Hi i am working on college task that involve a recursion drawing question and i am working with Qt.
my problem when the drawing function begin, the gui freezing until drawing finish,even though i used multi threading .
is there any way to avoid freezing while repainting main window ???
here is the code:
Qt Code: 
  1. class draw:public QThread
  2. {
  3. public :
  5.     QWidget *t;
  6.     draw(){}
  7.     void run()
  8.     {
  9.         Drawing(10,40,0,3.1415926535897932384626433832795/4,200,200,d);
  10.     }
  11.  
  12.     void Drawing(int n,double d,double q1,double q2,int x,int y,QPainter *dr)
  13.     {
  14.         if (n > 0)
  15.         {
  16.             int x1 = x - (sin(q1) * d);
  17.             int y1 = y - (cos(q1) * d);
  18.             dr->drawLine(x, y, x1, y1);
  19.             t->repaint();
  20.             int x2 = x1- (cos(q1) * d);
  21.             int y2 = y1 + (sin(q1) * d);
  22.             dr->drawLine(x1, y1, x2, y2);
  23.             t->repaint();
  24.             int x3 = x2 + (sin(q1) * d);
  25.             int y3 = y2 + (cos(q1) * d);
  26.             dr->drawLine(x2 , y2 , x3 , y3);
  27.             t->repaint();
  28.             dr->drawLine(x3 , y3 , x , y );
  29.             t->repaint();
  30.             double d1 = d / sqrt( 2.0 );      //d1 = d/?2
  31.             int x4 = x1 - ( cos(q2) * d1);
  32.             int y4 = y1 - ( sin(q2) * d1);            
  33.             Drawing(n - 1, d1, q1 - 3.1415926535897932384626433832795/4, q2 + 3.1415926535897932384626433832795/4 , x1 , y1,dr);
  34.  
  35.             Drawing(n - 1, d1, q1 + 3.1415926535897932384626433832795/4, q2 - 3.1415926535897932384626433832795/4 , x4 , y4,dr);
  36.         }
  37.     }
  38. };
  39.  
  40.  
  41. void MainWindow::on_pushButton_clicked()
  42. {
  43.     image=new QPixmap(this->geometry().width(),this->geometry().height());
  44.     image->fill(this,0,0);
  45.     dr=new QPainter(this->image);
  46.     r=this->geometry();
  47.     draw d;
  48.     d.d=dr;
  49.     d.t=this;
  50.     d.run();
  51.     delete dr;
  52. }
  53.  
  54.  
  55.  
  56.  
  57.  
  58. void MainWindow::paintEvent(QPaintEvent *e)
  59. {
  60.     QPainter p(this);
  61.     p.drawPixmap(r,*this->image);
  62. }
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