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 %TITLE 'SCRESCR - erase screen'
MODULE SCRESCR (				! Erase screen
		IDENT = '3-001'			! File: SCRESCR.BLI Edit: GB3001
		) =
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 outputs an erase screen sequence.
!
! ENVIRONMENT:	Runs at any access mode - AST reentrant
!
! AUTHOR: Bob Kushlis, CREATION DATE: September 8, 1979
!
! MODIFIED BY:
!
! 1-001	- Original.  DJS 12-Feb-1981.  This module was created by
!	extracting the routine EDT$$SC_ERAALL  from module SCREEN.
! 1-002	- Regularize headers.  JBS 13-Mar-1981
! 1-003 - Set message flag to zero when the screen is erased.  SMB 30-Aug-1982
! 1-004 - Add code to erase line by line if message flag set.  SMB 24-Sep-1982
! 1-005	- Revise the handling of MSGFLG.  JBS 06-Oct-1982
! 1-006	- Use the fancy screen clearing features of the VT100 to speed up screen
!	   clearing when the message line must be preserved.  JBS 06-Oct-1982
! 1-007	- Don't clear SCR_CHGD unless we are clearing the whole screen.  JBS 07-Oct-1982
! 1-008	- Fix clearing one line too many when clearing the text area.  JBS 09-Oct-1982
! 1-009	- Remove the call to EDT$$OUT_FMTBUF.  JBS 09-Oct-1982
! 1-010	- Set the cursor position before erasing.  JBS 23-Oct-1982
! 1-011	- If the cursor line is -1 (initial value) use 0.  JBS 11-Jan-1983
! 1-012	- Allow for new value of SCR_CHGD.  JBS 02-Mar-1983
! 3-001 - Add updates from V3 sources.  GB 03-May-1983
!--

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

REQUIRE 'EDTSRC:TRAROUNAM';

FORWARD ROUTINE
    EDT$$SC_ERAALL : NOVALUE;

!
! INCLUDE FILES:
!

REQUIRE 'EDTSRC:EDTREQ';

!
! MACROS:
!
!	NONE
!
! EQUATED SYMBOLS:
!

BIND
    ERS_S_52 = UPLIT (%STRING (%CHAR (ASC_K_ESC), 'J')),
    ERS_S_100 = UPLIT (%STRING (%CHAR (ASC_K_ESC), '[J')),
    ERS_S_100A = UPLIT (%STRING (%CHAR (ASC_K_ESC), '[1J'));

LITERAL
    ERS_S_52_LEN = 2,
    ERS_S_100_LEN = 3,
    ERS_S_100A_LEN = 4;

!
! OWN STORAGE:
!
!	NONE
!
! EXTERNAL REFERENCESD
!
!	In the routine

%SBTTL 'EDT$$SC_ERAALL  - erase screen'

GLOBAL ROUTINE EDT$$SC_ERAALL 			! Erase screen
    : NOVALUE =

!++
! FUNCTIONAL DESCRIPTION:
!
!	This routine erases the screen from the current location to
!	the end of the screen, or to just before the message line
!	if there is useful text in the message line.
!
! FORMAL PARAMETERS:
!
!	NONE
!
! IMPLICIT INPUTS:
!
!	CS_LNO
!	SCR_LNS
!	MSGFLG
!	TI_TYP
!	SCR_CHGD
!	TI_WID
!
! IMPLICIT OUTPUTS:
!
!	MSGFLG
!	SCR_CHGD
!
! ROUTINE VALUE:
!
!	NONE
!
! SIDE EFFECTS:
!
!	NONE
!
!--

    BEGIN

    EXTERNAL ROUTINE
	EDT$$SC_ERATOEOL : NOVALUE,		! Erase to end of line
	EDT$$SC_POSCSIF : NOVALUE,		! Position the cursor
	EDT$$FMT_LIT : NOVALUE;			! Output a string without expansion

    EXTERNAL
	CS_LNO,				! current cursor line
	SCR_LNS,				! number of screen lines
	MSGFLG,				! 1 = there is a message on the message line
	TI_TYP,				! Terminal type
	SCR_CHGD,			! non-zero = the screen must be erased completely
	TI_WID;				! The width of the screen

    LOCAL
	LINE_NO;

    LINE_NO = .CS_LNO;

    IF (.LINE_NO LSS 0) THEN LINE_NO = 0;

!+
! If the screen has been mangled then there can be nothing useful on the message line.
!-

    IF (.SCR_CHGD NEQ 0) THEN MSGFLG = 0;

!+
! Use different algorithms depending on whether or not we must protect the message line.
!-

    IF (.MSGFLG EQL 0)
    THEN
!+
! Erase to the end of the screen.
!-
	BEGIN
	EDT$$SC_POSCSIF (.LINE_NO, 0);

	IF (.TI_TYP EQL TERM_VT52)
	THEN
	    EDT$$FMT_LIT (CH$PTR (ERS_S_52), ERS_S_52_LEN)
	ELSE
	    IF (.TI_TYP EQL TERM_VT100)
	    THEN
		EDT$$FMT_LIT (CH$PTR (ERS_S_100), ERS_S_100_LEN);

!+
! If we are erasing the whole screen then the screen is no longer mangled.
!-

	IF (.LINE_NO EQL 0) THEN SCR_CHGD = 0;

	END
    ELSE
!+
! We must preserve the message line.  If we have a VT100 and are at the home position
! we can use a "clear from beginnning of screen to here" command.
!-
	BEGIN

	IF ((.TI_TYP EQL TERM_VT100) AND (.LINE_NO EQL 0))
	THEN
	    BEGIN
	    EDT$$SC_POSCSIF (.SCR_LNS - 1, .TI_WID - 1);
	    EDT$$FMT_LIT (CH$PTR (ERS_S_100A), ERS_S_100A_LEN);
	    END
	ELSE
!+
! Erase each line separately up to the message line.
!-

	    INCR I FROM .LINE_NO TO .SCR_LNS - 1 DO
		BEGIN
		EDT$$SC_POSCSIF (.I, 0);
		EDT$$SC_ERATOEOL ();
		END;

	END;

    END;					! of routine EDT$$SC_ERAALL

!<BLF/PAGE>

END						! of module EDT$SCRESCR

ELUDOM