SUB TrueView (FileName$, ULRow%, ULCol%, LRRow%, LRCol%, FGColr%, BGColr%, TBColrFG%, TBColrBG%, TBNumColrFG%, TBNumColrBG%, EOFColrFG%, EOFColrBG%)

    ' +----------------------------------------------------------------------+
    ' |                                                                      |
    ' |           ð  T R U E V I E W   F I L E   B R O W S E R  ð            |
    ' |              - - - - - - - -   - - - -   - - - - - - -               |
    ' |    (This SUB can be very easily made into a stand alone program.)    |
    ' +----------------------------------------------------------------------+
    ' +----------------------------------------------------------------------+
    ' |  TrueView.Bas written by Don Smith on 05/20/2002.  Written for       |
    ' |  QuickBASIC 4.5.  No special libraries are needed.  Released to      |
    ' |  the public domain. Programmers need not give my name. They can      |
    ' |  even change the name of the program.                                |
    ' |                                                                      |
    ' |  If this is to be made into a stand alone program, programmers       |
    ' |  will probably want to include an error screen using:                |
    ' |                   ON ERROR GOTO errorhandler                         |
    ' |----------------------------------------------------------------------|
    ' |  Information about the author:                                       |
    ' |  ----------------------------                                        |
    ' |  Hello, my name is Don Smith and I am a retired Math/History/Spanish |
    ' |  teacher currently residing in Orange County, California.            |
    ' |                                                                      |
    ' |  My email is: smithdonb@earthlink.net                                |
    ' |----------------------------------------------------------------------|
    ' |  TrueView is an ASCII text browser. TrueView is so written as to     |
    ' |  avoid having to rely on Dimensioning or Redimensioning.   It        |
    ' |  continuously keeps track of where the top line is, and it           |
    ' |  continuously opens and closes the COMMAND$ file.  There is never    |
    ' |  a need to worry about how much memory is needed.                    |
    ' |----------------------------------------------------------------------|
    ' |  If <UpArr> <DnArr> is pressed, the screen is saved and moved up     |
    ' |  or down and only one line is brought in to complete the screen.     |
    ' |  <RightArr> and <LeftArr> work also to move text up or down.  If     |
    ' |  <PgUp> <PgUp> is pressed then the next screen page is presented.    |
    ' |----------------------------------------------------------------------|
    ' |  Trueview probably shouldn't be used for huge files longer than      |
    ' |  10000 lines.  Beyond 10000 lines, it slows down a tad. I have a     |
    ' |  Pentium 4 2.65 CPU Ghz Gateway computer running under WindowsXP,    |
    ' |  and Trueview really did not lag in reading a 10,000 line file. I    |
    ' |  tried it out, however, on my old Pentium-S 166 Mhz computer, and    |
    ' |  it did lag a tiny bit, but not badly.
    ' |----------------------------------------------------------------------|
    ' |  Compiling:                                                          |
    ' |                                                                      |
    ' |             BC: TrueView /e         'use /e for errors               |
    ' |                                                                      |
    ' |             LINK: TrueView /noe                                      |
    ' |             LIB : BCom45                                             |
    ' |                                                                      |
    ' +----------------------------------------------------------------------+
    ' +---------------+------------------------------------------------------+
    ' | FileName$     |  The ASCII text file to view. As a stand alone       |
    ' |               |  program, FileName$ will be a give as a command      |
    ' |               |  line parameter and will look like this at the top   |
    ' |               |  of the program: FileName$ = COMMAND$                |
    ' |---------------+------------------------------------------------------|
    ' | ULRow%        |  Upper left row to place text.                       |
    ' |---------------+------------------------------------------------------|
    ' | ULCol%        |  Upper left column to place text.                    |
    ' |---------------+------------------------------------------------------|
    ' | LRRow%        |  Lower right row to place text.                      |
    ' |---------------+------------------------------------------------------|
    ' | LRCol%        |  Lower right column to place text.                   |
    ' |---------------+------------------------------------------------------|
    ' | FGColr%       |  Foreground color of text (0-15).                    |
    ' |---------------+------------------------------------------------------|
    ' | BGColr%       |  Back ground color of text (0-7).                    |
    ' |---------------+------------------------------------------------------|
    ' | TBColrFG%     |  Foreground color of top/bottom strips (0-15).       |
    ' |---------------+------------------------------------------------------|
    ' | TBColrBG%     |  Background color of the top/bottom strips (0-7).    |
    ' |---------------+------------------------------------------------------|
    ' | TBNumColrFG%  |  Foreground color of top line numbering (0-15).      |
    ' |---------------+------------------------------------------------------|
    ' | TBNumColrBG%  |  Background color of bottom line numbering (0-7).    |
    ' |---------------+------------------------------------------------------|
    ' | EOFColrFG%    |  Foreground color of "End Of File" message (0-15).   |
    ' |---------------+------------------------------------------------------|
    ' | EOFColrBG%    |  Background color of "End Of File" message (0-7).    |
    ' +---------------+------------------------------------------------------+

    FileName$ = RTRIM$(LTRIM$(FileName$))

    SR.UL.Row% = ULRow%     'Upper left row to save/restore screen.
