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Source:NetHack 3.1.0/vision.c

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Below is the full text to vision.c from the source code of NetHack 3.1.0. To link to a particular line, write [[NetHack 3.1.0/vision.c#line123]], for example.

Warning! This is the source code from an old release. For the latest release, see Source code

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1.    /*	SCCS Id: @(#)vision.c	3.1	92/11/14	*/
2.    /* Copyright (c) Dean Luick, with acknowledgements to Dave Cohrs, 1990.	*/
3.    /* NetHack may be freely redistributed.  See license for details.	*/
4.    #include "hack.h"
5.    
6.    /* Circles ==================================================================*/
7.    
8.    /*
9.     * These numbers are limit offsets for one quadrant of a circle of a given
10.    * radius (the first number of each line) from the source.  The number in
11.    * the comment is the element number (so pointers can be set up).  Each
12.    * "circle" has as many elements as its radius+1.  The radius is the number
13.    * of points away from the source that the limit exists.  The radius of the
14.    * offset on the same row as the source *is* included so we don't have to
15.    * make an extra check.  For example, a circle of radius 4 has offsets:
16.    *
17.    *				XXX	+2
18.    *				...X	+3
19.    *				....X	+4
20.    *				....X	+4
21.    *				@...X   +4
22.    *  
23.    */
24.   static char circle_data[] = {
25.   /*  0*/	 1, 1,
26.   /*  2*/	 2, 2, 1,
27.   /*  5*/	 3, 3, 2, 1,
28.   /*  9*/	 4, 4, 4, 3, 2,
29.   /* 14*/	 5, 5, 5, 4, 3, 2,
30.   /* 20*/	 6, 6, 6, 5, 5, 4, 2,
31.   /* 27*/	 7, 7, 7, 6, 6, 5, 4, 2,
32.   /* 35*/	 8, 8, 8, 7, 7, 6, 6, 4, 2,
33.   /* 44*/	 9, 9, 9, 9, 8, 8, 7, 6, 5, 3,
34.   /* 54*/	10,10,10,10, 9, 9, 8, 7, 6, 5, 3,
35.   /* 65*/	11,11,11,11,10,10, 9, 9, 8, 7, 5, 3,
36.   /* 77*/	12,12,12,12,11,11,10,10, 9, 8, 7, 5, 3,
37.   /* 90*/	13,13,13,13,12,12,12,11,10,10, 9, 7, 6, 3,
38.   /*104*/	14,14,14,14,13,13,13,12,12,11,10, 9, 8, 6, 3,
39.   /*119*/	15,15,15,15,14,14,14,13,13,12,11,10, 9, 8, 6, 3,
40.   /*135*/ 16 /* should be MAX_RADIUS+1; used to terminate range loops -dlc */
41.   };
42.   
43.   /*
44.    * These are the starting indexes into the circle_data[] array for a
45.    * circle of a given radius.
46.    */
47.   static char circle_start[] = {
48.   /*  */	  0,	/* circles of radius zero are not used */
49.   /* 1*/    0,
50.   /* 2*/	  2,
51.   /* 3*/	  5,
52.   /* 4*/	  9,
53.   /* 5*/	 14,
54.   /* 6*/	 20,
55.   /* 7*/	 27,
56.   /* 8*/	 35,
57.   /* 9*/	 44,
58.   /*10*/	 54,
59.   /*11*/	 65,
60.   /*12*/	 77,
61.   /*13*/	 90,
62.   /*14*/	104,
63.   /*15*/	119,
64.   };
65.   
66.   
67.   /*===========================================================================*/
68.   /* Vision (arbitrary line of sight) =========================================*/
69.   
70.   /*------ global variables ------*/
71.   
72.   #if 0	/* (moved to decl.c) */
73.   /* True if we need to run a full vision recalculation. */
74.   boolean	vision_full_recalc = 0;
75.   
76.   /* Pointers to the current vision array. */
77.   char	**viz_array;
78.   #endif
79.   char	*viz_rmin, *viz_rmax;		/* current vision cs bounds */
80.   
81.   
82.   /*------ local variables ------*/
83.   
84.   
85.   static char could_see[2][ROWNO][COLNO];		/* vision work space */
86.   static char *cs_rows0[ROWNO], *cs_rows1[ROWNO];
87.   static char  cs_rmin0[ROWNO],  cs_rmax0[ROWNO];
88.   static char  cs_rmin1[ROWNO],  cs_rmax1[ROWNO];
89.   
90.   static char  viz_clear[ROWNO][COLNO];		/* vision clear/blocked map */
91.   static char *viz_clear_rows[ROWNO];
92.   
93.   static char  left_ptrs[ROWNO][COLNO];		/* LOS algorithm helpers */
94.   static char right_ptrs[ROWNO][COLNO];
95.   
96.   /* Forward declarations. */
97.   static void FDECL(fill_point, (int,int));
98.   static void FDECL(dig_point, (int,int));
99.   static void NDECL(view_init);
100.  static void FDECL(view_from,(int,int,char **,char *,char *,int,
101.  			     void (*)(int,int,genericptr_t),genericptr_t));
102.  static void FDECL(get_unused_cs, (char ***,char **,char **));
103.  #ifdef REINCARNATION
104.  static void FDECL(rogue_vision, (char **,char *,char *));
105.  #endif
106.  
107.  /* Macro definitions that I can't find anywhere. */
108.  #define sign(z) ((z) < 0 ? -1 : ((z) ? 1 : 0 ))
109.  #define abs(z)  ((z) < 0 ? -(z) : (z))
110.  
111.  /*
112.   * vision_init()
113.   *
114.   * The one-time vision initialization routine.
115.   *
116.   * This must be called before mklev() is called in newgame() [allmain.c],
117.   * or before a game restore.   Else we die a horrible death.
118.   */
119.  void
120.  vision_init()
121.  {
122.      int i;
123.  
124.      /* Set up the pointers. */
125.      for (i = 0; i < ROWNO; i++) {
126.  	cs_rows0[i] = could_see[0][i];
127.  	cs_rows1[i] = could_see[1][i];
128.  	viz_clear_rows[i] = viz_clear[i];
129.      }
130.  
131.      /* Start out with cs0 as our current array */
132.      viz_array = cs_rows0;
133.      viz_rmin  = cs_rmin0;
134.      viz_rmax  = cs_rmax0;
135.  
136.      vision_full_recalc = 0;
137.      (void) memset((genericptr_t) could_see, 0, sizeof(could_see));
138.  
139.      /* Initialize the vision algorithm (currently C or D). */
140.      view_init();
141.  
142.  #ifdef VISION_TABLES
143.      /* Note:  this initializer doesn't do anything except guarantee that
144.  	      we're linked properly.
145.      */
146.      vis_tab_init();
147.  #endif
148.  }
149.  
150.  /*
151.   * does_block()
152.   *
153.   * Returns true if the level feature, object, or monster at (x,y) blocks
154.   * sight.
155.   */
156.  int
157.  does_block(x,y,lev)
158.      int x, y;
159.      register struct rm    *lev;
160.  {
161.      struct obj   *obj;
162.      struct monst *mon;
163.  
164.      /* Features that block . . */
165.      if (IS_ROCK(lev->typ) || (IS_DOOR(lev->typ) &&
166.  			    (lev->doormask & (D_CLOSED|D_LOCKED|D_TRAPPED) )))
167.  	return 1;
168.  
169.      if (lev->typ == CLOUD || lev->typ == WATER ||
170.  			(lev->typ == MOAT && Underwater))
171.  	return 1;
172.  
173.      /* Boulders block light. */
174.      for (obj = level.objects[x][y]; obj; obj = obj->nexthere)
175.  	if (obj->otyp == BOULDER) return 1;
176.  
177.      /* Mimics mimicing a door or boulder block light. */
178.      if ((mon = m_at(x,y)) && (!mon->minvis || See_invisible) &&
179.  	  ((mon->m_ap_type == M_AP_FURNITURE &&
180.  	  (mon->mappearance == S_hcdoor || mon->mappearance == S_vcdoor)) ||
181.  	  (mon->m_ap_type == M_AP_OBJECT && mon->mappearance == BOULDER)))
182.  	return 1;
183.  
184.      return 0;
185.  }
186.  
187.  /*
188.   * vision_reset()
189.   *
190.   * This must be called *after* the levl[][] structure is set with the new
191.   * level and the level monsters and objects are in place.
192.   */
193.  void
194.  vision_reset()
195.  {
196.      int y;
197.      register int x, i, dig_left, block;
198.      register struct rm    *lev;
199.  
200.      /* Start out with cs0 as our current array */
201.      viz_array = cs_rows0;
202.      viz_rmin  = cs_rmin0;
203.      viz_rmax  = cs_rmax0;
204.  
205.      (void) memset((genericptr_t) could_see, 0, sizeof(could_see));
206.  
207.      /* Reset the pointers and clear so that we have a "full" dungeon. */
208.      (void) memset((genericptr_t) viz_clear,        0, sizeof(viz_clear));
209.  
210.      /* Dig the level */
211.      for (y = 0; y < ROWNO; y++) {
212.  	dig_left = 0;
213.  	block = TRUE;	/* location (0,y) is always stone; it's !isok() */
214.  	lev = &levl[1][y];
215.  	for (x = 1; x < COLNO; x++, lev += ROWNO)
216.  	    if (block != (IS_ROCK(lev->typ) || does_block(x,y,lev))) {
217.  		if(block) {
218.  		    for(i=dig_left; i<x; i++) {
219.  			left_ptrs [y][i] = dig_left;
220.  			right_ptrs[y][i] = x-1;
221.  		    }
222.  		} else {
223.  		    i = dig_left;
224.  		    if(dig_left) dig_left--; /* point at first blocked point */
225.  		    for(; i<x; i++) {
226.  			left_ptrs [y][i] = dig_left;
227.  			right_ptrs[y][i] = x;
228.  			viz_clear[y][i] = 1;
229.  		    }
230.  		}
231.  		dig_left = x;
232.  		block = !block;
233.  	    }
234.  	/* handle right boundary; almost identical for blocked/unblocked */
235.  	i = dig_left;
236.  	if(!block && dig_left) dig_left--; /* point at first blocked point */
237.  	for(; i<COLNO; i++) {
238.  	    left_ptrs [y][i] = dig_left;
239.  	    right_ptrs[y][i] = (COLNO-1);
240.  	    viz_clear[y][i] = !block;
241.  	}
242.      }
243.  
244.      vision_full_recalc = 1;	/* we want to run vision_recalc() */
245.  }
246.  
247.  
248.  /*
249.   * get_unused_cs()
250.   *
251.   * Called from vision_recalc() and at least one light routine.  Get pointers
252.   * to the unused vision work area.
253.   */
254.  static void
255.  get_unused_cs(rows, rmin, rmax)
256.      char ***rows;
257.      char **rmin, **rmax;
258.  {
259.      register int  row;
260.      register char *nrmin, *nrmax;
261.  
262.      if (viz_array == cs_rows0) {
263.  	*rows = cs_rows1;
264.  	*rmin = cs_rmin1;
265.  	*rmax = cs_rmax1;
266.      } else {
267.  	*rows = cs_rows0;
268.  	*rmin = cs_rmin0;
269.  	*rmax = cs_rmax0;
270.      }
271.  
272.      /* return an initialized, unused work area */
273.      nrmin = *rmin;
274.      nrmax = *rmax;
275.  
276.      (void) memset((genericptr_t)**rows, 0, ROWNO*COLNO);  /* we see nothing */
277.      for (row = 0; row < ROWNO; row++) {		/* set row min & max */
278.  	*nrmin++ = COLNO-1;
279.  	*nrmax++ = 0;
280.      }
281.  }
282.  
283.  
284.  #ifdef REINCARNATION
285.  /*
286.   * rogue_vision()
287.   *
288.   * Set the "could see" and in sight bits so vision acts just like the old
289.   * rogue game:
290.   *
291.   *	+ If in a room, the hero can see to the room boundaries.
