How to Retrieve a Main Window Handle from its Process ID using EnumWindows()?

Retrieving Main Window Handle from Process ID using EnumWindows()

In various scenarios, it becomes necessary to retrieve the main window handle associated with a specific process ID. This allows you to manipulate the window's behavior, such as bringing it to the front or interacting with its controls.

Similar to the approach adopted by the .NET framework, you can leverage the EnumWindows() function to achieve this. Here's how you can implement it:

Implementation in C/C :

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);
}

This code defines a helper struct, handle_data, to store both the process ID and the window handle. The find_main_window() function uses EnumWindows() to enumerate all top-level windows, checks the process ID associated with each window, and filters out windows that are not main windows using the is_main_window() function. If the main window is found, the code stores its handle in the handle_data struct and returns it.

By following this approach, you can retrieve the main window handle from a process ID, enabling you to control its appearance or behavior as needed.

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