JUCE/modules/juce_gui_basics/native/juce_win32_DragAndDrop.cpp

/*
  ==============================================================================

   This file is part of the JUCE 7 technical preview.
   Copyright (c) 2022 - Raw Material Software Limited

   You may use this code under the terms of the GPL v3
   (see www.gnu.org/licenses).

   For the technical preview this file cannot be licensed commercially.

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

  ==============================================================================
*/

namespace juce
{

namespace DragAndDropHelpers
{
    //==============================================================================
    struct JuceDropSource   : public ComBaseClassHelper<IDropSource>
    {
        JuceDropSource() {}

        JUCE_COMRESULT QueryContinueDrag (BOOL escapePressed, DWORD keys) override
        {
            if (escapePressed)
                return DRAGDROP_S_CANCEL;

            if ((keys & (MK_LBUTTON | MK_RBUTTON)) == 0)
                return DRAGDROP_S_DROP;

            return S_OK;
        }

        JUCE_COMRESULT GiveFeedback (DWORD) override
        {
            return DRAGDROP_S_USEDEFAULTCURSORS;
        }
    };

    //==============================================================================
    struct JuceEnumFormatEtc   : public ComBaseClassHelper<IEnumFORMATETC>
    {
        JuceEnumFormatEtc (const FORMATETC* f)  : format (f) {}

        JUCE_COMRESULT Clone (IEnumFORMATETC** result) override
        {
            if (result == nullptr)
                return E_POINTER;

            auto newOne = new JuceEnumFormatEtc (format);
            newOne->index = index;
            *result = newOne;
            return S_OK;
        }

        JUCE_COMRESULT Next (ULONG celt, LPFORMATETC lpFormatEtc, ULONG* pceltFetched) override
        {
            if (pceltFetched != nullptr)
                *pceltFetched = 0;
            else if (celt != 1)
                return S_FALSE;

            if (index == 0 && celt > 0 && lpFormatEtc != nullptr)
            {
                copyFormatEtc (lpFormatEtc [0], *format);
                ++index;

                if (pceltFetched != nullptr)
                    *pceltFetched = 1;

                return S_OK;
            }

            return S_FALSE;
        }

        JUCE_COMRESULT Skip (ULONG celt) override
        {
            if (index + (int) celt >= 1)
                return S_FALSE;

            index += (int) celt;
            return S_OK;
        }

        JUCE_COMRESULT Reset() override
        {
            index = 0;
            return S_OK;
        }

    private:
        const FORMATETC* const format;
        int index = 0;

        static void copyFormatEtc (FORMATETC& dest, const FORMATETC& source)
        {
            dest = source;

            if (source.ptd != nullptr)
            {
                dest.ptd = (DVTARGETDEVICE*) CoTaskMemAlloc (sizeof (DVTARGETDEVICE));

                if (dest.ptd != nullptr)
                    *(dest.ptd) = *(source.ptd);
            }
        }

        JUCE_DECLARE_NON_COPYABLE (JuceEnumFormatEtc)
    };

    //==============================================================================
    class JuceDataObject  : public ComBaseClassHelper <IDataObject>
    {
    public:
        JuceDataObject (const FORMATETC* f, const STGMEDIUM* m)
            : format (f), medium (m)
        {
        }

        ~JuceDataObject()
        {
            jassert (refCount == 0);
        }

        JUCE_COMRESULT GetData (FORMATETC* pFormatEtc, STGMEDIUM* pMedium)
        {
            if ((pFormatEtc->tymed & format->tymed) != 0
                 && pFormatEtc->cfFormat == format->cfFormat
                 && pFormatEtc->dwAspect == format->dwAspect)
            {
                pMedium->tymed = format->tymed;
                pMedium->pUnkForRelease = nullptr;

                if (format->tymed == TYMED_HGLOBAL)
                {
                    auto len = GlobalSize (medium->hGlobal);
                    void* const src = GlobalLock (medium->hGlobal);
                    void* const dst = GlobalAlloc (GMEM_FIXED, len);

                    if (src != nullptr && dst != nullptr)
                        memcpy (dst, src, len);

                    GlobalUnlock (medium->hGlobal);

                    pMedium->hGlobal = dst;
                    return S_OK;
                }
            }

            return DV_E_FORMATETC;
        }

        JUCE_COMRESULT QueryGetData (FORMATETC* f)
        {
            if (f == nullptr)
                return E_INVALIDARG;

            if (f->tymed == format->tymed
                  && f->cfFormat == format->cfFormat
                  && f->dwAspect == format->dwAspect)
                return S_OK;

            return DV_E_FORMATETC;
        }

        JUCE_COMRESULT GetCanonicalFormatEtc (FORMATETC*, FORMATETC* pFormatEtcOut)
        {
            pFormatEtcOut->ptd = nullptr;
            return E_NOTIMPL;
        }

        JUCE_COMRESULT EnumFormatEtc (DWORD direction, IEnumFORMATETC** result)
        {
            if (result == nullptr)
                return E_POINTER;

            if (direction == DATADIR_GET)
            {
                *result = new JuceEnumFormatEtc (format);
                return S_OK;
            }

            *result = nullptr;
            return E_NOTIMPL;
        }

        JUCE_COMRESULT GetDataHere (FORMATETC*, STGMEDIUM*)                  { return DATA_E_FORMATETC; }
        JUCE_COMRESULT SetData (FORMATETC*, STGMEDIUM*, BOOL)                { return E_NOTIMPL; }
        JUCE_COMRESULT DAdvise (FORMATETC*, DWORD, IAdviseSink*, DWORD*)     { return OLE_E_ADVISENOTSUPPORTED; }
        JUCE_COMRESULT DUnadvise (DWORD)                                     { return E_NOTIMPL; }
        JUCE_COMRESULT EnumDAdvise (IEnumSTATDATA**)                         { return OLE_E_ADVISENOTSUPPORTED; }

    private:
        const FORMATETC* const format;
        const STGMEDIUM* const medium;

