project64/Source/Project64/UserInterface/WTLControls/ClistCtrl/DragDrop.h

#pragma once
#include <shlobj.h>
#include <vector>

using namespace std;

class CEnumFormatEtc : public IEnumFORMATETC
{
public:
    CEnumFormatEtc(const vector<FORMATETC> & vFormatEtc)
    {
        m_nRefCount = 0;
        m_nIndex = 0;
        m_vFormatEtc = vFormatEtc;
    }

protected:
    vector<FORMATETC> m_vFormatEtc;
    int m_nRefCount;
    int m_nIndex;

public:
    // IUnknown members
    STDMETHOD(QueryInterface)
    (REFIID refiid, void FAR * FAR * ppvObject)
    {
        *ppvObject = (refiid == IID_IUnknown || refiid == IID_IEnumFORMATETC) ? this : nullptr;

        if (*ppvObject != nullptr)
            ((LPUNKNOWN)*ppvObject)->AddRef();

        return *ppvObject == nullptr ? E_NOINTERFACE : S_OK;
    }

    STDMETHOD_(ULONG, AddRef)
    (void)
    {
        return ++m_nRefCount;
    }

    STDMETHOD_(ULONG, Release)
    (void)
    {
        int nRefCount = --m_nRefCount;
        if (nRefCount == 0)
            delete this;
        return nRefCount;
    }

    // IEnumFORMATETC members
    STDMETHOD(Next)
    (ULONG celt, LPFORMATETC lpFormatEtc, ULONG FAR * pceltFetched)
    {
        if (pceltFetched != nullptr)
            *pceltFetched = 0;

        ULONG cReturn = celt;

        if (celt <= 0 || lpFormatEtc == nullptr || m_nIndex >= (int)m_vFormatEtc.size())
            return S_FALSE;

        if (pceltFetched == nullptr && celt != 1) // pceltFetched can be nullptr only for 1 item request
            return S_FALSE;

        while (m_nIndex < (int)m_vFormatEtc.size() && cReturn > 0)
        {
            *lpFormatEtc++ = m_vFormatEtc[m_nIndex++];
            cReturn--;
        }

        if (pceltFetched != nullptr)
            *pceltFetched = celt - cReturn;

        return cReturn == 0 ? S_OK : S_FALSE;
    }

    STDMETHOD(Skip)
    (ULONG celt)
    {
        if ((m_nIndex + (int)celt) >= (int)m_vFormatEtc.size())
            return S_FALSE;
        m_nIndex += celt;
        return S_OK;
    }

    STDMETHOD(Reset)
    (void)
    {
        m_nIndex = 0;
        return S_OK;
    }

    STDMETHOD(Clone)
    (IEnumFORMATETC FAR * FAR * ppCloneEnumFormatEtc)
    {
        if (ppCloneEnumFormatEtc == nullptr)
            return E_POINTER;

        *ppCloneEnumFormatEtc = new CEnumFormatEtc(m_vFormatEtc);
        ((CEnumFormatEtc *)*ppCloneEnumFormatEtc)->AddRef();
        ((CEnumFormatEtc *)*ppCloneEnumFormatEtc)->m_nIndex = m_nIndex;

        return S_OK;
    }
};

class CDropSource : public IDropSource
{
public:
    CDropSource()
    {
        m_nRefCount = 0;
    }

protected:
    int m_nRefCount;

public:
    // IUnknown members
    STDMETHOD(QueryInterface)
    (REFIID refiid, void FAR * FAR * ppvObject)
    {
        *ppvObject = (refiid == IID_IUnknown || refiid == IID_IDropSource) ? this : nullptr;

        if (*ppvObject != nullptr)
            ((LPUNKNOWN)*ppvObject)->AddRef();

        return *ppvObject == nullptr ? E_NOINTERFACE : S_OK;
    }

    STDMETHOD_(ULONG, AddRef)
    (void)
    {
        return ++m_nRefCount;
    }

    STDMETHOD_(ULONG, Release)
    (void)
    {
        int nRefCount = --m_nRefCount;
        if (nRefCount == 0)
            delete this;
        return nRefCount;
    }

