/
dblbuf.asm
149 lines (131 loc) · 3.92 KB
/
dblbuf.asm
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;===================================================================================================
; Double Buffering
;
; Written By: Oded Cnaan (oded.8bit@gmail.com)
; Site: http://odedc.net
; Licence: GPLv3 (see LICENSE file)
; Package: GrLib
;
; Description:
; Double buffering implementation
;===================================================================================================
LOCALS @@
DATASEG
_DblBufferSeg dw 0
_IsDblBuffer db FALSE
CODESEG
;------------------------------------------------------------------------
; MACRO Description: Sets whether we use double buffering
;
; Input:
; state - TRUE or FALSE
;------------------------------------------------------------------------
MACRO SetDoubleBuffering state
mov [_IsDblBuffer], state
ENDM
;------------------------------------------------------------------------
; MACRO Description: saves double buffering segment
;
; Input:
; seg - the segment
;------------------------------------------------------------------------
MACRO SetDoubleBufferSeg seg
mov [_DblBufferSeg], seg
ENDM
;------------------------------------------------------------------------
; MACRO Description: Gets double buffering segment into a register
;
; Input:
; reg - register
;------------------------------------------------------------------------
MACRO GetDblBufferSeg reg
push [_DblBufferSeg]
pop reg
ENDM
;------------------------------------------------------------------------
; MACRO Description: Is using double buffering
;
; Input:
; jmpIfTrue - label to jump to in case NOT using double buffering
;------------------------------------------------------------------------
MACRO IsDblBuffering jmpIfFalse
cmp [_IsDblBuffer], FALSE
je jmpIfFalse
ENDM
;------------------------------------------------------------------------
; PROC Description: Allocate double buffer for VGA mode 320x200x256
; and clears the buffer (black)
;
; Assuming FreeProgramMem was already called
;------------------------------------------------------------------------
PROC AllocateDblBuffer
store_sp_bp
push ax bx
mov bx, VGA_SCREEN_WIDTH * VGA_SCREEN_HEIGHT
shr bx,4 ; bx/16
push bx
call malloc
cmp ax, 0
jz @@end
SetDoubleBufferSeg ax
SetDoubleBuffering TRUE
call ClearDblBuffer
@@end:
pop bx ax
restore_sp_bp
ret
ENDP AllocateDblBuffer
;------------------------------------------------------------------------
; PROC Description: Releases the buffer and stops double buffering
;------------------------------------------------------------------------
PROC ReleaseDblBuffer
store_sp_bp
push ax es
IsDblBuffering @@end
SetDoubleBuffering FALSE
GetDblBufferSeg ax
push ax
call mfree
@@end:
pop es ax
restore_sp_bp
ret
ENDP ReleaseDblBuffer
;------------------------------------------------------------------------
; PROC Description: clears entire double buffer
;------------------------------------------------------------------------
PROC ClearDblBuffer
store_sp_bp
push ax es di cx
IsDblBuffering @@end
GetDblBufferSeg es
xor di,di
xor ax,ax
mov ax,0
mov cx,VGA_SCREEN_WIDTH * VGA_SCREEN_HEIGHT
rep stosb ; Store AL at address ES:DI
@@end:
pop cx di es ax
restore_sp_bp
ret
ENDP ClearDblBuffer
;------------------------------------------------------------------------
; PROC Description: Copy double buffer to video memory (VGA)
;------------------------------------------------------------------------
PROC CopyDblBufToVideo
store_sp_bp
push si di cx es ds
IsDblBuffering @@end
mov cx, [GR_START_ADDR]
mov es, cx
GetDblBufferSeg ds
xor si,si
xor di,di
mov cx, VGA_SCREEN_WIDTH * VGA_SCREEN_HEIGHT
;DS:SI to address ES:DI
rep movsb
@@end:
pop ds es cx di si
restore_sp_bp
ret
ENDP CopyDblBufToVideo