    SR.UL.Col% = ULCol%     'Upper left column to save/restore screen
    SR.LR.Row% = LRRow%     'Lower right row to save/restore screen.
    SR.LR.Col% = LRCol%     'Lower right column to save/restore screen.
    '
    Temp.UL.Row% = SR.UL.Row% + 1
    Temp.LR.Row% = SR.LR.Row% - 1
    DownUp& = 1
    '
    'next 9 lines set up the beginning screen and then closes
    OpeningScreen% = LRRow% - ULRow% + 1
    OPEN FileName$ FOR INPUT AS #1
    COLOR FGColr%, BGColr%: CLS
    FOR BringIt% = 1 TO OpeningScreen%
        IF EOF(1) THEN EXIT FOR
        LINE INPUT #1, M$
        IF RTRIM$(LTRIM$(M$)) = CHR$(12) THEN M$ = SPACE$(80)
        LOCATE BringIt% + ULRow% - 1, ULCol%, 0, 0, 0
        LOCATE , , 0, 0, 0
        PRINT M$;
        CheckLines% = CheckLines% + 1
    NEXT
    IF CheckLines% < 23 THEN
        EndYes% = 1: EndPg% = 1: EndOfPage% = 1
    END IF
    GOSUB paint.top.bottom
    CLOSE #1
loopdeloop:
    DO
        IF DownUp& <= 0 THEN
            DownUp& = 1
        END IF
        COLOR TBNumColrFG%, TBNumColrBG%
        LOCATE ULRow% - 1, 71, 0, 0, 0: PRINT "        ";
        LOCATE ULRow% - 1, 71, 0, 0, 0: PRINT STR$(DownUp&);
        LOCATE LRRow% + 1, 71, 0, 0, 0: PRINT "          ";
        LOCATE LRRow% + 1, 71, 0, 0, 0: PRINT STR$(DownUp& + (LRRow% - ULRow%));
        COLOR FGColr%, BGColr%
        DO
            TheKey$ = INKEY$
        LOOP UNTIL LEN(TheKey$) > 0
        TheKey% = CVI(TheKey$ + CHR$(0))
        IF TheKey% = 20480 OR TheKey% = 19712 THEN  '<Down Arrow> <RightAr>
            IF Booboo% = 1 OR CheckLines% < 23 THEN
                GOTO loopdeloop
            ELSE
                EndYes% = 0: EndPg% = 0
                FileEnd% = 0
            END IF
            DnAr% = 1
            UpAr% = 0
           
            IF EndOfFile% <> 1 THEN
                SR.UL.Row% = Temp.UL.Row%
                SR.LR.Row% = Temp.LR.Row% + 1
                GOSUB save.true.screen
                CLOSE #1
                OPEN FileName$ FOR INPUT AS #1
                FOR DnIt& = 1 TO DownUp& + (LRRow% - ULRow% + 1)
                    IF EOF(1) THEN
                        EndOfFile% = 1
                        EndPg% = 1
                        CLOSE #1
                        EXIT FOR
                    END IF
                    LINE INPUT #1, Fox$
                    IF RTRIM$(LTRIM$(Fox$)) = CHR$(12) THEN Fox$ = SPACE$(80)
                    Fox$ = LEFT$(Fox$, 80)
                NEXT
                IF EndOfFile% <> 1 THEN
                    IF NOT EOF(1) THEN
                        LOCATE LRRow%, ULCol%, 0, 0, 0
                        PRINT SPACE$(LRCol% - ULCol% + 1);
                        LOCATE LRRow%, ULCol%, 0, 0, 0
                        PRINT Fox$;
                    ELSEIF EOF(1) THEN
                        LOCATE LRRow%, ULCol%, 0, 0, 0
                        COLOR EOFColrFG%, EOFColrBG%
                        SOUND 150, 2
                        PRINT STRING$(35, "-") + "End Of File" + STRING$(34, "-");
                    END IF
                END IF
                DownUp& = DownUp& + 1
            ELSEIF EndOfFile% = 1 THEN
                GOTO loopdeloop
            END IF
