How do i extract dragged & dropped filenames from a DROPFILES struct

Question

I have a window with no controls with WS_EX_ACCEPTFILES enabled and the event triggers successfully when dragging files from explorer. What I need to do is extract the files to a vector. From what I've read, the wParam is supposed to contain the location of the files within a DROPFILES struct but I don't know how to access them.

LRESULT CALLBACK StaticWndProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam, UINT_PTR 
uIdSubclass, DWORD_PTR dwRefData)
{
    if (uMsg == WM_DROPFILES)
    {
       // extract files here
       vector<string> files;

    }

    return DefSubclassProc(hwnd, uMsg, wParam, lParam);
}

I don't need to send them to any controls since my window is for an openGL application, I just need to retain them in a list, how can it be done?

Answer 1

Per the WM_DROPFILES documentation:

Parameters

hDrop

A handle to an internal structure describing the dropped files. Pass this handle to DragFinish, DragQueryFile, or DragQueryPoint() to retrieve information about the dropped files.

lParam

Must be zero.

Simply type-cast the wParam to HDROP and call the drag-drop functions as needed, eg:

LRESULT CALLBACK StaticWndProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam, UINT_PTR uIdSubclass, DWORD_PTR dwRefData)
{
    if (uMsg == WM_DROPFILES)
    {
       HDROP hDrop = reinterpret_cast<HDROP>(wParam);

       // extract files here
       vector<string> files;
       char filename[MAX_PATH];

       UINT count = DragQueryFileA(hDrop, -1, NULL, 0);
       for(UINT i = 0; i < count; ++i)
       {
          if (DragQueryFileA(hDrop, i, filename, MAX_PATH))
              files.push_back(filename);
       }

       DragFinish(hDrop);
       return 0;
    }

    return DefSubclassProc(hwnd, uMsg, wParam, lParam);
}

Alternatively:

LRESULT CALLBACK StaticWndProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam, UINT_PTR uIdSubclass, DWORD_PTR dwRefData)
{
    if (uMsg == WM_DROPFILES)
    {
       HDROP hDrop = reinterpret_cast<HDROP>(wParam);

       // extract files here
       vector<string> files;
       string filename;

       UINT count = DragQueryFileA(hDrop, -1, NULL, 0);
       for(UINT i = 0; i < count; ++i)
       {
          UINT size = DragQueryFileA(hDrop, i, NULL, 0);
          if (size > 0)
          {
              filename.resize(size);
              DragQueryFileA(hDrop, i, &filename[0], size+1);
              files.push_back(filename);
          }
       }

       DragFinish(hDrop);
       return 0;
    }

    return DefSubclassProc(hwnd, uMsg, wParam, lParam);
}