Customizing shapes using moving points by mouse - mfc

Question

I want to make 4 clicks using mouse in the client area. Once the 4th click is done, the 4 points should be connected to form a shape.I did this using the following code.(I am using MFC).
void CChildView::OnLButtonDown(UINT nFlags,CPoint point)
{
CDC* pDC=GetDC();
if(m_iPointCount==1)
{
m_FirstPoint.x=point.x;
m_FirstPoint.y=point.y;
pDC->TextOut(m_FirstPoint.x,m_FirstPoint.y,"1");
rgn1.CreateEllipticRgn((m_FirstPoint.x-50),(m_FirstPoint.y-50),(m_FirstPoint.x+50),(m_FirstPoint.y+50));
}
if(m_iPointCount==2)
{
m_SecondPoint.x=point.x;
m_SecondPoint.y=point.y;
pDC->TextOut(m_SecondPoint.x,m_SecondPoint.y,"2");
rgn2.CreateEllipticRgn((m_SecondPoint.x-50),(m_SecondPoint.y-50),(m_SecondPoint.x+50),(m_SecondPoint.y+50));
}
if(m_iPointCount==3)
{
m_ThirdPoint.x=point.x;
m_ThirdPoint.y=point.y;
pDC->TextOut(m_ThirdPoint.x,m_ThirdPoint.y,"3");
rgn3.CreateEllipticRgn((m_ThirdPoint.x-50),(m_ThirdPoint.y-50),(m_ThirdPoint.x+50),(m_ThirdPoint.y+50));
}
if(m_iPointCount==4)
{
m_FourthPoint.x=point.x;
m_FourthPoint.y=point.y;
pDC->TextOut(m_FourthPoint.x,m_FourthPoint.y,"4");
rgn4.CreateEllipticRgn((m_FourthPoint.x-50),(m_FourthPoint.y-50),(m_FourthPoint.x+50),(m_FourthPoint.y+50));
pDC->MoveTo(m_FirstPoint.x,m_FirstPoint.y);
pDC->LineTo(m_SecondPoint.x,m_SecondPoint.y);
pDC->LineTo(m_ThirdPoint.x,m_ThirdPoint.y);
pDC->LineTo(m_FourthPoint.x,m_FourthPoint.y);
pDC->LineTo(m_FirstPoint.x,m_FirstPoint.y);
}
m_iPointCount++;
}
Each time the point count is incremented.I have also created 4 regions around 4 points.What I want to do now is, when I click in any of the regions I created and drag it to a new place the point should move to the new place where the mouse button is released after dragging. So that the shape is changed. This should be applicable to all the 4 regions.
I know I have to use Mousemove and LButtonUp functions but I have no idea how to do it. Pls help .

