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C Library Functions  - arrowhead (3)

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NAME

arrowhead(3f) - [M_drawplus] Draw arrow head (for text boxes and line markers) (LICENSE:MIT)

CONTENTS

Synopsis
Description
Example
Author
License

SYNOPSIS

subroutine arrowhead(xpoint,ypoint,xstart,ystart,size,idraw)

     real,intent(in)    :: xpoint,ypoint
     real,intent(in)    :: xstart,ystart
     real,intent(in)    :: size
     integer,intent(in) :: idraw

DESCRIPTION

given line segment

     START --> POINT

draw an arrow head of overall length SIZE measured along the line segment. The arrow head is 2/3 SIZE wide and the indent is 1/3 SIZE.

if IDRAW is 0, draw line from x3 to START to P3 and leave current position at POINT.

    >                o START
    >                |
    >                |
    >                |
    >                |
    >                |  1/3*size
    >                |<------->
    >                |
    >                |
    >   P1  o .      |      . o P2   ---------
    >        \  .    |   .   /         ^
    >         \   .  | .    /          |
    >          \     o P3  / -------   |
    >           \         /     ^     SIZE
    >            \       /      |      |
    >             \     /    2/3*SIZE  |
    >              \   /        V      V
    >               \ /      -----------------
    >                o POINT

EXAMPLE

Sample program:

   program demo_arrowhead
   use :: M_draw
   use :: M_drawplus, only : arrowhead
   implicit none
   real :: xpoint,ypoint, xstart,ystart
   real :: PI, ang, size
   integer :: i, idraw, idum
   call prefsize(600,600)
   call vinit(’’)
   call ortho2(-10.0,10.0,-10.0,10.0)
   call linewidth(100)
   call color(D_WHITE)
   call clear()
   xstart=0.0
   ystart=0.0
   size=1.00
   idraw=0

   call color(D_RED)
   xpoint=9.0
   ypoint=0.0
   call arrowhead(xpoint,ypoint,xstart,ystart,size,idraw)

   call color(D_GREEN)
   xpoint=9.0
   ypoint=9.0
   call arrowhead(xpoint,ypoint,xstart,ystart,size,idraw)

   call color(D_BLACK)
   idraw=-1
   PI=4.0*atan(1.0)
   ang=PI/2.0
   do i=1,20+1
      xpoint=9.0*cos(ang)
      ypoint=9.0*sin(ang)
      call arrowhead(xpoint,ypoint,xstart,ystart,size,idraw)
      ang=ang+PI/20.0
   enddo
   idum=getkey()
   call vexit()
   end program demo_arrowhead

AUTHOR

John S. Urban

LICENSE

MIT License

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Nemo Release 3.1

arrowhead (3)

February 23, 2025

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