Thread: Geting "hwnds" without FindWindow

I'm about to start my version of taskmanager and I would like to know how the real taskmanager finds the files/proccesses, I'm pretty sure it dosen't use FindWindow but how... Also MSDN b*tches a lot about the TerminateProcess function saying that I shouldn't use it because it dosen't let the program know it's being closed and bla bla bla... Is there any real problem?

You may find the list-view control to be a better choice. You can clear a list-view with the ListView_DeleteAllItems macro.

Ok, I tried to implement a list-view but mine is not showing up, why?

Code:

#define WIN32_LEAN_AND_MEAN
#define _WIN32_IE 0x300
#include <windows.h>
#include <tlhelp32.h>
#include <commctrl.h>
#include "resource.h"

#pragma comment(lib, "gdi32.lib")
#pragma comment(lib, "comctl32.lib")

BOOL CALLBACK DlgProc(HWND hwnd, UINT Message, WPARAM wParam, LPARAM lParam)
{
    HWND hListView;

    switch(Message)
    {
        case WM_INITDIALOG:
        {
            HINSTANCE hInstance;
            LVCOLUMN lvc = { 0 };

            hListView = CreateWindow(WC_LISTVIEW, NULL, WS_CHILD | WS_VISIBLE | LVS_REPORT,
                                     14,38,236,178, hwnd, (HMENU) 500, hInstance, NULL);

            ListView_SetExtendedListViewStyle(hListView, LVS_EX_FULLROWSELECT | LVS_EX_HEADERDRAGDROP);

            lvc.mask = LVCF_TEXT | LVCF_SUBITEM | LVCF_WIDTH  | LVCF_FMT;
            lvc.fmt  = LVCFMT_LEFT;

            // Adding three columns to the list-view
            lvc.iSubItem = 0;
            lvc.cx       = 100;
            lvc.pszText  = TEXT("Process Name");
            ListView_InsertColumn(hListView, 0, &lvc);

            lvc.iSubItem = 1;
            lvc.cx       = 75;
            lvc.pszText  = TEXT("User name");
            ListView_InsertColumn(hListView, 1, &lvc);

            lvc.iSubItem = 2;
            lvc.cx       = 50;
            lvc.pszText  = TEXT("PID");
            ListView_InsertColumn(hListView, 2, &lvc);

            lvc.iSubItem = 3;
            lvc.cx       = 70;
            lvc.pszText  = TEXT("Memory use");
            ListView_InsertColumn(hListView, 3, &lvc);

            // SetTimer(hwnd, TIMER1, 1000, (TIMERPROC) NULL);
        }
		break;
        case WM_TIMER:
        {
            HANDLE hProcessSnap;
            PROCESSENTRY32 pe32;

            hProcessSnap = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
            if (hProcessSnap == INVALID_HANDLE_VALUE)
            {
                KillTimer(hwnd, TIMER1);
                MessageBox(hwnd, TEXT("Dam CreateToolhelp32Snapshot!"), TEXT("Error"), 
                           MB_OK | MB_ICONEXCLAMATION);
            }
            
            pe32.dwSize = sizeof(PROCESSENTRY32);

            if (!Process32First(hProcessSnap, &pe32))
            {
                KillTimer(hwnd, TIMER1);
                CloseHandle(hProcessSnap);
                MessageBox(hwnd, TEXT("Dam Process32First!"), TEXT("Error"), 
                           MB_OK | MB_ICONEXCLAMATION);
            }

            while(Process32Next(hProcessSnap, &pe32))
            {
                // Add the items when I manage to make the list show up
            }
            
            CloseHandle(hProcessSnap);
        }
        break;
        case WM_CLOSE:
            KillTimer(hwnd, TIMER1);
            EndDialog(hwnd, 0);
        break;
        default:
            return FALSE;
    }
    return TRUE;
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
	LPSTR lpCmdLine, int nCmdShow)
{
	return DialogBox(hInstance, MAKEINTRESOURCE(IDD_MAIN), NULL, DlgProc);
}

You need to call InitCommonControlsEx before creating a common control.

Code:

BOOL CALLBACK DlgProc(HWND hwnd, UINT Message, WPARAM wParam, LPARAM lParam)
{
    HWND hListView;

    switch(Message)
    {

hListView is an auto variable and its value will be lost each time DlgProc is called. You could make it static, or a global, or you could get its value each time with GetDlgItem:

Code:

        case WM_TIMER:
        {
            HANDLE hProcessSnap;
            PROCESSENTRY32 pe32;

            hListView = GetDlgItem(hwnd, 500);

Also, have you removed the // before your SetTimer call?

Hum...

>> I'm trying to leave a margin on each side, but only managed to do it on top and left, how about right and bottom? <<

You have tot take into account the left/top margin when you set the width/height. For example, if you want a 10 pixel margin:

Code:

            MoveWindow(hListView, 10, 10, LOWORD(lParam) - 20, HIWORD(lParam) - 20,TRUE);

>> Also how would I send the th32ProcessID (a DWORD) to the list? <<

You will need to format it to a string. You can do this with wsprintf:

Code:

TCHAR buf[100];
wsprintf(buf, TEXT("%lu"), th32ProcessID);

>> Now I used the ListView_DeleteAllItems before that while loop to clean the list and then update it, but the resuslts weren't like I expected... Each time it "updated" you loose your selection and position in the scrollbar not like taskmanager. <<

You could only add/delete the items that have changed to avoid that behaviour. Alternatively, you could record which item is selected (using ListView_GetSelectionMark) and restore it (using ListView_SetSelectionMark) after the update.

Once again thanks

All but one solution worked finely, I'm getting undefined reference to ListView_GetSelectionMark and ListView_SetSelectionMark, I even tried sending the LVM_GETSELECTIONMARK and the LVM_SETSELECTIONMARK but they were undefined as well...

I'm including commctrl.h, and linking to libcomctl32.a

Those constants are defined only if __WIN32_IE is at least 0x0400.

So I believe to solve the problem, you have to define __WIN32_IE before including the windows headers.

Code:

#define _WIN32_IE 0x0400
#include <windows.h>
#include <commctrl.h>

Thanks... It worked, but there was no difference, you still loose your selection and scrollbar position... How would I realise the second option: "You could only add/delete the items that have changed to avoid that behaviour.". My code so far:

Code:

             int mark = ListView_GetSelectionMark(hListView);
            ListView_DeleteAllItems(hListView);

            unsigned int i = 0;
            TCHAR buf[100];
            while(Process32Next(hProcessSnap, &pe32))
            {
                wsprintf(buf, TEXT("%lu"), pe32.th32ProcessID);

                lv.iItem = i;
                ListView_InsertItem(hListView, &lv);
                ListView_SetItemText(hListView, i, 0, pe32.szExeFile);
                ListView_SetItemText(hListView, i, 1, TEXT("Test"));
                ListView_SetItemText(hListView, i, 2, buf);
                ListView_SetItemText(hListView, i, 3, TEXT("Test"));
                i++;
            }
            ListView_SetSelectionMark(hListView, mark);
            CloseHandle(hProcessSnap);