Mouse Pointer Disappears When You Press F4 to Open the ComboBox Control (326254)

RESOLUTION

1. Handle the message CBN_DROPDOWN.
2. Call SendMessage(WM_SETCURSOR,0,0) from inside the dropdown handler function. This causes the pointer to appear when the ComboBox opens.

Examples

A Truncated Example from an MFC Dialog-based Application

CCombofixDlg::CCombofixDlg(CWnd* pParent /*=NULL*/)
	: CDialog(CCombofixDlg::IDD, pParent)
{
	//{{AFX_DATA_INIT(CCombofixDlg)
	// NOTE: the ClassWizard will add member initialization here
	//}}AFX_DATA_INIT
	// Note that LoadIcon does not require a DestroyIcon in Win32 after this
	m_hIcon = AfxGetApp()->LoadIcon(IDR_MAINFRAME);
}

void CCombofixDlg::DoDataExchange(CDataExchange* pDX)
{
	CDialog::DoDataExchange(pDX);
	//{{AFX_DATA_MAP(CCombofixDlg)
	// NOTE: the ClassWizard will add DDX and DDV calls here
	//}}AFX_DATA_MAP
}

BEGIN_MESSAGE_MAP(CCombofixDlg, CDialog)
	//{{AFX_MSG_MAP(CCombofixDlg)
	ON_WM_SYSCOMMAND()
	ON_WM_PAINT()
	ON_WM_QUERYDRAGICON()
	ON_CBN_DROPDOWN(IDC_COMBOMAIN, OnDropdownCombomain)
	//}}AFX_MSG_MAP
END_MESSAGE_MAP()


// CCombofixDlg message handlers
void CCombofixDlg::OnDropdownCombomain() 
{
	SendMessage(WM_SETCURSOR,0,0);	
}
				

A Simple Windows Program

#include <windows.h>
#include <commctrl.h>


LPSTR lpClassName = "TestWindow";	//Class of the window
HWND hWndMain,hWndComboBox;
HINSTANCE hInst;
MSG msg;

WNDCLASSEX MyWnd,MyCtrl;


LRESULT CALLBACK MyWndProc(HWND hWnd,
			UINT msg,
			WPARAM wParam,
			LPARAM lParam);


int WINAPI WinMain(HINSTANCE hInstance,
		HINSTANCE hPrevInstance,
		LPSTR lpCmdLine,
		int nShow)
{

	hInst = hInstance;

	ZeroMemory(&MyWnd,sizeof(MyWnd));

	MyWnd.cbSize = sizeof(MyWnd);
	MyWnd.lpfnWndProc =  MyWndProc;
	MyWnd.hInstance = hInstance;
	MyWnd.lpszClassName = lpClassName;
	MyWnd.hbrBackground =(HBRUSH)(COLOR_WINDOW+1);
	MyWnd.style = CS_VREDRAW |CS_HREDRAW;

	RegisterClassEx(&MyWnd);
	//Make the main window 
	hWndMain=CreateWindowEx(0,lpClassName,"Combo Control Test",
			WS_OVERLAPPEDWINDOW | WS_VISIBLE,
			CW_USEDEFAULT,CW_USEDEFAULT,
			CW_USEDEFAULT,CW_USEDEFAULT,
                                NULL,NULL,hInstance,NULL);

	//Now for the ComboBox control. 
	hWndComboBox = CreateWindowEx(0,"COMBOBOX","CTL",
				CBS_DROPDOWN | WS_CHILD |WS_VISIBLE,
				100,100,100,100,hWndMain,1234,
				hInstance,NULL);
	SendMessage(hWndComboBox, CB_ADDSTRING, 0, "hello world"); 
	UpdateWindow(hWndComboBox);

	while(GetMessage(&msg,NULL,0,0))
	{
		TranslateMessage(&msg);
		DispatchMessage(&msg);
	}
	
	return msg.wParam;

}


LRESULT CALLBACK MyWndProc(HWND hWnd,
			UINT msg,
			WPARAM wParam,
			LPARAM lParam)
{
	
	PAINTSTRUCT ps;

	switch (msg)
	{
		case WM_COMMAND:

			if(lParam == hWndComboBox)
			{
	//This is a command from the Combo box check to 
        //see if it is CBN_DROPDOWN, and if so, to 
        //force the cursor (pointer) to appear.
				if(HIWORD(wParam) == CBN_DROPDOWN)
					SendMessage(hWndMain,WM_SETCURSOR,0,0);
			}

			break;

		case WM_PAINT:
			BeginPaint(hWndMain,&ps);
			EndPaint(hWndMain,&ps);
	
			break;

		case WM_SETFOCUS:

			break;

		case WM_SIZE:
		
			break;

		case WM_CREATE:
					
			break;
		case WM_CLOSE:

			DestroyWindow(hWnd);
			break;

		case WM_DESTROY:
			PostQuitMessage(0);


			break;				
	
		default :
			return DefWindowProc(hWnd,msg,wParam,lParam);
	}

	return 0;

}