How to get main window handle from process id?

Question

How to get main window handle from process id?

I want to bring this window to the front.

It works well in "Process Explorer".

Answer 1

I checked how .NET determines the main window.

My finding showed that it also uses EnumWindows().

This code should do it similarly to the .NET way:

struct handle_data {     unsigned long process_id;     HWND window_handle; };  HWND find_main_window(unsigned long process_id) {     handle_data data;     data.process_id = process_id;     data.window_handle = 0;     EnumWindows(enum_windows_callback, (LPARAM)&data);     return data.window_handle; }  BOOL CALLBACK enum_windows_callback(HWND handle, LPARAM lParam) {     handle_data& data = *(handle_data*)lParam;     unsigned long process_id = 0;     GetWindowThreadProcessId(handle, &process_id);     if (data.process_id != process_id || !is_main_window(handle))         return TRUE;     data.window_handle = handle;     return FALSE;    }  BOOL is_main_window(HWND handle) {        return GetWindow(handle, GW_OWNER) == (HWND)0 && IsWindowVisible(handle); } 

Answer 2

I don't believe Windows (as opposed to .NET) provides a direct way to get that.

The only way I know of is to enumerate all the top level windows with EnumWindows() and then find what process each belongs to GetWindowThreadProcessID(). This sounds indirect and inefficient, but it's not as bad as you might expect -- in a typical case, you might have a dozen top level windows to walk through...