API

#include<Windows.h>
#include<vector>
using namespace std;

vector<HWND> Okna;
HINSTANCE glob;
unsigned short max_size = 10;
int skokx, skoky = 30;
TCHAR ClassName[] = TEXT("KLASA_OKIEN");

LRESULT CALLBACK WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    switch(uMsg)
    {
    case WM_DESTROY:
        PostQuitMessage(0); break;
    case WM_LBUTTONDOWN:
        {
            if(Okna.size() < max_size)
                Okna.push_back(CreateWindowEx(0, ClassName, TEXT("Okno"), WS_OVERLAPPEDWINDOW | WS_VISIBLE, 40+Okna.size()*skokx,40+Okna.size()*skoky, 300, 300, 0, 0, glob, 0));
            else
                MessageBox(hWnd, TEXT("ERROR: Za dużo okien"), TEXT("ERROR"), NULL);
        }
        break;
    case WM_RBUTTONDOWN:
        {
            for(int i=0; i < Okna.size(); ++i)
            {
                DestroyWindow(Okna[i]);
                Okna.erase(Okna.begin() +i);
            }
        }break;
    case WM_CLOSE:
        PostQuitMessage( 0 );
        break;
    default:
        return DefWindowProc(hWnd, uMsg, wParam, lParam);
    }
    return 0;
}

int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPTSTR lpCmdLine, int nCmdShow)
{
    glob = hInstance;
    WNDCLASSEX wc;
    ZeroMemory(&wc, sizeof(WNDCLASSEX));
    wc.cbClsExtra = 0;
    wc.cbSize = sizeof(WNDCLASSEX);
    wc.cbWndExtra = 0;
    wc.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
    wc.hCursor = LoadCursor(NULL, IDC_ARROW);
    wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wc.hInstance = hInstance;
    wc.lpfnWndProc = &WndProc;
    wc.lpszClassName = ClassName;
    wc.lpszMenuName = NULL;
    wc.style = 0;
    RegisterClassEx(&wc);
    if(RegisterClassEx(&wc)!=0)
    {
        MessageBox(NULL, TEXT("ERROR: Brak rejestracji"), TEXT("ERROR"), NULL);
        return 1;
    }
    Okna.push_back(CreateWindowEx(0, ClassName, TEXT("Okno"), WS_OVERLAPPEDWINDOW | WS_VISIBLE, 40,40, 300, 300, 0, 0, hInstance, 0 ));
    if(Okna.front() == NULL)
    {
        MessageBox(NULL, TEXT("ERROR: Brak okna"), TEXT("ERROR"), NULL);
        return 2;
    }
    ShowWindow(Okna.front(), nCmdShow);
    UpdateWindow(Okna.front());
    MSG msg;
    while(GetMessage(&msg,0,0,0))
    {
        TranslateMessage( &msg );
        DispatchMessage( &msg );
    }
    UnregisterClass( ClassName, hInstance );
    return static_cast<int>(msg.wParam);

}