input);
-        compiler->addFunctionCall(&broadcastAndWait);
-        compiler->addInput(input);
-        compiler->addFunctionCall(&checkBroadcast);
-    }
+    compiler->addInput(BROADCAST_INPUT);
+    compiler->addFunctionCall(&broadcastAndWait);
 }
 
 void EventBlocks::compileWhenBroadcastReceived(Compiler *compiler)
@@ -210,59 +181,23 @@ unsigned int EventBlocks::broadcast(VirtualMachine *vm)
     std::vector<int> broadcasts = vm->engine()->findBroadcasts(vm->getInput(0, 1)->toString());
 
     for (int index : broadcasts)
-        vm->engine()->broadcast(index);
+        vm->engine()->broadcast(index, vm);
 
     return 1;
 }
 
-unsigned int EventBlocks::broadcastByIndex(VirtualMachine *vm)
-{
-    vm->engine()->broadcast(vm->getInput(0, 1)->toLong());
-    return 1;
-}
-
 unsigned int EventBlocks::broadcastAndWait(VirtualMachine *vm)
 {
     std::vector<int> broadcasts = vm->engine()->findBroadcasts(vm->getInput(0, 1)->toString());
 
     for (int index : broadcasts)
-        vm->engine()->broadcast(index);
+        vm->engine()->broadcast(index, vm);
 
-    return 1;
-}
-
-unsigned int EventBlocks::broadcastByIndexAndWait(VirtualMachine *vm)
-{
-    vm->engine()->broadcast(vm->getInput(0, 1)->toLong());
-    return 1;
-}
-
-unsigned int EventBlocks::checkBroadcast(VirtualMachine *vm)
-{
-    bool running = false;
-
-    std::vector<int> broadcasts = vm->engine()->findBroadcasts(vm->getInput(0, 1)->toString());
-
-    for (int index : broadcasts) {
-        if (vm->engine()->broadcastRunning(index)) {
-            running = true;
-            break;
-        }
-    }
-
-    if (running)
-        vm->stop(true, true, true);
+    vm->promise();
 
     return 1;
 }
 
-unsigned int EventBlocks::checkBroadcastByIndex(VirtualMachine *vm)
-{
-    if (vm->engine()->broadcastRunning(vm->getInput(0, 1)->toLong()))
-        vm->stop(true, true, true);
-    return 1;
-}
-
 unsigned int EventBlocks::whenLoudnessGreaterThanPredicate(VirtualMachine *vm)
 {
     if (!audioInput)

src/blocks/eventblocks.h

@@ -56,11 +56,7 @@ class EventBlocks : public IBlockSection
         static unsigned int whenTouchingObjectPredicate(VirtualMachine *vm);
 
         static unsigned int broadcast(VirtualMachine *vm);
-        static unsigned int broadcastByIndex(VirtualMachine *vm);
         static unsigned int broadcastAndWait(VirtualMachine *vm);
-        static unsigned int broadcastByIndexAndWait(VirtualMachine *vm);
-        static unsigned int checkBroadcast(VirtualMachine *vm);
-        static unsigned int checkBroadcastByIndex(VirtualMachine *vm);
 
         static unsigned int whenLoudnessGreaterThanPredicate(VirtualMachine *vm);
         static unsigned int whenTimerGreaterThanPredicate(VirtualMachine *vm);

src/blocks/looksblocks.cpp

@@ -366,8 +366,6 @@ void LooksBlocks::compileSwitchBackdropToAndWait(Compiler *compiler)
 {
     compiler->addInput(BACKDROP);
     compiler->addFunctionCall(&switchBackdropToAndWait);
-    compiler->addFunctionCall(&backdropNumber);
-    compiler->addFunctionCall(&checkBackdropScripts);
 }
 
 void LooksBlocks::compileNextBackdrop(Compiler *compiler)
@@ -894,7 +892,7 @@ void LooksBlocks::startBackdropScripts(VirtualMachine *vm, bool wait)
 {
     if (Stage *stage = vm->engine()->stage()) {
         if (stage->costumes().size() > 0)
-            vm->engine()->startBackdropScripts(stage->currentCostume()->broadcast());
+            vm->engine()->startBackdropScripts(stage->currentCostume()->broadcast(), vm);
     }
 }
 
@@ -976,6 +974,7 @@ unsigned int LooksBlocks::switchBackdropToAndWait(VirtualMachine *vm)
 {
     switchBackdropToImpl(vm);
     startBackdropScripts(vm, true);
+    vm->promise();
 
     return 1;
 }
@@ -988,14 +987,6 @@ unsigned int LooksBlocks::nextBackdrop(VirtualMachine *vm)
     return 0;
 }
 
-unsigned int LooksBlocks::nextBackdropAndWait(VirtualMachine *vm)
-{
-    nextBackdropImpl(vm);
-    startBackdropScripts(vm, true);
-
-    return 0;
-}
-
 unsigned int LooksBlocks::previousBackdrop(VirtualMachine *vm)
 {
     previousBackdropImpl(vm);
@@ -1004,14 +995,6 @@ unsigned int LooksBlocks::previousBackdrop(VirtualMachine *vm)
     return 0;
 }
 
