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Manual Reference Pages  - viewport (3m_pixel)

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NAME

viewport(3f) - [M_pixel] Specify which part of the screen to draw in. (LICENSE:PD)

CONTENTS

Synopsis
Description
Example
Author
License

SYNOPSIS

definition:

   subroutine viewport(left, right, bottom, top)
   real,intent(in) :: left, right, bottom, top

DESCRIPTION

Specify which part of the screen to draw in. Left, right, bottom, and top are real values in screen coordinates (0:n,0:m).

If a pixel array has been declared to be real :: array(600,400)

        o-----> X                         (right=600,top=0)
        | #------------------------------------#
        | |                                    |
        | |                                    |
        V |                                    |
        Y |                                    |
          #------------------------------------#

(left=0,bottom=400)

EXAMPLE

Sample program

   program demo_viewport
   use :: M_pixel
   use :: M_pixel__writegif, only : writegif
   implicit none
      call prefsize(400, 400) ! set up drawing surface
      call vinit()
      call color(7)
      call linewidth(40)
      call clear()
      call ortho2(-88.0, 88.0, -88.0, 88.0)
      ! draw the same circle, just changing viewport

      call viewport(   0.0, 200.0,   0.0, 200.0 ); call draw_circle(1)
      call viewport( 200.0, 400.0,   0.0, 200.0 ); call draw_circle(2)
      call viewport(   0.0, 200.0, 200.0, 400.0 ); call draw_circle(3)
      call viewport( 200.0, 400.0, 200.0, 400.0 ); call draw_circle(4)
      call viewport( 250.0, 350.0, 150.0, 300.0 ); call draw_circle(5)

      call writegif(’viewport.3M_pixel.gif’,P_pixel,P_colormap)
      !call execute_command_line(’display viewport.3M_pixel.gif’)
      call vexit()
   contains
   subroutine draw_circle(icolor)
   integer,intent(in) :: icolor
      call color(0)
      call rect(-88.0,-88.0,88.0,88.0)
      call color(icolor)
      call makepoly()
      call circle(0.0,0.0,88.0)
      call closepoly()
   end subroutine draw_circle
   end program demo_viewport

AUTHOR

John S. Urban

LICENSE

Public Domain

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Nemo Release 3.1

viewport (3m_pixel)

April 21, 2023

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