Move Callback implementation to separate header file

include/wx/msw/wrl/event.h

@@ -0,0 +1,104 @@
+///////////////////////////////////////////////////////////////////////////////
+// Name:        wx/msw/wrl/event.h
+// Purpose:     WRL event callback implementation
+// Author:      nns52k
+// Created:     2021-02-25
+// Copyright:   (c) 2021 wxWidgets team
+// Licence:     wxWindows licence
+///////////////////////////////////////////////////////////////////////////////
+
+#ifndef _WX_MSW_PRIVATE_WRL_H_
+#define _WX_MSW_PRIVATE_WRL_H_
+
+#include <atomic>
+
+template <typename baseT, typename ...argTs>
+class CInvokable : public baseT
+{
+public:
+    CInvokable() : m_nRefCount(0) {}
+    virtual ~CInvokable() {}
+    // IUnknown methods
+    HRESULT STDMETHODCALLTYPE QueryInterface(REFIID riid, void** ppvObj) override
+    {
+        if (riid == __uuidof(baseT) || riid == IID_IUnknown)
+        {
+            *ppvObj = this;
+            AddRef();
+            return S_OK;
+        }
+
+        *ppvObj = NULL;
+        return E_NOINTERFACE;
+    }
+    ULONG STDMETHODCALLTYPE AddRef() override
+    {
+        return ++m_nRefCount;
+    }
+    ULONG STDMETHODCALLTYPE Release() override
+    {
+        size_t ret = --m_nRefCount;
+        if (ret == 0)
+            delete this;
+        return ret;
+    }
+private:
+    std::atomic<size_t> m_nRefCount;
+};
+
+template <typename baseT, typename ...argTs>
+class CInvokableLambda : public CInvokable<baseT, argTs...>
+{
+public:
+    CInvokableLambda(std::function<HRESULT(argTs...)> lambda)
+        : m_lambda(lambda)
+    {}
+    // baseT method
+    HRESULT STDMETHODCALLTYPE Invoke(argTs ...args) override
+    {
+        return m_lambda(args...);
+    }
+private:
+    std::function<HRESULT(argTs...)> m_lambda;
+};
+
+template <typename baseT, typename contextT, typename ...argTs>
+class CInvokableMethod : public CInvokable<baseT, argTs...>
+{
+public:
+    CInvokableMethod(contextT* ctx, HRESULT(contextT::* mthd)(argTs...))
+        : m_ctx(ctx), m_mthd(mthd)
+    {}
+    // baseT method
+    HRESULT STDMETHODCALLTYPE Invoke(argTs ...args) override
+    {
+        return (m_ctx->*m_mthd)(args...);
+    }
+private:
+    contextT* m_ctx;
+    HRESULT(contextT::* m_mthd)(argTs...);
+};
+
+// the function templates to generate concrete classes from above class templates
+template <
+    typename baseT, typename lambdaT, // base type & lambda type
+    typename LT, typename ...argTs // for capturing argument types of lambda
+>
+wxCOMPtr<baseT> Callback_impl(lambdaT&& lambda, HRESULT(LT::*)(argTs...) const)
+{
+    return wxCOMPtr<baseT>(new CInvokableLambda<baseT, argTs...>(lambda));
+}
+
+template <typename baseT, typename lambdaT>
+wxCOMPtr<baseT> Callback(lambdaT&& lambda)
+{
+    return Callback_impl<baseT>(std::move(lambda), &lambdaT::operator());
+}
+
+template <typename baseT, typename contextT, typename ...argTs>
+wxCOMPtr<baseT> Callback(contextT* ctx, HRESULT(contextT::* mthd)(argTs...))
+{
+    return wxCOMPtr<baseT>(new CInvokableMethod<baseT, contextT, argTs...>(ctx, mthd));
+}
+
+#endif // _WX_MSW_PRIVATE_WRL_H_