292.   *	+ The hero can always see adjacent squares.
293.   *
294.   * We set the in_sight bit here as well to escape a bug that shows up
295.   * due to the one-sided lit wall hack.
296.   */
297.  static void
298.  rogue_vision(next, rmin, rmax)
299.      char **next;	/* could_see array pointers */
300.      char *rmin, *rmax;
301.  {
302.      int rnum = levl[u.ux][u.uy].roomno - ROOMOFFSET; /* no SHARED... */
303.      int start, stop, in_door;
304.      register int zx, zy;
305.  
306.      /* If in a lit room, we are able to see to its boundaries. */
307.      /* If dark, set COULD_SEE so various spells work -dlc */
308.      if (rnum >= 0) {
309.  	for (zy = rooms[rnum].ly-1; zy <= rooms[rnum].hy+1; zy++) {
310.  	    rmin[zy] = start = rooms[rnum].lx-1;
311.  	    rmax[zy] = stop  = rooms[rnum].hx+1;
312.  
313.  	    for (zx = start; zx <= stop; zx++) {
314.  		if (rooms[rnum].rlit) {
315.  		    next[zy][zx] = COULD_SEE | IN_SIGHT;
316.  		    levl[zx][zy].seen = 1;	/* see the walls */
317.  		} else
318.  		    next[zy][zx] = COULD_SEE;
319.  	    }
320.  	}
321.      }
322.  
323.      in_door = levl[u.ux][u.uy].typ == DOOR;
324.  
325.      /* Can always see adjacent. */
326.      for (zy = u.uy-1; zy <= u.uy+1; zy++) {
327.  	rmin[zy] = min(rmin[zy],u.ux-1);
328.  	rmax[zy] = max(rmax[zy],u.ux+1);
329.  
330.  	for (zx = u.ux-1; zx <= u.ux+1; zx++) {
331.  	    next[zy][zx] = COULD_SEE | IN_SIGHT;
332.  	    /*
333.  	     * Yuck, update adjacent non-diagonal positions when in a doorway.
334.  	     * We need to do this to catch the case when we first step into
335.  	     * a room.  The room's walls were not seen from the outside, but
336.  	     * now are seen (the seen bit is set just above).  However, the
337.  	     * positions are not updated because they were already in sight.
338.  	     * So, we have to do it here.
339.  	     */
340.  	    if (in_door && (zx == u.ux || zy == u.uy)) newsym(zx,zy);
341.  	}
342.      }
343.  }
344.  #endif /* REINCARNATION */
345.  
346.  
347.  /*
348.   * vision_recalc()
349.   *
350.   * Do all of the heavy vision work.  Recalculate all locations that could
351.   * possibly be seen by the hero --- if the location were lit, etc.  Note
352.   * which locations are actually seen because of lighting.  Then add to
353.   * this all locations that be seen by hero due to night vision and x-ray
354.   * vision.  Finally, compare with what the hero was able to see previously.
355.   * Update the difference.
356.   *
357.   * This function is usually called only when the variable 'vision_full_recalc'
358.   * is set.  The following is a list of places where this function is called,
359.   * with three valid values for the control flag parameter:
360.   *
361.   * Control flag = 0.  A complete vision recalculation.  Generate the vision
362.   * tables from scratch.  This is necessary to correctly set what the hero
363.   * can see.  (1) and (2) call this routine for synchronization purposes, (3)
364.   * calls this routine so it can operate correctly.
365.   *
366.   *	+ After the monster move, before input from the player. [moveloop()]
367.   *	+ At end of moveloop. [moveloop() ??? not sure why this is here]
368.   *	+ Right before something is printed. [pline()]
369.   *	+ Right before we do a vision based operation. [do_clear_area()]
370.   *	+ screen redraw, so we can renew all positions in sight. [docrt()]
371.   *
372.   * Control flag = 1.  An adjacent vision recalculation.  The hero has moved
373.   * one square.  Knowing this, it might be possible to optimize the vision
374.   * recalculation using the current knowledge.  This is presently unimplemented
375.   * and is treated as a control = 0 call.
376.   *
377.   *	+ Right after the hero moves. [domove()]
378.   *
379.   * Control flag = 2.  Turn off the vision system.  Nothing new will be
380.   * displayed, since nothing is seen.  This is usually done when you need
381.   * a newsym() run on all locations in sight, or on some locations but you
382.   * don't know which ones.
383.   *
384.   *	+ Before a screen redraw, so all positions are renewed. [docrt()]
385.   *	+ Right before the hero arrives on a new level. [goto_level()]
386.   *	+ Right after a scroll of light is read. [litroom()]
387.   *	+ After an option has changed that affects vision [parseoptions()]
388.   *	+ Right after the hero is swallowed. [gulpmu()]
389.   *	+ Just before bubbles are moved. [movebubbles()]
390.   */
391.  void
392.  vision_recalc(control)
393.      int control;
394.  {
395.      char **temp_array;	/* points to the old vision array */
396.      char **next_array;	/* points to the new vision array */
397.      char *next_row;	/* row pointer for the new array */
398.      char *old_row;	/* row pointer for the old array */
399.      char *next_rmin;	/* min pointer for the new array */
400.      char *next_rmax;	/* max pointer for the new array */
401.      char *ranges;	/* circle ranges -- used for xray & night vision */
402.      int row;		/* row counter (outer loop)  */
403.      int start, stop;	/* inner loop starting/stopping index */
404.      int dx, dy;		/* one step from a lit door or lit wall (see below) */
405.      register int col;	/* inner loop counter */
406.      register struct rm *lev;	/* pointer to current pos */
407.      struct rm *flev;	/* pointer to position in "front" of current pos */
408.  
409.      vision_full_recalc = 0;			/* reset flag */
410.  
411.  #ifdef GCC_WARN
412.      row = 0;
413.  #endif
414.  
415.      /*
416.       * Either the light sources have been taken care of, or we must
417.       * recalculate them here.
418.       */
419.  
420.      /* Get the unused could see, row min, and row max arrays. */
421.      get_unused_cs(&next_array, &next_rmin, &next_rmax);
422.  
423.      /* You see nothing, nothing can see you --- if swallowed or refreshing. */
424.      if (u.uswallow || control == 2) {
425.  	/* do nothing -- get_unused_cs() nulls out the new work area */
426.  
427.      } else if (Blind) {
428.  	/*
429.  	 * Calculate the could_see array even when blind so that monsters
430.  	 * can see you, even if you can't see them.  Note that the current
431.  	 * setup allows:
432.  	 *
433.  	 *	+ Monsters to see with the "new" vision, even on the rogue
434.  	 *	  level.
435.  	 *
436.  	 *	+ Monsters to see you even when you're in a pit.
437.  	 */
438.  	view_from(u.uy, u.ux, next_array, next_rmin, next_rmax,
439.  					0,(void(*)())0,(genericptr_t)0);
440.  
441.  	/*
442.  	 * Our own version of the update loop below.  We know we can't see
443.  	 * anything, so we only need update positions we used to be able
444.  	 * to see.
445.  	 */
446.  	temp_array = viz_array;	/* set viz_array so newsym() will work */
447.  	viz_array = next_array;
448.  
449.  	for (row = 0; row < ROWNO; row++) {
450.  	    old_row = temp_array[row];
451.  
452.  	    /* Find the min and max positions on the row. */
453.  	    start = min(viz_rmin[row], next_rmin[row]);
454.  	    stop  = max(viz_rmax[row], next_rmax[row]);
455.  
456.  	    for (col = start; col <= stop; col++)
457.  		if (old_row[col] & IN_SIGHT) newsym(col,row);
458.  	}
459.  
460.  	/* skip the normal update loop */
461.  	goto skip;
462.      }
463.  #ifdef REINCARNATION
464.      else if (Is_rogue_level(&u.uz)) {
465.  	rogue_vision(next_array,next_rmin,next_rmax);
466.      }
467.  #endif
468.      else {
469.  	int has_night_vision = 1;	/* hero has night vision */
470.  
471.  	if (Underwater && !Is_waterlevel(&u.uz)) {
472.  	    /*
473.  	     * The hero is under water.  Only see surrounding locations if
474.  	     * they are also underwater.  This overrides night vision but
475.  	     * does not override x-ray vision.
476.  	     */
477.  	    has_night_vision = 0;
478.  
479.  	    for (row = u.uy-1; row <= u.uy+1; row++)
480.  		for (col = u.ux-1; col <= u.ux+1; col++) {
481.  		    if (!isok(col,row) || !is_pool(col,row)) continue;
482.  
483.  		    next_rmin[row] = min(next_rmin[row], col);
484.  		    next_rmax[row] = max(next_rmax[row], col);
485.  		    next_array[row][col] = IN_SIGHT;
486.  		}
487.  	    }
488.  
489.  	/* if in a pit, just update for immediate locations */
490.  	else if (u.utrap && u.utraptype == TT_PIT) {
491.  	    for (row = u.uy-1; row <= u.uy+1; row++) {
492.  		if (row < 0) continue;	if (row >= ROWNO) break;
493.  
494.  		next_rmin[row] = max(      0, u.ux - 1);
495.  		next_rmax[row] = min(COLNO-1, u.ux + 1);
496.  		next_row = next_array[row];
497.  
498.  		for(col=next_rmin[row]; col <= next_rmax[row]; col++)
499.  		    next_row[col] = IN_SIGHT;
500.  	    }
501.  	} else
502.  	    view_from(u.uy, u.ux, next_array, next_rmin, next_rmax,
503.  					0,(void(*)())0,(genericptr_t)0);
504.  
505.  	/*
506.  	 * Set the IN_SIGHT bit for xray and night vision.
507.  	 */
508.  	if (u.xray_range >= 0) {
509.  	    if (u.xray_range) {
510.  		ranges = circle_ptr(u.xray_range);
511.  
512.  		for (row = u.uy-u.xray_range; row <= u.uy+u.xray_range; row++) {
513.  		    if (row < 0) continue;	if (row >= ROWNO) break;
514.  		    dy = abs(u.uy-row);		next_row = next_array[row];
515.  
516.  		    start = max(      0, u.ux - ranges[dy]);
517.  		    stop  = min(COLNO-1, u.ux + ranges[dy]);
518.  
519.  		    for (col = start; col <= stop; col++) {
520.  			next_row[col] |= IN_SIGHT;
521.  			levl[col][row].seen = 1;	/* we see walls */
522.  		    }
523.  
524.  		    next_rmin[row] = min(start, next_rmin[row]);
525.  		    next_rmax[row] = max(stop, next_rmax[row]);
526.  		}
527.  
528.  	    } else {	/* range is 0 */
529.  		next_array[u.uy][u.ux] |= IN_SIGHT;
530.  		levl[u.ux][u.uy].seen = 1;
531.  		next_rmin[u.uy] = min(u.ux, next_rmin[u.uy]);
532.  		next_rmax[u.uy] = max(u.ux, next_rmax[u.uy]);
533.  	    }
534.  	}
535.  
536.  	if (has_night_vision && u.xray_range < u.nv_range) {
537.  	    if (!u.nv_range) {	/* range is 0 */
538.  		next_array[u.uy][u.ux] |= IN_SIGHT;
539.  		levl[u.ux][u.uy].seen = 1;
540.  		next_rmin[u.uy] = min(u.ux, next_rmin[u.uy]);
541.  		next_rmax[u.uy] = max(u.ux, next_rmax[u.uy]);
542.  	    } else if (u.nv_range > 0) {
543.  		ranges = circle_ptr(u.nv_range);
544.  
545.  		for (row = u.uy-u.nv_range; row <= u.uy+u.nv_range; row++) {
546.  		    if (row < 0) continue;	if (row >= ROWNO) break;
547.  		    dy = abs(u.uy-row);		next_row = next_array[row];
548.  
549.  		    start = max(      0, u.ux - ranges[dy]);
550.  		    stop  = min(COLNO-1, u.ux + ranges[dy]);
551.  