    // IDropSource members
    STDMETHOD(QueryContinueDrag)
    (BOOL bEscapePressed, DWORD dwKeyState)
    {
        if (bEscapePressed)
            return DRAGDROP_S_CANCEL;

        if (!(dwKeyState & (MK_LBUTTON | MK_RBUTTON)))
            return DRAGDROP_S_DROP;

        return S_OK;
    }

    STDMETHOD(GiveFeedback)
    (DWORD /*dwEffect*/)
    {
        return DRAGDROP_S_USEDEFAULTCURSORS;
    }
};

class CDataObject : public IDataObject
{
public:
    CDataObject(CDropSource * pDropSource)
    {
        m_nRefCount = 0;
        m_pDropSource = pDropSource;
        m_bSwappedButtons = GetSystemMetrics(SM_SWAPBUTTON);
    }

    virtual ~CDataObject()
    {
        for (vector<STGMEDIUM>::iterator posStgMedium = m_vStgMedium.begin(); posStgMedium != m_vStgMedium.end(); posStgMedium++)
            ReleaseStgMedium(&(*posStgMedium));
    }

protected:
    CDropSource * m_pDropSource;
    int m_nRefCount;
    BOOL m_bSwappedButtons;

    vector<FORMATETC> m_vFormatEtc;
    vector<STGMEDIUM> m_vStgMedium;

public:
    // IUnknown members
    STDMETHOD(QueryInterface)
    (REFIID refiid, void FAR * FAR * ppvObject)
    {
        *ppvObject = (refiid == IID_IUnknown || refiid == IID_IDataObject) ? this : nullptr;

        if (*ppvObject != nullptr)
            ((LPUNKNOWN)*ppvObject)->AddRef();

        return *ppvObject == nullptr ? E_NOINTERFACE : S_OK;
    }

    STDMETHOD_(ULONG, AddRef)
    (void)
    {
        return ++m_nRefCount;
    }

    STDMETHOD_(ULONG, Release)
    (void)
    {
        int nRefCount = --m_nRefCount;
        if (nRefCount == 0)
            delete this;
        return nRefCount;
    }

    // IDataObject members
    STDMETHOD(GetData)
    (FORMATETC __RPC_FAR * pformatetcIn, STGMEDIUM __RPC_FAR * pmedium)
    {
        if (pformatetcIn == nullptr || pmedium == nullptr)
            return E_INVALIDARG;

        ZeroMemory(pmedium, sizeof(STGMEDIUM));

        for (int nFormatEtc = 0; nFormatEtc < (int)m_vFormatEtc.size(); nFormatEtc++)
        {
            if (pformatetcIn->tymed & m_vFormatEtc[nFormatEtc].tymed && pformatetcIn->dwAspect == m_vFormatEtc[nFormatEtc].dwAspect && pformatetcIn->cfFormat == m_vFormatEtc[nFormatEtc].cfFormat)
            {
                if (m_vStgMedium[nFormatEtc].tymed == TYMED_NULL)
                    return OnRenderData(m_vFormatEtc[nFormatEtc], pmedium, (GetAsyncKeyState(m_bSwappedButtons ? VK_RBUTTON : VK_LBUTTON) >= 0)) ? S_OK : DV_E_FORMATETC;

                CopyMedium(pmedium, m_vStgMedium[nFormatEtc], m_vFormatEtc[nFormatEtc]);
                return S_OK;
            }
        }

        return DV_E_FORMATETC;
    }

    STDMETHOD(GetDataHere)
    (FORMATETC __RPC_FAR * /*pformatetc*/, STGMEDIUM __RPC_FAR * /*pmedium*/)
    {
        return E_NOTIMPL;
    }

    STDMETHOD(QueryGetData)
    (FORMATETC __RPC_FAR * pformatetc)
    {
        if (pformatetc == nullptr)
            return E_INVALIDARG;

        if (!(pformatetc->dwAspect & DVASPECT_CONTENT))
            return DV_E_DVASPECT;