        JUCE_DECLARE_NON_COPYABLE (JuceDataObject)
    };

    //==============================================================================
    static HDROP createHDrop (const StringArray& fileNames)
    {
        size_t totalBytes = 0;
        for (int i = fileNames.size(); --i >= 0;)
            totalBytes += CharPointer_UTF16::getBytesRequiredFor (fileNames[i].getCharPointer()) + sizeof (WCHAR);

        struct Deleter
        {
            void operator() (void* ptr) const noexcept { GlobalFree (ptr); }
        };

        auto hDrop = std::unique_ptr<void, Deleter> ((HDROP) GlobalAlloc (GMEM_MOVEABLE | GMEM_ZEROINIT, sizeof (DROPFILES) + totalBytes + 4));

        if (hDrop != nullptr)
        {
            auto pDropFiles = (LPDROPFILES) GlobalLock (hDrop.get());

            if (pDropFiles == nullptr)
                return nullptr;

            pDropFiles->pFiles = sizeof (DROPFILES);
            pDropFiles->fWide = true;

            auto* fname = reinterpret_cast<WCHAR*> (addBytesToPointer (pDropFiles, sizeof (DROPFILES)));

            for (int i = 0; i < fileNames.size(); ++i)
            {
                auto bytesWritten = fileNames[i].copyToUTF16 (fname, 2048);
                fname = reinterpret_cast<WCHAR*> (addBytesToPointer (fname, bytesWritten));
            }

            *fname = 0;

            GlobalUnlock (hDrop.get());
        }

        return static_cast<HDROP> (hDrop.release());
    }

    struct DragAndDropJob   : public ThreadPoolJob
    {
        DragAndDropJob (FORMATETC f, STGMEDIUM m, DWORD d, std::function<void()>&& cb)
            : ThreadPoolJob ("DragAndDrop"),
              format (f), medium (m), whatToDo (d),
              completionCallback (std::move (cb))
        {
        }

        JobStatus runJob() override
        {
            ignoreUnused (OleInitialize (nullptr));

            auto* source = new JuceDropSource();
            auto* data = new JuceDataObject (&format, &medium);

            DWORD effect;
            DoDragDrop (data, source, whatToDo, &effect);

            data->Release();
            source->Release();

            OleUninitialize();

            if (completionCallback != nullptr)
                MessageManager::callAsync (std::move (completionCallback));

            return jobHasFinished;
        }

        FORMATETC format;
        STGMEDIUM medium;
        DWORD whatToDo;

        std::function<void()> completionCallback;
    };

    class ThreadPoolHolder   : private DeletedAtShutdown
    {
    public:
        ThreadPoolHolder() = default;

        ~ThreadPoolHolder()
        {
            // Wait forever if there's a job running. The user needs to cancel the transfer
            // in the GUI.
            pool.removeAllJobs (true, -1);

            clearSingletonInstance();
        }

        JUCE_DECLARE_SINGLETON_SINGLETHREADED (ThreadPoolHolder, false)

        // We need to make sure we don't do simultaneous text and file drag and drops,
        // so use a pool that can only run a single job.
        ThreadPool pool { 1 };
    };

    JUCE_IMPLEMENT_SINGLETON (ThreadPoolHolder)
}

//==============================================================================
bool DragAndDropContainer::performExternalDragDropOfFiles (const StringArray& files, const bool canMove,
                                                           Component*, std::function<void()> callback)
{
    if (files.isEmpty())
        return false;

    FORMATETC format = { CF_HDROP, nullptr, DVASPECT_CONTENT, -1, TYMED_HGLOBAL };
    STGMEDIUM medium = { TYMED_HGLOBAL, { nullptr }, nullptr };

    medium.hGlobal = DragAndDropHelpers::createHDrop (files);

    auto& pool = DragAndDropHelpers::ThreadPoolHolder::getInstance()->pool;
    pool.addJob (new DragAndDropHelpers::DragAndDropJob (format, medium,
                                                         canMove ? (DROPEFFECT_COPY | DROPEFFECT_MOVE) : DROPEFFECT_COPY,
                                                         std::move (callback)),
                true);

    return true;
}

bool DragAndDropContainer::performExternalDragDropOfText (const String& text, Component*, std::function<void()> callback)
{
    if (text.isEmpty())
        return false;

    FORMATETC format = { CF_TEXT, nullptr, DVASPECT_CONTENT, -1, TYMED_HGLOBAL };
    STGMEDIUM medium = { TYMED_HGLOBAL, { nullptr }, nullptr };

    auto numBytes = CharPointer_UTF16::getBytesRequiredFor (text.getCharPointer());

    medium.hGlobal = GlobalAlloc (GMEM_MOVEABLE | GMEM_ZEROINIT, numBytes + 2);

    if (medium.hGlobal == nullptr)
        return false;

    auto* data = static_cast<WCHAR*> (GlobalLock (medium.hGlobal));

    text.copyToUTF16 (data, numBytes + 2);
    format.cfFormat = CF_UNICODETEXT;

    GlobalUnlock (medium.hGlobal);

    auto& pool = DragAndDropHelpers::ThreadPoolHolder::getInstance()->pool;
    pool.addJob (new DragAndDropHelpers::DragAndDropJob (format,
                                                        medium,
                                                        DROPEFFECT_COPY | DROPEFFECT_MOVE,
                                                        std::move (callback)),
                 true);

    return true;
}

} // namespace juce