;=============================================================================
; scrl.asm - Simple Horizontal Scroller.
; File created: 11/21/93
; Copyright (c) 1993, Carlos Hasan Last modified: 11/21/93
;
; Description:
; Just a simple scroller in VGA ModeX and an external proportional
; font file in VLA chars format. Mainly based on VLA scrollers.
;
; Dependency:
; Requires Turbo Assembler 3.2 or later to be assembled.
; Dependant on the IBM PC 286 or better processor.
;=============================================================================
ideal
model small,pascal
jumps
p286
dosseg
stack 1024
ends
IFDEF LinkFont
global FontFAR:byte ; SCRL.FNT linked file.
ENDIF
;=========================== VLA Font Header =================================
struc FontHeader
Magic db "VGACH" ; Font Signature
First db ? ; First Char
Width db ? ; Font Width
Height db ? ; Font Height
Total db ? ; Number of Chars
ends FontHeader
;=========================== Data Segment ====================================
dataseg
SCREENWIDTH equ (2*320+8) ; Logical Screen Width
; Enough Space for Double-Window
; and the working hidden area
SCROLLROW equ 180 ; Scroller Window Start Row.
WinOffs dw ? ; Window Offset
CharOffs dw ? ; Char BitMap Offset
MesgOffs dw ? ; Ascii-Message Offset
FontHead FontHeader ? ; Font Header
CharColumn db ? ; Cur Char Column
FontFirst db ? ; Font First Char
FontWidth db ? ; Font Max Width
FontHeight db ? ; Font Height
FontDataOfs dw ? ; Font Data Offset
FontDataSeg dw ? ; Font Data Segment
FontWidths db 256 dup(?) ; Font Width Table
FontSize dw ? ; Font Char Size (Width*Height)
IFNDEF LinkFont
FontFileName db "SCRL.FNT",0 ; Font File Name
ENDIF
TheMessage db " ... Hello out there ... "
db " "
db " ... I am PELUSA from Chile ... "
db " "
db " ... Just a simple scroller... "
db " "
db " ... only useful to say that it's the FAKE demo ... "
db " "
db " ... you probably could have guessed that ... "
db " "
db " ... I hate scrollers because i have nothing to say..."
db " "
db " ... now enjoy the rest of this LAME thing ... "
db " ",0
codeseg
;-----------------------------------------------------------------------------
; SetModeX - Sets the VGA in Tweaked ModeX 320x400x256.
;-----------------------------------------------------------------------------
proc SetModeX
mov ax,0013h ; Sets VGA linear 320x200x256
int 10h
mov dx,3C4h ; Disable Chain-Four
mov ax,0604h
out dx,ax
mov dx,3C4h ; Enable Write to All Four Planes
mov ax,0F02h
out dx,ax
mov ax,0A000h ; Clear Display Memory
mov es,ax
xor di,di
xor ax,ax
mov cx,8000h
cld
rep stosw
mov dx,3D4h ; Reprogram CRT Controller:
mov ax,00014h ; turn off dword mode
out dx,ax
mov ax,0e317h ; turn on byte mode
out dx,ax
mov ax,00009h ; cell height
out dx,ax
mov dx,3D4h ; Sets Logical Screen Width
mov al,13h
mov ah,SCREENWIDTH/8
out dx,ax
ret
endp SetModeX
;-----------------------------------------------------------------------------
; WaitVR - Waits the Next VGA Vertical Retrace Ending.
;-----------------------------------------------------------------------------
proc WaitVR
mov dx,3DAh
WaitStartVR:
in al,dx
test al,8
je WaitStartVR
WaitEndVR:
in al,dx
test al,8
jne WaitEndVR
ret
endp WaitVR
;-----------------------------------------------------------------------------
; InitScroll - Initializes the Scroller Variables.
; Out:
; CF=1 if function was not successful.
; CF=0 if function was successful.
;-----------------------------------------------------------------------------
proc InitScroll
mov [WinOffs],0 ; Start Window Column
mov [CharColumn],0 ; Start with a ZeroWidth Char
mov [CharOffs],0 ; ZeroWidth Char BitMap Address
lea ax,[TheMessage] ; Sets Message Address
mov [MesgOffs],ax
call LoadFont ; Load Font Data
ret
endp InitScroll
;-----------------------------------------------------------------------------
; DoneScroll - Done Scroller Variables.