        HRESULT hResult = DV_E_TYMED;
        for (int nFormatEtc = 0; nFormatEtc < (int)m_vFormatEtc.size(); nFormatEtc++)
        {
            if (!(pformatetc->tymed & m_vFormatEtc[nFormatEtc].tymed))
            {
                hResult = DV_E_TYMED;
                continue;
            }

            if (pformatetc->cfFormat == m_vFormatEtc[nFormatEtc].cfFormat)
                return S_OK;

            hResult = DV_E_CLIPFORMAT;
        }

        return hResult;
    }

    STDMETHOD(GetCanonicalFormatEtc)
    (FORMATETC __RPC_FAR * /*pformatectIn*/, FORMATETC __RPC_FAR * pformatetcOut)
    {
        return pformatetcOut == nullptr ? E_INVALIDARG : DATA_S_SAMEFORMATETC;
    }

    STDMETHOD(SetData)
    (FORMATETC __RPC_FAR * pformatetc, STGMEDIUM __RPC_FAR * pmedium, BOOL bRelease)
    {
        if (pformatetc == nullptr || pmedium == nullptr)
            return E_INVALIDARG;

        m_vFormatEtc.push_back(*pformatetc);

        STGMEDIUM StgMedium = *pmedium;

        if (!bRelease)
            CopyMedium(&StgMedium, *pmedium, *pformatetc);

        m_vStgMedium.push_back(StgMedium);

        return S_OK;
    }

    STDMETHOD(EnumFormatEtc)
    (DWORD dwDirection, IEnumFORMATETC __RPC_FAR * __RPC_FAR * ppenumFormatEtc)
    {
        if (ppenumFormatEtc == nullptr)
            return E_POINTER;

        switch (dwDirection)
        {
        case DATADIR_GET:
            *ppenumFormatEtc = new CEnumFormatEtc(m_vFormatEtc);
            ((CEnumFormatEtc *)*ppenumFormatEtc)->AddRef();
            return S_OK;
        default:
            *ppenumFormatEtc = nullptr;
            return E_NOTIMPL;
        }
    }

    STDMETHOD(DAdvise)
    (FORMATETC __RPC_FAR * /*pformatetc*/, DWORD /*advf*/, IAdviseSink __RPC_FAR * /*pAdvSink*/, DWORD __RPC_FAR * /*pdwConnection*/)
    {
        return OLE_E_ADVISENOTSUPPORTED;
    }

    STDMETHOD(DUnadvise)
    (DWORD /*dwConnection*/)
    {
        return E_NOTIMPL;
    }

    STDMETHOD(EnumDAdvise)
    (IEnumSTATDATA __RPC_FAR * __RPC_FAR * /*ppenumAdvise*/)
    {
        return OLE_E_ADVISENOTSUPPORTED;
    }

    void CopyMedium(STGMEDIUM * pMedDest, STGMEDIUM & MedSrc, FORMATETC & FmtSrc)
    {
        switch (MedSrc.tymed)
        {
        case TYMED_HGLOBAL:
            pMedDest->hGlobal = (HGLOBAL)OleDuplicateData(MedSrc.hGlobal, FmtSrc.cfFormat, NULL);
            break;
        case TYMED_GDI:
            pMedDest->hBitmap = (HBITMAP)OleDuplicateData(MedSrc.hBitmap, FmtSrc.cfFormat, NULL);
            break;
        case TYMED_MFPICT:
            pMedDest->hMetaFilePict = (HMETAFILEPICT)OleDuplicateData(MedSrc.hMetaFilePict, FmtSrc.cfFormat, NULL);
            break;
        case TYMED_ENHMF:
            pMedDest->hEnhMetaFile = (HENHMETAFILE)OleDuplicateData(MedSrc.hEnhMetaFile, FmtSrc.cfFormat, NULL);
            break;
        case TYMED_FILE:
            pMedDest->lpszFileName = (LPOLESTR)OleDuplicateData(MedSrc.lpszFileName, FmtSrc.cfFormat, NULL);
            break;
        case TYMED_ISTREAM:
            pMedDest->pstm = MedSrc.pstm;
            MedSrc.pstm->AddRef();
            break;
        case TYMED_ISTORAGE:
            pMedDest->pstg = MedSrc.pstg;
            MedSrc.pstg->AddRef();
            break;
        }