        ELSEIF TheKey% = 20736 THEN           '<Page Down>
            IF EndPg% = 1 OR EndYes% = 1 OR EndOfPage% = 1 OR CheckLines% < 23 THEN
                GOTO loopdeloop
            END IF
            IF FileEnd% = 0 THEN
                CLOSE #1
                FileEnd% = 1
            END IF
            PgDn& = DownUp& + LRRow% - ULRow%
                CLOSE #1
                OPEN FileName$ FOR INPUT AS #1
                FOR PgDn1& = 1 TO PgDn&
                    IF EOF(1) THEN
                       FileEnd% = 1
                       CLOSE #1
                       EXIT FOR
                    END IF
                    LINE INPUT #1, M$
                    IF RTRIM$(LTRIM$(M$)) = CHR$(12) THEN M$ = SPACE$(80)
                    M$ = LEFT$(M$, 80)
                NEXT
                DownUp& = DownUp& + (LRRow% - ULRow% + 1)
                FOR PgDn2% = 1 TO (LRRow% - ULRow% + 1)
                    IF EndPg% = 0 THEN
                        IF EOF(1) THEN
                            FileEnd% = 1
                            CLOSE #1
                            GOSUB da.end.james
                            EXIT FOR
                        END IF
                    END IF
                    LINE INPUT #1, M$
                    IF RTRIM$(LTRIM$(M$)) = CHR$(12) THEN M$ = SPACE$(80)
                    M$ = LEFT$(M$, 80)
                    LOCATE PgDn2% + 1, ULCol%, 0, 0, 0
                    PRINT SPACE$(LRCol% - ULCol% + 1);
                    LOCATE PgDn2% + 1, ULCol%, 0, 0, 0
                    PRINT M$;
                NEXT
        ELSEIF TheKey% = 18688 THEN            '<Page Up>
            Booboo% = 0
            EndYes% = 0: EndPg% = 0
            IF PgDn& > LRRow% - ULRow% + 1 OR DownUp& > (LRRow% - ULRow% + 1) THEN
                PgUp& = DownUp& - (LRRow% - ULRow% + 1)
                CLOSE #1
                OPEN FileName$ FOR INPUT AS #1
                FOR PgUp1& = 1 TO PgUp& - 1
                    LINE INPUT #1, M$
                    IF RTRIM$(LTRIM$(M$)) = CHR$(12) THEN M$ = SPACE$(80)
                    M$ = LEFT$(M$, 80)
                NEXT
                FOR PgUp2& = 1 TO (LRRow% - ULRow% + 1)
                    LINE INPUT #1, M$
                    IF RTRIM$(LTRIM$(M$)) = CHR$(12) THEN M$ = SPACE$(80)
                    M$ = LEFT$(M$, 80)
                    LOCATE PgUp2& + 1, ULCol%, 0, 0, 0
                    PRINT SPACE$(LRCol% - ULCol% + 1);
                    LOCATE PgUp2& + 1, ULCol%, 0, 0, 0
                    PRINT M$;
                NEXT
                DownUp& = DownUp& - (LRRow% - ULRow% + 1)
            ELSE
                GOSUB home.james
            END IF
        ELSEIF TheKey% = 18432 OR TheKey% = 19200 THEN '<Up Arrow> <LeftArr>
            Booboo% = 0
            EndYes% = 0: EndPg% = 0
            EndOfFile% = 0
            EndPg% = 0
            FileEnd% = 0
            DnAr% = 0
            UpAr% = 1
            DownUp& = DownUp& - 1
            IF DownUp& = 1 THEN
                 GOSUB home.james
            ELSEIF DownUp& > 1 THEN
                SR.UL.Row% = Temp.UL.Row% - 1
                SR.LR.Row% = Temp.LR.Row%
                GOSUB save.true.screen