552.  		    for (col = start; col <= stop; col++)
553.  			if (next_row[col]) next_row[col] |= IN_SIGHT;
554.  
555.  		    next_rmin[row] = min(start, next_rmin[row]);
556.  		    next_rmax[row] = max(stop, next_rmax[row]);
557.  		}
558.  	    }
559.  	}
560.      }
561.  
562.  
563.      /*
564.       * Make the viz_array the new array so that cansee() will work correctly.
565.       */
566.      temp_array = viz_array;
567.      viz_array = next_array;
568.  
569.      /*
570.       * The main update loop.  Here we do two things:
571.       *
572.       *	    + Set the IN_SIGHT bit for places that we could see and are lit.
573.       *	    + Reset changed places.
574.       *
575.       * There are two things that make deciding what the hero can see
576.       * difficult:
577.       *
578.       *  1.  Walls.  Walls are only seen as walls from the inside of a room.
579.       *	    On the outside they look like stone.  The "seen" bit in the rm
580.       *	    structure is used in the display system to decide what to
581.       *	    display, but it is here where we decide to set the seen bit.
582.       *	    In this case the wall must already be in sight (either by night
583.       *	    vision or could be seen and lit) *and* we must see the wall
584.       *	    from across a room-typ square.
585.       *
586.       *  2.  Directional lighting.  Items that block light create problems.
587.       *      The worst offenders are doors.  Suppose a door to a lit room
588.       *      is closed.  It is lit on one side, but not on the other.  How
589.       *      do you know?  You have to check the closest adjacent position.
590.       *	    Even so, that is not entirely correct.  But it seems close
591.       *	    enough for now.
592.       */
593.      for (row = 0; row < ROWNO; row++) {
594.  	dy = u.uy - row;                dy = sign(dy);
595.  	next_row = next_array[row];     old_row = temp_array[row];
596.  
597.  	/* Find the min and max positions on the row. */
598.  	start = min(viz_rmin[row], next_rmin[row]);
599.  	stop  = max(viz_rmax[row], next_rmax[row]);
600.  	lev = &levl[start][row];
601.  
602.  	for (col = start; col <= stop; col++, lev += ROWNO) {
603.  	    if (next_row[col] & IN_SIGHT) {
604.  		/*
605.  		 * We see this position because of night- or xray-vision.
606.  		 *
607.  		 * Check for "unseen" walls.
608.  		 */
609.  		if ( (!lev->seen || (lev->diggable & W_REPAIRED)) && 
610.  		     (IS_WALL(lev->typ) || lev->typ == SDOOR) ) {
611.  		    /* Check the closest adjacent position. */
612.  		    dx = u.ux - col;	dx = sign(dx);
613.  		    flev = &(levl[col+dx][row+dy]);
614.  
615.  		    /* If it was a non-corridor "open" area, we see the wall */
616.  		    if ((ZAP_POS(flev->typ) && (flev->typ != CORR)) ||
617.  			(lev->diggable & W_REPAIRED)) {
618.  			lev->seen = 1;	/* we've seen it */
619.  			lev->diggable &= ~W_REPAIRED;
620.  
621.  			/* Make sure newly "seen" walls show up */
622.  			newsym(col,row);
623.  		    }
624.  
625.  		    /* Update position if it was not in sight before. */
626.  		    else if (!(old_row[col]&IN_SIGHT)) newsym(col,row);
627.  		}
628.  
629.  		/* Update position if it was not in sight before. */
630.  		else if ( !(old_row[col] & IN_SIGHT) ) {
631.  		    lev->seen = 1;
632.  		    newsym(col,row);
633.  		}
634.  	    }
635.  
636.  	    else if ( next_row[col] && lev->lit ) {
637.  		/*
638.  		 * We see this position because it is lit.
639.  		 *
640.  		 * It is assumed here that lit walls are lit from the
641.  		 * inside of the room,  Hence, walls are not "seen"
642.  		 * unless we can see them from across a lit room square.
643.  		 */
644.  		if (IS_WALL(lev->typ) || lev->typ == SDOOR) {
645.  
646.  		    /* Check the closest adjacent position. */
647.  		    dx = u.ux - col;	dx = sign(dx);
648.  		    flev = &(levl[col+dx][row+dy]);
649.  		    /*
650.  		     * If it is a non-corridor "open" area, and it is lit,
651.  		     * then we see the wall as a wall.
652.  		     *
653.  		     * What happens when the hero is standing on this
654.  		     * location (dx == dy == 0)?
655.  		     */
656.  		    if (ZAP_POS(flev->typ) && (flev->typ != CORR) &&
657.  								flev->lit) {
658.  			next_row[col] |= IN_SIGHT;	/* we see it */
659.  			if (!lev->seen || (lev->diggable & W_REPAIRED)) {
660.  			    lev->seen = 1;		/* see it as a wall */
661.  			    lev->diggable &= ~W_REPAIRED;
662.  			    /*
663.  			     * Force an update on the position, even if it
664.  			     * was previously in sight.  Reason:  the hero
665.  			     * could have been in a corridor or outside of
666.  			     * an undiscovered wall and then teleported into
667.  			     * the room.  The wall was in sight before, but
668.  			     * seen as stone.  Now we need to see it as a
669.  			     * wall.
670.  			     */
671.  			    newsym(col,row);
672.  			}
673.  		    } else
674.  			goto not_in_sight;	/* we don't see it */
675.  
676.  		} else if (IS_DOOR(lev->typ) && !viz_clear[row][col]) {
677.  		    /*
678.  		     * Make sure doors, boulders or mimics don't show up
679.  		     * at the end of dark hallways.  We do this by checking
680.  		     * the adjacent position.  If it is lit, then we can see
681.  		     * the door, otherwise we can't.
682.  		     */
683.  		    dx = u.ux - col;	dx = sign(dx);
684.  		    flev = &(levl[col+dx][row+dy]);
685.  		    if (flev->lit) {
686.  			next_row[col] |= IN_SIGHT;	/* we see it */
687.  
688.  			/* Update position if it was not in sight before. */
689.  			if (!(old_row[col] & IN_SIGHT)) newsym(col,row);
690.  		    } else
691.  			goto not_in_sight;	/* we don't see it */
692.  
693.  		} else {
694.  		    next_row[col] |= IN_SIGHT;	/* we see it */
695.  
696.  		    /* Update position if it was not in sight before. */
697.  		    if ( !(old_row[col] & IN_SIGHT) ) {
698.  			lev->seen = 1;
699.  			newsym(col,row);
700.  		    }
701.  		}
702.  	    } else if (next_row[col] && lev->waslit ) {
703.  		/*
704.  		 * If we make it here, the hero _could see_ the location
705.  		 * (next_row[col] is true), but doesn't see it (lit is false).
706.  		 * However, the hero _remembers_ it as lit (waslit is true).
707.  		 * The hero can now see that it is not lit, so change waslit
708.  		 * and update the location.
709.  		 */
710.  		lev->waslit = 0; /* remember lit condition */
711.  		newsym(col,row);
712.  	    }
713.  	    /*
714.  	     * At this point we know that the row position is *not* in
715.  	     * sight.  If the old one *was* in sight, then clean up the
716.  	     * position.
717.  	     */
718.  	    else {
719.  not_in_sight:
720.  		if (old_row[col] & IN_SIGHT) newsym(col,row);
721.  	    }
722.  
723.  	} /* end for col . . */
724.      }	/* end for row . .  */
725.  
726.  skip:
727.      newsym(u.ux,u.uy);		/* Make sure the hero shows up! */
728.  
729.      /* Set the new min and max pointers. */
730.      viz_rmin  = next_rmin;
731.      viz_rmax = next_rmax;
732.  }
733.  
734.  
735.  /*
736.   * block_point()
737.   *
738.   * Make the location opaque to light.
739.   */
740.  void
741.  block_point(x,y)
742.      int x, y;
743.  {
744.      fill_point(y,x);
745.  
746.      /* recalc light sources here? */
747.  
748.      /*
749.       * We have to do a full vision recalculation if we "could see" the
750.       * location.  Why? Suppose some monster opened a way so that the
751.       * hero could see a lit room.  However, the position of the opening
752.       * was out of night-vision range of the hero.  Suddenly the hero should
753.       * see the lit room.
754.       */
755.      if (viz_array[y][x]) vision_full_recalc = 1;
756.  }
757.  
758.  /*
759.   * unblock_point()
760.   *
761.   * Make the location transparent to light.
762.   */
763.  void
764.  unblock_point(x,y)
765.      int x, y;
766.  {
767.      dig_point(y,x);
768.  
769.      /* recalc light sources here? */
770.  
771.      if (viz_array[y][x]) vision_full_recalc = 1;
772.  }
773.  
774.  
775.  /*===========================================================================*\
776.   |									     |
777.   |	Everything below this line uses (y,x) instead of (x,y) --- the	     |
778.   |	algorithms are faster if they are less recursive and can scan	     |
779.   |	on a row longer.						     |
780.   |									     |
781.  \*===========================================================================*/
782.  
783.  
784.  /* ========================================================================= *\
785.  			Left and Right Pointer Updates
786.  \* ========================================================================= */
787.  
788.  /*
789.   *			LEFT and RIGHT pointer rules
790.   *
791.   *
792.   * **NOTE**  The rules changed on 4/4/90.  This comment reflects the
793.   * new rules.  The change was so that the stone-wall optimization
794.   * would work.
795.   *
796.   * OK, now the tough stuff.  We must maintain our left and right
797.   * row pointers.  The rules are as follows:
798.   *  
799.   * Left Pointers:
800.   * ______________
801.   *
802.   * + If you are a clear spot, your left will point to the first
803.   *   stone to your left.  If there is none, then point the first
804.   *   legal position in the row (0).
805.   *
806.   * + If you are a blocked spot, then your left will point to the
807.   *   left-most blocked spot to your left that is connected to you.
808.   *   This means that a left-edge (a blocked spot that has an open
809.   *   spot on its left) will point to itself.
810.   *
811.   *
812.   * Right Pointers:
813.   * ---------------
814.   * + If you are a clear spot, your right will point to the first
815.   *   stone to your right.  If there is none, then point the last
816.   *   legal position in the row (COLNO-1).
817.   *
818.   * + If you are a blocked spot, then your right will point to the
819.   *   right-most blocked spot to your right that is connected to you.
820.   *   This means that a right-edge (a blocked spot that has an open
821.   *    spot on its right) will point to itself.
822.   */
823.  static void
824.  dig_point(row,col)
825.      int row,col;
826.  {
827.      int i;
828.  
829.      if (viz_clear[row][col]) return;		/* already done */
830.  
831.      viz_clear[row][col] = 1;
832.  
833.      /*
834.       * Boundary cases first.
835.       */
836.      if (col == 0) {				/* left edge */
837.  	if (viz_clear[row][1]) {
838.  	    right_ptrs[row][0] = right_ptrs[row][1];
839.  	} else {
840.  	    right_ptrs[row][0] = 1;
841.  	    for (i = 1; i <= right_ptrs[row][1]; i++)
842.  		left_ptrs[row][i] = 1;
843.  	}
844.      } else if (col == (COLNO-1)) {		/* right edge */
845.  
846.  	if (viz_clear[row][COLNO-2]) {
847.  	    left_ptrs[row][COLNO-1] = left_ptrs[row][COLNO-2];
848.  	} else {
849.  	    left_ptrs[row][COLNO-1] = COLNO-2;
850.  	    for (i = left_ptrs[row][COLNO-2]; i < COLNO-1; i++)
851.  		right_ptrs[row][i] = COLNO-2;
852.  	}
853.      }
854.       
855.      /*
856.       * At this point, we know we aren't on the boundaries.
857.       */
858.      else if (viz_clear[row][col-1] && viz_clear[row][col+1]) {
859.  	/* Both sides clear */
860.  	for (i = left_ptrs[row][col-1]; i <= col; i++) {
861.  	    if (!viz_clear[row][i]) continue;	/* catch non-end case */
862.  	    right_ptrs[row][i] = right_ptrs[row][col+1];
863.  	}
864.  	for (i = col; i <= right_ptrs[row][col+1]; i++) {
865.  	    if (!viz_clear[row][i]) continue;	/* catch non-end case */
866.  	    left_ptrs[row][i] = left_ptrs[row][col-1];
867.  	}
868.  