        pMedDest->tymed = MedSrc.tymed;
        pMedDest->pUnkForRelease = nullptr;

        if (MedSrc.pUnkForRelease != nullptr)
        {
            pMedDest->pUnkForRelease = MedSrc.pUnkForRelease;
            MedSrc.pUnkForRelease->AddRef();
        }
    }

    virtual BOOL OnRenderData(FORMATETC & /*FormatEtc*/, STGMEDIUM * /*pStgMedium*/, BOOL /*bDropComplete*/)
    {
        return FALSE;
    }
};

class CDropTarget : public IDropTarget
{
public:
    CDropTarget(HWND hTargetWnd)
    {
        m_hTargetWnd = hTargetWnd;
        m_nRefCount = 0;
        m_bAllowDrop = FALSE;
        m_pDropTargetHelper = nullptr;
        ZeroMemory(&m_FormatEtc, sizeof(FORMATETC));
        ZeroMemory(&m_StgMedium, sizeof(STGMEDIUM));

        if (FAILED(CoCreateInstance(CLSID_DragDropHelper, nullptr, CLSCTX_INPROC_SERVER, IID_IDropTargetHelper, (LPVOID *)&m_pDropTargetHelper)))
            m_pDropTargetHelper = nullptr;
    }

    virtual ~CDropTarget()
    {
        if (m_pDropTargetHelper != nullptr)
        {
            m_pDropTargetHelper->Release();
            m_pDropTargetHelper = nullptr;
        }
    }

protected:
    HWND m_hTargetWnd;
    int m_nRefCount;
    struct IDropTargetHelper * m_pDropTargetHelper;
    vector<FORMATETC> m_vFormatEtc;
    BOOL m_bAllowDrop;
    FORMATETC m_FormatEtc;
    STGMEDIUM m_StgMedium;

public:
    // IUnknown members
    STDMETHOD(QueryInterface)
    (REFIID refiid, void FAR * FAR * ppvObject)
    {
        *ppvObject = (refiid == IID_IUnknown || refiid == IID_IDropTarget) ? this : nullptr;

        if (*ppvObject != nullptr)
            ((LPUNKNOWN)*ppvObject)->AddRef();

        return *ppvObject == nullptr ? E_NOINTERFACE : S_OK;
    }

    STDMETHOD_(ULONG, AddRef)
    (void)
    {
        return ++m_nRefCount;
    }

    STDMETHOD_(ULONG, Release)
    (void)
    {
        int nRefCount = --m_nRefCount;
        if (nRefCount == 0)
            delete this;
        return nRefCount;
    }

    STDMETHOD(DragEnter)
    (IDataObject __RPC_FAR * pDataObject, DWORD dwKeyState, POINTL pt, DWORD __RPC_FAR * pdwEffect)
    {
        if (pDataObject == nullptr)
            return E_INVALIDARG;

        if (m_pDropTargetHelper != nullptr)
            m_pDropTargetHelper->DragEnter(m_hTargetWnd, pDataObject, (LPPOINT)&pt, *pdwEffect);

        ZeroMemory(&m_FormatEtc, sizeof(FORMATETC));
        if (m_StgMedium.tymed != TYMED_NULL)
            ReleaseStgMedium(&m_StgMedium);
        ZeroMemory(&m_StgMedium, sizeof(STGMEDIUM));

        for (int nFormatEtc = 0; nFormatEtc < (int)m_vFormatEtc.size(); nFormatEtc++)
        {
            STGMEDIUM StgMedium;
            m_bAllowDrop = (pDataObject->GetData(&m_vFormatEtc[nFormatEtc], &StgMedium) == S_OK);

            if (m_bAllowDrop)
            {
                // Store drag data for later use in DragOver
                m_FormatEtc = m_vFormatEtc[nFormatEtc];
                m_StgMedium = StgMedium;

                // Get client cursor position
                CWindow hWnd(m_hTargetWnd);
                CPoint point(pt.x, pt.y);
                hWnd.ScreenToClient(&point);

