WM_GetInsideRect results when WM_CF_HASTRANS is used

#include "GUI.h"
#include <stdlib.h>


GUI_RECT Rect1;
GUI_RECT Rect2;


void Callback1(WM_MESSAGE *pMsg)
{
	WM_HWIN hWin;
	hWin = pMsg->hWin;
	switch (pMsg->MsgId)
	{
	case WM_PAINT:
		WM_GetInsideRect(&Rect1);
		GUI_SetBkColor(GUI_BLACK);
		GUI_SetColor(GUI_WHITE);
		GUI_ClearRectEx(&Rect1);
		GUI_DrawRectEx(&Rect1);
		break;
	default:
		WM_DefaultProc(pMsg);
		break;
	}
}


void Callback2(WM_MESSAGE *pMsg)
{
	WM_HWIN hWin;
	hWin = pMsg->hWin;
	switch (pMsg->MsgId)
	{
	case WM_PAINT:
		WM_GetInsideRect(&Rect2);
		GUI_SetBkColor(GUI_BLACK);
		GUI_SetColor(GUI_WHITE);
		GUI_ClearRectEx(&Rect2);
		GUI_DrawRectEx(&Rect2);
		break;
	default:
		WM_DefaultProc(pMsg);
		break;
	}
}


void MainTask(void)
{
  GUI_Init();


  GUI_SetBkColor(GUI_GRAY_3F);
  GUI_Clear();


  WM_HWIN hWin1, hWin2;


  hWin1 = WM_CreateWindowAsChild(10, 10, 80, 45, WM_HBKWIN,
			WM_CF_SHOW , Callback1, 0);


  hWin2 = WM_CreateWindowAsChild(10, 60, 80, 45, WM_HBKWIN,
			WM_CF_SHOW | WM_CF_HASTRANS, Callback2, 0);


  GUI_Delay(20);
  while(1)
  {
  	GUI_Delay(2000);
  }
}