Answer 1

Hi I finally figured out how to do this.
The OnPaint event is as follows:
void CChildView::OnPaint()
{
CPaintDC dc(this); // device context for painting
{
dc.MoveTo(m_FirstPoint.x,m_FirstPoint.y);
dc.LineTo(m_SecondPoint.x,m_SecondPoint.y);
dc.LineTo(m_ThirdPoint.x,m_ThirdPoint.y);
dc.LineTo(m_FourthPoint.x,m_FourthPoint.y);
dc.LineTo(m_FirstPoint.x,m_FirstPoint.y);
}
}
The LButtonDown is as follows:
void CChildView::OnLButtonDown(UINT nFlags,CPoint point)
{
CDC* pDC=GetDC();
if(m_iPointCount==1)
{
m_FirstPoint.x=point.x;
m_FirstPoint.y=point.y;
pDC->TextOut(m_FirstPoint.x,m_FirstPoint.y,"1");
rgn1.CreateEllipticRgn((m_FirstPoint.x-50),(m_FirstPoint.y-50),(m_FirstPoint.x+50),(m_FirstPoint.y+50));
}
if(m_iPointCount==2)
{
m_SecondPoint.x=point.x;
m_SecondPoint.y=point.y;
pDC->TextOut(m_SecondPoint.x,m_SecondPoint.y,"2");
rgn2.CreateEllipticRgn((m_SecondPoint.x-50),(m_SecondPoint.y-50),(m_SecondPoint.x+50),(m_SecondPoint.y+50));
}
if(m_iPointCount==3)
{
m_ThirdPoint.x=point.x;
m_ThirdPoint.y=point.y;
pDC->TextOut(m_ThirdPoint.x,m_ThirdPoint.y,"3");
rgn3.CreateEllipticRgn((m_ThirdPoint.x-50),(m_ThirdPoint.y-50),(m_ThirdPoint.x+50),(m_ThirdPoint.y+50));
}
if(m_iPointCount==4)
{
m_FourthPoint.x=point.x;
m_FourthPoint.y=point.y;
pDC->TextOut(m_FourthPoint.x,m_FourthPoint.y,"4");
rgn4.CreateEllipticRgn((m_FourthPoint.x-50),(m_FourthPoint.y-50),(m_FourthPoint.x+50),(m_FourthPoint.y+50));
InvalidateRect(0);
}
if(m_iPointCount>4)
{
if(PtInRegion(rgn1,point.x,point.y))
{
m_fflag=true;
}
if(PtInRegion(rgn2,point.x,point.y))
{
m_sflag=true;
}
if(PtInRegion(rgn3,point.x,point.y))
{
m_tflag=true;
}
if(PtInRegion(rgn4,point.x,point.y))
{
m_foflag=true;
}
}
m_iPointCount++;
}
The MouseMove as follows:
void CChildView::OnMouseMove(UINT nFlags,CPoint point)
{
if(m_iPointCount>4)
if((nFlags & MK_LBUTTON)==MK_LBUTTON)
{
if(m_fflag==true)
{
m_FirstPoint=point;
InvalidateRect(0);
}
if(m_sflag==true)
{
m_SecondPoint=point;
InvalidateRect(0);
}
if(m_tflag==true)
{
m_ThirdPoint=point;
InvalidateRect(0);
}
if(m_foflag==true)
{
m_FourthPoint=point;
InvalidateRect(0);
}
}
}
The LButtonUp event is as follows:
void CChildView::OnLButtonUp(UINT nFlags,CPoint point)
{
CDC* pDC=GetDC();
if(m_fflag==true)
{
m_fflag=false;
rgn1.DeleteObject();
rgn1.CreateEllipticRgn((m_FirstPoint.x-50),(m_FirstPoint.y-50),(m_FirstPoint.x+50),(m_FirstPoint.y+50));
}
if(m_sflag==true)
{
m_sflag=false;
rgn2.DeleteObject();
rgn2.CreateEllipticRgn((m_SecondPoint.x-50),(m_SecondPoint.y-50),(m_SecondPoint.x+50),(m_SecondPoint.y+50));
}
if(m_tflag==true)
{
m_tflag=false;
rgn3.DeleteObject();
rgn3.CreateEllipticRgn((m_ThirdPoint.x-50),(m_ThirdPoint.y-50),(m_ThirdPoint.x+50),(m_ThirdPoint.y+50));
}
if(m_foflag==true)
{
m_foflag=false;
rgn4.DeleteObject();
rgn4.CreateEllipticRgn((m_FourthPoint.x-50),(m_FourthPoint.y-50),(m_FourthPoint.x+50),(m_FourthPoint.y+50));
}
}
Here is how this works:
1)An integer m_iPointCount is initialized to 1. This is used to store the number of points.
2) Four flags are initially set to false m_fflag=false;m_sflag=false;
m_tflag=false;m_foflag=false;(Four flags corresponds to four points of the polygon).
3)When the mouse is clicked for first 4 times the 4 points are saved in m_Firstpoint,m_Secondpoint,m_Thirdpoint and m_Fourthpoint.Correspondingly four regions are created(rgn1,rgn2,rgn3,rgn4 near to the 4 points). The 4 points are connected to form a polygon.
4)When the click is made for the 5th time(after we get the polygon),the check is made using if condition to find out the point lies in any one of the 4 regions.Accordingly the flags are set to true.(If the point lies in rgn1 then m_fflag is set to true and so on).
5)Consider the 5th click is made in rgn1 and now m_fflag is true,and the mouse is moved,Here the points used to draw the polygon in the paint message is updated and paint method is called using InvalidateRect(0). The polygon is redrawn.The m_Firstpoint is now updated to the new position.
6)When the mouse button is released after dragging,the flag is set to false and the old region is deleted and created near the new point.So that the region is also updated.
7) I have explained it for the first point, This is applicable for all the points.
Thanks.