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https://github.com/electronicarts/CnC_Red_Alert.git
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Initial commit of Command & Conquer Red Alert source code.
This commit is contained in:
LFeenanEA
464
WIN32LIB/SRCDEBUG/DRAWLINE.ASM
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464
WIN32LIB/SRCDEBUG/DRAWLINE.ASM
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;
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; Command & Conquer Red Alert(tm)
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; Copyright 2025 Electronic Arts Inc.
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;
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; This program is free software: you can redistribute it and/or modify
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; it under the terms of the GNU General Public License as published by
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; the Free Software Foundation, either version 3 of the License, or
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; (at your option) any later version.
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;
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; This program is distributed in the hope that it will be useful,
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; but WITHOUT ANY WARRANTY; without even the implied warranty of
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; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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; GNU General Public License for more details.
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;
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; You should have received a copy of the GNU General Public License
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; along with this program. If not, see <http://www.gnu.org/licenses/>.
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;
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;***************************************************************************
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;** C O N F I D E N T I A L --- W E S T W O O D A S S O C I A T E S **
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;***************************************************************************
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;* *
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;* Project Name : Westwood 32 bit Library *
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;* *
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;* File Name : DRAWLINE.ASM *
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;* *
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;* Programmer : Phil W. Gorrow *
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;* *
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;* Start Date : June 16, 1994 *
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;* *
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;* Last Update : August 30, 1994 [IML] *
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;* *
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;*-------------------------------------------------------------------------*
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;* Functions: *
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;* VVC::Scale -- Scales a virtual viewport to another virtual viewport *
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;* Normal_Draw -- jump loc for drawing scaled line of normal pixel *
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;* __DRAW_LINE -- Assembly routine to draw a line *
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;* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - *
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IDEAL
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P386
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MODEL USE32 FLAT
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INCLUDE ".\drawbuff.inc"
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INCLUDE ".\gbuffer.inc"
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CODESEG
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;***************************************************************************
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;* VVC::DRAW_LINE -- Scales a virtual viewport to another virtual viewport *
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;* *
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;* INPUT: WORD sx_pixel - the starting x pixel position *
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;* WORD sy_pixel - the starting y pixel position *
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;* WORD dx_pixel - the destination x pixel position *
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;* WORD dy_pixel - the destination y pixel position *
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;* WORD color - the color of the line to draw *
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;* *
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;* Bounds Checking: Compares sx_pixel, sy_pixel, dx_pixel and dy_pixel *
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;* with the graphic viewport it has been assigned to. *
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;* *
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;* HISTORY: *
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;* 06/16/1994 PWG : Created. *
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;* 08/30/1994 IML : Fixed clipping bug. *
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;*=========================================================================*
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PROC Buffer_Draw_Line C NEAR
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USES eax,ebx,ecx,edx,esi,edi
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;*==================================================================
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;* Define the arguements that the function takes.
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;*==================================================================
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ARG this_object:DWORD ; associated graphic view port
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ARG x1_pixel:DWORD ; the start x pixel position
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ARG y1_pixel:DWORD ; the start y pixel position
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ARG x2_pixel:DWORD ; the dest x pixel position
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ARG y2_pixel:DWORD ; the dest y pixel position
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ARG color:DWORD ; the color we are drawing
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;*==================================================================
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;* Define the local variables that we will use on the stack
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;*==================================================================
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LOCAL clip_min_x:DWORD
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LOCAL clip_max_x:DWORD
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LOCAL clip_min_y:DWORD
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LOCAL clip_max_y:DWORD
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LOCAL clip_var:DWORD
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LOCAL accum:DWORD
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LOCAL bpr:DWORD
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;*==================================================================
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;* Take care of find the clip minimum and maximums
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;*==================================================================
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mov ebx,[this_object]
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xor eax,eax
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mov [clip_min_x],eax
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mov [clip_min_y],eax
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mov eax,[(GraphicViewPort ebx).GVPWidth]
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mov [clip_max_x],eax
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add eax,[(GraphicViewPort ebx).GVPXAdd]
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add eax,[(GraphicViewPort ebx).GVPPitch]
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mov [bpr],eax
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mov eax,[(GraphicViewPort ebx).GVPHeight]
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mov [clip_max_y],eax
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;*==================================================================
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;* Adjust max pixels as they are tested inclusively.
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;*==================================================================
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dec [clip_max_x]
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dec [clip_max_y]
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;*==================================================================
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;* Set the registers with the data for drawing the line
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;*==================================================================
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mov eax,[x1_pixel] ; eax = start x pixel position
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mov ebx,[y1_pixel] ; ebx = start y pixel position
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mov ecx,[x2_pixel] ; ecx = dest x pixel position
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mov edx,[y2_pixel] ; edx = dest y pixel position
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;*==================================================================
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;* This is the section that "pushes" the line into bounds.