;-----------------------------------------------------------------------------
proc DoneScroll
IFNDEF LinkFont
mov es,[FontDataSeg] ; Free Font Data Segment
mov ah,49h
int 21h
ENDIF
ret
endp DoneScroll
;-----------------------------------------------------------------------------
; LoadFont - Loads a New VGA Font.
; Out:
; CF=1 if function was not successful.
; CF=0 if function was successful.
;-----------------------------------------------------------------------------
proc LoadFont
IFDEF LinkFont
mov ax,SEG FontFAR ; Load Font File Address
mov es,ax
mov [FontDataSeg],ax
mov [FontDataOfs],Size FontHeader
mov al,[es:FontHeader.First] ; Get Font First Char
mov [FontFirst],al
mov al,[es:FontHeader.Width] ; Get Font Data Size
mov ah,[es:FontHeader.Height]
mov [FontWidth],al
mov [FontHeight],ah
mul ah
mov [FontSize],ax
mov dl,[es:FontHeader.Total]
xor dh,dh
mul dx
add ax,Size FontHeader ; Copy Font Widths.
mov si,ax
xor di,di
mov cl,[es:FontHeader.Total]
xor ch,ch
CopyWidths:
mov al,[es:si]
mov [FontWidths+di],al
inc si
inc di
loop CopyWidths
ELSE
mov [FontDataSeg],0
mov ax,3D00h ; Open Font File
lea dx,[FontFileName]
int 21h
jc LoadFontExit
mov bx,ax
mov ah,3Fh ; Read Font Header
lea dx,[FontHead]
mov cx,Size FontHeader
int 21h
jc LoadFontExit
mov al,[FontHead.First] ; Get Font First Char
mov [FontFirst],al
mov al,[FontHead.Width] ; Get Font Data Size
mov ah,[FontHead.Height]
mov [FontWidth],al
mov [FontHeight],ah
mul ah
mov [FontSize],ax
mov dl,[FontHead.Total]
xor dh,dh
mul dx
push ax
push bx ; Alloc Space for Font Data
mov bx,ax
shr bx,4
inc bx
mov ah,48h
int 21h
pop bx
pop cx
jc LoadFontExit
push ds ; Read Font Data
mov [FontDataSeg],ax
mov [FontDataOfs],0
mov ds,ax
xor dx,dx
mov ah,3Fh
int 21h
pop ds
jc LoadFontExit
lea dx,[FontWidths] ; Read Font Widths
mov cl,[FontHead.Total]
xor ch,ch
mov ah,3Fh
int 21h
jc LoadFontExit
mov ah,3Eh ; Close Font File
int 21h
ENDIF
LoadFontExit:
ret
endp LoadFont
;-----------------------------------------------------------------------------
; DrawScroll - Polls the Horizontal Scroller.
; Out:
; CF=1 If no more scroll message.
; CF=0 If more scroll message.
;-----------------------------------------------------------------------------
proc DrawScroll
mov bx,[WinOffs] ; Loads Window Offset
add bx,2
mov dx,3D4h ; Sets VGA Start Address
mov al,0Dh
mov ah,bl
out dx,ax
dec al
mov ah,bh
out dx,ax
sub [CharColumn],4 ; Advance 4 pixels
jg NoNewChar ; Need a New Char?
