Scroll Back Screen

 BBS: Inland Empire Archive
Date: 04-11-92 (13:54)             Number: 153
From: JEAN CREPEAU                 Refer#: NONE
  To: MARK SWEENEY                  Recvd: NO  
Subj: Scroll Back Screen             Conf: (2) Quik_Bas

In a message to ALL, MARK SWEENEY wrote:
MS=> I'm trying to write a frontend for an online game on delphi. I need  a
    scroll back  screen like  the one  in telix  but am  not sure how to go
    about writeing it any help would be welcome.

        You could try  to store each  line in a  different string variable.
You just have to use a string array as a queue. For example, if you want to
remember 1000 lines, use the following routines:

'****************************************************************
'* Initial Scroll Back buffer                                   *
'****************************************************************
DIM SHARED ScrlBack$(999)               ' To remeber 1000 lines

'****************************************************************
'* This subroutine clears the Scroll Back buffer                *
'****************************************************************
SUB ClearQueue
SHARED QSize,QCur
QSize=0
QCur=0
ERASE ScrlBack$
END SUB

'****************************************************************
'* This subroutine adds a line in the Scroll Back buffer        *
'* If the Buffer is full, the oldest line is removed            *
'* Entry: X$ contains the line to add to the queue              *
'****************************************************************
SUB WriteQueue(x$)
SHARED QSize,QCur
ScrlBack$(QCur)=x$
QCur=QCur+1
        IF QCur>UBOUND(ScrlBack$,1) THEN QCur=0
        IF QSize<UBOUND(ScrlBack$,1)+1 THEN QSize=QSize+1
END SUB

'****************************************************************
'* This subroutine reads a line from the scroll back buffer     *
'* Entry: N is the line number                                  *
'*      if N=>0, N represents the Nth line in the buffer        *
'*      if N<0, N represents the -Nth last line in the buffer   *
'*              (N=0 returns the first line, N=1 the second     *
'*                      one, while N=-1 returns the last one)   *
'* Exit: ReadQueue$ is the line in the buffer if it exists      *
'*      Blank lines are added a space (ASCII 20h).              *
'*      If the line number is out-of-range, ReadQueue$ = ""     *
'****************************************************************
FUNCTION ReadQueue$(n)
SHARED QSize,QCur
ARS=UBOUND(ScrlBack$,1)+1
IF N<0 AND QSize+N=>0 THEN
        Q=QCur-N
        IF Q=>ARS THEN Q=Q-ARS
ELSEIF N=>0 AND QSize>N THEN
        Q=QCur-QSize+N
        IF Q<0 THEN Q=Q+ARS
ELSE
        Q=-1
ENDIF
IF Q<0 THEN
        Z$=""
ELSE
        Z$=ScrlBack$(Q):IF Z$="" THEN Z$=" "
ENDIF
ScrlBack$=Z$
END FUNCTION
---
 * Origin: INTERACESS Montreal (QC) Canada (514) 528-1415 (1:167/280)