305 lines
6.8 KiB
C++
305 lines
6.8 KiB
C++
/*
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* Portions of this file are copyright Rebirth contributors and licensed as
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* described in COPYING.txt.
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* Portions of this file are copyright Parallax Software and licensed
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* according to the Parallax license below.
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* See COPYING.txt for license details.
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THE COMPUTER CODE CONTAINED HEREIN IS THE SOLE PROPERTY OF PARALLAX
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SOFTWARE CORPORATION ("PARALLAX"). PARALLAX, IN DISTRIBUTING THE CODE TO
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END-USERS, AND SUBJECT TO ALL OF THE TERMS AND CONDITIONS HEREIN, GRANTS A
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ROYALTY-FREE, PERPETUAL LICENSE TO SUCH END-USERS FOR USE BY SUCH END-USERS
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IN USING, DISPLAYING, AND CREATING DERIVATIVE WORKS THEREOF, SO LONG AS
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SUCH USE, DISPLAY OR CREATION IS FOR NON-COMMERCIAL, ROYALTY OR REVENUE
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FREE PURPOSES. IN NO EVENT SHALL THE END-USER USE THE COMPUTER CODE
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CONTAINED HEREIN FOR REVENUE-BEARING PURPOSES. THE END-USER UNDERSTANDS
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AND AGREES TO THE TERMS HEREIN AND ACCEPTS THE SAME BY USE OF THIS FILE.
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COPYRIGHT 1993-1998 PARALLAX SOFTWARE CORPORATION. ALL RIGHTS RESERVED.
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*/
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/*
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*
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* Graphical routines for drawing lines.
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*
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*/
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#include <stdlib.h>
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#include "u_mem.h"
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#include "gr.h"
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#include "grdef.h"
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#include "maths.h"
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#include "clip.h"
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#ifdef OGL
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#include "ogl_init.h"
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#endif
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/*
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Symmetric Double Step Line Algorithm
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by Brian Wyvill
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from "Graphics Gems", Academic Press, 1990
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*/
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/* non-zero flag indicates the pixels needing EXCHG back. */
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static void plot(int x,int y,int flag)
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{
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if (flag)
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gr_upixel(y, x);
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else
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gr_upixel(x, y);
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}
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static int gr_hline(int x1, int x2, int y)
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{
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int i;
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if (x1 > x2) EXCHG(x1,x2);
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for (i=x1; i<=x2; i++ )
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gr_upixel( i, y );
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return 0;
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}
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static int gr_vline(int y1, int y2, int x)
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{
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int i;
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if (y1 > y2) EXCHG(y1,y2);
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for (i=y1; i<=y2; i++ )
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gr_upixel( x, i );
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return 0;
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}
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static void gr_universal_uline(int a1, int b1, int a2, int b2)
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{
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int dx, dy, incr1, incr2, D, x, y, xend, c, pixels_left;
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int x1, y1;
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int sign_x = 1, sign_y = 1, step, reverse, i;
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if (a1==a2) {
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gr_vline(b1,b2,a1);
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return;
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}
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if (b1==b2) {
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gr_hline(a1,a2,b1);
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return;
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}
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dx = a2 - a1;
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dy = b2 - b1;
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if (dx < 0) {
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sign_x = -1;
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dx *= -1;
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}
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if (dy < 0) {
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sign_y = -1;
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dy *= -1;
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}
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/* decide increment sign by the slope sign */
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if (sign_x == sign_y)
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step = 1;
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else
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step = -1;
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if (dy > dx) { /* chooses axis of greatest movement (make * dx) */
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EXCHG(a1, b1);
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EXCHG(a2, b2);
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EXCHG(dx, dy);
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reverse = 1;
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} else
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reverse = 0;
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/* note error check for dx==0 should be included here */
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if (a1 > a2) { /* start from the smaller coordinate */
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x = a2;
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y = b2;
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x1 = a1;
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y1 = b1;
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} else {
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x = a1;
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y = b1;
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x1 = a2;
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y1 = b2;
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}
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/* Note dx=n implies 0 - n or (dx+1) pixels to be set */
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/* Go round loop dx/4 times then plot last 0,1,2 or 3 pixels */
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/* In fact (dx-1)/4 as 2 pixels are already plottted */
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xend = (dx - 1) / 4;
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pixels_left = (dx - 1) % 4; /* number of pixels left over at the
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* end */
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plot(x, y, reverse);
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plot(x1, y1, reverse); /* plot first two points */
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incr2 = 4 * dy - 2 * dx;
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if (incr2 < 0) { /* slope less than 1/2 */
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c = 2 * dy;
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incr1 = 2 * c;
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D = incr1 - dx;
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for (i = 0; i < xend; i++) { /* plotting loop */
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++x;
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--x1;
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if (D < 0) {
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/* pattern 1 forwards */
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plot(x, y, reverse);
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plot(++x, y, reverse);
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/* pattern 1 backwards */
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plot(x1, y1, reverse);
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plot(--x1, y1, reverse);
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D += incr1;
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} else {
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if (D < c) {
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/* pattern 2 forwards */
