C Library Functions - viewport (3)
NAME
viewport(3f) - [M_draw:VIEWPORT] Specify which part of screen to draw in (LICENSE:PD)
CONTENTS
Synopsis
Description
Examples
SYNOPSIS
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 device has been declared to be 600 x 400
o-----> X (right=600,top=0) | #------------------------------------# | | | | | | V | | Y | | #------------------------------------#(left=0,bottom=400)
EXAMPLES
Sample program:
program demo_viewport ! ! using non-square viewports, ! the associated distortion -- and how to fix it ! use M_draw implicit nonecharacter(len=50) :: device character(len=120) :: buf real xfact, yfact integer :: ios, idum
print*,’Enter output device:’ read(*,’(a)’,iostat=ios)device if(ios.ne.0)device=’ ’
call vinit(device)
call color(D_BLACK) call clear() ! ! Make the viewport the same size as the screen/window. ! call getfactors(xfact, yfact) call viewport(-1.0, xfact, -1.0, yfact) ! ! Draw a square. (Looks like a rectangle, if the viewport ! wasn’t "accidentally" square) ! call color(D_RED) call rect(-0.5, -0.5, 0.5, 0.5) ! ! Tell them what it is. ! call move2(-1.0, 0.9) write(buf,& & ’(’’Distorted square (viewport(-1, ’’, F7.3, ’’, -1, ’’, F7.3, ’’))’’)’)& & xfact, yfact call drawstr(buf)
idum=getkey() ! ! Fix up the distortion (The actual formula to fix ! the distortion is (viewport.xmax * (1 + xfact) / 2.0), ! and similar for the y axis. ! call ortho2(-1.0, xfact, -1.0, yfact) ! ! Draw another square (Really is square this time) ! call color(D_YELLOW) call rect(-0.5, -0.5, 0.5, 0.5) ! ! Tell them what it is. ! call move2(-1.0, -0.9) write(buf,& & ’(’’Fixed up square with ortho2(-1, ’’, F7.3, ’’, -1, ’’, F7.3, ’’)’’)’)& & xfact, yfact call drawstr(buf)
idum=getkey() ! ! Do it with world coords going from 0 - 5, 0 - 5. ! Reset square viewport. ! call color(D_BLACK) call clear()
call viewport(-1.0, 1.0, -1.0, 1.0) call ortho2(0.0, 5.0, 0.0, 5.0) call textsize(0.1, 0.1) ! ! Square from 1 to 3. (Really is square) ! call color(D_GREEN) call rect(1.0, 1.0, 3.0, 3.0)
call move2(0.0, 4.5) call drawstr(’Square from 0 - 3, 0 - 3’)
idum=getkey() ! ! Distort it with a non-square viewport. ! call viewport(-1.0, xfact, -1.0, yfact)
call color(D_BLUE) call rect(1.0, 1.0, 3.0, 3.0)
call move2(0.0, 0.5) call drawstr(’Distorted square from 0 - 3, 0 - 3’)
idum=getkey() ! ! Fix the distortion. ! call ortho2(0.0, 5.0 * (1.0 + xfact) / 2.0, 0.0, 5.0 * (1.0 + yfact) / 2.0)
call color(D_MAGENTA) call rect(1.0, 1.0, 3.0, 3.0)
call move2(0.0, 2.5) call drawstr(’Fixed up square from 0 - 3, 0 - 3’)
idum=getkey()
call vexit()
end program demo_viewport
| Nemo Release 3.1 | viewport (3) | February 23, 2025 |
