Make interactive console/window interaction in gui application - c++

Question

What i want:
An application, where there are a gui window and console window. Window can be clicked on, dragged, etcetera. At any given moment, console can be chosen, and a line entered, that will be processed.
What i already have:
An application, that allocates and attaches console to itself, then redirects standard streams to it. Code is:
AllocConsole() ;
AttachConsole( GetCurrentProcessId());
freopen("CONIN$","rb",stdin); // reopen stdin handle as console window input
freopen("CONOUT$","wb",stdout); // reopen stout handle as console window output
freopen("CONOUT$","wb",stderr); // reopen stderr handle as console window output
Then registers window class, creates and shows a window. Output into console works fine, interaction with window is correct.
However, i cannot input anything into console. I can make a guess about it: if i call something like std::cin >> my_string, i will be able to enter a line - but interaction with a window will stop until the input is completed. Is that correct? How can i make application behave in a way i described above?
update:
I have found related question: Test if stdin has input for C++ (windows and/or linux)
The code for determining, whether there are characters in console input was given there as follows:
bool StdinOpen() {
static HANDLE handle = GetStdHandle(STD_INPUT_HANDLE);
DWORD bytes_left;
PeekNamedPipe(handle, NULL, 0, NULL, &bytes_left, NULL);
return bytes_left;
}
However, it returns some exorbitant numbers, as if there always is input in console.

Answer 1

I'd start by initializing the bytes_left variable and check the return value.
bool StdinOpen() {
static HANDLE handle = GetStdHandle(STD_INPUT_HANDLE);
DWORD bytes_left = 0;
if (!PeekNamedPipe(handle, NULL, 0, NULL, &bytes_left, NULL))
return false;
return bytes_left != 0;
}