std::pair<int, int> HelloMultitouchApp::normScreenToWindowPx(float screen_x, float screen_y){
    Vec2i rect = getWindowSize();

    int x_px;
    int y_px;
    if (!use_pixels)
    {
        x_px = static_cast<int>(screen_x * screen_width);
        y_px = static_cast<int>(screen_y * screen_height);
    }
    else
    {
        x_px = static_cast<int>(screen_x);
        y_px = static_cast<int>(screen_y);
    }

    int x = x_px - getWindowPosX();
    int y = y_px - getWindowPosY();

    return std::pair<int, int>(x, y);
}