visual c++ GetWindow member function

[mikehp]

Hi, my question is regarding the visual c++ 'GetWindow' member function. An application I support has the ability to limit concurrent user sessions. It does this by counting the number of existing sessions on the desktop whenever a user attempts to open another session. It does this via a dll file which contains a function called uWindowCount. uWindowCount uses the c++ GetWindow member function and GW_HWNDFIRST to count any existing sessions and return the number back to the calling application (code below).

My problem is that when the application is run on a windows xp desktop; existing sessions that are minimized are not being counted, so as long as a user minimizes existing sessions before opening a new session they can open as many as they like. On a terminal server this does not occur, all sessions (minimized or not) are counted and the application is able to control a users concurrent sessions successfully.


#include "csutil.h"

#define MAX_PROCESS 100 // precautionary over-run count.
#define MAX_NAME 100 // buffer space to allocate for window names.

//XEXPORT(long) uWindowCount(void)
XEXPORT(long) UWINDOWCOUNT(void)
{
HWND hWndUniface, hWnd, hWndParent = 0;
int iLenName, iCount=0;
int iFound;
char szTitleWindow[MAX_NAME+2];
char szTitle[MAX_NAME+1];


iFound = 0;
szTitle[0] = 0;

UGETREGS(REG0,szTitle,sizeof(szTitle)-1);

// exit with error code if empty window title is detected.

if(strlen(szTitle) == 0)
{
UPUTMESS("uWindowCount: empty window title supplied.");
UPUTREG(REG1,-1L);
return SUCCESS;
}

/* Start with handle of Uniface Window */
hWndUniface = GetActiveWindow();

/* Get first window handle */
hWnd = GetWindow(hWndUniface, GW_HWNDFIRST);

/* loop through all windows */
while (hWnd)
{
/* control loop */
if (iCount++ > MAX_PROCESS)
break;

/* Get title of this window */
iLenName = GetWindowTextLength(hWnd);

if (iLenName > MAX_NAME)
iLenName = MAX_NAME ;

iLenName = GetWindowText(hWnd, szTitleWindow, iLenName+1);

/* See if window is the one we want */
if (strncmp(szTitleWindow, szTitle, strlen(szTitle)) == 0)
++iFound;

/* Get next window */
hWnd = GetWindow(hWnd, GW_HWNDNEXT);
}

UPUTREG(REG1,iFound);

return SUCCESS;
}

[guestgulkan]

I know windows has an BOOL IsIconic(HWND hWnd) function to check whether a windows is minimized or not. Maybe that might be of some use.

[webJose]

Is the DLL loaded in the address space of the executable that you count windows of? If so, wouldn't it be better to count sessions via a more stable method? Maybe you can increase a counter whenever the DLL is loaded.

Or if you are bound to count windows, why not use a CBT hook that alerts you reliably whenever a window is created and destroyed? You can use Spy++ or the new one (forgot the name) that comes with the Windows 7 SDK to determine the window class name.