869.      } else if (viz_clear[row][col-1]) {
870.  	/* Left side clear, right side blocked. */
871.  	for (i = col+1; i <= right_ptrs[row][col+1]; i++)
872.  	    left_ptrs[row][i] = col+1;
873.  
874.  	for (i = left_ptrs[row][col-1]; i <= col; i++) {
875.  	    if (!viz_clear[row][i]) continue;	/* catch non-end case */
876.  	    right_ptrs[row][i] = col+1;
877.  	}
878.  	left_ptrs[row][col] = left_ptrs[row][col-1];
879.  
880.      } else if (viz_clear[row][col+1]) {
881.  	/* Right side clear, left side blocked. */
882.  	for (i = left_ptrs[row][col-1]; i < col; i++)
883.  	    right_ptrs[row][i] = col-1;
884.  
885.  	for (i = col; i <= right_ptrs[row][col+1]; i++) {
886.  	    if (!viz_clear[row][i]) continue;	/* catch non-end case */
887.  	    left_ptrs[row][i] = col-1;
888.  	}
889.  	right_ptrs[row][col] = right_ptrs[row][col+1];
890.  
891.      } else {
892.  	/* Both sides blocked */
893.  	for (i = left_ptrs[row][col-1]; i < col; i++)
894.  	    right_ptrs[row][i] = col-1;
895.  
896.  	for (i = col+1; i <= right_ptrs[row][col+1]; i++)
897.  	    left_ptrs[row][i] = col+1;
898.  
899.  	left_ptrs[row][col]  = col-1;
900.  	right_ptrs[row][col] = col+1;
901.      }
902.  }
903.  
904.  static void
905.  fill_point(row,col)
906.      int row, col;
907.  {
908.      int i;
909.  
910.      if (!viz_clear[row][col]) return;
911.  
912.      viz_clear[row][col] = 0;
913.  
914.      if (col == 0) {
915.  	if (viz_clear[row][1]) {			/* adjacent is clear */
916.  	    right_ptrs[row][0] = 0;
917.  	} else {
918.  	    right_ptrs[row][0] = right_ptrs[row][1];
919.  	    for (i = 1; i <= right_ptrs[row][1]; i++)
920.  		left_ptrs[row][i] = 0;
921.  	}
922.      } else if (col == COLNO-1) {
923.  	if (viz_clear[row][COLNO-2]) {		/* adjacent is clear */
924.  	    left_ptrs[row][COLNO-1] = COLNO-1;
925.  	} else {
926.  	    left_ptrs[row][COLNO-1] = left_ptrs[row][COLNO-2];
927.  	    for (i = left_ptrs[row][COLNO-2]; i < COLNO-1; i++)
928.  		right_ptrs[row][i] = COLNO-1;
929.  	}
930.      }
931.  
932.      /*
933.       * Else we know that we are not on an edge.
934.       */
935.      else if (viz_clear[row][col-1] && viz_clear[row][col+1]) {
936.  	/* Both sides clear */
937.  	for (i = left_ptrs[row][col-1]+1; i <= col; i++)
938.  	    right_ptrs[row][i] = col;
939.  
940.  	if (!left_ptrs[row][col-1])		/* catch the end case */
941.  	    right_ptrs[row][0] = col;
942.  
943.  	for (i = col; i < right_ptrs[row][col+1]; i++)
944.  	    left_ptrs[row][i] = col;
945.  
946.  	if (right_ptrs[row][col+1] == COLNO-1)	/* catch the end case */
947.  	    left_ptrs[row][COLNO-1] = col;
948.  
949.      } else if (viz_clear[row][col-1]) {
950.  	/* Left side clear, right side blocked. */
951.  	for (i = col; i <= right_ptrs[row][col+1]; i++)
952.  	    left_ptrs[row][i] = col;
953.  
954.  	for (i = left_ptrs[row][col-1]+1; i < col; i++)
955.  	    right_ptrs[row][i] = col;
956.  
957.  	if (!left_ptrs[row][col-1])		/* catch the end case */
958.  	    right_ptrs[row][i] = col;
959.  
960.  	right_ptrs[row][col] = right_ptrs[row][col+1];
961.  
962.      } else if (viz_clear[row][col+1]) {
963.  	/* Right side clear, left side blocked. */
964.  	for (i = left_ptrs[row][col-1]; i <= col; i++)
965.  	    right_ptrs[row][i] = col;
966.  
967.  	for (i = col+1; i < right_ptrs[row][col+1]; i++)
968.  	    left_ptrs[row][i] = col;
969.  
970.  	if (right_ptrs[row][col+1] == COLNO-1)	/* catch the end case */
971.  	    left_ptrs[row][i] = col;
972.  
973.  	left_ptrs[row][col] = left_ptrs[row][col-1];
974.  
975.      } else {
976.  	/* Both sides blocked */
977.  	for (i = left_ptrs[row][col-1]; i <= col; i++)
978.  	    right_ptrs[row][i] = right_ptrs[row][col+1];
979.  
980.  	for (i = col; i <= right_ptrs[row][col+1]; i++)
981.  	    left_ptrs[row][i] = left_ptrs[row][col-1];
982.      }
983.  }
984.  
985.  
986.  /*===========================================================================*/
987.  /*===========================================================================*/
988.  /* Use either algorithm C or D.  See the config.h for more details. =========*/
989.  
990.  /*
991.   * Variables local to both Algorithms C and D.
992.   */
993.  static int  start_row;
994.  static int  start_col;
995.  static int  step;
996.  static char **cs_rows;
997.  static char *cs_left;
998.  static char *cs_right;
999.  
1000. static void FDECL((*vis_func), (int,int,genericptr_t));
1001. static genericptr_t varg;
1002. 
1003. /*
1004.  * Both Algorithms C and D use the following macros.
1005.  *
1006.  *      good_row(z)	  - Return TRUE if the argument is a legal row.
1007.  *      set_cs(rowp,col)  - Set the local could see array.
1008.  *      set_min(z)	  - Save the min value of the argument and the current
1009.  *  			      row minimum.
1010.  *      set_max(z)	  - Save the max value of the argument and the current
1011.  *  			      row maximum.
1012.  *  
1013.  * The last three macros depend on having local pointers row_min, row_max,
1014.  * and rowp being set correctly.
1015.  */
1016. #define set_cs(rowp,col) (rowp[col] = COULD_SEE)
1017. #define good_row(z) ((z) >= 0 && (z) < ROWNO)
1018. #define set_min(z) if (*row_min > (z)) *row_min = (z)
1019. #define set_max(z) if (*row_max < (z)) *row_max = (z)
1020. #define is_clear(row,col) viz_clear_rows[row][col]
1021. 
1022. /*
1023.  * clear_path()		expanded into 4 macros/functions:
1024.  *
1025.  *	q1_path()
1026.  *	q2_path()
1027.  *	q3_path()
1028.  *	q4_path()
1029.  *
1030.  * "Draw" a line from the start to the given location.  Stop if we hit
1031.  * something that blocks light.  The start and finish points themselves are
1032.  * not checked, just the points between them.  These routines do _not_
1033.  * expect to be called with the same starting and stopping point.
1034.  *
1035.  * These routines use the generalized integer Bresenham's algorithm (fast
1036.  * line drawing) for all quadrants.  The algorithm was taken from _Procedural
1037.  * Elements for Computer Graphics_, by David F. Rogers.  McGraw-Hill, 1985.
1038.  */
1039. #ifdef MACRO_CPATH	/* quadrant calls are macros */
1040. 
1041. /*
1042.  * When called, the result is in "result".
1043.  * The first two arguments (srow,scol) are one end of the path.  The next
1044.  * two arguments (row,col) are the destination.  The last argument is
1045.  * used as a C language label.  This means that it must be different
1046.  * in each pair of calls.
1047.  */
1048. 
1049. /*
1050.  *  Quadrant I (step < 0).
1051.  */
1052. #define q1_path(srow,scol,y2,x2,label)		       	\
1053. {							\
1054.     int dx, dy;						\
1055.     register int k, err, x, y, dxs, dys;		\
1056. 							\
1057.     x  = (scol);	y  = (srow);			\
1058.     dx = (x2) - x;	dy = y - (y2);			\
1059. 							\
1060.     result = 0;		 /* default to a blocked path */\
1061. 							\
1062.     dxs = dx << 1;	   /* save the shifted values */\
1063.     dys = dy << 1;					\
1064.     if (dy > dx) {					\
1065. 	err = dxs - dy;					\
1066. 							\
1067. 	for (k = dy-1; k; k--) {			\
1068. 	    if (err >= 0) {				\
1069. 		x++;					\
1070. 		err -= dys;				\
1071. 	    }						\
1072. 	    y--;					\
1073. 	    err += dxs;					\
1074. 	    if (!is_clear(y,x)) goto label;/* blocked */\
1075. 	}						\
1076.     } else {						\
1077. 	err = dys - dx;					\
1078. 							\
1079. 	for (k = dx-1; k; k--) {			\
1080. 	    if (err >= 0) {				\
1081. 		y--;					\
1082. 		err -= dxs;				\
1083. 	    }						\
1084. 	    x++;					\
1085. 	    err += dys;					\
1086. 	    if (!is_clear(y,x)) goto label;/* blocked */\
1087. 	}						\
1088.     }							\
1089. 							\
1090.     result = 1;						\
1091. }
1092. 
1093. /*
1094.  * Quadrant IV (step > 0).
1095.  */
1096. #define q4_path(srow,scol,y2,x2,label)			\
1097. {							\
1098.     int dx, dy;						\
1099.     register int k, err, x, y, dxs, dys;		\
1100. 							\
1101.     x  = (scol);	y  = (srow);			\
1102.     dx = (x2) - x;	dy = (y2) - y;			\
1103. 							\
1104.     result = 0;		 /* default to a blocked path */\
1105. 							\
1106.     dxs = dx << 1;	   /* save the shifted values */\
1107.     dys = dy << 1;					\
1108.     if (dy > dx) {					\
1109. 	err = dxs - dy;					\
1110. 							\
1111. 	for (k = dy-1; k; k--) {			\
1112. 	    if (err >= 0) {				\
1113. 		x++;					\
1114. 		err -= dys;				\
1115. 	    }						\
1116. 	    y++;					\
1117. 	    err += dxs;					\
1118. 	    if (!is_clear(y,x)) goto label;/* blocked */\
1119. 	}						\
1120. 							\
1121.     } else {						\
1122. 	err = dys - dx;					\
1123. 							\
1124. 	for (k = dx-1; k; k--) {			\
1125. 	    if (err >= 0) {				\
1126. 		y++;					\
1127. 		err -= dxs;				\
1128. 	    }						\
1129. 	    x++;					\
1130. 	    err += dys;					\
1131. 	    if (!is_clear(y,x)) goto label;/* blocked */\
1132. 	}						\
1133.     }							\
1134. 							\
1135.     result = 1;						\
1136. }
1137. 
1138. /*
1139.  * Quadrant II (step < 0).