                *pdwEffect = OnDragEnter(m_FormatEtc, m_StgMedium, dwKeyState, point);

                break;
            }
        }

        QueryDrop(dwKeyState, pdwEffect);

        return S_OK;
    }

    STDMETHOD(DragOver)
    (DWORD dwKeyState, POINTL pt, DWORD __RPC_FAR * pdwEffect)
    {
        if (m_pDropTargetHelper)
            m_pDropTargetHelper->DragOver((LPPOINT)&pt, *pdwEffect);

        if (m_bAllowDrop && m_FormatEtc.cfFormat != CF_NULL && m_StgMedium.tymed != TYMED_NULL)
        {
            // Get client cursor position
            CWindow hWnd(m_hTargetWnd);
            CPoint point(pt.x, pt.y);
            hWnd.ScreenToClient(&point);

            *pdwEffect = OnDragOver(m_FormatEtc, m_StgMedium, dwKeyState, point);
        }

        QueryDrop(dwKeyState, pdwEffect);

        return S_OK;
    }

    STDMETHOD(DragLeave)
    (void)
    {
        if (m_pDropTargetHelper)
            m_pDropTargetHelper->DragLeave();

        OnDragLeave();

        m_bAllowDrop = FALSE;

        ZeroMemory(&m_FormatEtc, sizeof(FORMATETC));
        if (m_StgMedium.tymed != TYMED_NULL)
            ReleaseStgMedium(&m_StgMedium);
        ZeroMemory(&m_StgMedium, sizeof(STGMEDIUM));

        return S_OK;
    }

    STDMETHOD(Drop)
    (IDataObject __RPC_FAR * pDataObject, DWORD dwKeyState, POINTL pt, DWORD __RPC_FAR * pdwEffect)
    {
        if (pDataObject == nullptr)
            return E_INVALIDARG;

        if (m_pDropTargetHelper)
            m_pDropTargetHelper->Drop(pDataObject, (LPPOINT)&pt, *pdwEffect);

        if (m_bAllowDrop && m_FormatEtc.cfFormat != CF_NULL && QueryDrop(dwKeyState, pdwEffect))
        {
            STGMEDIUM StgMedium;
            if (pDataObject->GetData(&m_FormatEtc, &StgMedium) == S_OK)
            {
                // Get client cursor position
                CWindow hWnd(m_hTargetWnd);
                CPoint point(pt.x, pt.y);
                hWnd.ScreenToClient(&point);

                if (!OnDrop(m_FormatEtc, StgMedium, *pdwEffect, point))
                    *pdwEffect = DROPEFFECT_NONE;

                ReleaseStgMedium(&StgMedium);
            }
        }

        m_bAllowDrop = FALSE;

        ZeroMemory(&m_FormatEtc, sizeof(FORMATETC));
        if (m_StgMedium.tymed != TYMED_NULL)
            ReleaseStgMedium(&m_StgMedium);
        ZeroMemory(&m_StgMedium, sizeof(STGMEDIUM));

        return S_OK;
    }

    void AddSupportedFormat(FORMATETC & FormatEtc)
    {
        m_vFormatEtc.push_back(FormatEtc);
    }

    void AddSupportedFormat(CLIPFORMAT cfFormat)
    {
        FORMATETC FormatEtc;
        ZeroMemory(&FormatEtc, sizeof(FORMATETC));

        FormatEtc.cfFormat = cfFormat;
        FormatEtc.dwAspect = DVASPECT_CONTENT;
        FormatEtc.lindex = -1;
        FormatEtc.tymed = TYMED_HGLOBAL;

        AddSupportedFormat(FormatEtc);
    }

    BOOL QueryDrop(DWORD dwKeyState, LPDWORD pdwEffect)
    {
        DWORD dwEffects = *pdwEffect;

        if (!m_bAllowDrop)
        {
            *pdwEffect = DROPEFFECT_NONE;
            return FALSE;
        }

