Drag and Drop on a Tray Icon

/*********************************************************/
/* overlay window to support drag-drop onto systray icon */
/*********************************************************/

BOOL _TrayTools_CreateTrayDragDropWnd(TSysTray *in_TrayInfo, TSysTrayEntry *in_Entry)
{
    /* locals */
    VOID    *lv_CP[2];
    RECT     lv_Rect;
    HWND     lv_hAnchor;
    HWND     lv_hNotiTB;
    WNDCLASS lv_WndClass;


  // already created?
  if (in_Entry->DragDrop.hDropWnd && IsWindow(in_Entry->DragDrop.hDropWnd))
    return TRUE;

  // get the notification toolbar
  // (Shell_TrayWnd/TrayNotifyWnd/SysPager/TOOLBARCLASSNAME)
  lv_hNotiTB = Shell_GetSysTaskbarNotifyWindowTB();

  // get the notification area as parent/anchor of the overlay window
  // (Shell_TrayWnd/TrayNotifyWnd)
  lv_hAnchor = Shell_GetSysTaskbarNotifyWindow();

  // no tray/explorer running?
  if (!lv_hNotiTB || !lv_hAnchor)
    return NULL;

  // get initial rectangle of icon
  //
  // Note: if the icon is hidden and placed into a popup tray (win7) then
  // this routine returns the rectangle of the arrow button, for ALL the dropable
  // systray icons and dropping the file will send the file to any of the icons
  if (!TrayTools_GetSysTrayIconRect(in_TrayInfo, in_Entry->Def.TrayID, &lv_Rect))
    return FALSE;

  // class not yet registered?
  if (!GetClassInfo(gv_AppInfo.hInstance, CLASSNAME_TRAYDRAGDROP, &lv_WndClass))
  {
    // set up and register window class
    memset(&lv_WndClass, 0, sizeof(WNDCLASS));
    lv_WndClass.style         = CS_DBLCLKS;
    lv_WndClass.lpfnWndProc   = _TrayTools_TrayDragDropWndProc;
    lv_WndClass.hInstance     = gv_AppInfo.hInstance;
    lv_WndClass.lpszClassName = CLASSNAME_TRAYDRAGDROP;
    lv_WndClass.cbWndExtra    = TRAYDRAGDROP_GWLP_LAST;
    lv_WndClass.hCursor       = LoadCursor(NULL, IDC_ARROW);
    //lv_WndClass.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);
    RegisterClass(&lv_WndClass);
  }

  // store info of tray,
  // - our transparent window is child of taskbar instead of the notification
  //   window otherwise large delays occur as moves
  //   Update 1: the delays are solved via posting a message to self instead
  //   of creating the overlay right after the Shell_NotifyIcon call
  //   Btw: the old method using taskbar still hang on Win7, it worked on XP
  //   Update 2: use TrayNotifyWnd as parent instead of the toolbar because
  //   we must be able to places us on top of bottom of the toolbar
  // - the received mouse messages must be forwarded to the toolbar
  in_Entry->DragDrop.hAnchor   = lv_hAnchor;
  in_Entry->DragDrop.hNotifyTB = lv_hNotiTB;

  // prepare passing the parameters to the wndproc
  lv_CP[0] = in_TrayInfo;
  lv_CP[1] = in_Entry;

  // from screen coordinates to clientcoordinates of taskbar
  ScreenToClientRect(in_Entry->DragDrop.hAnchor, &lv_Rect);

  // create the window as child of the tray window with tray as parent
  // (windows does not set parent if child style is not specified and will not
  //  destroy our window if not set as parent)
  in_Entry->DragDrop.hDropWnd = CreateWindowEx(
    WS_EX_TRANSPARENT | WS_EX_NOACTIVATE,
    CLASSNAME_TRAYDRAGDROP, NULL,
    WS_VISIBLE | WS_CHILD,  // WS_DISABLED |
    lv_Rect.left, lv_Rect.top,
    lv_Rect.right  - lv_Rect.left,
    lv_Rect.bottom - lv_Rect.top,
    in_Entry->DragDrop.hAnchor, NULL, gv_AppInfo.hInstance, lv_CP);

  // check
  if (!in_Entry->DragDrop.hDropWnd)
    return FALSE;

  // place transparent window on top of the tasbbar
  SetWindowPos(
    in_Entry->DragDrop.hDropWnd, HWND_TOP, 0,0,0,0,
    SWP_NOMOVE|SWP_NOSIZE|SWP_NOACTIVATE);

  // done
  return TRUE;
}



BOOL _TrayTools_DoneTrayDragDropWnd(TSysTrayEntry *in_Entry)
{
  // if created
  if (in_Entry->DragDrop.hDropWnd)
  {
    // destroy our window
    DestroyWindow(in_Entry->DragDrop.hDropWnd);

    // clear
    in_Entry->DragDrop.hDropWnd = NULL;
  }

  // done
  return TRUE;
}




LRESULT CALLBACK _TrayTools_TrayDragDropWndProc
(
  HWND   in_hWnd,
  UINT   in_uMsg,
  WPARAM in_wParam,
  LPARAM in_lParam
)
{
    /* locals */
    UINT_PTR      *lv_CP;
    RECT           lv_Rect1;
    RECT           lv_Rect2;
    TSysTray      *lv_TrayInfo;
    TSysTrayEntry *lv_Entry;


  // create message?
  if (in_uMsg == WM_CREATE)
  {
    // get the param and check it
    if ((lv_CP = (UINT_PTR*)((CREATESTRUCT *)in_lParam)->lpCreateParams) == NULL)
      return -1;

