Category : Files from Magazines
Archive   : PJ91.ZIP
Filename : MONOSCRN.ASM

;*******************************************************************************
;| |
;| Module: Monochrome Screen access from Windows 3.0 |
;| |
;| Description: This module demonstrates how to access memory mapped |
;| devices within the Windows environment. |
;| |
;| Author: Chris Schwartz (c) 10/25/90 |
;| |
;*******************************************************************************

.MODEL SMALL

PUBLIC DllInit ;dll entry point
PUBLIC WEP ;dll exit point

PUBLIC VioInit
PUBLIC VioWrtStrAttr
PUBLIC DpmActiveMode
PUBLIC DpmSelectorFromSegment

.DATA

bogusData dw 8 DUP(0) ;just to keep windows from wigging out
wVideoSeg dw 0

.CODE
;*******************************************************************************
;| |
;| FAR PASCAL Calling Convention |
;| |
;| BOOL DllInit(VOID); - Dll entry point, called by windows during loading|
;| |
;| Entry Values: DS = Library Data Segment ES = Command Line Sel |
;| DI = Module Handle SI = Command Line Off |
;| CX = Local Heap Size |
;| |
;| Return Values: AX = 0 Failed, don't load |
;| AX != 0 Success, load this puppy. |
;| |
;*******************************************************************************
;-------------------------------------------------------------------------------
DllInit PROC FAR
mov ax, 1 ;load this puppy
ret
DllInit ENDP

;*******************************************************************************
;| |
;| FAR PASCAL Calling Convention |
;| |
;| BOOL WEP(WORD wExitMode); - Dll exit point |
;| |
;| Return Values: AX = 0 Failed Cleanup |
;| AX != 0 Success |
;| |
;*******************************************************************************
;-------------------------------------------------------------------------------
WEP PROC FAR
mov ax, 1 ;goodbye
ret 2
WEP ENDP

;*******************************************************************************
;| |
;| FAR PASCAL Calling Convention |
;| |
;| BOOL DpmActiveMode(VOID); |
;| |
;| Return Values: AX = 0 Protected Mode under DPMI |
;| AX != 0 Real mode, or not under DPMI |
;| |
;*******************************************************************************
;-------------------------------------------------------------------------------
DpmActiveMode PROC FAR
mov ax, 1686h ;DPMI Mode Detection Op Code
int 2Fh ;only changes the AX register
ret
DpmActiveMode ENDP

;*******************************************************************************
;| |
;| FAR PASCAL Calling Convention |
;| |
;| WORD DpmSelectorFromSegment(WORD); |
;| |
;| Return Value: AX = 0 Then function failed, else we have a selector. |
;| |
;*******************************************************************************
;-------------- Formal Parameters ----------------------------------------------
wRealSegment equ [bp+06]
;-------------------------------------------------------------------------------
DpmSelectorFromSegment PROC FAR
push bp
mov bp, sp

mov ax, 02h
mov bx, wRealSegment
int 31h
jnc DpmSFSExit ;return protected mode selector

xor ax, ax ;return error code
DpmSFSExit:
pop bp
ret 2
DpmSelectorFromSegment ENDP

;*******************************************************************************
;| |
;| FAR PASCAL Calling Convention |
;| |
;| VOID VioInit(VOID); |
;| |
;*******************************************************************************
;-------------------------------------------------------------------------------
VioInit PROC FAR
push ds
mov ax, DGROUP
mov ds, ax ;fixup the dll's data segment

call DpmActiveMode
or ax, ax
je VioInitProtMode

mov wVideoSeg, 0B000h
ret
VioInitProtMode:
mov ax, 0B000h ;monochrome segment value
push ax
call DpmSelectorFromSegment
or ax, ax
je VioInitExit

mov wVideoSeg, ax
VioInitExit:
pop ds
ret
VioInit ENDP

;*******************************************************************************
;| |
;*******************************************************************************
ScreenOffset PROC NEAR
mov bx, ax
mov cx, 6
shl ax, cl
sub cx, 2
shl bx, cl
add ax, bx
add ax, dx
shl ax, 1
mov dx, wVideoSeg
ret
ScreenOffset ENDP

;*******************************************************************************
;| |
;| FAR PASCAL Calling Convention |
;| |
;| VioWrtStrAttr(lpData, wLen, wRow, wCol, lpAttr) |
;| |
;*******************************************************************************
;-------------- Formal Parameters ----------------------------------------------
lpData equ [bp+16]
wLen equ [bp+14]
wRow equ [bp+12]
wCol equ [bp+10]
lpAttr equ [bp+06]
;-------------------------------------------------------------------------------
VioWrtStrAttr PROC FAR
push bp
mov bp, sp
push ds
mov ax, DGROUP
mov ds, ax ;fixup dll's data segment
push es
push di
push si

mov ax, wRow
mov dx, wCol

call ScreenOffset ;returns proper video address
or dx, dx
je VioWrtStrAttrExit

mov es, dx
mov di, ax
mov cx, wLen

lds si, lpAttr
lodsb
mov ah, al
lds si, lpData

VioWrtStrAttrLoop:

lodsb
stosw
loop VioWrtStrAttrLoop ;cook those puppies

VioWrtStrAttrExit:
pop si
pop di
pop es
pop ds
pop bp
ret 14
VioWrtStrAttr ENDP
END DllInit