-unsigned int LooksBlocks::previousBackdropAndWait(VirtualMachine *vm)
-{
-    previousBackdropImpl(vm);
-    startBackdropScripts(vm, true);
-
-    return 0;
-}
-
 unsigned int LooksBlocks::randomBackdrop(VirtualMachine *vm)
 {
     randomBackdropImpl(vm);
@@ -1020,27 +1003,6 @@ unsigned int LooksBlocks::randomBackdrop(VirtualMachine *vm)
     return 0;
 }
 
-unsigned int LooksBlocks::randomBackdropAndWait(VirtualMachine *vm)
-{
-    randomBackdropImpl(vm);
-    startBackdropScripts(vm, true);
-
-    return 0;
-}
-
-unsigned int LooksBlocks::checkBackdropScripts(VirtualMachine *vm)
-{
-    if (Stage *stage = vm->engine()->stage()) {
-        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 1;
-}
-
 unsigned int LooksBlocks::goToFront(VirtualMachine *vm)
 {
     Sprite *sprite = dynamic_cast<Sprite *>(vm->target());

src/blocks/looksblocks.h

@@ -142,12 +142,8 @@ class LooksBlocks : public IBlockSection
         static unsigned int switchBackdropTo(VirtualMachine *vm);
         static unsigned int switchBackdropToAndWait(VirtualMachine *vm);
         static unsigned int nextBackdrop(VirtualMachine *vm);
-        static unsigned int nextBackdropAndWait(VirtualMachine *vm);
         static unsigned int previousBackdrop(VirtualMachine *vm);
-        static unsigned int previousBackdropAndWait(VirtualMachine *vm);
         static unsigned int randomBackdrop(VirtualMachine *vm);
-        static unsigned int randomBackdropAndWait(VirtualMachine *vm);
-        static unsigned int checkBackdropScripts(VirtualMachine *vm);
 
         static unsigned int goToFront(VirtualMachine *vm);
         static unsigned int goToBack(VirtualMachine *vm);

src/engine/internal/engine.cpp

@@ -433,22 +433,24 @@ VirtualMachine *Engine::startScript(std::shared_ptr<Block> topLevelBlock, Target
     return pushThread(topLevelBlock, target).get();
 }
 
-void Engine::broadcast(int index)
+void Engine::broadcast(int index, VirtualMachine *sender)
 {
     if (index < 0 || index >= m_broadcasts.size())
         return;
 
-    broadcastByPtr(m_broadcasts[index].get());
+    broadcastByPtr(m_broadcasts[index].get(), sender);
 }
 
-void Engine::broadcastByPtr(Broadcast *broadcast)
+void Engine::broadcastByPtr(Broadcast *broadcast, VirtualMachine *sender)
 {
     startHats(HatType::BroadcastReceived, { { HatField::BroadcastOption, broadcast } }, nullptr);
+    addBroadcastPromise(broadcast, sender);
 }
 
-void Engine::startBackdropScripts(Broadcast *broadcast)
+void Engine::startBackdropScripts(Broadcast *broadcast, VirtualMachine *sender)
 {
     startHats(HatType::BackdropChanged, { { HatField::Backdrop, broadcast->name() } }, nullptr);
+    addBroadcastPromise(broadcast, sender);
 }
 
 void Engine::stopScript(VirtualMachine *vm)
@@ -583,6 +585,48 @@ void Engine::step()
     // Check running threads (must be done here)
     m_frameActivity = !m_threads.empty();
 
+    // Resolve stopped broadcast scripts
+    std::vector<Broadcast *> resolved;
+
+    for (const auto &[broadcast, senderThread] : m_broadcastSenders) {
+        std::unordered_map<Broadcast *, std::vector<Script *>> *broadcastMap = nullptr;
+
+        if (broadcast->isBackdropBroadcast()) {
+            // This broadcast belongs to a backdrop
+            assert(m_broadcastMap.find(broadcast) == m_broadcastMap.cend());
+            broadcastMap = &m_backdropBroadcastMap;
+        } else {
+            // This is a regular broadcast
+            assert(m_backdropBroadcastMap.find(broadcast) == m_backdropBroadcastMap.cend());
+            broadcastMap = &m_broadcastMap;
+        }
+
+        bool found = false;
+
+        if (broadcastMap->find(broadcast) != broadcastMap->cend()) {
+            const auto &scripts = (*broadcastMap)[broadcast];
+
+            for (auto script : scripts) {
+                if (std::find_if(m_threads.begin(), m_threads.end(), [script](std::shared_ptr<VirtualMachine> thread) { return thread->script() == script; }) != m_threads.end()) {
+                    found = true;
+                    break;
+                }
+            }
+        }
+
+        if (!found) {
+            VirtualMachine *th = senderThread;
+
+            if (std::find_if(m_threads.begin(), m_threads.end(), [th](std::shared_ptr<VirtualMachine> thread) { return thread.get() == th; }) != m_threads.end())
+                th->resolvePromise();
+
+            resolved.push_back(broadcast);
+        }
+    }
+
+    for (Broadcast *broadcast : resolved)
+        m_broadcastSenders.erase(broadcast);
+
     m_redrawRequested = false;
 