1140.  */
1141. #define q2_path(srow,scol,y2,x2,label)		       	\
1142. {							\
1143.     int dx, dy;						\
1144.     register int k, err, x, y, dxs, dys;		\
1145. 							\
1146.     x  = (scol);	y  = (srow);			\
1147.     dx = x - (x2);	dy = y - (y2);			\
1148. 							\
1149.     result = 0;		 /* default to a blocked path */\
1150. 							\
1151.     dxs = dx << 1;	   /* save the shifted values */\
1152.     dys = dy << 1;					\
1153.     if (dy > dx) {					\
1154. 	err = dxs - dy;					\
1155. 							\
1156. 	for (k = dy-1; k; k--) {			\
1157. 	    if (err >= 0) {				\
1158. 		x--;					\
1159. 		err -= dys;				\
1160. 	    }						\
1161. 	    y--;					\
1162. 	    err += dxs;					\
1163. 	    if (!is_clear(y,x)) goto label;/* blocked */\
1164. 	}						\
1165.     } else {						\
1166. 	err = dys - dx;					\
1167. 							\
1168. 	for (k = dx-1; k; k--) {			\
1169. 	    if (err >= 0) {				\
1170. 		y--;					\
1171. 		err -= dxs;				\
1172. 	    }						\
1173. 	    x--;					\
1174. 	    err += dys;					\
1175. 	    if (!is_clear(y,x)) goto label;/* blocked */\
1176. 	}						\
1177.     }							\
1178. 							\
1179.     result = 1;						\
1180. }
1181. 
1182. /*
1183.  * Quadrant III (step > 0).
1184.  */
1185. #define q3_path(srow,scol,y2,x2,label)			\
1186. {							\
1187.     int dx, dy;						\
1188.     register int k, err, x, y, dxs, dys;		\
1189. 							\
1190.     x  = (scol);	y  = (srow);			\
1191.     dx = x - (x2);	dy = (y2) - y;			\
1192. 							\
1193.     result = 0;		 /* default to a blocked path */\
1194. 							\
1195.     dxs = dx << 1;	   /* save the shifted values */\
1196.     dys = dy << 1;					\
1197.     if (dy > dx) {					\
1198. 	err = dxs - dy;					\
1199. 							\
1200. 	for (k = dy-1; k; k--) {			\
1201. 	    if (err >= 0) {				\
1202. 		x--;					\
1203. 		err -= dys;				\
1204. 	    }						\
1205. 	    y++;					\
1206. 	    err += dxs;					\
1207. 	    if (!is_clear(y,x)) goto label;/* blocked */\
1208. 	}						\
1209. 							\
1210.     } else {						\
1211. 	err = dys - dx;					\
1212. 							\
1213. 	for (k = dx-1; k; k--) {			\
1214. 	    if (err >= 0) {				\
1215. 		y++;					\
1216. 		err -= dxs;				\
1217. 	    }						\
1218. 	    x--;					\
1219. 	    err += dys;					\
1220. 	    if (!is_clear(y,x)) goto label;/* blocked */\
1221. 	}						\
1222.     }							\
1223. 							\
1224.     result = 1;						\
1225. }
1226. 
1227. #else   /* quadrants are really functions */
1228. 
1229. static int FDECL(_q1_path, (int,int,int,int));
1230. static int FDECL(_q2_path, (int,int,int,int));
1231. static int FDECL(_q3_path, (int,int,int,int));
1232. static int FDECL(_q4_path, (int,int,int,int));
1233. 
1234. #define q1_path(sy,sx,y,x,dummy) result = _q1_path(sy,sx,y,x)
1235. #define q2_path(sy,sx,y,x,dummy) result = _q2_path(sy,sx,y,x)
1236. #define q3_path(sy,sx,y,x,dummy) result = _q3_path(sy,sx,y,x)
1237. #define q4_path(sy,sx,y,x,dummy) result = _q4_path(sy,sx,y,x)
1238. 
1239. /*
1240.  * Quadrant I (step < 0).
1241.  */
1242. static int
1243. _q1_path(srow,scol,y2,x2)
1244.     int scol, srow, y2, x2;
1245. {
1246.     int dx, dy;
1247.     register int k, err, x, y, dxs, dys;
1248. 
1249.     x  = scol;		y  = srow;
1250.     dx = x2 - x;	dy = y - y2;
1251. 
1252.     dxs = dx << 1;	   /* save the shifted values */
1253.     dys = dy << 1;
1254.     if (dy > dx) {
1255. 	err = dxs - dy;
1256. 
1257. 	for (k = dy-1; k; k--) {
1258. 	    if (err >= 0) {
1259. 		x++;
1260. 		err -= dys;
1261. 	    }
1262. 	    y--;
1263. 	    err += dxs;
1264. 	    if (!is_clear(y,x)) return 0; /* blocked */
1265. 	}
1266.     } else {
1267. 	err = dys - dx;
1268. 
1269. 	for (k = dx-1; k; k--) {
1270. 	    if (err >= 0) {
1271. 		y--;
1272. 		err -= dxs;
1273. 	    }
1274. 	    x++;
1275. 	    err += dys;
1276. 	    if (!is_clear(y,x)) return 0;/* blocked */
1277. 	}
1278.     }
1279. 
1280.     return 1;
1281. }
1282. 
1283. /*
1284.  * Quadrant IV (step > 0).
1285.  */
1286. static int
1287. _q4_path(srow,scol,y2,x2)
1288.     int scol, srow, y2, x2;
1289. {
1290.     int dx, dy;
1291.     register int k, err, x, y, dxs, dys;
1292. 
1293.     x  = scol;		y  = srow;
1294.     dx = x2 - x;	dy = y2 - y;
1295. 
1296.     dxs = dx << 1;	   /* save the shifted values */
1297.     dys = dy << 1;
1298.     if (dy > dx) {
1299. 	err = dxs - dy;
1300. 
1301. 	for (k = dy-1; k; k--) {
1302. 	    if (err >= 0) {
1303. 		x++;
1304. 		err -= dys;
1305. 	    }
1306. 	    y++;
1307. 	    err += dxs;
1308. 	    if (!is_clear(y,x)) return 0; /* blocked */
1309. 	}
1310.     } else {
1311. 	err = dys - dx;
1312. 
1313. 	for (k = dx-1; k; k--) {
1314. 	    if (err >= 0) {
1315. 		y++;
1316. 		err -= dxs;
1317. 	    }
1318. 	    x++;
1319. 	    err += dys;
1320. 	    if (!is_clear(y,x)) return 0;/* blocked */
1321. 	}
1322.     }
1323. 
1324.     return 1;
1325. }
1326. 
1327. /*
1328.  * Quadrant II (step < 0).
1329.  */
1330. static int
1331. _q2_path(srow,scol,y2,x2)
1332.     int scol, srow, y2, x2;
1333. {
1334.     int dx, dy;
1335.     register int k, err, x, y, dxs, dys;
1336. 
1337.     x  = scol;		y  = srow;
1338.     dx = x - x2;	dy = y - y2;
1339. 
1340.     dxs = dx << 1;	   /* save the shifted values */
1341.     dys = dy << 1;
1342.     if (dy > dx) {
1343. 	err = dxs - dy;
1344. 
1345. 	for (k = dy-1; k; k--) {
1346. 	    if (err >= 0) {
1347. 		x--;
1348. 		err -= dys;
1349. 	    }
1350. 	    y--;
1351. 	    err += dxs;
1352. 	    if (!is_clear(y,x)) return 0; /* blocked */
1353. 	}
1354.     } else {
1355. 	err = dys - dx;
1356. 
1357. 	for (k = dx-1; k; k--) {
1358. 	    if (err >= 0) {
1359. 		y--;
1360. 		err -= dxs;
1361. 	    }
1362. 	    x--;
1363. 	    err += dys;
1364. 	    if (!is_clear(y,x)) return 0;/* blocked */
1365. 	}
1366.     }
1367. 
1368.     return 1;
1369. }
1370. 
1371. /*
1372.  * Quadrant III (step > 0).
1373.  */
1374. static int
1375. _q3_path(srow,scol,y2,x2)
1376.     int scol, srow, y2, x2;
1377. {
1378.     int dx, dy;
1379.     register int k, err, x, y, dxs, dys;
1380. 
1381.     x  = scol;		y  = srow;
1382.     dx = x - x2;	dy = y2 - y;
1383. 
1384.     dxs = dx << 1;	   /* save the shifted values */
1385.     dys = dy << 1;
1386.     if (dy > dx) {
1387. 	err = dxs - dy;
1388. 
1389. 	for (k = dy-1; k; k--) {
1390. 	    if (err >= 0) {
1391. 		x--;
1392. 		err -= dys;
1393. 	    }
1394. 	    y++;
1395. 	    err += dxs;
1396. 	    if (!is_clear(y,x)) return 0; /* blocked */
1397. 	}
1398.     } else {
1399. 	err = dys - dx;
1400. 
1401. 	for (k = dx-1; k; k--) {
1402. 	    if (err >= 0) {
1403. 		y++;
1404. 		err -= dxs;
1405. 	    }
1406. 	    x--;
1407. 	    err += dys;
1408. 	    if (!is_clear(y,x)) return 0;/* blocked */
1409. 	}
1410.     }
1411. 
1412.     return 1;
1413. }
1414. 
1415. #endif	/* quadrants are functions */
1416. 
1417. /*
1418.  * Use vision tables to determine if there is a clear path from
1419.  * (col1,row1) to (col2,row2).  This is used by:
1420.  *		m_cansee()
1421.  *		m_canseeu()
1422.  */
1423. boolean
1424. clear_path(col1,row1,col2,row2)
1425.     int col1, row1, col2, row2;
1426. {
1427.     int result;
1428. 
1429.     if(col1 < col2) {
1430. 	if(row1 > row2) {
1431. 	    q1_path(row1,col1,row2,col2,cleardone);
1432. 	} else {
1433. 	    q4_path(row1,col1,row2,col2,cleardone);
1434. 	}
1435.     } else {
1436. 	if(row1 > row2) {
1437. 	    q2_path(row1,col1,row2,col2,cleardone);
1438. 	} else if(row1 == row2 && col1 == col2) {
1439. 	    result = 1;
1440. 	} else {
1441. 	    q3_path(row1,col1,row2,col2,cleardone);
1442. 	}
1443.     }
1444. cleardone:
1445.     return result;
1446. }
1447. 
1448. #ifdef VISION_TABLES
1449. /*===========================================================================*\
1450. 			    GENERAL LINE OF SIGHT
1451. 				Algorithm D
1452. \*===========================================================================*/
1453. 
1454. 
1455. /*
1456.  * Indicate caller for the shadow routines.
1457.  */
1458. #define FROM_RIGHT 0
1459. #define FROM_LEFT  1
1460. 
1461. 
1462. /*
1463.  * Include the table definitions.
1464.  */
1465. #include "vis_tab.h"
1466. 
1467. 
1468. /* 3D table pointers. */
1469. static close2d *close_dy[CLOSE_MAX_BC_DY];
1470. static far2d   *far_dy[FAR_MAX_BC_DY];
1471. 
1472. static void FDECL(right_side, (int,int,int,int,int,int,int,char*));
1473. static void FDECL(left_side, (int,int,int,int,int,int,int,char*));
1474. static int FDECL(close_shadow, (int,int,int,int));
1475. static int FDECL(far_shadow, (int,int,int,int));
1476. 
1477. /*
1478.  * Initialize algorithm D's table pointers.  If we don't have these,
1479.  * then we do 3D table lookups.  Verrrry slow.
1480.  */
1481. static void
1482. view_init()
1483. {
1484.     int i;
1485. 
1486.     for (i = 0; i < CLOSE_MAX_BC_DY; i++)
1487. 	close_dy[i] = &close_table[i];
1488. 
1489.     for (i = 0; i < FAR_MAX_BC_DY; i++)
1490. 	far_dy[i] = &far_table[i];
1491. }
1492. 
1493. 
1494. /*
1495.  * If the far table has an entry of OFF_TABLE, then the far block prevents
1496.  * us from seeing the location just above/below it.  I.e. the first visible
1497.  * location is one *before* the block.
1498.  */
1499. #define OFF_TABLE 0xff
1500. 
1501. static int
1502. close_shadow(side,this_row,block_row,block_col)
1503.     int side,this_row,block_row,block_col;
1504. {
1505.     register int sdy, sdx, pdy, offset;
1506. 
1507.     /*
1508.      * If on the same column (block_row = -1), then we can see it.
1509.      */
1510.     if (block_row < 0) return block_col;
1511. 