                CLOSE #1
                OPEN FileName$ FOR INPUT AS #1
                FOR UpIt& = 1 TO DownUp&
                    LINE INPUT #1, M$
                NEXT
                IF RTRIM$(LTRIM$(M$)) = CHR$(12) THEN M$ = SPACE$(80)
                M$ = LEFT$(M$, 80)
                LOCATE ULRow%, ULCol%, 0, 0, 0
                PRINT SPACE$(LRCol% - ULCol% + 1);
                LOCATE ULRow%, ULCol%, 0, 0, 0
                PRINT M$;
            END IF
        ELSEIF TheKey% = 18176 THEN           '<Home>
            EndYes% = 0: EndPg% = 0: Booboo% = 0
            GOSUB home.james
        ELSEIF TheKey% = 20224 THEN           '<End>
            EndPg% = 0: Booboo% = 0
            IF EndYes% = 0 THEN
               GOSUB da.end.james
            END IF
        ELSEIF TheKey% = 27 THEN
            CLOSE #1
            EXIT SUB
        END IF
    LOOP
  
paint.top.bottom:
    ' +---------------------------------------------------------------------+
    ' | When this subroutine is called, the top and bottom                  |
    ' | rows are displayed.                                                 |
    ' +---------------------------------------------------------------------+
    COLOR TBColrFG%, TBColrBG%
    LOCATE ULRow% - 1, 1, 0, 0, 0
    PRINT SPACE$(LRCol% - ULCol% + 1);
    LOCATE ULRow% - 1, 31, 0, 0, 0
    PRINT CHR$(240) + " TrueView Program " + CHR$(240);
    LOCATE ULRow% - 1, 62, 0, 0, 0
    PRINT "Top Line:";
    LOCATE ULRow% - 1, 2, 0, 0, 0
    PRINT "File: " + ComFile$
    LOCATE LRRow% + 1, 1, 0, 0, 0
    PRINT SPACE$(LRCol% - ULCol% + 1);
    LOCATE LRRow% + 1, 2, 0, 0, 0
    PRINT "EXIT: <Esc>   MOVE: ";
    LOCATE LRRow% + 1, 21, 0, 0, 0
    PRINT "<" + CHR$(24) + "> <" + CHR$(25) + "> <PgUp> <PgDn> <End> <Home>";
    LOCATE LRRow% + 1, 59, 0, 0, 0
    PRINT "Bottom Line: ";
    COLOR FGColr%, BGColr%
    RETURN

da.end.james:
    ' +---------------------------------------------------------------------+
    ' | when the end of a file is reached, the                              |
    ' | program branches to this procedure:                                 |
    ' +---------------------------------------------------------------------+
    EndYes% = 1: EndPg% = 1
    COLOR TBColrFG%, TBColrBG%
    LOCATE 1, 22, 0, 0, 0: PRINT "- Please Wait -" + SPACE$(14)
    DownUp& = 0
    EndOfFile% = 0
    FileEnd% = 0
    CountLines& = 0
    CLOSE #1
    OPEN FileName$ FOR INPUT AS #1
    DO
        LINE INPUT #1, ThrowAway$
        IF EOF(1) THEN EXIT DO
        CountLines& = CountLines& + 1
    LOOP UNTIL EOF(1)
    CLOSE #1
    OPEN FileName$ FOR INPUT AS #1
    FOR LastScrn& = 1 TO CountLines& + 1 - (LRRow% - ULRow% + 1)
        IF EOF(1) THEN
            EXIT FOR
        END IF
        LINE INPUT #1, M$
        IF RTRIM$(LTRIM$(M$)) = CHR$(12) THEN M$ = SPACE$(80)
        M$ = LEFT$(M$, 80)
        ManyLines& = ManyLines& + 1
        COLOR TBColrFG%, TBColrBG%
        LOCATE 1, 40, 0, 0, 0: PRINT "Loading:";
        LOCATE 1, 49, 0, 0, 0: PRINT RTRIM$(LTRIM$(STR$(ManyLines&)));
    NEXT
    GOSUB paint.top.bottom
    FOR TheLastScrn% = ULRow% TO LRRow%
        IF EOF(1) THEN
            EXIT FOR