     // Step threads
@@ -1160,7 +1204,30 @@ void Engine::addBroadcastScript(std::shared_ptr<Block> whenReceivedBlock, int fi
 
 void Engine::addBackdropChangeScript(std::shared_ptr<Block> hatBlock, int fieldId)
 {
+    Stage *stage = this->stage();
+
+    if (!stage)
+        return;
+
+    // TODO: This assumes the first field holds the broadcast pointer, maybe this is not the best way (e. g. if an extension uses this method)
+    assert(hatBlock->fieldAt(0));
+    const std::string &backdropName = hatBlock->fieldAt(0)->value().toString();
+    auto backdrop = stage->costumeAt(stage->findCostume(backdropName));
+    Broadcast *broadcast = backdrop->broadcast();
+    assert(broadcast->isBackdropBroadcast());
+
     Script *script = m_scripts[hatBlock].get();
+    auto it = m_backdropBroadcastMap.find(broadcast);
+
+    if (it != m_backdropBroadcastMap.cend()) {
+        auto &scripts = it->second;
+        auto scriptIt = std::find(scripts.begin(), scripts.end(), script);
+
+        if (scriptIt == scripts.end())
+            scripts.push_back(script);
+    } else
+        m_backdropBroadcastMap[broadcast] = { script };
+
     addHatToMap(m_backdropChangeHats, script);
     addHatField(script, HatField::Backdrop, fieldId);
 }
@@ -1873,6 +1940,20 @@ void Engine::addRunningScript(std::shared_ptr<VirtualMachine> vm)
     m_threads.push_back(vm);
 }
 
+void Engine::addBroadcastPromise(Broadcast *broadcast, VirtualMachine *sender)
+{
+    assert(broadcast);
+    assert(sender);
+
+    // Resolve broadcast promise if it's already running
+    auto it = m_broadcastSenders.find(broadcast);
+
+    if (it != m_broadcastSenders.cend() && std::find_if(m_threads.begin(), m_threads.end(), [&it](std::shared_ptr<VirtualMachine> thread) { return thread.get() == it->second; }) != m_threads.end())
+        it->second->resolvePromise();
+
+    m_broadcastSenders[broadcast] = sender;
+}
+
 std::shared_ptr<VirtualMachine> Engine::pushThread(std::shared_ptr<Block> block, Target *target)
 {
     // https://github.com/scratchfoundation/scratch-vm/blob/f1aa92fad79af17d9dd1c41eeeadca099339a9f1/src/engine/runtime.js#L1649-L1661

src/engine/internal/engine.h

@@ -35,9 +35,9 @@ class Engine : public IEngine
         void start() override;
         void stop() override;
         VirtualMachine *startScript(std::shared_ptr<Block> topLevelBlock, Target *target) override;
-        void broadcast(int index) override;
-        void broadcastByPtr(Broadcast *broadcast) override;
-        void startBackdropScripts(Broadcast *broadcast) override;
+        void broadcast(int index, VirtualMachine *sender) override;
+        void broadcastByPtr(Broadcast *broadcast, VirtualMachine *sender) override;
+        void startBackdropScripts(Broadcast *broadcast, VirtualMachine *sender) override;
         void stopScript(VirtualMachine *vm) override;
         void stopTarget(Target *target, VirtualMachine *exceptScript) override;
         void initClone(std::shared_ptr<Sprite> clone) override;
@@ -220,6 +220,8 @@ class Engine : public IEngine
         void updateFrameDuration();
         void addRunningScript(std::shared_ptr<VirtualMachine> vm);
 
+        void addBroadcastPromise(Broadcast *broadcast, VirtualMachine *sender);
+
         std::shared_ptr<VirtualMachine> pushThread(std::shared_ptr<Block> block, Target *target);
         void stopThread(VirtualMachine *thread);
         std::shared_ptr<VirtualMachine> restartThread(std::shared_ptr<VirtualMachine> thread);
@@ -237,6 +239,8 @@ class Engine : public IEngine
         std::vector<std::shared_ptr<Target>> m_targets;
         std::vector<std::shared_ptr<Broadcast>> m_broadcasts;
         std::unordered_map<Broadcast *, std::vector<Script *>> m_broadcastMap;
+        std::unordered_map<Broadcast *, std::vector<Script *>> m_backdropBroadcastMap;
+        std::unordered_map<Broadcast *, VirtualMachine *> m_broadcastSenders; // used for resolving broadcast promises
         std::vector<std::shared_ptr<Monitor>> m_monitors;
         std::vector<std::string> m_extensions;
         std::vector<Target *> m_executableTargets; // sorted by layer (reverse order of execution)