        *pdwEffect = (dwKeyState & MK_CONTROL) ? ((dwKeyState & MK_SHIFT) ? DROPEFFECT_LINK : DROPEFFECT_COPY) : ((dwKeyState & MK_SHIFT) ? DROPEFFECT_MOVE : 0);
        if (*pdwEffect == 0)
        {
            if (dwEffects & DROPEFFECT_COPY)
                *pdwEffect = DROPEFFECT_COPY;
            else if (dwEffects & DROPEFFECT_MOVE)
                *pdwEffect = DROPEFFECT_MOVE;
            else if (dwEffects & DROPEFFECT_LINK)
                *pdwEffect = DROPEFFECT_LINK;
            else
                *pdwEffect = DROPEFFECT_NONE;
        }
        else if (!(*pdwEffect & dwEffects))
            *pdwEffect = DROPEFFECT_NONE;

        return (*pdwEffect != DROPEFFECT_NONE);
    }

    virtual DWORD OnDragEnter(FORMATETC & /*FormatEtc*/, STGMEDIUM & /*StgMedium*/, DWORD /*dwKeyState*/, CPoint /*point*/)
    {
        return FALSE;
    }

    virtual DWORD OnDragOver(FORMATETC & /*FormatEtc*/, STGMEDIUM & /*StgMedium*/, DWORD /*dwKeyState*/, CPoint /*point*/)
    {
        return FALSE;
    }

    virtual BOOL OnDrop(FORMATETC & /*FormatEtc*/, STGMEDIUM & /*StgMedium*/, DWORD /*dwEffect*/, CPoint /*point*/)
    {
        return FALSE;
    }

    virtual void OnDragLeave()
    {
    }
};

template <class T>
class CDropTargetT : public CDropTarget
{
public:
    CDropTargetT(HWND hTargetWnd) :
        CDropTarget(hTargetWnd)
    {
        m_pDelegate = nullptr;
    }

protected:
    T * m_pDelegate;

public:
    BOOL Register(T * pDelegate)
    {
        m_pDelegate = pDelegate;
        return TRUE;
    }

    virtual DWORD OnDragEnter(FORMATETC & FormatEtc, STGMEDIUM & StgMedium, DWORD dwKeyState, CPoint point)
    {
        return m_pDelegate == nullptr ? DROPEFFECT_NONE : m_pDelegate->OnDragEnter(FormatEtc, StgMedium, dwKeyState, point);
    }

    virtual DWORD OnDragOver(FORMATETC & FormatEtc, STGMEDIUM & StgMedium, DWORD dwKeyState, CPoint point)
    {
        return m_pDelegate == nullptr ? DROPEFFECT_NONE : m_pDelegate->OnDragOver(FormatEtc, StgMedium, dwKeyState, point);
    }

    virtual BOOL OnDrop(FORMATETC & FormatEtc, STGMEDIUM & StgMedium, DWORD dwEffect, CPoint point)
    {
        return m_pDelegate == nullptr ? FALSE : m_pDelegate->OnDrop(FormatEtc, StgMedium, dwEffect, point);
    }

    virtual void OnDragLeave()
    {
        if (m_pDelegate != nullptr)
            m_pDelegate->OnDragLeave();
    }
};

template <class T>
class CDataObjectT : public CDataObject
{
public:
    CDataObjectT(CDropSource * pDropSource) :
        CDataObject(pDropSource)
    {
        m_pDelegate = FALSE;
    }

protected:
    T * m_pDelegate;

public:
    BOOL Register(T * pDelegate)
    {
        m_pDelegate = pDelegate;
        return TRUE;
    }

    virtual BOOL OnRenderData(FORMATETC & FormatEtc, STGMEDIUM * pStgMedium, BOOL bDropComplete)
    {
        return m_pDelegate == nullptr ? FALSE : m_pDelegate->OnRenderData(FormatEtc, pStgMedium, bDropComplete);
    }
};

template <class T>
class CDragDrop
{
public:
    CDragDrop()
    {
        m_pDropSource = nullptr;
        m_pDataObject = nullptr;
        m_pDropTarget = nullptr;
        m_hTargetWnd = nullptr;
    }

    virtual ~CDragDrop()
    {
        if (m_pDropSource != nullptr)
            m_pDropSource->Release();
        if (m_pDataObject != nullptr)
            m_pDataObject->Release();
    }

protected:
    CDropSource * m_pDropSource;
    CDataObjectT<T> * m_pDataObject;
    CDropTargetT<T> * m_pDropTarget;
    HWND m_hTargetWnd;

public:
    BOOL Register(T * pDelegate, BOOL bDropSource = TRUE)
    {
        m_hTargetWnd = pDelegate->m_hWnd;

