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 %TITLE 'SCRNEWDEL - delete a line from the screen'
MODULE SCRNEWDEL (				! delete a line from the screen
		IDENT = '1-005'			! File: SCRNEWDEL.BLI Edit: JBS1005
		) =
BEGIN
!COPYRIGHT (c) DIGITAL EQUIPMENT CORPORATION 1981, 1988.  ALL RIGHTS RESERVED.
!
!THIS SOFTWARE IS FURNISHED UNDER A LICENSE AND MAY BE USED AND COPIED ONLY
!IN ACCORDANCE WITH THE TERMS OF SUCH LICENSE AND WITH THE INCLUSION OF 
!THE ABOVE COPYRIGHT NOTICE.  THIS SOFTWARE OR ANY OTHER COPIES THEREOF MAY 
!NOT BE PROVIDED OR OTHERWISE MADE AVAILABLE TO ANY OTHER PERSON.  NO TITLE
!TO AND OWNERSHIP OF THE SOFTWARE IS HEREBY TRANSFERRED.
!
!THE INFORMATION IN THIS SOFTWARE IS SUBJECT TO CHANGE WITHOUT NOTICE AND 
!SHOULD NOT BE CONSTRUED AS A COMMITMENT BY DIGITAL EQUIPMENT CORPORATION.
!
!DIGITAL ASSUMES NO RESPONSIBILITY FOR THE USE OR RELIABILITY OF ITS 
!SOFTWARE ON EQUIPMENT THAT IS NOT SUPPLIED BY DIGITAL.
!
!
!++
! FACILITY:	EDT -- The DEC Standard Editor
!
! ABSTRACT:
!
!	This module updates the screen information data structure to
!	reflect the deletion of a line.
!
! ENVIRONMENT:	Runs at any access mode - AST reentrant
!
! AUTHOR: Sharon M. Burlingame, CREATION DATE: September 15, 1982
!
! MODIFIED BY:
!
! 1-001	- Original.  SMB 15-Sep-1982.
! 1-002 - Fix up the original to conform to new design.  SMB 10-Oct-1982
! 1-003 - Add more code to remove existing bugs.  SMB 26-Oct-1982
! 1-004	- Change updating of the screen pointers.  JBS 29-Oct-1982
! 1-005	- Don't set the rebuild flag.  JBS 03-Jan-1983
!--

%SBTTL 'Declarations'
!
! TABLE OF CONTENTS:
!

REQUIRE 'EDTSRC:TRAROUNAM';

FORWARD ROUTINE
    EDT$$SC_LNDEL : NOVALUE;

!
! INCLUDE FILES:
!

REQUIRE 'EDTSRC:EDTREQ';

!
! MACROS:
!
!	NONE
!
! EQUATED SYMBOLS:
!
!	NONE
!
! OWN STORAGE:
!
!	NONE
!
! EXTERNAL REFERENCES:
!
!	In the routine

%SBTTL 'EDT$$SC_LNDEL  - delete a line from the screen'

GLOBAL ROUTINE EDT$$SC_LNDEL (			! Delete a line from the screen
    SCRPTR					! Screen pointer to delete
    ) : NOVALUE =

!++
! FUNCTIONAL DESCRIPTION:
!
!	Update the screen line information structure by
!	releasing the memory to the pool of available storage.
!	Update various screen line pointers as necessary.
!
! FORMAL PARAMETERS:
!
!	NONE
!
! IMPLICIT INPUTS:
!
!	MEM_CNT
!	BOT_SCRPTR
!	EOB_SCRPTR
!	TOP_SCRPTR
!	FST_AVLN
!	FST_SCRPTR
!	LST_SCRPTR
!	CSR_SCRPTR
!	CUR_SCRLN
!
! IMPLICIT OUTPUTS:
!
!	MEM_CNT
!	BOT_SCRPTR
!	EOB_SCRPTR
!	TOP_SCRPTR
!	FST_AVLN
!	FST_SCRPTR
!	LST_SCRPTR
!	CSR_SCRPTR
!	CUR_SCRLN
!
! ROUTINE VALUE:
!
!	NONE
!
! SIDE EFFECTS:
!
!	NONE
!
!--

    BEGIN

    EXTERNAL
	MEM_CNT,				! Allocated memory count
	BOT_SCRPTR : REF SCREEN_LINE,		! Bottom screen pointer
	EOB_SCRPTR : REF SCREEN_LINE,		! EOB screen pointer
	TOP_SCRPTR : REF SCREEN_LINE,		! Top screen pointer
	FST_AVLN : REF SCREEN_LINE,		! First available screen info memory
	FST_SCRPTR : REF SCREEN_LINE,		! Pointer to first screen line info
	LST_SCRPTR : REF SCREEN_LINE;		! Pointer to last screen line info

    MAP
	SCRPTR : REF SCREEN_LINE;		! Screen pointer parameter

    LOCAL
	NXT_ADDR : REF SCREEN_LINE,		! Address of next line info
	PREV_ADDR : REF SCREEN_LINE;		! Address of previous line info

!+
! Find the next and previous pointers of the line being deleted.
!-
    NXT_ADDR = .SCRPTR [SCR_NXT_LINE];
    PREV_ADDR = .SCRPTR [SCR_PRV_LINE];
!+
! Check for deleting the first line of the screen data base.
!-

    IF (.FST_SCRPTR EQLA .SCRPTR)
    THEN
	BEGIN
	FST_SCRPTR = .NXT_ADDR;
	FST_SCRPTR [SCR_PRV_LINE] = 0;
	END;

!+
! Check for deleting the last line of the screen data base.
!-

    IF (.SCRPTR EQLA .LST_SCRPTR)
    THEN
	BEGIN
	LST_SCRPTR = .PREV_ADDR;
	LST_SCRPTR [SCR_NXT_LINE] = 0;
	END;

!+
! Check for EOB deleted off the screen
!-

    IF (.EOB_SCRPTR EQLA .SCRPTR) THEN EOB_SCRPTR = 0;

!+
! Check for deleting the top line from the data base.
!-

    IF (.TOP_SCRPTR EQLA .SCRPTR) THEN TOP_SCRPTR = 0;

!+
! Check for deleting the bottom line from the data base.
!-

    IF (.BOT_SCRPTR EQLA .SCRPTR) THEN BOT_SCRPTR = 0;

!+
! Fix up the previous and next pointers.
!-

    IF (.PREV_ADDR NEQA 0) THEN PREV_ADDR [SCR_NXT_LINE] = .NXT_ADDR;

    IF (.NXT_ADDR NEQA 0) THEN NXT_ADDR [SCR_PRV_LINE] = .PREV_ADDR;

!+
! The line being deleted is indicated by SCRPTR.  If there
! are no screen line buffers in the free list, then start
! a new list; otherwise add the memory to the front of the current list.
!-
    SCRPTR [SCR_NXT_LINE] = .FST_AVLN;
    SCRPTR [SCR_PRV_LINE] = -1;			! For debugging
    FST_AVLN = .SCRPTR;
    MEM_CNT = .MEM_CNT - 1;

    END;					! of routine EDT$$SC_INSLN

!<BLF/PAGE>

END						! of module EDT$SCRNEWDEL

ELUDOM