Tech Arsenal 1/Tech Arsenal (Arsenal Computer).ISO/tek-01/xlib04.zip/XCLIPPBM.ASM

Assembly Source File | 1992-11-12 | 12KB | 496 lines

;-----------------------------------------------------------------------
; MODULE XCLIPPBM
;
; This module was written by Matthew MacKenzie
; [e-mail]
;
; Clipped transfer of planar bitmaps from system memory to video memory.
;
; Compile with TASM.
; C near-callable.
;
; ****** XLIB - Mode X graphics library                ****************
; ******                                               ****************
; ****** Written By Themie Gouthas                     ****************
;
; [e-mail]
; [e-mail]
;-----------------------------------------------------------------------

include xlib.inc
include xclippbm.inc


    .data

    align 2

; global clipping variables
_TopBound       dw      (?)
_BottomBound    dw      (?)
_LeftBound      dw      (?)
_RightBound     dw      (?)

; VGA plane masks
ColumnMask      db      011h,022h,044h,088h

; bit delay timers
LeftDelay       db      0, 1, 2, 4
RightDelay      db      0, 4, 2, 1


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; _x_clip_pbm
;
; C near-callable as:
;
; void x_clip_pbm (int X, int Y, int ScreenOffs, char far * Bitmap);
;
; Bitmap is a planar bitmap, in the regular Xlib format.
;
; ax, bx, cx, and dx go south.

    .code

    public _x_clip_pbm
    align   2
_x_clip_pbm proc
ARG     X:word, Y:word, ScreenOffs:word, Bitmap:dword
LOCAL   left_counter, right_counter,column,clipped_height,clipped_width,screen_pos,bitmap_pos,bitmap_size,VGA_mask,width_copy,height_temp,screen_width:word=LocalStk
; Tasm 1.0 does not allow the \ line continuation
;LOCAL   left_counter:word, right_counter:word, \
;        column:word, clipped_height:word, clipped_width:word, \
;        screen_pos:word, bitmap_pos:word, bitmap_size:word, \
;        VGA_mask:word, width_copy, height_temp:word, \
;        screen_width:word=LocalStk

    push bp
    mov bp, sp
    sub sp, LocalStk
    push si
    push di
    push ds

; sociopathic cases: are the clipping bounds out of order?
    mov ax, _TopBound
    cmp ax, _BottomBound
    jg @@GetOut
    mov ax, _LeftBound
    cmp ax, _RightBound
    jle @@ReasonableAndProper
@@GetOut:
    jmp @@OuttaHere     ; for conditional branches

@@ReasonableAndProper:

; we need to use both the tables in ds and the height and width of the bitmap
    les si, Bitmap

; vertical position
    xor cx, cx
    mov cl, byte ptr es:[si + 1] ; height of bitmap
    xor ax, ax
    mov al, byte ptr es:[si] ; width of bitmap
    mul cx
    mov bitmap_size, ax
    mov ax, Y
    cmp ax, _BottomBound ; top edge below clipping box?
    jg @@GetOut

    mov bx, cx
    add bx, ax
    dec bx              ; bottom edge = Y + height - 1
    cmp bx, _TopBound
    jl @@GetOut
    sub bx, _BottomBound ; bottom margin = bottom edge - BottomBound
    jle @@NoBottomBound
    sub cx, bx          ; clip bottom margin from height
@@NoBottomBound:
    mov bx, _TopBound
    sub bx, ax          ; top margin = TopBound - Y
    jle @@NoTopBound
    add ax, bx          ; top edge = Y + top margin
    sub cx, bx          ; clip top margin from height
    jmp @@KeepMargin
@@NoTopBound:
    xor bx, bx
@@KeepMargin:
    mov clipped_height, cx

    mul _ScrnLogicalByteWidth
    mov di, ax
    add di, ScreenOffs  ; row of upper-left corner of blit

    mov cl, byte ptr es:[si] ; width of bitmap (ch is still 0 from height)
    mov ax, cx
    mul bx
    add si, ax
    add si, 2           ; starting position in bitmap

; horizontal position
    mov width_copy, cx
    mov dx, X
    cmp dx, _RightBound
    jg @@GetOut
    mov dx, 0           ; unclipped value for right delay

    mov ax, cx
    shl ax, 2           ; width in pixels
    add ax, X
    dec ax              ; right edge = X + width in pixels - 1
    cmp ax, _LeftBound
    jl @@GetOut
    sub ax, _RightBound  ; right margin = right edge - RightBound
    jle @@NoRightBound
    mov bx, ax
    and bx, 3
    mov dl, RightDelay[bx]
    shr ax, 2
    sub cx, ax          ; subtract clipped bytes from width
@@NoRightBound:
    mov right_counter, dx
    mov dx, 0           ; unclipped value for left delay
    mov ax, _LeftBound
    sub ax, X           ; left margin = LeftBound - X
    jle @@NoLeftBound
    mov bx, ax
    and bx, 3
    mov dl, LeftDelay[bx]
    add ax, 3
    shr ax, 2           ; left margin/4, rounded up
    sub cx, ax          ; subtract clipped bytes from width
    add si, ax          ; move starting position in bitmap past margin
    add di, ax          ; move starting position on screen past margin
@@NoLeftBound:
    mov left_counter, dx
    mov clipped_width, cx

