FPS camera rotating by itself. QT 4.8 + OpenGL + C++ -

i'm trying port height map visualization program written on c++, sfml qt, can shown on widget , controlled gui elements.

the problem when start application, camera starts roll around center fast(actually, looks terrain mesh flying around camera, earth around sun :), without actions side(e.g moving mouse, pressing buttons).

camera should move forward, back, left, right when press w,a,s,d , around when move mouse(just typical fps camera behavior).

i think problem in program's main loop, because it's no standard while(true){ //do something// } approach in qt, , it's little confusing.

here's code:

oglwidget class(here i'm drawing stuff. problem somewhere here think) :

class oglwidget :     public qglwidget {     q_object  public:     oglwidget(qwidget *parent = 0);     ~oglwidget(void);  public:     void paintgl();     void initializegl();     void resizegl();  public:     void updatecamera();  public slots:     void mainloop();  protected:     void keypressevent(qkeyevent *e);     void keyreleaseevent(qkeyevent *e);  private:     terrain _terrain;     camera  _camera;  private:     int           _keypressed;     qtimer        _timer;     qelapsedtimer _elapsedtimer;     float         _simulationtime;     float         _fps; };   oglwidget::oglwidget(qwidget *parent)  : qglwidget(parent) {     _terrain.loadheightmap("normalheightmap256_2.png");      _camera.setscreendimension(this->width(), this->height());      //setting vertical sync     qglformat frmt;     frmt.setswapinterval(1);     setformat(frmt);      setmousetracking(true);      setfocus();      _simulationtime = 0;      _fps = 1.f / 60.f;      connect(&_timer, signal(timeout()), this, slot(mainloop()));     _timer.start();      _elapsedtimer.start(); }   oglwidget::~oglwidget(void) { }  void oglwidget::mainloop() {     _simulationtime += _elapsedtimer.elapsed();     _elapsedtimer.restart();      while(_simulationtime > _fps)     {         _simulationtime -= _fps;         updatecamera();     }      updategl(); }  void oglwidget::updatecamera() {     qpoint p = mapfromglobal(qcursor::pos());      _camera.computematrices(p.x(), p.y(), _fps, _keypressed);      glm::mat4 viewmatrix = _camera.getviewmatrix();     glm::mat4 projectionmatrix = _camera.getprojectionmatrix();     glm::mat4 modelmatrix = glm::mat4(1.0);      _terrain.setmvp(projectionmatrix * viewmatrix * modelmatrix);      qpoint center = maptoglobal(qpoint(this->width() / 2, this->height() / 2));     qcursor::setpos(center); }  void oglwidget::initializegl() {     glewexperimental = gl_true;      if (glewinit() != glew_ok)      {         return;     }      glviewport(0, 0, this->width(), this->height());     _terrain.init(); }  void oglwidget::paintgl() {     _terrain.draw(); }  void oglwidget::resizegl() {     glviewport(0, 0, this->width(), this->height()); }  void oglwidget::keypressevent(qkeyevent *e) {     switch(e->key())     {     case qt::key::key_escape:         exit(0);         break;      case qt::key::key_w:         _keypressed = key::key_pressed_up;         break;      case qt::key::key_s:         _keypressed = key::key_pressed_down;         break;      case qt::key::key_a:         _keypressed = key::key_pressed_left;         break;      case qt::key::key_d:         _keypressed = key::key_pressed_right;         break;     } }  void oglwidget::keyreleaseevent(qkeyevent *e) {     if(e->key() == qt::key::key_w ||        e->key() == qt::key::key_s ||        e->key() == qt::key::key_a ||        e->key() == qt::key::key_d)        _keypressed = key_released; } 

i'm absolutely sure terrain , camera classes working correct, because haven't changed code since sfml project(except of using qimage instead of sf::image, it's working correct too)

*camera main algorithm: *

void camera::computematrices(int mousexpos, int mouseypos, float deltatime, int keypressed) {     _horizontalangle += _mousespeed * deltatime * float(_screenwidth / 2 - mousexpos);     _verticalangle += _mousespeed * deltatime * float(_screenheight / 2 - mouseypos);      _direction = glm::vec3     (         cos(_verticalangle) * sin(_horizontalangle),         sin(_verticalangle),         cos(_verticalangle) * cos(_horizontalangle)     );      glm::vec3 right = glm::vec3     (         sin(_horizontalangle - 3.14f/2.0f),          0,         cos(_horizontalangle - 3.14f/2.0f)     );      glm::vec3 = glm::cross( right, _direction );      switch(keypressed)     {     case key::key_pressed_up:         _position += _direction * deltatime * _speed;         break;      case key::key_pressed_down:         _position -= _direction * deltatime * _speed;         break;      case key::key_pressed_left:         _position -= right * deltatime * _speed;         break;      case key::key_pressed_right:         _position += right * deltatime * _speed;         break;      case key::key_released:         break;     }      _projectionmatrix = glm::perspective(_initialfov, 4.0f / 3.0f, 0.1f, 1000.0f);      _viewmatrix = glm::lookat     (         _position,            // camera here         _position+_direction, // , looks here : @ same position, plus "direction"                            // head (set 0,-1,0 upside-down)     ); } 

help me fix issue.

ok, figured out problem spinning camera. cause of hardcoded aspect ratio in camera::computematrices, , used resolution of widget doesn't match it:

_projectionmatrix = glm::perspective ( _initialfov,  4.0f / 3.0f, //here 0.1f,  1000.0f ); 

i changed 4.0f / 3.0f on (float)_screenwidth / (float)_screenheight didn't too.

so changed resolution of widget 800 x 600 , helped.

the new problem it works on 4/3 dimensions(e.g 800x600, 1024x768).