Get hwnd by process id c++

Question

How can I get the HWND of application, if I know the process ID? Anyone could post a sample please? I'm using MSV C++ 2010. I found Process::MainWindowHandle but I don't know how to use it.

Vallery

A process isn't limited to 1 window. – Bodnar

A process can have several windows, and this have several hwnds. – Panhellenism

so, maby is it possible to get all HWNDs and select these, wich have this process ID? – Vallery

What's wrong with Process::MainWindowHandle? isn't it what you're looking for? – Ube

Possible duplicate of How to get main window handle from process id? – Cary

I don't understand how to do that in .net c++ – Vallery

#3269890 has some very good code doing exactly this – Fledge

A process can have also zero windows. – Palmitin

Answer 1

HWND g_HWND=NULL;
BOOL CALLBACK EnumWindowsProcMy(HWND hwnd,LPARAM lParam)
{
    DWORD lpdwProcessId;
    GetWindowThreadProcessId(hwnd,&lpdwProcessId);
    if(lpdwProcessId==lParam)
    {
        g_HWND=hwnd;
        return FALSE;
    }
    return TRUE;
}
EnumWindows(EnumWindowsProcMy,m_ProcessId);

Adalbert

One needs to point out that PID must belong to the same desktop (or interactive user/logon session) as the process you call this method from. Otherwise EnumWindows will not enumerate its window handle. For instance, you cannot use this method from a service, or if the process in question runs under a different logged on user account, or to retrieve the HWND for a screensaver if the workstation is locked, etc. – Selenodont

Just converted this code in free pascal and works like cheese for me too:) – Invoke

Care to explain your code for us less-knowledgeable programmers? – Chock

Answer 2

A single PID (Process ID) can be associated with more than one window (HWND). For example if the application is using several windows.
The following code locates the handles of all windows per a given PID.

void GetAllWindowsFromProcessID(DWORD dwProcessID, std::vector <HWND> &vhWnds)
{
    // find all hWnds (vhWnds) associated with a process id (dwProcessID)
    HWND hCurWnd = NULL;
    do
    {
        hCurWnd = FindWindowEx(NULL, hCurWnd, NULL, NULL);
        DWORD dwProcID = 0;
        GetWindowThreadProcessId(hCurWnd, &dwProcID);
        if (dwProcID == dwProcessID)
        {
            vhWnds.push_back(hCurWnd);  // add the found hCurWnd to the vector
            wprintf(L"Found hWnd %d\n", hCurWnd);
        }
    }
    while (hCurWnd != NULL);
}

Longley

this fails on premium WUP apps as you are not the owner of the package – Tergal

Answer 3

You can use EnumWindows and GetWindowThreadProcessId() functions as mentioned in this MSDN article.

Chiaroscuro

Answer 4

Thanks to Michael Haephrati, I slightly corrected your code for modern Qt C++ 11:

#include <iostream>
#include "windows.h"
#include "tlhelp32.h"
#include "tchar.h"
#include "vector"
#include "string"

using namespace std;

void GetAllWindowsFromProcessID(DWORD dwProcessID, std::vector <HWND> &vhWnds)
{
    // find all hWnds (vhWnds) associated with a process id (dwProcessID)
    HWND hCurWnd = nullptr;
    do
    {
        hCurWnd = FindWindowEx(nullptr, hCurWnd, nullptr, nullptr);
        DWORD checkProcessID = 0;
        GetWindowThreadProcessId(hCurWnd, &checkProcessID);
        if (checkProcessID == dwProcessID)
        {
            vhWnds.push_back(hCurWnd);  // add the found hCurWnd to the vector
            //wprintf(L"Found hWnd %d\n", hCurWnd);
        }
    }
    while (hCurWnd != nullptr);
}

Stocker

Thanks. Not everyone uses Qt but for the ones that do… – Longley