;-------------------------------------------------------------------------------
; 2021-02-06
;
; bitologia diffusion symbol
;
; wojtek[at]bitologia.org
; maciek[at]bitologia.org
;-------------------------------------------------------------------------------

.model tiny
.code
        org 100h
start:



        ;;mov ax, 0003h ; CLS
        ;;int 10h
        mov ax, 0b800h
        mov es, ax   ; TODO: DRY!
        xor di, di
        mov ah, 7    ; color attribute
        mov al, 255d ; standard CLS (mov ax, 0003h) fills screen with 0
        mov cx, 4000 ; which is replaced by something during the procedure
        cld          ; thus, we have to clean the screen with another blank:ASCII=255
        rep stosw    ; CLS with ASCII=255 instead of ASCII=0
    
        mov ah, 01h  ; "hide" cursor
        mov cx, 2607h
        int 10h


esc_:   mov cx, 13d   ; draw 13 frames (not lines!) each frame is three lines
        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 cs
        pop ds
        push bx
        push cs
        pop es
        mov bp, offset FRAME_01  ; start with FRAME_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 ; this time we have fixed offset below
;        shl bx, cl
        add bp, bx
        
        ; ... easy :)

        mov cx, 240d; 80d########################
        mov dx, 0d
        mov bx, 1000h
        mov ax, 1100h
        int 10h
        pop bx
        mov ax, 0b800h
;        add ax, bx ; don't jump over the line this time
        mov es, ax


;        xor di, di
	mov di, 1760 ; BITOLOGIA DIFFUSION should be centered vertically!

        mov cx, 240d; 80d;#######################
        xor al, al
load01: mov es:[di], al ; instead of ASCII_MAP
                        ; - just take consecutive integers from 0 to 240d
        inc al
        inc di ; skip the byte of attributes (responsible for colours
               ;                              -- for a future use maybe)
 mov byte ptr es:[di], 2 ; ASCII attribute
        inc di
        loop load01
        pop di
        call slow_down
        pop cx
                      ; this time we have fixed offset:
        add bx, 3840d ; draw (jump to) next line (offset)
                      ; that is: 240x16=3840
        ret
draw_line_01 endp
;------------------------------------------------------------------------------
slow_down proc
        push cx
        xor cx, cx
        mov dx, 4510h ; 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_*.c