;-------------------------------------------------------------------------------
; 2021-01-30 single line
; 2021-02-05 fix cursor appearance (just hide it)!, proper CLS and display
;            three lines at once to intensify the effect of an old CRT
; "full picture" in text mode
; wojtek[at]bitologia.org
;-------------------------------------------------------------------------------

.model tiny
.code
        org 100h
start:  mov ax, 0b800h
        mov es, ax
        xor di, di
        mov ax, 00ffh ; standard CLS (mov ax, 0003h) fills screen with 0
        mov cx, 4000  ; which is replaced by something during the procedure
        cld           ; thus, we must clean the screen with another blank
        rep stosw     ; ASCII=255 instead of ASCII=0

        mov ah, 01h   ; "hide" cursor
        mov cx, 2607h
        int 10h

        mov al, 10h
        mov dx, 3c0h
        out dx, al
        in al, dx
        and al, 00000100b ; do not copy 9th line of ASCII between C0h and DFh
        out dx, al

esc_:   mov cx, 25d   ; 25 lines (80 columns) in 0x03 DOS text mode
        xor bx, bx
draw:   call draw_line_01
        loop draw
        in al, 60h    ;
        cmp al, 1     ;
        jne esc_      ; loop until ESC-pressed
        mov ax, 0003h
        int 10h       ; restore standard ASCII set
        mov ax, 4c00h
        int 21h       ; back to DOS
;------------------------------------------------------------------------------
draw_line_01 proc
        push cx
        push di
;       push si       ; TODO: check carefully whether SI should be preserved!
        push cs
        pop ds
        push bx
        push cs
        pop es
        mov bp, offset LINE_01  ; start with LINE_01 and skip 80 bytes every loop (~mod 25)

        ; starting with LINE_01 one must jump to the next LINE_02 and so on...
        ; by skipping 80*16 bytes every time
        ; every jump is actually controlled by BX which increases by 10d
        ; hence, it is enough to multiply every offset by 128
        ; that is to shift BX by 7 to the left and finally add the result to BP
        ; ...
        mov cl, 7
        shl bx, cl
        add bp, bx
        ; ... easy :)

        mov cx, 80d ;####################### MUST BE PARMETRIZED!
        mov dx, 0d
        mov bx, 1000h
        mov ax, 1100h
        int 10h
        pop bx
        mov ax, 0b800h
        add ax, bx
        mov es, ax
        xor di, di
        mov cx, 80d ;####################### MUST BE PARMETRIZED!
        xor al, al
load01: mov es:[di], al ; instead of ASCII_MAP
                        ; - just take consecutive integers from 0 to 80d
        inc al
        inc di ; skip the byte of attributes (responsible for colours
               ;                              -- for a future use maybe)
        mov BYTE ptr es:[di], 7 ; ASCII attribute
        inc di
        loop load01
;       pop si
        pop di
        call slow_down
        call drop_line
        pop cx
        add bx, 10d ; draw (jump to) next line (offset)
        ret
draw_line_01 endp
;------------------------------------------------------------------------------
drop_line proc
        push cx
        push di
        push cs
        pop ds
        mov ax, 0b800h
        add ax, bx
        mov es, ax
        xor di, di
        mov cx, 80d
clear:  mov al, 255d
        mov es:[di], al
        inc di
        inc di
        loop clear
        pop di
        pop cx
        ret
drop_line endp
;------------------------------------------------------------------------------
slow_down proc
        push cx
        xor cx, cx
        mov dx, 8510h ; wait CX:DX RTC-microseconds
        mov ah, 86h
        int 15h
        pop cx
        ret
slow_down endp

;------------------------------------------------------------------------------
; each line in LINE_XX is a single ASCII character
; (every byte is an 8-bit row times 16 of them which gives a matrix 8x16
; of std. ASCII char.)
; 80 in total in a single row, and 25 in vertical ==> #(SCREEN)=2000

; ALL BELOW SHOULD BE CREATED AUTOMATICALLY BY ASCII_F.c

; end start ;; here or after "... CD 21"?