zntg/addons/drop/drop_windows.c

#include <Windows.h>
#include <shellapi.h>
#include <stdint.h>

#include "_cgo_export.h"

#define droppedFilePathSize 32767

BOOL dropHookInitialized = FALSE;
HHOOK nextHook;

LRESULT CALLBACK DragAndDropHook(
    _In_ int nCode,
    _In_ WPARAM wParam,
    _In_ LPARAM lParam)
{
    if (nCode < 0 || wParam == 0)
        return CallNextHookEx(nextHook, nCode, wParam, lParam);

    LPMSG message = (LPMSG)lParam;
    switch (message->message)
    {
    case WM_DROPFILES:
    {
        wchar_t droppedFilePath[droppedFilePathSize];

        clearDrop();
        HDROP drop = (HDROP)message->wParam;
        UINT numberOfFiles = DragQueryFile(drop, 0xFFFFFFFF, NULL, 0);
        for (UINT fileIndex = 0; fileIndex < numberOfFiles; fileIndex++)
        {
            UINT length = DragQueryFileW(drop, fileIndex, droppedFilePath, droppedFilePathSize);
            addDroppedFile(&droppedFilePath[0], length);
        }
        POINT position;
        DragQueryPoint(drop, &position);

        dropFinished(position.x, position.y);
    }
    break;
    }
    return CallNextHookEx(nextHook, nCode, wParam, lParam);
}

void initDropHook(HWND windowHandle)
{
    if (dropHookInitialized == TRUE)
        return;

    DWORD threadId = GetWindowThreadProcessId(windowHandle, NULL);
    nextHook = SetWindowsHookEx(WH_GETMESSAGE, DragAndDropHook, NULL, threadId);

    dropHookInitialized = TRUE;
}

void SetDragAndDropHook(void *window)
{
    HWND windowHandle = (HWND)window;
    initDropHook(windowHandle);

    DragAcceptFiles(windowHandle, TRUE);
}