        END IF
        LINE INPUT #1, M$
        IF RTRIM$(LTRIM$(M$)) = CHR$(12) THEN M$ = SPACE$(80)
        M$ = LEFT$(M$, 80)
        COLOR FGColr%, BGColr%
        LOCATE TheLastScrn%, ULCol%, 0, 0, 0
        PRINT SPACE$(LRCol% - ULCol% + 1);
        LOCATE TheLastScrn%, ULCol%, 0, 0, 0
        PRINT M$;
    NEXT
    CLOSE #1
    DownUp& = CountLines& - (LRRow% - ULRow% + 1) + 1
    COLOR TBColrFG%, TBColrBG%
    LOCATE 1, 22, 0, 0, 0: PRINT "         - TrueView Program -       ";
    COLOR FGColr%, BGColr%
    ManyLines& = 0
    RETURN
home.james:
    ' +---------------------------------------------------------------------+
    ' | when the top of a file is reached, the program                      |
    ' | branches to this subroutine:                                        |
    ' +---------------------------------------------------------------------+
    CLOSE #1
    OPEN FileName$ FOR INPUT AS #1
    FOR HomePage% = ULRow% TO LRRow%
        IF EOF(1) THEN
            EXIT FOR
        END IF
        LOCATE HomePage%, ULCol%, 0, 0, 0
        PRINT SPACE$(LRCol% - ULCol% + 1);
        LINE INPUT #1, M$
        IF RTRIM$(LTRIM$(M$)) = CHR$(12) THEN M$ = SPACE$(80)
        M$ = LEFT$(M$, 80)
        LOCATE HomePage%, ULCol%, 0, 0, 0
        PRINT M$;
    NEXT
    DownUp& = 1
    GOSUB paint.top.bottom
    RETURN

save.true.screen:
    ' +---------------------------------------------------------------------+
    ' | When the program asks for GOSUB save.screen, the following          |
    ' | six lines saves the screen from row 2 to row 24:                    |
    ' +---------------------------------------------------------------------+
    REDIM ReadLine$(25)
    FOR ViewIt% = SR.UL.Row% TO SR.LR.Row%
        FOR Horizon% = SR.UL.Col% TO SR.LR.Col%
            ReadLine$(ViewIt%) = ReadLine$(ViewIt%) + CHR$(SCREEN(ViewIt%, Horizon%))
        NEXT
    NEXT
restore.true.screen:
    ' +---------------------------------------------------------------------+
    ' |This subroutine restores the above saved screen, except the saved    |
    ' |screen is moved either up or down. If the down arrow is pressed, then|
    ' |DnAr% = 1 and the saved screen is moved up one place and a new line  |
    ' |is brought in and displayed at row 24. If the up arrow is pressed,   |
    ' |then UpAr% = 1 and the saved screen is moved down one row and a new  |
    ' |line is displayed at row 2, just under the top linebar.              |
    ' +---------------------------------------------------------------------+
    IF DnAr% = 1 THEN
        StartSite% = SR.UL.Row% - 1
        StopSite% = SR.LR.Row% - 1
    ELSEIF UpAr% = 1 THEN
        StartSite% = SR.UL.Row% + 1
        StopSite% = SR.LR.Row% + 1
    END IF
    FOR FindRow% = StartSite% TO StopSite%
          LOCATE FindRow%, SR.UL.Col%, 0, 0, 0
          PRINT SPACE$(LRRow% - ULRow% + 1);
          LOCATE FindRow%, SR.UL.Col%, 0, 0, 0
          COLOR FGColr%, BGColr%
          IF DnAr% = 1 THEN
              PRINT ReadLine$(FindRow% + DnAr%);
          ELSEIF UpAr% = 1 THEN
              PRINT ReadLine$(FindRow% - UpAr%);
          END IF
    NEXT
    ERASE ReadLine$
    RETURN
END SUB