Finding module name from the window handle

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Introduction

A few days back, in one of my projects, I needed to enumerate all the visible windows, and then needed to determine if a given application was running or not. I first struggled a little, but soon found a simple method to do that.

Enumerating the windows

With the EnumWindows API, I filtered out the visible windows. Next, with GetWindowThreadProcessId, I found the process ID of that window, and with that, I found the name of the executable file.

Below is the callback function for EnumWindows:

BOOL CALLBACK CProcessDlg::EnumWindowsProc (HWND hWnd, LPARAM lParam)
{
    CProcessDlg *pDlg = (CProcessDlg *)lParam;

    int nItem = 0;

    //Make sure that the window is visible
    TCHAR szWindowText [MAX_PATH];
    if (!::IsWindowVisible (hWnd))
        return TRUE;

    //Get the text on the title bar
    ::GetWindowText (hWnd, szWindowText, MAX_PATH);

    //If the window is Process Manager then don't display it
    if (_tcsstr (_T("Program Manager"), szWindowText))
        return TRUE;

    //Get process ID
    DWORD dwProcessID;
    GetWindowThreadProcessId (hWnd, &dwProcessID);
    
    //Get the name of the executable file
    CString strEXEName = pDlg->GetEXEName (dwProcessID);

    //Add the info to the list control
    nItem = pDlg->m_List.InsertItem (0, szWindowText);
    pDlg->m_List.SetItemText (nItem, 1, strEXEName);    

    return TRUE;
}

Finding module name

The GetEXEName procedure returns the name of the executable file from its process ID:

#include "psapi.h"
#pragma comment(lib, "psapi.lib")

CString GetEXEName(DWORD dwProcessID)
{
    DWORD aProcesses [1024], cbNeeded, cProcesses;
    unsigned int i;
        
    //Enumerate all processes
    if (!EnumProcesses(aProcesses, sizeof(aProcesses), &cbNeeded))
        return NULL;

    // Calculate how many process identifiers were returned.
    cProcesses = cbNeeded / sizeof(DWORD);

    TCHAR szEXEName[MAX_PATH];
    //Loop through all process to find the one that matches
    //the one we are looking for
    for (i = 0; i < cProcesses; i++)
    {
        if (aProcesses [i] == dwProcessID)
        {
            // Get a handle to the process
            HANDLE hProcess = OpenProcess(PROCESS_QUERY_INFORMATION |
                              PROCESS_VM_READ, FALSE, dwProcessID);
        
            // Get the process name
            if (NULL != hProcess)
            {
                HMODULE hMod;
                DWORD cbNeeded;
            
                if(EnumProcessModules(hProcess, &hMod, 
                                      sizeof(hMod), &cbNeeded))
                {
                    //Get the name of the exe file
                    GetModuleBaseName(hProcess, hMod, szEXEName, 
                        sizeof(szEXEName)/sizeof(TCHAR));

                    return CString (szEXEName);
                }
            }
        }    
    }

    return NULL;
}

Conclusion

The code is very easy to understand and follow, please see the demo project if you have any trouble using it.

I hope you find it useful.