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;* I have marked the section with PORTABLE start and end to signify
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;* how much of this routine is 100% portable between graphics modes.
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;* It was just as easy to have variables as it would be for constants
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;* so the global vars ClipMaxX,ClipMinY,ClipMaxX,ClipMinY are used
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;* to clip the line (default is the screen)
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;* PORTABLE start
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;*==================================================================
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cmp eax,[clip_min_x]
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jl short ??clip_it
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cmp eax,[clip_max_x]
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jg short ??clip_it
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cmp ebx,[clip_min_y]
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jl short ??clip_it
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cmp ebx,[clip_max_y]
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jg short ??clip_it
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cmp ecx,[clip_min_x]
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jl short ??clip_it
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cmp ecx,[clip_max_x]
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jg short ??clip_it
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cmp edx,[clip_min_y]
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jl short ??clip_it
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cmp edx,[clip_max_y]
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jle short ??on_screen
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;*==================================================================
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;* Takes care off clipping the line.
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;*==================================================================
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??clip_it:
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call NEAR PTR ??set_bits
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xchg eax,ecx
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xchg ebx,edx
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mov edi,esi
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call NEAR PTR ??set_bits
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mov [clip_var],edi
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or [clip_var],esi
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jz short ??on_screen
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test edi,esi
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jne short ??off_screen
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shl esi,2
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call [DWORD PTR cs:??clip_tbl+esi]
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jc ??clip_it
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xchg eax,ecx
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xchg ebx,edx
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shl edi,2
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call [DWORD PTR cs:??clip_tbl+edi]
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jmp ??clip_it
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??on_screen:
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jmp ??draw_it
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??off_screen:
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jmp ??out
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;*==================================================================
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;* Jump table for clipping conditions
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;*==================================================================
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??clip_tbl DD ??nada,??a_up,??a_dwn,??nada
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DD ??a_lft,??a_lft,??a_dwn,??nada
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DD ??a_rgt,??a_up,??a_rgt,??nada
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DD ??nada,??nada,??nada,??nada
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??nada:
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clc
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retn
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??a_up:
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mov esi,[clip_min_y]
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call NEAR PTR ??clip_vert
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stc
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retn
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??a_dwn:
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mov esi,[clip_max_y]
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neg esi
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neg ebx
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neg edx
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call NEAR PTR ??clip_vert
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neg ebx
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neg edx
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stc
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retn
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;*==================================================================
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;* xa'=xa+[(miny-ya)(xb-xa)/(yb-ya)]
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;*==================================================================
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??clip_vert:
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push edx
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push eax
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mov [clip_var],edx ; clip_var = yb
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sub [clip_var],ebx ; clip_var = (yb-ya)
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neg eax ; eax=-xa
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add eax,ecx ; (ebx-xa)
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mov edx,esi ; edx=miny
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sub edx,ebx ; edx=(miny-ya)
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imul edx
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idiv [clip_var]
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pop edx
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add eax,edx
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pop edx
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mov ebx,esi
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retn
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??a_lft:
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mov esi,[clip_min_x]
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call NEAR PTR ??clip_horiz
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stc
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retn
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??a_rgt:
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mov esi,[clip_max_x]
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neg eax
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neg ecx
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neg esi
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call NEAR PTR ??clip_horiz
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neg eax
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neg ecx
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stc
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retn
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;*==================================================================
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;* ya'=ya+[(minx-xa)(yb-ya)/(xb-xa)]
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;*==================================================================
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??clip_horiz:
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push edx
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mov [clip_var],ecx ; clip_var = xb
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sub [clip_var],eax ; clip_var = (xb-xa)
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sub edx,ebx ; edx = (yb-ya)
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neg eax ; eax = -xa
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add eax,esi ; eax = (minx-xa)
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imul edx ; eax = (minx-xa)(yb-ya)
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idiv [clip_var] ; eax = (minx-xa)(yb-ya)/(xb-xa)
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add ebx,eax ; ebx = xa+[(minx-xa)(yb-ya)/(xb-xa)]
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pop edx
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mov eax,esi
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retn
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;*==================================================================
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;* Sets the condition bits
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;*==================================================================
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??set_bits:
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xor esi,esi
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cmp ebx,[clip_min_y] ; if y >= top its not up
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jge short ??a_not_up
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or esi,1
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??a_not_up:
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cmp ebx,[clip_max_y] ; if y <= bottom its not down
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jle short ??a_not_down
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or esi,2
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??a_not_down:
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cmp eax,[clip_min_x] ; if x >= left its not left
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jge short ??a_not_left
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or esi,4
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??a_not_left:
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cmp eax,[clip_max_x] ; if x <= right its not right
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jle short ??a_not_right
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or esi,8
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??a_not_right:
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retn
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;*==================================================================
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;* Draw the line to the screen.