1512.     /* Take explicit absolute values.  Adjust. */
1513.     if ((sdy = (start_row-block_row)) < 0) sdy = -sdy; --sdy;	/* src   dy */
1514.     if ((sdx = (start_col-block_col)) < 0) sdx = -sdx;		/* src   dx */
1515.     if ((pdy = (block_row-this_row))  < 0) pdy = -pdy;		/* point dy */
1516. 
1517.     if (sdy < 0 || sdy >= CLOSE_MAX_SB_DY || sdx >= CLOSE_MAX_SB_DX ||
1518. 						    pdy >= CLOSE_MAX_BC_DY) {
1519. 	impossible("close_shadow:  bad value");
1520. 	return block_col;
1521.     }
1522.     offset = close_dy[sdy]->close[sdx][pdy];
1523.     if (side == FROM_RIGHT)
1524. 	return block_col + offset;
1525. 
1526.     return block_col - offset;
1527. }
1528. 
1529. 
1530. static int
1531. far_shadow(side,this_row,block_row,block_col)
1532.     int side,this_row,block_row,block_col;
1533. {
1534.     register int sdy, sdx, pdy, offset;
1535. 
1536.     /*
1537.      * Take care of a bug that shows up only on the borders.
1538.      *
1539.      * If the block is beyond the border, then the row is negative.  Return
1540.      * the block's column number (should be 0 or COLNO-1).
1541.      *
1542.      * Could easily have the column be -1, but then wouldn't know if it was
1543.      * the left or right border.
1544.      */
1545.     if (block_row < 0) return block_col;
1546. 
1547.     /* Take explicit absolute values.  Adjust. */
1548.     if ((sdy = (start_row-block_row)) < 0) sdy = -sdy;		/* src   dy */
1549.     if ((sdx = (start_col-block_col)) < 0) sdx = -sdx; --sdx;	/* src   dx */
1550.     if ((pdy = (block_row-this_row))  < 0) pdy = -pdy; --pdy;	/* point dy */
1551. 
1552.     if (sdy >= FAR_MAX_SB_DY || sdx < 0 || sdx >= FAR_MAX_SB_DX ||
1553. 					    pdy < 0 || pdy >= FAR_MAX_BC_DY) {
1554. 	impossible("far_shadow:  bad value");
1555. 	return block_col;
1556.     }
1557.     if ((offset = far_dy[sdy]->far_q[sdx][pdy]) == OFF_TABLE) offset = -1;
1558.     if (side == FROM_RIGHT)
1559. 	return block_col + offset;
1560. 
1561.     return block_col - offset;
1562. }
1563. 
1564. 
1565. /*
1566.  * right_side()
1567.  *
1568.  * Figure out what could be seen on the right side of the source.
1569.  */
1570. static void
1571. right_side(row, cb_row, cb_col, fb_row, fb_col, left, right_mark, limits)
1572.     int row;		/* current row */
1573.     int	cb_row, cb_col;	/* close block row and col */
1574.     int	fb_row, fb_col;	/* far block row and col */
1575.     int left;		/* left mark of the previous row */
1576.     int	right_mark;	/* right mark of previous row */
1577.     char *limits;	/* points at range limit for current row, or NULL */
1578. {
1579.     register int  i;
1580.     register char *rowp;
1581.     int  hit_stone = 0;
1582.     int  left_shadow, right_shadow, loc_right;
1583.     int  lblock_col;		/* local block column (current row) */
1584.     int  nrow, deeper;
1585.     char *row_min;		/* left most */
1586.     char *row_max;		/* right most */
1587.     int		  lim_max;	/* right most limit of circle */
1588. 
1589.     nrow    = row + step;
1590.     deeper  = good_row(nrow) && (!limits || (*limits >= *(limits+1)));
1591.     if(!vis_func) {
1592. 	rowp    = cs_rows[row];
1593. 	row_min = &cs_left[row];
1594. 	row_max = &cs_right[row];
1595.     }
1596.     if(limits) {
1597. 	lim_max = start_col + *limits;
1598. 	if(lim_max > COLNO-1) lim_max = COLNO-1;
1599. 	if(right_mark > lim_max) right_mark = lim_max;
1600. 	limits++; /* prepare for next row */
1601.     } else
1602. 	lim_max = COLNO-1;
1603. 
1604.     /*
1605.      * Get the left shadow from the close block.  This value could be
1606.      * illegal.
1607.      */
1608.     left_shadow = close_shadow(FROM_RIGHT,row,cb_row,cb_col);
1609. 
1610.     /*
1611.      * Mark all stone walls as seen before the left shadow.  All this work
1612.      * for a special case.
1613.      *
1614.      * NOTE.  With the addition of this code in here, it is now *required* 
1615.      * for the algorithm to work correctly.  If this is commented out,
1616.      * change the above assignment so that left and not left_shadow is the
1617.      * variable that gets the shadow.
1618.      */
1619.     while (left <= right_mark) {
1620. 	loc_right = right_ptrs[row][left];
1621. 	if(loc_right > lim_max) loc_right = lim_max;
1622. 	if (viz_clear_rows[row][left]) {
1623. 	    if (loc_right >= left_shadow) {
1624. 		left = left_shadow;	/* opening ends beyond shadow */
1625. 		break;
1626. 	    }
1627. 	    left = loc_right;
1628. 	    loc_right = right_ptrs[row][left];
1629. 	    if(loc_right > lim_max) loc_right = lim_max;
1630. 	    if (left == loc_right) return;	/* boundary */
1631. 
1632. 	    /* Shadow covers opening, beyond right mark */
1633. 	    if (left == right_mark && left_shadow > right_mark) return;
1634. 	}
1635. 
1636. 	if (loc_right > right_mark)	/* can't see stone beyond the mark */
1637. 	    loc_right = right_mark;
1638. 
1639. 	if(vis_func) {
1640. 	    for (i = left; i <= loc_right; i++) (*vis_func)(i, row, varg);
1641. 	} else {
1642. 	    for (i = left; i <= loc_right; i++) set_cs(rowp,i);
1643. 	    set_min(left);	set_max(loc_right);
1644. 	}
1645. 
1646. 	if (loc_right == right_mark) return;	/* all stone */
1647. 	if (loc_right >= left_shadow) hit_stone = 1;
1648. 	left = loc_right + 1;
1649.     }
1650. 
1651.     /*
1652.      * At this point we are at the first visible clear spot on or beyond
1653.      * the left shadow, unless the left shadow is an illegal value.  If we
1654.      * have "hit stone" then we have a stone wall just to our left.
1655.      */
1656. 
1657.     /*
1658.      * Get the right shadow.  Make sure that it is a legal value.
1659.      */
1660.     if ((right_shadow = far_shadow(FROM_RIGHT,row,fb_row,fb_col)) >= COLNO)
1661. 	right_shadow = COLNO-1;
1662.     /*
1663.      * Make vertical walls work the way we want them.  In this case, we
1664.      * note when the close block blocks the column just above/beneath
1665.      * it (right_shadow < fb_col [actually right_shadow == fb_col-1]).  If
1666.      * the location is filled, then we want to see it, so we put the
1667.      * right shadow back (same as fb_col).
1668.      */
1669.     if (right_shadow < fb_col && !viz_clear_rows[row][fb_col])
1670. 	right_shadow = fb_col;
1671.     if(right_shadow > lim_max) right_shadow = lim_max;
1672. 
1673.     /*
1674.      * Main loop.  Within the range of sight of the previous row, mark all
1675.      * stone walls as seen.  Follow open areas recursively.
1676.      */
1677.     while (left <= right_mark) {
1678. 	/* Get the far right of the opening or wall */
1679. 	loc_right = right_ptrs[row][left];
1680. 	if(loc_right > lim_max) loc_right = lim_max;
1681. 
1682. 	if (!viz_clear_rows[row][left]) {
1683. 	    hit_stone = 1;	/* use stone on this row as close block */
1684. 	    /*
1685. 	     * We can see all of the wall until the next open spot or the
1686. 	     * start of the shadow caused by the far block (right).
1687. 	     *
1688. 	     * Can't see stone beyond the right mark.
1689. 	     */
1690. 	    if (loc_right > right_mark) loc_right = right_mark;
1691. 
1692. 	    if(vis_func) {
1693. 		for (i = left; i <= loc_right; i++) (*vis_func)(i, row, varg);
1694. 	    } else {
1695. 		for (i = left; i <= loc_right; i++) set_cs(rowp,i);
1696. 		set_min(left);	set_max(loc_right);
1697. 	    }
1698. 
1699. 	    if (loc_right == right_mark) return;	/* hit the end */
1700. 	    left = loc_right + 1;
1701. 	    loc_right = right_ptrs[row][left];
1702. 	    if(loc_right > lim_max) loc_right = lim_max;
1703. 	    /* fall through... we know at least one position is visible */
1704. 	}
1705. 
1706. 	/*
1707. 	 * We are in an opening.
1708. 	 *
1709. 	 * If this is the first open spot since the could see area  (this is
1710. 	 * true if we have hit stone), get the shadow generated by the wall
1711. 	 * just to our left.
1712. 	 */
1713. 	if (hit_stone) {
1714. 	    lblock_col = left-1;	/* local block column */
1715. 	    left = close_shadow(FROM_RIGHT,row,row,lblock_col);
1716. 	    if (left > lim_max) break;		/* off the end */
1717. 	}
1718. 
1719. 	/*
1720. 	 * Check if the shadow covers the opening.  If it does, then
1721. 	 * move to end of the opening.  A shadow generated on from a
1722. 	 * wall on this row does *not* cover the wall on the right
1723. 	 * of the opening.
1724. 	 */
1725. 	if (left >= loc_right) {
1726. 	    if (loc_right == lim_max) {		/* boundary */
1727. 		if (left == lim_max) {
1728. 		    if(vis_func) (*vis_func)(lim_max, row, varg);
1729. 		    else {
1730. 			set_cs(rowp,lim_max);	/* last pos */
1731. 			set_max(lim_max);
1732. 		    }
1733. 		}
1734. 		return;					/* done */
1735. 	    }
1736. 	    left = loc_right;
1737. 	    continue;
1738. 	}
1739. 
1740. 	/*
1741. 	 * If the far wall of the opening (loc_right) is closer than the
1742. 	 * shadow limit imposed by the far block (right) then use the far
1743. 	 * wall as our new far block when we recurse.
1744. 	 *
1745. 	 * If the limits are the the same, and the far block really exists
1746. 	 * (fb_row >= 0) then do the same as above.
1747. 	 *
1748. 	 * Normally, the check would be for the far wall being closer OR EQUAL
1749. 	 * to the shadow limit.  However, there is a bug that arises from the
1750. 	 * fact that the clear area pointers end in an open space (if it
1751. 	 * exists) on a boundary.  This then makes a far block exist where it
1752. 	 * shouldn't --- on a boundary.  To get around that, I had to
1753. 	 * introduce the concept of a non-existent far block (when the
1754. 	 * row < 0).  Next I have to check for it.  Here is where that check
1755. 	 * exists.
1756. 	 */
1757. 	if ((loc_right < right_shadow) ||
1758. 				(fb_row >= 0 && loc_right == right_shadow)) {
1759. 	    if(vis_func) {
1760. 		for (i = left; i <= loc_right; i++) (*vis_func)(i, row, varg);
1761. 	    } else {
1762. 		for (i = left; i <= loc_right; i++) set_cs(rowp,i);
1763. 		set_min(left);	set_max(loc_right);
1764. 	    }
1765. 
1766. 	    if (deeper) {
1767. 		if (hit_stone)
1768. 		    right_side(nrow,row,lblock_col,row,loc_right,
1769. 							left,loc_right,limits);
1770. 		else
1771. 		    right_side(nrow,cb_row,cb_col,row,loc_right,
1772. 							left,loc_right,limits);
1773. 	    }
1774. 