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plot(x, y, reverse);
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plot(++x, y += step, reverse);
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/* pattern 2 backwards */
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plot(x1, y1, reverse);
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plot(--x1, y1 -= step, reverse);
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} else {
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/* pattern 3 forwards */
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plot(x, y += step, reverse);
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plot(++x, y, reverse);
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/* pattern 3 backwards */
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plot(x1, y1 -= step, reverse);
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plot(--x1, y1, reverse);
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}
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D += incr2;
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}
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} /* end for */
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/* plot last pattern */
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if (pixels_left) {
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if (D < 0) {
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plot(++x, y, reverse); /* pattern 1 */
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if (pixels_left > 1)
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plot(++x, y, reverse);
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if (pixels_left > 2)
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plot(--x1, y1, reverse);
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} else {
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if (D < c) {
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plot(++x, y, reverse); /* pattern 2 */
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if (pixels_left > 1)
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plot(++x, y += step, reverse);
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if (pixels_left > 2)
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plot(--x1, y1, reverse);
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} else {
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/* pattern 3 */
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plot(++x, y += step, reverse);
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if (pixels_left > 1)
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plot(++x, y, reverse);
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if (pixels_left > 2)
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plot(--x1, y1 -= step, reverse);
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}
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}
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} /* end if pixels_left */
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}
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/* end slope < 1/2 */
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else { /* slope greater than 1/2 */
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c = 2 * (dy - dx);
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incr1 = 2 * c;
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D = incr1 + dx;
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for (i = 0; i < xend; i++) {
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++x;
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--x1;
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if (D > 0) {
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/* pattern 4 forwards */
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plot(x, y += step, reverse);
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plot(++x, y += step, reverse);
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/* pattern 4 backwards */
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plot(x1, y1 -= step, reverse);
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plot(--x1, y1 -= step, reverse);
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D += incr1;
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} else {
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if (D < c) {
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/* pattern 2 forwards */
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plot(x, y, reverse);
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plot(++x, y += step, reverse);
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/* pattern 2 backwards */
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plot(x1, y1, reverse);
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plot(--x1, y1 -= step, reverse);
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} else {
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/* pattern 3 forwards */
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plot(x, y += step, reverse);
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plot(++x, y, reverse);
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/* pattern 3 backwards */
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plot(x1, y1 -= step, reverse);
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plot(--x1, y1, reverse);
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}
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D += incr2;
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}
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} /* end for */
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/* plot last pattern */
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if (pixels_left) {
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if (D > 0) {
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plot(++x, y += step, reverse); /* pattern 4 */
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if (pixels_left > 1)
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plot(++x, y += step, reverse);
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if (pixels_left > 2)
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plot(--x1, y1 -= step, reverse);
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} else {
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if (D < c) {
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plot(++x, y, reverse); /* pattern 2 */
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if (pixels_left > 1)
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plot(++x, y += step, reverse);
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if (pixels_left > 2)
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plot(--x1, y1, reverse);
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} else {
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/* pattern 3 */
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plot(++x, y += step, reverse);
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if (pixels_left > 1)
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plot(++x, y, reverse);
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if (pixels_left > 2) {
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if (D > c) /* step 3 */
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plot(--x1, y1 -= step, reverse);
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else /* step 2 */
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plot(--x1, y1, reverse);
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}
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}
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}
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}
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}
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}
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//unclipped version just calls clipping version for now
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int gr_uline(fix _a1, fix _b1, fix _a2, fix _b2)
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{
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int a1,b1,a2,b2;
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a1 = f2i(_a1); b1 = f2i(_b1); a2 = f2i(_a2); b2 = f2i(_b2);
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switch(TYPE)
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{
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#ifdef OGL
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case BM_OGL:
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ogl_ulinec(a1,b1,a2,b2,COLOR);
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return 0;
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#endif
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case BM_LINEAR:
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gr_universal_uline( a1,b1,a2,b2);
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return 0;
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}
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return 2;
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}
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// Returns 0 if drawn with no clipping, 1 if drawn but clipped, and
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// 2 if not drawn at all.
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int gr_line(fix a1, fix b1, fix a2, fix b2)
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{
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int x1, y1, x2, y2;
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int clipped=0;
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x1 = i2f(MINX);
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y1 = i2f(MINY);
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x2 = i2f(MAXX);
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y2 = i2f(MAXY);
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CLIPLINE(a1,b1,a2,b2,x1,y1,x2,y2,return 2,clipped=1, FIXSCALE );
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gr_uline( a1, b1, a2, b2 );
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return clipped;
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}
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