        // Instantiate new drop target object
        m_pDropTarget = new CDropTargetT<T>(m_hTargetWnd);
        m_pDropTarget->Register(pDelegate);

        // Register drop target
        if (FAILED(RegisterDragDrop(m_hTargetWnd, m_pDropTarget)))
        {
            delete m_pDropTarget;
            m_pDropTarget = nullptr;
            return FALSE;
        }

        // Is this a drop target only?
        if (!bDropSource)
            return TRUE;

        // Instantiate new drop source object
        m_pDropSource = new CDropSource;
        m_pDropSource->AddRef();

        m_pDataObject = new CDataObjectT<T>(m_pDropSource);
        m_pDataObject->AddRef();

        // Register drop source delegate for data render
        return m_pDataObject->Register(pDelegate);
    }

    BOOL Revoke()
    {
        m_pDropTarget = nullptr;
        return (RevokeDragDrop(m_hTargetWnd) == S_OK);
    }

    BOOL AddTargetFormat(CLIPFORMAT cfFormat)
    {
        if (m_pDropTarget == nullptr)
            return FALSE;
        m_pDropTarget->AddSupportedFormat(cfFormat);
        return TRUE;
    }

    BOOL AddSourceFormat(CLIPFORMAT cfFormat)
    {
        if (m_pDataObject == nullptr)
            return FALSE;

        FORMATETC FormatEtc;
        ZeroMemory(&FormatEtc, sizeof(FORMATETC));

        FormatEtc.cfFormat = cfFormat;
        FormatEtc.dwAspect = DVASPECT_CONTENT;
        FormatEtc.lindex = -1;
        FormatEtc.tymed = TYMED_HGLOBAL;

        STGMEDIUM StgMedium;
        ZeroMemory(&StgMedium, sizeof(STGMEDIUM));

        return SUCCEEDED(m_pDataObject->SetData(&FormatEtc, &StgMedium, TRUE));
    }

    BOOL SetClipboard(FORMATETC & FormatEtc, STGMEDIUM & StgMedium)
    {
        if (m_pDataObject == nullptr)
            return DROPEFFECT_NONE;

        if (FAILED(m_pDataObject->SetData(&FormatEtc, &StgMedium, TRUE)))
            return DROPEFFECT_NONE;

        return (OleSetClipboard(m_pDataObject) == S_OK);
    }

    BOOL FlushClipboard()
    {
        return (OleFlushClipboard() == S_OK);
    }

    DWORD DoDragDrop(SHDRAGIMAGE * pDragImage = nullptr, DWORD dwValidEffects = DROPEFFECT_COPY | DROPEFFECT_MOVE | DROPEFFECT_LINK)
    {
        if (m_pDataObject == nullptr)
            return DROPEFFECT_NONE;

        IDragSourceHelper * pDragSourceHelper = nullptr;

        // Instantiate drag source helper object
        if (pDragImage != nullptr)
        {
            if (FAILED(CoCreateInstance(CLSID_DragDropHelper, nullptr, CLSCTX_INPROC_SERVER, IID_IDragSourceHelper, (LPVOID *)&pDragSourceHelper)))
                pDragSourceHelper = nullptr;

            if (pDragSourceHelper != nullptr)
                pDragSourceHelper->InitializeFromBitmap(pDragImage, m_pDataObject);
        }

        DWORD dwEffects = DROPEFFECT_NONE;
        dwEffects = ::DoDragDrop(m_pDataObject, m_pDropSource, dwValidEffects, &dwEffects) == DRAGDROP_S_DROP ? DROPEFFECT_NONE : dwEffects;

        // Destroy drag source helper object
        if (pDragSourceHelper != nullptr)
            pDragSourceHelper->Release();

        return dwEffects;
    }
};