    mov ax, X           ; add x coordinate to screen position
    mov bx, ax
    shr ax, 2
    add di, ax

    mov dx, SC_INDEX
    mov al, MAP_MASK
    out dx, al
    inc dx

    and bx, 3           ; initial mask
    xor ax, ax
    mov al, ColumnMask[bx]
    mov VGA_mask, ax
    out dx, al          ; initial mask

    mov column, 4
    mov bitmap_pos, si
    mov screen_pos, di
    mov ax, _ScrnLogicalByteWidth
    mov screen_width, ax ; since we move ds

; we've used all our tables, so we can change ds to point to the bitmap,
; and es to point to the screen
    mov ds, word ptr [Bitmap + 2]
    mov ax, SCREEN_SEG
    mov es, ax

    cld                 ; strings go forward
    mov bx, width_copy
    sub bx, clipped_width ; bytes to advance one line in bitmap

; let's actually draw something for a change
@@WritePlane:
    mov ax, clipped_height
    mov height_temp, ax
    mov dx, screen_width
    sub dx, clipped_width ; bytes to advance one line across screen

@@WriteLine:
    mov cx, clipped_width
    shr cx, 1
    rep movsw           ; in they went, two by two...
    adc cx, 0
    rep movsb           ; catch stray last byte, if it's there
    add si, bx          ; advance one bitmap line
    add di, dx          ; advance one screen line

    dec height_temp
    jnz @@WriteLine

    dec column
    jz @@OuttaHere      ; only four columns per customer, please
    mov dx, SC_INDEX + 1
    rol byte ptr VGA_mask, 1
    adc screen_pos, 0   ; add to location if we've wrapped to plane 0
    mov al, byte ptr VGA_mask
    out dx, al          ; set VGA for next column

    shr right_counter, 1
    jnc @@NoRightCounter
    dec clipped_width   ; cut off right edge for later planes
    inc bx
@@NoRightCounter:
    shr left_counter, 1
    jnc @@NoLeftCounter
    inc clipped_width   ; add to left edge for later planes
    dec bx
    dec bitmap_pos
    dec screen_pos
@@NoLeftCounter:
    mov si, bitmap_pos
    add si, bitmap_size
    mov bitmap_pos, si
    mov di, screen_pos
    jmp @@WritePlane

@@OuttaHere:
    pop ds
    pop di
    pop si
    mov sp, bp
    pop bp

    ret
_x_clip_pbm endp


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; _x_clip_masked_pbm
;
; C near-callable as:
;
; void x_clip_masked_pbm (int X, int Y, int ScreenOffs, char far * Bitmap);
;
; Bitmap is a planar bitmap, in the regular Xlib format.
; The width of the bitmap cannot be greater than 90 bytes, however.
; Ain't that just criminal?
;
; ax, bx, cx, and dx go south.


; one branch per pixel is more than enough -- we'll unroll the line-writing
; loop all the way to try to get a little speed (at the expense, as usual,
; of a chunk of memory)

MaskedPoint macro offset
    mov al, [si + offset]
    or al, al
    jz $+6
    mov es:[di + offset], al
    endm

MaskedPointSize     equ     11

    public _x_clip_masked_pbm
    align   2
_x_clip_masked_pbm proc
ARG     X:word, Y:word, ScreenOffs:word, Bitmap:dword
; Tasm 1.0 does not allow the \ line continuation
LOCAL   left_counter,right_counter,column:word,clipped_height,screen_pos,bitmap_pos,bitmap_size,VGA_mask,width_copy,height_temp,screen_width:word=LocalStk
;LOCAL   left_counter:word, right_counter:word, \
;        column:word, clipped_height:word, \
;        screen_pos:word, bitmap_pos:word, bitmap_size:word, \
;        VGA_mask:word, width_copy, height_temp:word, \
;        screen_width:word=LocalStk
    push bp
    mov bp, sp
    sub sp, LocalStk
    push si
    push di
    push ds

; sociopathic cases: are the clipping bounds out of order?
    mov ax, _TopBound
    cmp ax, _BottomBound
    jg @@GetOut
    mov ax, _LeftBound
    cmp ax, _RightBound
    jle @@ReasonableAndProper
@@GetOut:
    jmp @@OuttaHere     ; for conditional branches

@@ReasonableAndProper:

; we need to use both the tables in ds and the height and width of the bitmap
    les si, Bitmap

