!@(#)  This program shows some of the simple primitives.
!
        program fshapes

#include "interface.h"

        integer   BLACK, RED, GREEN, BLUE, MAGENTA, WHITE
        parameter(BLACK = 0)
        parameter(RED = 1, GREEN = 2, BLUE = 4, MAGENTA = 5, WHITE = 7)
        character*50 device

        print*,'Enter output device:'
        read(*,'(a)')device

        call vinit(device)

! 
! the two lines below clear the screen to white if we have
! colours, on a monochrome device color is ignored so the
! screen will be cleared to its background color, normally black.
!
        call color(BLACK)
        call clear()

!
! set the screen to be 2.0 units wide and 2.0 units wide, with
! the drawable coordinates going from -1.0 to 1.0.
!
        call ortho2(-1.0, 1.0, -1.0, 1.0)

!
! set the text size. After this call no characters in the
! current font will be wider than 0.1 or higher than 0.1 in
! world units. As the window is currently 2.0 units wide and
! 2.0 units high text will be about one twentieth of the screen
! size.
!
        call textsize(0.1, 0.1)

        call color(MAGENTA)

!
! okay, so we want to draw in the range -1 to 1, but we
! only want to draw in the top lefthand corner of the
! screen. The call to viewport allows us to do this. As
! viewport always takes screen coordinates, which are 
! always in the range of -1 to 1 we can change always
! change the viewport to somewhere else on the screen
! by giving a range in -1 to 1.
!
        call viewport(-1.0, 0.0, 0.0, 1.0)

!
! write out a heading
!
        call move2(-0.9, -0.5)
        call drawstr('rect')

!
! draw a rectangle around the points (-0.2, -0.2), (-0.2, 0.2),
! (0.3, 0.2), and (0.3, -0.2).
!
        call rect(-0.2, -0.2, 0.3, 0.2)

        call color(BLUE)

!
! now we want to draw in the top right corner of the screen
!
        call viewport(0.0, 1.0, 0.0, 1.0)

        call move2(-0.9, -0.5)
        call drawstr('circle')

!
! draw a circle of radius 0.4 around the point (0.0, 0.0)
!
        call circle(0.0, 0.0, 0.4)

        call color(GREEN)

!
! draw in bottom left corner 
!
        call viewport(-1.0, 0.0, -1.0, 0.0)

        call move2(-0.9, -0.5)
        call drawstr('ellipse')

!
! To draw an ellipse we change the aspect ratio so it is no longer
! 1 and call circle. In this case we use ortho2 to make the square
! viewport appear to be higher than it is wide. Alternatively you
! could use arc to construct one.
!
! The call to pushmatrix saves the current viewing transformation.
! After the ortho2 has been done, we restore the current viewing
! transformation with a call to popmatrix. (Otherwise everything
! after the call to ortho would come out looking squashed as the
! world aspect ratio is no longer 1).
!
        call pushmatrix()
                call ortho2(-1.0, 1.0, -1.0, 2.0)
                call circle(0.0, 0.5, 0.4)
        call popmatrix()

        call color(RED)
!
! now draw in bottom right corner
!
        call viewport(0.0, 1.0, -1.0, 0.0)

        call move2(-0.9, -0.5)
        call drawstr('arc')

!
! draw an arc centered at (0.0, 0.0), radius of 0.4. 0.0 is the start
! angle and 90.0 is the end angle of the arc being drawn. So this
! draws a quarter circle.
!
        call arc(0.0, 0.0, 0.4, 0.0, 90.0)

        idum=getkey()

        call vexit()

        end