1775. 	    /*
1776. 	     * The following line, setting hit_stone, is needed for those
1777. 	     * walls that are only 1 wide.  If hit stone is *not* set and
1778. 	     * the stone is only one wide, then the close block is the old
1779. 	     * one instead one on the current row.  A way around having to
1780. 	     * set it here is to make left = loc_right (not loc_right+1) and
1781. 	     * let the outer loop take care of it.  However, if we do that
1782. 	     * then we then have to check for boundary conditions here as
1783. 	     * well.
1784. 	     */
1785. 	    hit_stone = 1;
1786. 
1787. 	    left = loc_right+1;
1788. 	}
1789. 	/*
1790. 	 * The opening extends beyond the right mark.  This means that
1791. 	 * the next far block is the current far block.
1792. 	 */
1793. 	else {
1794. 	    if(vis_func) {
1795. 		for (i=left; i <= right_shadow; i++) (*vis_func)(i, row, varg);
1796. 	    } else {
1797. 		for (i = left; i <= right_shadow; i++) set_cs(rowp,i);
1798. 		set_min(left);	set_max(right_shadow);
1799. 	    }
1800. 
1801. 	    if (deeper) {
1802. 		if (hit_stone)
1803. 		    right_side(nrow,   row,lblock_col,fb_row,fb_col,
1804. 						     left,right_shadow,limits);
1805. 		else
1806. 		    right_side(nrow,cb_row,    cb_col,fb_row,fb_col,
1807. 						     left,right_shadow,limits);
1808. 	    }
1809. 
1810. 	    return;	/* we're outta here */
1811. 	}
1812.     }
1813. }
1814. 
1815. 
1816. /*
1817.  * left_side()
1818.  *
1819.  * This routine is the mirror image of right_side().  Please see right_side()
1820.  * for blow by blow comments.
1821.  */
1822. static void
1823. left_side(row, cb_row, cb_col, fb_row, fb_col, left_mark, right, limits)
1824.     int row;		/* the current row */
1825.     int	cb_row, cb_col;	/* close block row and col */
1826.     int	fb_row, fb_col;	/* far block row and col */
1827.     int	left_mark;	/* left mark of previous row */
1828.     int right;		/* right mark of the previous row */
1829.     char *limits;
1830. {
1831.     register int  i;
1832.     register char *rowp;
1833.     int  hit_stone = 0;
1834.     int  left_shadow, right_shadow, loc_left;
1835.     int  lblock_col;		/* local block column (current row) */
1836.     int  nrow, deeper;
1837.     char *row_min;		/* left most */
1838.     char *row_max;		/* right most */
1839.     int		  lim_min;
1840. 
1841.     nrow    = row + step;
1842.     deeper  = good_row(nrow) && (!limits || (*limits >= *(limits+1)));
1843.     if(!vis_func) {
1844. 	rowp    = cs_rows[row];
1845. 	row_min = &cs_left[row];
1846. 	row_max = &cs_right[row];
1847.     }
1848.     if(limits) {
1849. 	lim_min = start_col - *limits;
1850. 	if(lim_min < 0) lim_min = 0;
1851. 	if(left_mark < lim_min) left_mark = lim_min;
1852. 	limits++; /* prepare for next row */
1853.     } else
1854. 	lim_min = 0;
1855. 
1856.     /* This value could be illegal. */
1857.     right_shadow = close_shadow(FROM_LEFT,row,cb_row,cb_col);
1858. 
1859.     while ( right >= left_mark ) {
1860. 	loc_left = left_ptrs[row][right];
1861. 	if(loc_left < lim_min) loc_left = lim_min;
1862. 	if (viz_clear_rows[row][right]) {
1863. 	    if (loc_left <= right_shadow) {
1864. 		right = right_shadow;	/* opening ends beyond shadow */
1865. 		break;
1866. 	    }
1867. 	    right = loc_left;
1868. 	    loc_left = left_ptrs[row][right];
1869. 	    if(loc_left < lim_min) loc_left = lim_min;
1870. 	    if (right == loc_left) return;	/* boundary */
1871. 	}
1872. 
1873. 	if (loc_left < left_mark)	/* can't see beyond the left mark */
1874. 	    loc_left = left_mark;
1875. 
1876. 	if(vis_func) {
1877. 	    for (i = loc_left; i <= right; i++) (*vis_func)(i, row, varg);
1878. 	} else {
1879. 	    for (i = loc_left; i <= right; i++) set_cs(rowp,i);
1880. 	    set_min(loc_left);	set_max(right);
1881. 	}
1882. 
1883. 	if (loc_left == left_mark) return;	/* all stone */
1884. 	if (loc_left <= right_shadow) hit_stone = 1;
1885. 	right = loc_left - 1;
1886.     }
1887. 
1888.     /* At first visible clear spot on or beyond the right shadow. */
1889. 
1890.     if ((left_shadow = far_shadow(FROM_LEFT,row,fb_row,fb_col)) < 0)
1891. 	left_shadow = 0;
1892.     
1893.     /* Do vertical walls as we want. */
1894.     if (left_shadow > fb_col && !viz_clear_rows[row][fb_col])
1895. 	left_shadow = fb_col;
1896.     if(left_shadow < lim_min) left_shadow = lim_min;
1897. 
1898.     while (right >= left_mark) {
1899. 	loc_left = left_ptrs[row][right];
1900. 
1901. 	if (!viz_clear_rows[row][right]) {
1902. 	    hit_stone = 1;	/* use stone on this row as close block */
1903. 
1904. 	    /* We can only see walls until the left mark */
1905. 	    if (loc_left < left_mark) loc_left = left_mark;
1906. 
1907. 	    if(vis_func) {
1908. 		for (i = loc_left; i <= right; i++) (*vis_func)(i, row, varg);
1909. 	    } else {
1910. 		for (i = loc_left; i <= right; i++) set_cs(rowp,i);
1911. 		set_min(loc_left);	set_max(right);
1912. 	    }
1913. 
1914. 	    if (loc_left == left_mark) return;	/* hit end */
1915. 	    right = loc_left - 1;
1916. 	    loc_left = left_ptrs[row][right];
1917. 	    if (loc_left < lim_min) loc_left = lim_min;
1918. 	    /* fall through...*/
1919. 	}
1920. 
1921. 	/* We are in an opening. */
1922. 	if (hit_stone) {
1923. 	    lblock_col = right+1;	/* stone block (local) */
1924. 	    right = close_shadow(FROM_LEFT,row,row,lblock_col);
1925. 	    if (right < lim_min) return;	/* off the end */
1926. 	}
1927. 
1928. 	/*  Check if the shadow covers the opening. */
1929. 	if (right <= loc_left) {
1930. 	    /*  Make a boundary condition work. */
1931. 	    if (loc_left == lim_min) {	/* at boundary */
1932. 		if (right == lim_min) {
1933. 		    if(vis_func) (*vis_func)(lim_min, row, varg);
1934. 		    else {
1935. 			set_cs(rowp,lim_min);	/* caught the last pos */
1936. 			set_min(lim_min);
1937. 		    }
1938. 		}
1939. 		return;			/* and break out the loop */
1940. 	    }
1941. 
1942. 	    right = loc_left;
1943. 	    continue;
1944. 	}
1945. 
1946. 	/* If the far wall of the opening is closer than the shadow limit. */
1947. 	if ((loc_left > left_shadow) ||
1948. 				    (fb_row >= 0 && loc_left == left_shadow)) {
1949. 	    if(vis_func) {
1950. 		for (i = loc_left; i <= right; i++) (*vis_func)(i, row, varg);
1951. 	    } else {
1952. 		for (i = loc_left; i <= right; i++) set_cs(rowp,i);
1953. 		set_min(loc_left);	set_max(right);
1954. 	    }
1955. 
1956. 	    if (deeper) {
1957. 		if (hit_stone)
1958. 		    left_side(nrow,row,lblock_col,row,loc_left,
1959. 							loc_left,right,limits);
1960. 		else
1961. 		    left_side(nrow,cb_row,cb_col,row,loc_left,
1962. 							loc_left,right,limits);
1963. 	    }
1964. 
1965. 	    hit_stone = 1;	/* needed for walls of width 1 */
1966. 	    right = loc_left-1;
1967. 	}
1968. 	/*  The opening extends beyond the left mark. */
1969. 	else {
1970. 	    if(vis_func) {
1971. 		for (i=left_shadow; i <= right; i++) (*vis_func)(i, row, varg);
1972. 	    } else {
1973. 		for (i = left_shadow; i <= right; i++) set_cs(rowp,i);
1974. 		set_min(left_shadow);	set_max(right);
1975. 	    }
1976. 
1977. 	    if (deeper) {
1978. 		if (hit_stone)
1979. 		    left_side(nrow,row,lblock_col,fb_row,fb_col,
1980. 						     left_shadow,right,limits);
1981. 		else
1982. 		    left_side(nrow,cb_row,cb_col,fb_row,fb_col,
1983. 						     left_shadow,right,limits);
1984. 	    }
1985. 
1986. 	    return;	/* we're outta here */
1987. 	}
1988. 
1989.     }
1990. }
1991. 
1992. /*
1993.  * view_from
1994.  *  
1995.  * Calculate a view from the given location.  Initialize and fill a
1996.  * ROWNOxCOLNO array (could_see) with all the locations that could be
1997.  * seen from the source location.  Initialize and fill the left most
1998.  * and right most boundaries of what could be seen.
1999.  */
2000. static void
2001. view_from(srow,scol,loc_cs_rows,left_most,right_most, range, func, arg)
2002.     int  srow, scol;			/* source row and column */
2003.     char **loc_cs_rows;			/* could_see array (row pointers) */
2004.     char *left_most, *right_most;	/* limits of what could be seen */
2005.     int range;		/* 0 if unlimited */
2006.     void FDECL((*func), (int,int,genericptr_t));
2007.     genericptr_t arg;
2008. {
2009.     register int i;
2010.     char	 *rowp;
2011.     int		 nrow, left, right, left_row, right_row;
2012.     char	 *limits;
2013. 
2014.     /* Set globals for near_shadow(), far_shadow(), etc. to use. */
2015.     start_col = scol;
2016.     start_row = srow;
2017.     cs_rows   = loc_cs_rows;
2018.     cs_left   = left_most;
2019.     cs_right  = right_most;
2020.     vis_func = func;
2021.     varg = arg;
2022. 
2023.     /*  Find the left and right limits of sight on the starting row. */
2024.     if (viz_clear_rows[srow][scol]) {
2025. 	left  = left_ptrs[srow][scol];
2026. 	right = right_ptrs[srow][scol];
2027.     } else {
2028. 	left  = (!scol) ? 0 :
2029. 	    (viz_clear_rows[srow][scol-1] ?  left_ptrs[srow][scol-1] : scol-1);
2030. 	right = (scol == COLNO-1) ? COLNO-1 :
2031. 	    (viz_clear_rows[srow][scol+1] ? right_ptrs[srow][scol+1] : scol+1);
2032.     }
2033. 
2034.     if(range) {
2035. 	if(range > MAX_RADIUS || range < 1)
2036. 	    panic("view_from called with range %d", range);
2037. 	limits = circle_ptr(range) + 1; /* start at next row */
2038. 	if(left < scol - range) left = scol - range;
2039. 	if(right > scol + range) right = scol + range;
2040.     } else
2041. 	limits = (char*) 0;
2042. 
2043.     if(func) {
2044. 	for (i = left; i <= right; i++) (*func)(i, srow, arg);
2045.     } else {
2046. 	/* Row optimization */
2047. 	rowp = cs_rows[srow];
2048. 
2049. 	/* We know that we can see our row. */
2050. 	for (i = left; i <= right; i++) set_cs(rowp,i);
2051. 	cs_left[srow]  = left;
2052. 	cs_right[srow] = right;
2053.     }
2054. 
2055.     /* The far block has a row number of -1 if we are on an edge. */
2056.     right_row = (right == COLNO-1) ? -1 : srow;
2057.     left_row  = (!left)		   ? -1 : srow;
2058. 
2059.     /*
2060.      *  Check what could be seen in quadrants.
