winPeep

#include <windows.h>

int gScreenHeight; /* A global variable used to store the height of the screen. */
const int TM = 20; /* Change this value if you want a different top margin. */
const int BM = 60; /* Change this value if you want a different bottom margin, but mind the task bar. */
const int timerInterval = 40; /* Increase this value if you want smoother movement (be careful with that). */

void peepWindow()
{
    /* Retrieve the handle to the foreground window. */
    HWND hwnd = GetForegroundWindow();
    /* Obtain dimensions of the foreground window. */
    RECT wndRect;
    GetWindowRect(hwnd, &wndRect);
    int wndHeight = wndRect.bottom - wndRect.top;
    /* Check if the foreground window height is greater than the screen height excluding the previously set margins. */
    if(wndHeight > gScreenHeight - TM - BM)
    {
        /* Obtain the mouse cursor position. */
        POINT mousePoint;
        GetCursorPos(&mousePoint);
        /* Calculate a new position of the foreground window. */
        double C = ((double)(wndHeight))/((double)(TM + BM - gScreenHeight));
        int newWndPos = (int)((1.0+C)*((double)(mousePoint.y)) - C*((double)(TM)));
        /* Place the foreground window in the new position. */
        SetWindowPos(hwnd, NULL, wndRect.left, newWndPos, 100, 100, SWP_NOSIZE);
    }
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT Message, WPARAM wParam, LPARAM lParam)
{
    switch(Message)
    {
        case WM_DESTROY:
        {
            PostQuitMessage(0);
            break;
        }
        case WM_TIMER:
        {
            peepWindow();
            break;
        }
        default:
            return DefWindowProc(hwnd, Message, wParam, lParam);
    }
    return 0;
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
    /* Set the global variable. */
    gScreenHeight = GetSystemMetrics(SM_CYSCREEN);

    WNDCLASSEX wc;
    HWND hwnd;
    MSG Msg;

    memset(&wc,0,sizeof(wc));
    wc.cbSize        = sizeof(WNDCLASSEX);
    wc.lpfnWndProc   = WndProc;
    wc.hInstance     = hInstance;
    wc.hCursor       = LoadCursor(NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
    wc.lpszClassName = "WindowClass";
    wc.hIcon         = LoadIcon(NULL, IDI_APPLICATION);
    wc.hIconSm       = LoadIcon(NULL, IDI_APPLICATION);

    if(!RegisterClassEx(&wc))
    {
        MessageBox(NULL, "Window Registration Failed!","Error!",MB_ICONEXCLAMATION|MB_OK);
        return 0;
    }

    hwnd = CreateWindowEx(WS_EX_CLIENTEDGE,"WindowClass","winPeep",WS_VISIBLE|WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        640,
        480,
        NULL,NULL,hInstance,NULL);

    if(hwnd == NULL)
    {
        MessageBox(NULL, "Window Creation Failed!","Error!",MB_ICONEXCLAMATION|MB_OK);
        return 0;
    }

    /* Create a timer. */
    SetTimer(hwnd, 1, timerInterval, (TIMERPROC)NULL);

    while(GetMessage(&Msg, NULL, 0, 0) > 0)
    {
        TranslateMessage(&Msg);
        DispatchMessage(&Msg);
    }
    return Msg.wParam;
}