How to draw a straight line with a solid arrow in MFC

Work encountered in the flow of the project, need to draw a straight line with arrows, after groping, solve;

(1) two points (P1,P2) determine a line, with one end of the line (assuming P2) as the origin, set an angle

(2) the vector P2P1 (p) is obtained at the origin of the P2, the vector p rotates theta angle to get the vector P1, the vector p rotates-theta angle to get the vector P2

(3) Stretch vector to length, translate variable to end of line

(4) Now there are 3 points, draw the line can be

The specific code is as follows:

void Cworkflowdlg::D rawline (CPoint p1, CPoint p2) {CCLIENTDC dc (this);//Get Client window DC CPen pen,pen1,*oldpen; int penlinewidth=2;//to set the size of the arrows according to the line width pen.    CreatePen (Ps_solid, Penlinewidth, RGB (0, 0, 0)); Pen1.    CreatePen (Ps_solid, Penlinewidth, RGB (0, 0, 0)); Oldpen=dc.        SelectObject (&pen);    Double theta=3.1415926/15*penlinewidth;//converted to radians double px,py,p1x,p1y,p2x,p2y;    The vector p2p1 (P) px=p1.x-p2.x is obtained with P2 as the origin.    PY=P1.Y-P2.Y;    Vector p Rotates theta angle to get vector P1 P1x=px*cos (theta)-py*sin (theta);    P1y=px*sin (theta) +py*cos (theta);    Vector p rotates-theta angle to get vector P2 P2x=px*cos (-theta)-py*sin (-theta);    P2y=px*sin (-theta) +py*cos (-theta);    Stretch vector to length double x1,x2;    int length=10;    X1=SQRT (P1X*P1X+P1Y*P1Y);    p1x=p1x*length/x1;    p1y=p1y*length/x1;    X2=SQRT (P2X*P2X+P2Y*P2Y);    p2x=p2x*length/x2;    p2y=p2y*length/x2;    Shift the variable to the end of the line p1x=p1x+p2.x;    P1Y=P1Y+P2.Y;    p2x=p2x+p2.x;        P2Y=P2Y+P2.Y; dc.    MoveTo (P1.X,P1.Y); dc.    LineTo (P2.X,P2.Y); dc. SelectObject (&p en1); dc.    MoveTo (P2.X,P2.Y); dc.    LineTo (P1X,P1Y); dc.    MoveTo (P2.X,P2.Y); dc.    LineTo (P2X,P2Y); dc.    MoveTo (P1X,P1Y); dc.    LineTo (P2X,P2Y);    CPoint Ptvertex[3];    ptvertex[0].x = p2.x;    Ptvertex[0].y = p2.y;    ptvertex[1].x = p1x;    Ptvertex[1].y = p1y;    ptvertex[2].x = P2X;        Ptvertex[2].y = P2Y;      Fill Triangle Area CBrush br (RGB (40,130,170));     CRGN Rgn; Rgn.    CreatePolygonRgn (ptvertex,3,alternate); dc.      Fillrgn (&rgn, &BR); dc.    SelectObject (Oldpen); Br.      DeleteObject (); Rgn.   DeleteObject ();}

In this case, the CREATEPOLYONRGN function is used as follows:

BOOL Crgn::createpolygonrgn (lppoint lpPoints, int ncount, int nmode); [description] Creates an area surrounded by a series of points. Windows automatically connects the last point to the 1th when needed to close the polygon [parameter table]lppoint--------The first POINTAPI structure in Pointapi,ncount POINTAPI structure ncount---------Long, The polygon's number of points Npolyfillmode-Long, which describes the polygon fill pattern. Can be a alternate or winding constant. Npolyfillmode is alternate by default, mode alternate: It draws a ray horizontally from a point in the enclosing area to infinity, and the enclosing area is filled only when the ray crosses an odd number of border lines, which is not populated if even. , Mode winding: method, such as an odd number, fill the area, if the even is the direction of the border line to judge: if the border line through the border lines in different directions of equal numbers, then not filled, such as unequal, is filled. [Return value] Long, execution succeeds for the created zone handle, failure is 0

How to draw a straight line with a solid arrow in MFC