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;* PORTABLE end
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;*==================================================================
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??draw_it:
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sub edx,ebx ; see if line is being draw down
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jnz short ??not_hline ; if not then its not a hline
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jmp short ??hline ; do special case h line
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??not_hline:
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jg short ??down ; if so there is no need to rev it
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neg edx ; negate for actual pixel length
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xchg eax,ecx ; swap x's to rev line draw
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sub ebx,edx ; get old edx
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??down:
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push edx
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push eax
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mov eax,[bpr]
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mul ebx
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mov ebx,eax
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mov eax,[this_object]
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add ebx,[(GraphicViewPort eax).GVPOffset]
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pop eax
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pop edx
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mov esi,1 ; assume a right mover
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sub ecx,eax ; see if line is right
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jnz short ??not_vline ; see if its a vertical line
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jmp ??vline
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??not_vline:
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jg short ??right ; if so, the difference = length
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??left:
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neg ecx ; else negate for actual pixel length
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neg esi ; negate counter to move left
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??right:
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cmp ecx,edx ; is it a horiz or vert line
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jge short ??horiz ; if ecx > edx then |x|>|y| or horiz
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??vert:
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xchg ecx,edx ; make ecx greater and edx lesser
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mov edi,ecx ; set greater
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mov [accum],ecx ; set accumulator to 1/2 greater
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shr [accum],1
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;*==================================================================
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;* at this point ...
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;* eax=xpos ; ebx=page line offset; ecx=counter; edx=lesser; edi=greater;
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;* esi=adder; accum=accumulator
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;* in a vertical loop the adder is conditional and the inc constant
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;*==================================================================
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??vert_loop:
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add ebx,eax
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mov eax,[color]
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??v_midloop:
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mov [ebx],al
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dec ecx
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jl ??out
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add ebx,[bpr]
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sub [accum],edx ; sub the lesser
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jge ??v_midloop ; any line could be new
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add [accum],edi ; add greater for new accum
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add ebx,esi ; next pixel over
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jmp ??v_midloop
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??horiz:
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mov edi,ecx ; set greater
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mov [accum],ecx ; set accumulator to 1/2 greater
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shr [accum],1
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;*==================================================================
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;* at this point ...
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;* eax=xpos ; ebx=page line offset; ecx=counter; edx=lesser; edi=greater;
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;* esi=adder; accum=accumulator
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;* in a vertical loop the adder is conditional and the inc constant
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;*==================================================================
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??horiz_loop:
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add ebx,eax
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mov eax,[color]
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??h_midloop:
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mov [ebx],al
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dec ecx ; dec counter
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jl ??out ; end of line
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add ebx,esi
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sub [accum],edx ; sub the lesser
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jge ??h_midloop
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add [accum],edi ; add greater for new accum
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add ebx,[bpr] ; goto next line
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jmp ??h_midloop
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;*==================================================================
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;* Special case routine for horizontal line draws
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;*==================================================================
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??hline:
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cmp eax,ecx ; make eax < ecx
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jl short ??hl_ac
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xchg eax,ecx
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??hl_ac:
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sub ecx,eax ; get len
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inc ecx
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push edx
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push eax
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mov eax,[bpr]
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mul ebx
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mov ebx,eax
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mov eax,[this_object]
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add ebx,[(GraphicViewPort eax).GVPOffset]
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pop eax
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pop edx
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add ebx,eax
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mov edi,ebx
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cmp ecx,15
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jg ??big_line
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mov al,[byte color]
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rep stosb ; write as many words as possible
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jmp short ??out ; get outt
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??big_line:
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mov al,[byte color]
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mov ah,al
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mov ebx,eax
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shl eax,16
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mov ax,bx
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test edi,3
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jz ??aligned
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mov [edi],al
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inc edi
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dec ecx
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test edi,3
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jz ??aligned
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mov [edi],al
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inc edi
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dec ecx
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test edi,3
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jz ??aligned
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mov [edi],al
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inc edi
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dec ecx
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??aligned:
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mov ebx,ecx
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shr ecx,2
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rep stosd
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mov ecx,ebx
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and ecx,3
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rep stosb
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jmp ??out
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;*==================================================================
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;* a special case routine for vertical line draws
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;*==================================================================
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??vline:
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mov ecx,edx ; get length of line to draw
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inc ecx
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add ebx,eax
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mov eax,[color]
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??vl_loop:
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mov [ebx],al ; store bit
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add ebx,[bpr]
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dec ecx
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jnz ??vl_loop
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??out:
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ret
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ENDP Buffer_Draw_Line
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END
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