chocjsinterrupt.diff

diff --git a/choc/javascript/choc_javascript.h b/choc/javascript/choc_javascript.h
index 95f1678..3abefcf 100644
--- a/choc/javascript/choc_javascript.h
+++ b/choc/javascript/choc_javascript.h
@@ -97,6 +97,7 @@ namespace choc::javascript
         operator bool() const                               { return pimpl != nullptr; }
 
         //==============================================================================
+        
         /// This callback is used by the run() method.
         using CompletionHandler = std::function<void(const std::string& error,
                                                      const choc::value::ValueView& result)>;
@@ -162,6 +163,14 @@ namespace choc::javascript
         /// Pumps the message loop in an engine-specific way - may have no effect on some platforms.
         void pumpMessageLoop();
 
+        /// If supported by the engine, attempts tp cancel the execution of the JS code.
+        /// If the JS code is stuck in a blocking call itself, this won't work, but will
+        /// work if the JS code is running a loop, for example.
+        /// This obviously has to be called from another thread, so for example if your JS engine
+        /// is running in a worker thread, the GUI thread can call this. 
+        /// If the cancellation worked, an exception will be thrown.
+        /// Currently only implemented in the QuickJS engine.
+        void cancel();
         //==============================================================================
         /// @internal
         struct Pimpl;
@@ -235,7 +244,7 @@ struct Context::Pimpl
     virtual void pushArg (double) = 0;
     virtual void pushArg (bool) = 0;
     virtual void pumpMessageLoop() = 0;
-
+    virtual void cancel() {};
     void pushArg (const std::string& v)   { pushArg (std::string_view (v)); }
     void pushArg (const char* v)          { pushArg (std::string_view (v)); }
     void pushArg (uint64_t v)             { pushArg (static_cast<int64_t> (v)); }
@@ -318,6 +327,12 @@ inline void Context::pumpMessageLoop()
     pimpl->pumpMessageLoop();
 }
 
+inline void Context::cancel()
+{
+    CHOC_ASSERT (pimpl != nullptr); // cannot call this on a moved-from context!
+    pimpl->cancel();
+}
+
 inline std::string makeSafeIdentifier (std::string s)
 {
     constexpr static std::string_view reservedWords[] =
diff --git a/choc/javascript/choc_javascript_QuickJS.h b/choc/javascript/choc_javascript_QuickJS.h
index 0617307..94982f5 100644
--- a/choc/javascript/choc_javascript_QuickJS.h
+++ b/choc/javascript/choc_javascript_QuickJS.h
@@ -64052,10 +64052,23 @@ struct QuickJSContext  : public Context::Pimpl
         context = JS_NewContext (runtime);
         CHOC_ASSERT (context != nullptr);
         JS_SetContextOpaque (context, this);
+        JS_SetInterruptHandler(runtime, [](JSRuntime *, void *opaque)
+        {
+            auto qjctx = static_cast<QuickJSContext*>(opaque);
+            if (qjctx && qjctx->shouldCancel.load())
+            {
+                qjctx->shouldCancel.store(false);
+                return 1;
+            }
+            return 0;}, this);
     }
 
     void pumpMessageLoop() override {}
-
+    void cancel() override
+    {
+        shouldCancel.store(true);
+    }
+    
     void pushObjectOrArray (const choc::value::ValueView& v) override { functionArgs.push_back (valueToJS (v).release()); }
     void pushArg (std::string_view v) override                        { functionArgs.push_back (stringToJS (v).release()); }
     void pushArg (int32_t v) override                                 { functionArgs.push_back (JS_NewInt32   (context, v)); }
@@ -64350,7 +64363,7 @@ struct QuickJSContext  : public Context::Pimpl
     std::vector<Context::NativeFunction> registeredFunctions;
     std::vector<JSValue> functionArgs;
     JSAtom functionToCall = {};
-
+    std::atomic<bool> shouldCancel{false};
     static constexpr const char* objectNameAttribute = "_objectName";
 };