Merge pull request #335 from scratchcpp/stop_event_loop

Add stopEventLoop() method to IEngine

Author: adazem009

include/scratchcpp/iengine.h

@@ -91,6 +91,9 @@ class LIBSCRATCHCPP_EXPORT IEngine
          */
         virtual void runEventLoop() = 0;
 
+        /*! Stops the event loop which is running in another thread. */
+        virtual void stopEventLoop() = 0;
+
         /*! Sets the function which is called on every frame. */
         virtual void setRedrawHandler(const std::function<void()> &handler) = 0;
 

src/engine/internal/engine.cpp

@@ -322,6 +322,13 @@ void Engine::runEventLoop()
     eventLoop();
 }
 
+void Engine::stopEventLoop()
+{
+    m_stopEventLoopMutex.lock();
+    m_stopEventLoop = true;
+    m_stopEventLoopMutex.unlock();
+}
+
 void Engine::setRedrawHandler(const std::function<void()> &handler)
 {
     m_redrawHandler = handler;
@@ -331,6 +338,7 @@ void Engine::eventLoop(bool untilProjectStops)
 {
     updateFrameDuration();
     m_newScripts.clear();
+    m_stopEventLoop = false;
 
     while (true) {
         auto frameStart = m_clock->currentSteadyTime();
@@ -369,6 +377,16 @@ void Engine::eventLoop(bool untilProjectStops)
                 }
             }
 
+            // Stop the event loop if stopEventLoop() was called
+            m_stopEventLoopMutex.lock();
+
+            if (m_stopEventLoop) {
+                stop = true;
+                break;
+            }
+
+            m_stopEventLoopMutex.unlock();
+
             currentTime = m_clock->currentSteadyTime();
             elapsedTime = std::chrono::duration_cast<std::chrono::milliseconds>(currentTime - frameStart);
             sleepTime = m_frameDuration - elapsedTime;

src/engine/internal/engine.h

@@ -8,6 +8,7 @@
 #include <unordered_map>
 #include <memory>
 #include <chrono>
+#include <mutex>
 
 #include "blocksectioncontainer.h"
 
@@ -37,8 +38,10 @@ class Engine : public IEngine
         void stopTarget(Target *target, VirtualMachine *exceptScript) override;
         void initClone(libscratchcpp::Sprite *clone) override;
         void deinitClone(libscratchcpp::Sprite *clone) override;
+
         void run() override;
         void runEventLoop() override;
+        void stopEventLoop() override;
 
         void setRedrawHandler(const std::function<void()> &handler) override;
 
@@ -183,6 +186,8 @@ class Engine : public IEngine
         bool m_running = false;
         bool m_redrawRequested = false;
         std::function<void()> m_redrawHandler = nullptr;
+        bool m_stopEventLoop = false;
+        std::mutex m_stopEventLoopMutex;
 };
 
 } // namespace libscratchcpp

test/engine/engine_test.cpp

@@ -7,6 +7,7 @@
 #include <scratchcpp/list.h>
 #include <timermock.h>
 #include <clockmock.h>
+#include <thread>
 
 #include "../common.h"
 #include "testsection.h"
@@ -68,6 +69,16 @@ TEST(EngineTest, IsRunning)
     ASSERT_FALSE(engine.isRunning());
 }
 
+TEST(EngineTest, EventLoop)
+{
+    Engine engine;
+
+    std::thread th([&engine]() { engine.runEventLoop(); });
+    std::this_thread::sleep_for(std::chrono::milliseconds(100));
+    engine.stopEventLoop();
+    th.join(); // should return immediately
+}
+
 TEST(EngineTest, Fps)
 {
     Engine engine;

test/mocks/enginemock.h

@@ -23,8 +23,10 @@ class EngineMock : public IEngine
         MOCK_METHOD(void, stopTarget, (Target *, VirtualMachine *), (override));
         MOCK_METHOD(void, initClone, (Sprite *), (override));
         MOCK_METHOD(void, deinitClone, (Sprite *), (override));
+
         MOCK_METHOD(void, run, (), (override));
         MOCK_METHOD(void, runEventLoop, (), (override));
+        MOCK_METHOD(void, stopEventLoop, (), (override));
 
         MOCK_METHOD(void, setRedrawHandler, (const std::function<void()> &), (override));