mfc - Dragging points to change the shapes -

i have managed connect 4 points mouse click made using following code.(i using mfc).

  void cchildview::onlbuttondown(uint nflags,cpoint point)   {       if(m_lastpoint.x!=-1 && m_ipointamount<6)   {     cdc* pdc= getdc();     pdc->moveto(m_lastpoint.x,m_lastpoint.y);     pdc->lineto(point.x,point.y);   }     m_lastpoint=point;     m_ipointamount++;   } 

the variables initialized in constructor follows.

 m_lastpoint.x=-1;  m_lastpoint.y=-1;  m_ipointamount=1; 

i want following now.

1.whenever mouse click made on 1 of points , dragged, point should relocate new position.(so shape changed).

2.this should applicable 4 points.

pls guide me on how achieve this.

how works

start clicking on window until reach amount sepcified in m_ipolygonmaximumsides. when reach amount of points specified polygon closed, able select point. click near point select it, drag keep going until click again. reset polygon have close window.

code

in cpp file of cchildview class add following include, because used calculate square root

#include <math.h> 

in cchildview class add following methods , variables

clist<cpoint> m_pointlist; cpoint m_selectedpoint; int m_ipolygonmaximumsides; afx_msg void onmousemove(uint nflags, cpoint point); void drawpolygonfromlist(); 

in message map of cchildview class add these lines

on_wm_lbuttondown() on_wm_mousemove() 

in cchildview constructor initialize m_ipolygonmaximumsides amount want (4) , m_selectedpoint (-1,-1) like

m_ipolygonmaximumsides = 4; m_selectedpoint = cpoint(-1,-1); 

then added cchildview cpp file, these moethods used

void cchildview::onlbuttondown(uint nflags, cpoint point) {      //check if reached maximum point number     if (m_pointlist.getsize() == m_ipolygonmaximumsides)     {         //check if point selected, , in drag mode         if (m_selectedpoint.x !=-1)         {             //if point selected means want stop dragging,             //so set x -1             m_selectedpoint.x =-1;         }         else         {             //if didn't have point selected have check if point clicked 1 of our points             //so use search out point             (position pos = m_pointlist.getheadposition();pos != null;m_pointlist.getnext(pos))             {                 cpoint currentpoint = m_pointlist.getat(pos);                 //this pythagorean theorem find distance between 2 points , b                 // distance = squareroot( (a.x-b.x)^2+(a.y-b.y)^2)                 int distancebetweenpoints = floor(sqrt(pow(double(currentpoint.x-point.x),2)+pow(double(currentpoint.y-point.y),2)));                 //if distance less 10 pixels, accept click on our points                 //this tollerance, can reduce or increment                 //the smaller tollerance nearer have click able select point                 if (distancebetweenpoints <= 10)                 {                     //if tollerance met set point our selected point                     m_selectedpoint = currentpoint;                     //interrupt iteration, because don't need further                     break;                 }             }         }     }     //if didn't reach maximum point amount means still have keep going on getting points     else if (m_pointlist.getsize() > 0)     {         cdc* pdc= getdc();         cpoint lastpoint = m_pointlist.gettail();         //draw line previous (last) point new 1         pdc->moveto(lastpoint.x,lastpoint.y);         pdc->lineto(point.x,point.y);          //if going reach maximum amount of points have close polygon         if (m_pointlist.getsize()==m_ipolygonmaximumsides-1)         {             cpoint firstpoint = m_pointlist.gethead();             //draw line current point first point             pdc->moveto(point.x,point.y);             pdc->lineto(firstpoint.x,firstpoint.y);         }     }     //add point list after have done everything, if didn't reachthe maximum amount     if (m_pointlist.getsize() < m_ipolygonmaximumsides)         m_pointlist.addtail(point); }   void cchildview::onmousemove(uint nflags, cpoint point) {     //check if have maximum number of points     if (m_pointlist.getsize()==m_ipolygonmaximumsides)     {         //check         if (m_selectedpoint.x != -1)         {             //check if find point             position posfound = m_pointlist.find(m_selectedpoint);             if (posfound != null)             {                 //update selected point new 1                 m_selectedpoint=point;                 //now update list                 m_pointlist.setat(posfound,point);                 //draw polygon                 drawpolygonfromlist();             }         }     } }  void cchildview::drawpolygonfromlist() {     //this checked again because might want use function in place     if (m_pointlist.getsize()==m_ipolygonmaximumsides)     {         //use clear window         redrawwindow();         //this used draw         cdc* pdc= getdc();         position pos = m_pointlist.getheadposition();         //load first , second point         cpoint pointbefore = m_pointlist.getnext(pos);         cpoint currentpoint = m_pointlist.getnext(pos);         //draw line connecting first , second point         pdc->moveto(pointbefore.x,pointbefore.y);         pdc->lineto(currentpoint.x,currentpoint.y);          //draw intermediary points         while (pos != null)          {             pointbefore = currentpoint;             currentpoint = m_pointlist.getnext(pos);             pdc->moveto(pointbefore.x,pointbefore.y);             pdc->lineto(currentpoint.x,currentpoint.y);         }          //now close poligon         pointbefore = currentpoint;         currentpoint = m_pointlist.gethead();         pdc->moveto(pointbefore.x,pointbefore.y);         pdc->lineto(currentpoint.x,currentpoint.y);     } }