rcornwell.sims/display/iii.c

/*
 * Copyright (c) 2020 Lars Brinkhoff
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * Except as contained in this notice, the names of the authors shall
 * not be used in advertising or otherwise to promote the sale, use or
 * other dealings in this Software without prior written authorization
 * from the authors.
 */

#include "display.h"                    /* XY plot interface */
#include "iii.h"


#if defined(__cplusplus)
extern "C" {
#endif

int iii_init(void *dev, int debug)
{
  return display_init(DIS_III, 1, dev);
}

void iii_point (int x, int y, int l)
{
  display_point(x + 512, y + 512, l, 0);
}

int iii_cycle(int us, int slowdown)
{
  return display_age(us, slowdown);
}

/* Draw a line between two points */
void
iii_draw_line(int x1, int y1, int x2, int y2, int l)
{
    int                 dx, ax;
    int                 dy;
    int                 i, j;
    int                 pu, pd, ws, et;
    int                 ipc, fpc;

    /* Origin us to 0 */
    x1 += 512;
    y1 += 512;
    x2 += 512;
    y2 += 512;

    /* Always draw top to bottom */
    if (y1 > y2) {
       int temp;
       temp = y1;
       y1 = y2;
       y2 = temp;
       temp = x1;
       x1 = x2;
       x2 = temp;
    }

    /* Figure out distances */
    dx = x2 - x1;
    dy = y2 - y1;
    /* Figure out whether we're going left or right */
    if (dx < 0) {
        ax = -1;
        dx = -dx;
    } else {
        ax = 1;
    }

    /* Vertical line */
    if (dx == 0) {
        for (i = 1; i < dy; i++) {
            display_point(x1, y1, l, 0);
            y1++;
        }
        return;
    }
    /* Horizontal line */
    if (dy == 0) {
        for (i = 1; i < dx; i++) {
            display_point(x1, y1, l, 0);
	    x1+=ax;
        }
        return;
    } 
    /* Diagnonal line */
    if (dx == dy) {
        for (i = 1; i < dx; i++) {
            display_point(x1, y1, l, 0);
            x1 += ax;
            y1 ++;
        }
        return;
    }
    /* Determine whether the line is X or Y major */
    if (dx >= dy) {
        /* X major line */
        ws = dx / dy;
        /* Adjust for each y by 1 step */
        pu = (dx % dy) * 2;
        /* Overrun error */
        pd = dy * 2;
        et = (dx % dy) - (dy * 2);

        ipc = (ws / 2) + 1;
        fpc = ipc;
        if ((pu == 0) && (ws & 1) == 0)
           ipc--;
        if ((ws & 1) != 0)
           et += dy;
        /* Draw run in x direction */
        for (j = 0; j < ipc; j++) {
             display_point(x1, y1, l, 0);
             x1 += ax;
        }
        y1++;
        /* Draw rest */
        for (i = 0; i< (dy-1); i++) {
            int rl = ws;
            if ((et += pu) > 0) {
                rl++;
                et -= pd;
            }
            for (j = 0; j < rl; j++) {
                 display_point(x1, y1, l, 0);
                 x1 += ax;
            }
            y1++;
        }
        for (j = 0; j < fpc; j++) {
             display_point(x1, y1, l, 0);
             x1 += ax;
        }
    } else {
        ws = dy / dx;
        pu = (dy % dx) * 2;
        pd = dx * 2;
        et = (dy % dx) - (dx * 2);
        ipc = (ws / 2) + 1;
        fpc = ipc;
        if ((pu == 0) && ((ws & 1) == 0))
           ipc--;
        if ((ws & 1) != 0)
           et += dx;
        
        /* Draw run in y direction */
        for (j = 0; j < ipc; j++) {
             display_point(x1, y1, l, 0);
             y1 ++;
        }
        x1 += ax;
        /* Draw rest */
        for (i = 0; i< (dx-1); i++) {
            int rl = ws;
            if ((et += pu) > 0) {
                rl++;
                et -= pd;
            }
            for (j = 0; j < rl; j++) {
                 display_point(x1, y1, l, 0);
                 y1 ++;
            }
            x1 += ax;
        }
        for (j = 0; j < fpc; j++) {
             display_point(x1, y1, l, 0);
             y1 ++;
        }
    }
}

#if defined(__cplusplus)
}
#endif