call GetsNewChar ; Yes, Draw a New Char
jc DrawScrollExit
NoNewChar:
mov ax,0A000h ; Loads Display Memory Segment
mov es,ax
mov bl,[FontWidth] ; Loads Font Width and Height
mov cl,[FontHeight]
xor bh,bh
xor ch,ch
mov bp,SCREENWIDTH/4 ; Loads Logical Screen Width
mov dx,3C4h ; Enable Write to Plane 1
mov ax,0102h
out dx,ax
mov si,[CharOffs] ; Loads Char BitMap Address
mov di,[WinOffs] ; Loads VGA Window Dest Address
add di,SCROLLROW*SCREENWIDTH/4
push cx
push ds
mov ds,[FontDataSeg]
DrawCharColumn1:
mov al,[ds:si]
mov [es:di],al
mov [es:di+SCREENWIDTH/8],al
add si,bx
add di,bp
loop DrawCharColumn1
pop ds
pop cx
mov dx,3C4h ; Enable Write to Plane 2
mov ax,0202h
out dx,ax
mov si,[CharOffs] ; Loads Char BitMap Address
mov di,[WinOffs] ; Loads VGA Window Dest Address
inc si
add di,SCROLLROW*SCREENWIDTH/4
push cx
push ds
mov ds,[FontDataSeg]
DrawCharColumn2:
mov al,[ds:si]
mov [es:di],al
mov [es:di+SCREENWIDTH/8],al
add si,bx
add di,bp
loop DrawCharColumn2
pop ds
pop cx
mov dx,3C4h ; Enable Write to Plane 3
mov ax,0402h
out dx,ax
mov si,[CharOffs] ; Loads Char BitMap Address
mov di,[WinOffs] ; Loads VGA Window Dest Address
add si,2
add di,SCROLLROW*SCREENWIDTH/4
push cx
push ds
mov ds,[FontDataSeg]
DrawCharColumn3:
mov al,[ds:si]
mov [es:di],al
mov [es:di+SCREENWIDTH/8],al
add si,bx
add di,bp
loop DrawCharColumn3
pop ds
pop cx
mov dx,3C4h ; Enable Write to Plane 4
mov ax,0802h
out dx,ax
mov si,[CharOffs] ; Loads Char BitMap Address
mov di,[WinOffs] ; Loads VGA Window Dest Address
add si,3
add di,SCROLLROW*SCREENWIDTH/4
push cx
push ds
mov ds,[FontDataSeg]
DrawCharColumn4:
mov al,[ds:si]
mov [es:di],al
mov [es:di+SCREENWIDTH/8],al
add si,bx
add di,bp
loop DrawCharColumn4
pop ds
pop cx
inc [WinOffs] ; Advance Window by 4 pixels
cmp [WinOffs],SCREENWIDTH/8
jb DontWrapWindow
mov [WinOffs],0
DontWrapWindow:
add [CharOffs],4 ; Advance Char Column by 4
clc
DrawScrollExit:
ret
endp DrawScroll
;-----------------------------------------------------------------------------
; GetsNewChar - Gets the next message Character.
; Out:
; CF=1 If no more characters
; CF=0 If more characters
;-----------------------------------------------------------------------------
proc GetsNewChar
mov si,[MesgOffs] ; Loads the Message Offset
GetCharLoop:
lodsb ; Gets the Character
test al,al ; if End of Message ReStart
jne DrawCharNow
stc
jmp GetsNewCharExit
DrawCharNow:
mov [MesgOffs],si ; Save Message Offset
sub al,[FontFirst] ; Compute the Char BitMap Address
xor ah,ah
mov bx,ax
mov dx,[FontSize]
mul dx
add ax,[FontDataOfs]
mov [CharOffs],ax
mov al,[FontWidths+bx] ; Set the Char Width
mov [CharColumn],al
clc
GetsNewCharExit:
ret
endp GetsNewChar
;-----------------------------------------------------------------------------
; Start - Start the Demostration. Called from DOS.
;-----------------------------------------------------------------------------
proc Start
mov ax,@Data ; Sets Data Segment.
mov ds,ax
mov bx,sp ; Shrink Program Memory Block.
shr bx,4
inc bx
mov ax,ss
mov dx,es
sub ax,dx
add bx,ax
mov ah,4Ah
int 21h
call SetModeX ; Sets VGA ModeX.
call InitScroll ; Init Scroller.
jc DemoExit
cld
DemoLoop:
call WaitVR ; Waits Vertical Retrace.
call DrawScroll ; Draw the Scroller.
jc DemoBreak
mov ah,1 ; Any Key Pressed?
int 16h ; No, Loop.
je DemoLoop
DemoBreak:
call DoneScroll ; Done Scroller.
DemoExit:
mov ax,0003h ; Set Text Mode.
int 10h
mov ax,4C00h ; Exit to DOS.
int 21h
endp Start
end Start
