; Viewport Example
; ----------------

Graphics 640,480,0,2
SetBuffer BackBuffer()

SeedRnd MilliSecs()

; Bouncing balls that roam the whole screen
Dim bx#(7),by#(7),vx#(7),vy#(7)
For i=0 To 7
    bx(i)=Rnd(0,600)
    by(i)=Rnd(40,440)
    vx(i)=Rnd(2,4)
    vy(i)=Rnd(2,4)
Next

port=1

While Not KeyDown(1)

    ; Space toggles the clipping viewport on and off
    If KeyHit(57) Then port=1-port

    ; Full-screen viewport first so Cls wipes everything
    Viewport 0,0,640,480
    Cls

    ; Show where the clipping window sits
    Color 80,80,80
    Rect 158,118,324,244,0

    ; Restrict all following drawing to a 320x240 window
    If port Then Viewport 160,120,320,240

    ; The balls still move everywhere, but drawing is clipped when on
    For i=0 To 7
        bx(i)=bx(i)+vx(i)
        by(i)=by(i)+vy(i)
        If bx(i)<0 Or bx(i)>604 Then vx(i)=-vx(i)
        If by(i)<0 Or by(i)>444 Then vy(i)=-vy(i)
        Color 60+i*24,180,255-i*24
        Oval bx(i),by(i),36,36,1
    Next

    ; Back to full screen so the overlay is never clipped
    Viewport 0,0,640,480
    Color 255,255,255
    Text 0,0,"Space: toggle clipping   Esc: exit"
    If port Then
        Text 0,20,"Viewport 160,120,320,240 - drawing is clipped to the grey box"
    Else
        Text 0,20,"Viewport 0,0,640,480 - full screen, no clipping"
    EndIf

    Flip

Wend

End