    // store param
    SetWindowLongAsPtr(in_hWnd, TRAYDRAGDROP_GWLP_TRAYINFO,  lv_CP[0]);
    SetWindowLongAsPtr(in_hWnd, TRAYDRAGDROP_GWLP_TRAYENTRY, lv_CP[1]);

    // get the param
    lv_TrayInfo = (TSysTray*)     lv_CP[0];
    lv_Entry    = (TSysTrayEntry*)lv_CP[1];
  }
  else
  {
    // get the param
    lv_TrayInfo = (TSysTray*)     GetWindowLongAsPtr(in_hWnd, TRAYDRAGDROP_GWLP_TRAYINFO);
    lv_Entry    = (TSysTrayEntry*)GetWindowLongAsPtr(in_hWnd, TRAYDRAGDROP_GWLP_TRAYENTRY);
  }



  // process message not depedent on the entry information
  switch (in_uMsg)
  {
    // create message
    case WM_CREATE:
    {
      // register dragdrop
      ShellDD_RegisterWindow(in_hWnd);

      // done
      break;
    }


    // destroy: happens when explorer/tray gets destroyed (for instances if explorer crashes)
    case WM_NCDESTROY:
    {
      // unregister dragdrop
      ShellDD_UnregisterWindow(in_hWnd);

      // ensure timer is stopped
      if (lv_Entry->DragDrop.TimerID)
        KillTimer(in_hWnd, lv_Entry->DragDrop.TimerID);

      // clear
      lv_Entry->DragDrop.TimerID  = 0;
      lv_Entry->DragDrop.hDropWnd = NULL;

      // done
      break;
    }
  }



  // check the presence of the entry information
  if (lv_TrayInfo && lv_Entry)
  {
    // process message depedent on the entry information
    switch (in_uMsg)
    {
      // if mouse message
      case WM_MOUSEMOVE:
      case WM_LBUTTONUP:
      case WM_LBUTTONDOWN:
      case WM_LBUTTONDBLCLK:
      case WM_RBUTTONUP:
      case WM_RBUTTONDOWN:
      case WM_RBUTTONDBLCLK:
      case WM_NCHITTEST:
      {
        // place overlay into the background so from now on mousemessages
        // are immediately delivered to the toolbar, this is done to get the
        // tooltips working and to prevent the contextmenu of the taskbar showing up
        SetWindowPos(in_hWnd, HWND_BOTTOM, 0,0,0,0, SWP_NOMOVE|SWP_NOSIZE|SWP_NOACTIVATE);

        // init time of last mouse message
        lv_Entry->DragDrop.LastMouseTime = GetTickCount();

        // start timer to restore overlay back to the top after a delay
        if (!lv_Entry->DragDrop.TimerID)
          lv_Entry->DragDrop.TimerID = SetTimer(in_hWnd, 987, 3000, 0);

        // convert coordinates to client coordinates of the toolbar
        ClientToClientPoint16(in_hWnd, lv_Entry->DragDrop.hNotifyTB, (POINT16*)&in_lParam);

        // forward the message
        return SendMessage(lv_Entry->DragDrop.hNotifyTB, in_uMsg, in_wParam, in_lParam);
      }


      // if timer
      case WM_TIMER:
      {
        // timer to bring overlay back to the top?
        if (lv_Entry->DragDrop.TimerID == in_wParam)
        {
          // check the last activity time
          if (GetTickCount() - lv_Entry->DragDrop.LastMouseTime > 1000)
          {
            // bring back to the top
            SetWindowPos(in_hWnd, HWND_TOP, 0,0,0,0, SWP_NOMOVE|SWP_NOSIZE|SWP_NOACTIVATE);

            // stop the timer
            KillTimer(in_hWnd, lv_Entry->DragDrop.TimerID);

            // timer is stopped
            lv_Entry->DragDrop.TimerID = 0;
          }
        }

        // done
        break;
      }


      // forward other messages without conversion
      case WM_SETCURSOR:
        return SendMessage(lv_Entry->DragDrop.hNotifyTB, in_uMsg, in_wParam, in_lParam);


      // detect movement of icon at paint message
      case WM_PAINT:
      {
        // get current rectangle of icon
        if (TrayTools_GetSysTrayIconRect(lv_TrayInfo, lv_Entry->Def.TrayID, &lv_Rect1))
        {
          // get current overlay rectangle
          GetWindowRect(in_hWnd, &lv_Rect2);

          // need to move?
          if (lv_Rect1.left   != lv_Rect2.left  ||
              lv_Rect1.top    != lv_Rect2.top   ||
              lv_Rect1.right  != lv_Rect2.right ||
              lv_Rect1.bottom != lv_Rect2.bottom)
          {
            // from screen coordinates to clientcoordinates of anchor
            ScreenToClientRect(lv_Entry->DragDrop.hAnchor, &lv_Rect1);

            // move overlay at same location as the toolbar button
            SetWindowPos(
              lv_Entry->DragDrop.hDropWnd, HWND_TOP,
              lv_Rect1.left,
              lv_Rect1.top,
              lv_Rect1.right  - lv_Rect1.left,
              lv_Rect1.bottom - lv_Rect1.top,
              SWP_NOACTIVATE);
          }
        }

        // further default processing
        break;
      }


      // and then there was a drop
      case WM_DROPFILES:
      {
        // call the callback
        if (lv_Entry->Def.DropFileProc)
          lv_Entry->Def.DropFileProc((HDROP)in_wParam);

        // done
        break;
      }
    }
  }

  // default handling
  return DefWindowProc(in_hWnd, in_uMsg, in_wParam, in_lParam);
}