title	'Screen Switch module'

;****************************************************************
;*								*
;*	This module is the entry point for a screen switch	*
;*	FILE NAME: switch.a86					*
;*	LAST UPDATE: 2/13/84					*
;*								*
;****************************************************************

include system.lib
include flags.equ
include	serdata.equ

eject

	dseg

extrn	ocdesctbl:word
extrn   f30_tbl:  word

	cseg

public	io_switch
extrn	io_statline:near                ;; in statlin.a86
extrn   vs_switch:near                  ;; in vscreen.a86
extrn   supif:near		        ;; in headentr.a86
         
;=========
io_switch:	; Function 7:  Switch Screen
;=========
;
;	input:	dl = Vcon to switch to
;		dh = Pcon to do the switch on
;

	push dx			               ;; save the Pcon and Vcon

        call vs_switch                         ;; does fully buffered screen
                                               ;; switch.

        pop dx                                 ;; DH -> pcon, DL -> vcon
        call set_up_bx                         ;; BX -> output Q ctl structure

check_graph:         
        mov CUR_VCON[bx],dl
        push dx ! push bx		       ;; and check for a graphics
        xor bh,bh			       ;; process that was flagwaited
        mov bl,dl
	shl bx,1
	mov bx, f30_tbl[bx]
        test bx, 010H			       ;; 010h = graphics is on
	  jz go_stat
	xor dh,dh
        add dl, V_FLAG			       ;; Flag # = virt cons + bias	
        mov cl, f_flagset		       ;; Do the system flag set.
	  call supif
go_stat:
	 pop bx ! pop dx		       ;; DL -> phys cons #
         mov CUR_VCON[bx],dl
	 mov dl, dh                            ;; get pcon
          jmp io_statline                      ;; update status line


;-----------
set_up_bx:
;-----------

	xor bx, bx
	mov bl, dh		               ;; use Pcon to index into the Xmit Q's
	shl bx, 1
	mov bx, ocdesctbl[bx]	               ;; bx -> Xmit Q control
        ret


	end