; vertical position
    xor cx, cx
    mov cl, byte ptr es:[si + 1] ; height of bitmap
    xor ax, ax
    mov al, byte ptr es:[si] ; width of bitmap
    mul cx
    mov bitmap_size, ax
    mov ax, Y
    cmp ax, _BottomBound ; top edge below clipping box?
    jg @@GetOut

    mov bx, cx
    add bx, ax
    dec bx              ; bottom edge = Y + height - 1
    cmp bx, _TopBound
    jl @@GetOut
    sub bx, _BottomBound ; bottom margin = bottom edge - BottomBound
    jle @@NoBottomBound
    sub cx, bx          ; clip bottom margin from height
@@NoBottomBound:
    mov bx, _TopBound
    sub bx, ax          ; top margin = TopBound - Y
    jle @@NoTopBound
    add ax, bx          ; top edge = Y + top margin
    sub cx, bx          ; clip top margin from height
    jmp @@KeepMargin
@@NoTopBound:
    xor bx, bx
@@KeepMargin:
    mov clipped_height, cx

    mul _ScrnLogicalByteWidth
    mov di, ax
    add di, ScreenOffs  ; row of upper-left corner of blit

    mov cl, byte ptr es:[si] ; width of bitmap (ch is still 0 from height)
    mov ax, cx
    mul bx
    add si, ax
    add si, 2           ; starting position in bitmap

; horizontal position
    mov width_copy, cx
    mov dx, X
    cmp dx, _RightBound
    jg @@GetOut
    mov dx, 0           ; unclipped value for right delay

    mov ax, cx
    shl ax, 2           ; width in pixels
    add ax, X
    dec ax              ; right edge = X + width in pixels - 1
    cmp ax, _LeftBound
    jl @@GetOut
    sub ax, _RightBound ; right margin = right edge - RightBound
    jle @@NoRightBound
    mov bx, ax
    and bx, 3
    mov dl, RightDelay[bx]
    shr ax, 2
    sub cx, ax          ; subtract clipped bytes from width
@@NoRightBound:
    mov right_counter, dx
    mov dx, 0           ; unclipped value for left delay
    mov ax, _LeftBound
    sub ax, X           ; left margin = LeftBound - X
    jle @@NoLeftBound
    mov bx, ax
    and bx, 3
    mov dl, LeftDelay[bx]
    add ax, 3
    shr ax, 2           ; left margin/4, rounded up
    sub cx, ax          ; subtract clipped bytes from width
    add si, ax          ; move starting position in bitmap past margin
    add di, ax          ; move starting position on screen past margin
@@NoLeftBound:
    mov left_counter, dx
    mov ax, cx
    imul ax, (-1 * MaskedPointSize)
    add ax, offset @@LineDone + 2
    mov cx, ax          ; jump offset for plotting

    mov ax, X           ; add x coordinate to screen position
    mov bx, ax
    shr ax, 2
    add di, ax

    mov dx, SC_INDEX
    mov al, MAP_MASK
    out dx, al
    inc dx

    and bx, 3           ; initial mask
    xor ax, ax
    mov al, ColumnMask[bx]
    mov VGA_mask, ax
    out dx, al

    mov column, 4
    mov bitmap_pos, si
    mov screen_pos, di
    mov ax, _ScrnLogicalByteWidth
    mov screen_width, ax ; since we move ds

; we've used all our tables, so we can change ds to point to the bitmap,
; and es to point to the screen
    mov ds, word ptr [Bitmap + 2]
    mov ax, SCREEN_SEG
    mov es, ax

    mov bx, width_copy

; let's actually draw something for a change
    mov ax, clipped_height
    mov height_temp, ax
    mov dx, screen_width
    jmp cx

; 90 bottles of beer on the wall...
    PointLoop = 89
    rept 89
        MaskedPoint PointLoop
        PointLoop = PointLoop - 1
    endm
; one bottle of beer...

; final point needs a different branch offset, so we don't use MaskedPoint
    mov al, [si]
    or al, al
    jz @@LineDone
    mov es:[di], al

@@LineDone:
    add si, bx          ; advance one bitmap line
    add di, dx          ; advance one screen line
    dec height_temp
    jz @@PlaneDone
    jmp cx

@@PlaneDone:
    dec column
    jz @@OuttaHere      ; only four columns per customer, please
    mov dx, SC_INDEX + 1
    rol byte ptr VGA_mask, 1
    adc screen_pos, 0   ; move to new column if we've wrapped to plane 0
    mov al, byte ptr VGA_mask
    out dx, al          ; set VGA for next column

    shr right_counter, 1
    jnc @@NoRightCounter
    add cx, MaskedPointSize ; cut off right edge for later planes
@@NoRightCounter:
    shr left_counter, 1
    jnc @@NoLeftCounter
    sub cx, MaskedPointSize ; add to left edge for later planes
    dec bitmap_pos
    dec screen_pos
@@NoLeftCounter:
    mov si, bitmap_pos
    add si, bitmap_size
    mov bitmap_pos, si
    mov di, screen_pos

    mov ax, clipped_height
    mov height_temp, ax
    mov dx, screen_width
    jmp cx

@@OuttaHere:
    pop ds
    pop di
    pop si
    mov sp, bp
    pop bp

    ret
_x_clip_masked_pbm endp

    end