2061.      */
2062.     if ( (nrow = srow+1) < ROWNO ) {
2063. 	step =  1;	/* move down */
2064. 	if (scol<COLNO-1)
2065. 	    right_side(nrow,-1,scol,right_row,right,scol,right,limits);
2066. 	if (scol)
2067. 	    left_side(nrow,-1,scol,left_row, left, left, scol,limits);
2068.     }
2069. 
2070.     if ( (nrow = srow-1) >= 0 ) {
2071. 	step = -1;	/* move up */
2072. 	if (scol<COLNO-1)
2073. 	    right_side(nrow,-1,scol,right_row,right,scol,right,limits);
2074. 	if (scol)
2075. 	    left_side(nrow,-1,scol,left_row, left, left, scol,limits);
2076.     }
2077. }
2078. 
2079. 
2080. #else	/*===== End of algorithm D =====*/
2081. 
2082. 
2083. /*===========================================================================*\
2084. 			    GENERAL LINE OF SIGHT
2085. 				Algorithm C
2086. \*===========================================================================*/
2087. 
2088. /*
2089.  * Defines local to Algorithm C.  
2090.  */
2091. static void FDECL(right_side, (int,int,int,char*));
2092. static void FDECL(left_side, (int,int,int,char*));
2093. 
2094. /* Initialize algorithm C (nothing). */
2095. static void
2096. view_init()
2097. {
2098. }
2099. 
2100. /*
2101.  * Mark positions as visible on one quadrant of the right side.  The
2102.  * quadrant is determined by the value of the global variable step.
2103.  */
2104. static void
2105. right_side(row, left, right_mark, limits)
2106.     int row;		/* current row */
2107.     int left;		/* first (left side) visible spot on prev row */
2108.     int right_mark;	/* last (right side) visible spot on prev row */
2109.     char *limits;	/* points at range limit for current row, or NULL */
2110. {
2111.     int		  right;	/* right limit of "could see" */
2112.     int		  right_edge;	/* right edge of an opening */
2113.     int		  nrow;		/* new row (calculate once) */
2114.     int		  deeper;	/* if TRUE, call self as needed */
2115.     int		  result;	/* set by q?_path() */
2116.     register int  i;		/* loop counter */
2117.     register char *rowp;	/* row optimization */
2118.     char	  *row_min;	/* left most  [used by macro set_min()] */
2119.     char	  *row_max;	/* right most [used by macro set_max()] */
2120.     int		  lim_max;	/* right most limit of circle */
2121. 
2122. #ifdef GCC_WARN
2123.     rowp = row_min = row_max = 0;
2124. #endif
2125.     nrow    = row + step;
2126.     /*
2127.      * Can go deeper if the row is in bounds and the next row is within
2128.      * the circle's limit.  We tell the latter by checking to see if the next
2129.      * limit value is the start of a new circle radius (meaning we depend
2130.      * on the structure of circle_data[]).
2131.      */
2132.     deeper  = good_row(nrow) && (!limits || (*limits >= *(limits+1)));
2133.     if(!vis_func) {
2134. 	rowp    = cs_rows[row];	/* optimization */
2135. 	row_min = &cs_left[row];
2136. 	row_max = &cs_right[row];
2137.     }
2138.     if(limits) {
2139. 	lim_max = start_col + *limits;
2140. 	if(lim_max > COLNO-1) lim_max = COLNO-1;
2141. 	if(right_mark > lim_max) right_mark = lim_max;
2142. 	limits++; /* prepare for next row */
2143.     } else
2144. 	lim_max = COLNO-1;
2145. 
2146.     while (left <= right_mark) {
2147. 	right_edge = right_ptrs[row][left];
2148. 	if(right_edge > lim_max) right_edge = lim_max;
2149. 
2150. 	if (!is_clear(row,left)) {
2151. 	    /*
2152. 	     * Jump to the far side of a stone wall.  We can set all
2153. 	     * the points in between as seen.
2154. 	     *
2155. 	     * If the right edge goes beyond the right mark, check to see
2156. 	     * how much we can see.
2157. 	     */
2158. 	    if (right_edge > right_mark) {
2159. 		/*
2160. 		 * If the mark on the previous row was a clear position, 
2161. 		 * the odds are that we can actually see part of the wall
2162. 		 * beyond the mark on this row.  If so, then see one beyond
2163. 		 * the mark.  Otherwise don't.  This is a kludge so corners
2164. 		 * with an adjacent doorway show up in nethack.
2165. 		 */
2166. 		right_edge = is_clear(row-step,right_mark) ?
2167. 						    right_mark+1 : right_mark;
2168. 	    }
2169. 	    if(vis_func) {
2170. 		for (i = left; i <= right_edge; i++) (*vis_func)(i, row, varg);
2171. 	    } else {
2172. 		for (i = left; i <= right_edge; i++) set_cs(rowp,i);
2173. 		set_min(left);      set_max(right_edge);
2174. 	    }
2175. 	    left = right_edge + 1; /* no limit check necessary */
2176. 	    continue;
2177. 	}
2178. 
2179. 	/* No checking needed if our left side is the start column. */
2180. 	if (left != start_col) { 
2181. 	    /*
2182. 	     * Find the left side.  Move right until we can see it or we run
2183. 	     * into a wall.
2184. 	     */
2185. 	    for (; left <= right_edge; left++) {
2186. 		if (step < 0) {
2187. 		    q1_path(start_row,start_col,row,left,rside1);
2188. 		} else {
2189. 		    q4_path(start_row,start_col,row,left,rside1);
2190. 		}
2191. rside1:					/* used if q?_path() is a macro */
2192. 		if (result) break;
2193. 	    }
2194. 
2195. 	    /*
2196. 	     * Check for boundary conditions.  We *need* check (2) to break
2197. 	     * an infinite loop where:
2198. 	     *
2199. 	     *		left == right_edge == right_mark == lim_max.
2200. 	     * 
2201. 	     */
2202. 	    if (left > lim_max) return;	/* check (1) */
2203. 	    if (left == lim_max) {	/* check (2) */
2204. 		if(vis_func) (*vis_func)(lim_max, row, varg);
2205. 		else {
2206. 		    set_cs(rowp,lim_max);
2207. 		    set_max(lim_max);
2208. 		}
2209. 		return;
2210. 	    }
2211. 	    /*
2212. 	     * Check if we can see any spots in the opening.  We might
2213. 	     * (left == right_edge) or might not (left == right_edge+1) have
2214. 	     * been able to see the far wall.  Make sure we *can* see the
2215. 	     * wall (remember, we can see the spot above/below this one)
2216. 	     * by backing up.
2217. 	     */
2218. 	    if (left >= right_edge) {
2219. 		left = right_edge;	/* for the case left == right_edge+1 */
2220. 		continue;
2221. 	    }
2222. 	}
2223. 
2224. 	/*
2225. 	 * Find the right side.  If the marker from the previous row is
2226. 	 * closer than the edge on this row, then we have to check
2227. 	 * how far we can see around the corner (under the overhang).  Stop
2228. 	 * at the first non-visible spot or we actually hit the far wall.
2229. 	 *
2230. 	 * Otherwise, we know we can see the right edge of the current row.
2231. 	 *
2232. 	 * This must be a strict less than so that we can always see a
2233. 	 * horizontal wall, even if it is adjacent to us.
2234. 	 */
2235. 	if (right_mark < right_edge) {
2236. 	    for (right = right_mark; right <= right_edge; right++) {
2237. 		if (step < 0) {
2238. 		    q1_path(start_row,start_col,row,right,rside2);
2239. 		} else {
2240. 		    q4_path(start_row,start_col,row,right,rside2);
2241. 		}
2242. rside2:					/* used if q?_path() is a macro */
2243. 		if (!result) break;
2244. 	    }
2245. 	    --right;	/* get rid of the last increment */
2246. 	}
2247. 	else
2248. 	    right = right_edge;
2249. 
2250. 	/*
2251. 	 * We have the range that we want.  Set the bits.  Note that
2252. 	 * there is no else --- we no longer handle splinters.
2253. 	 */
2254. 	if (left <= right) {
2255. 	    /*
2256. 	     * An ugly special case.  If you are adjacent to a vertical wall
2257. 	     * and it has a break in it, then the right mark is set to be
2258. 	     * start_col.  We *want* to be able to see adjacent vertical
2259. 	     * walls, so we have to set it back.
2260. 	     */
2261. 	    if (left == right && left == start_col &&
2262. 			start_col < (COLNO-1) && !is_clear(row,start_col+1))
2263. 		right = start_col+1;
2264. 
2265. 	    if(right > lim_max) right = lim_max;
2266. 	    /* set the bits */
2267. 	    if(vis_func)
2268. 		for (i = left; i <= right; i++) (*vis_func)(i, row, varg);
2269. 	    else {
2270. 		for (i = left; i <= right; i++) set_cs(rowp,i);
2271. 		set_min(left);      set_max(right);
2272. 	    }
2273. 
2274. 	    /* recursive call for next finger of light */
2275. 	    if (deeper) right_side(nrow,left,right,limits);
2276. 	    left = right + 1; /* no limit check necessary */
2277. 	}
2278.     }
2279. }
2280. 
2281. 
2282. /*
2283.  * This routine is the mirror image of right_side().  See right_side() for
2284.  * extensive comments.
2285.  */
2286. static void
2287. left_side(row, left_mark, right, limits)
2288.     int row, left_mark, right;
2289.     char *limits;
2290. {
2291.     int		  left, left_edge, nrow, deeper, result;
2292.     register int  i;
2293.     register char *rowp;
2294.     char	  *row_min, *row_max;
2295.     int		  lim_min;
2296. 
2297. #ifdef GCC_WARN
2298.     rowp = row_min = row_max = 0;
2299. #endif
2300.     nrow    = row+step;
2301.     deeper  = good_row(nrow) && (!limits || (*limits >= *(limits+1)));
2302.     if(!vis_func) {
2303. 	rowp    = cs_rows[row];
2304. 	row_min = &cs_left[row];
2305. 	row_max = &cs_right[row];
2306.     }
2307.     if(limits) {
2308. 	lim_min = start_col - *limits;
2309. 	if(lim_min < 0) lim_min = 0;
2310. 	if(left_mark < lim_min) left_mark = lim_min;
2311. 	limits++; /* prepare for next row */
2312.     } else
2313. 	lim_min = 0;
2314. 
2315.     while (right >= left_mark) {
2316. 	left_edge = left_ptrs[row][right];
2317. 	if(left_edge < lim_min) left_edge = lim_min;
2318. 
2319. 	if (!is_clear(row,right)) {
2320. 	    /* Jump to the far side of a stone wall. */
2321. 	    if (left_edge < left_mark) {
2322. 		/* Maybe see more (kludge). */
2323. 		left_edge = is_clear(row-step,left_mark) ?
2324. 						    left_mark-1 : left_mark;
2325. 	    }
2326. 	    if(vis_func) {
2327. 		for (i = left_edge; i <= right; i++) (*vis_func)(i, row, varg);
2328. 	    } else {
2329. 		for (i = left_edge; i <= right; i++) set_cs(rowp,i);
2330. 		set_min(left_edge); set_max(right);
2331. 	    }
2332. 	    right = left_edge - 1; /* no limit check necessary */
2333. 	    continue;
2334. 	}
2335. 
2336. 	if (right != start_col) {
2337. 	    /* Find the right side. */
2338. 	    for (; right >= left_edge; right--) {
2339. 		if (step < 0) {
2340. 		    q2_path(start_row,start_col,row,right,lside1);
2341. 		} else {
2342. 		    q3_path(start_row,start_col,row,right,lside1);
2343. 		}
2344. lside1:					/* used if q?_path() is a macro */
2345. 		if (result) break;
2346. 	    }
2347. 
2348. 	    /* Check for boundary conditions. */
2349. 	    if (right < lim_min) return;
2350. 	    if (right == lim_min) {
2351. 		if(vis_func) (*vis_func)(lim_min, row, varg);
2352. 		else {
2353. 		    set_cs(rowp,lim_min);
2354. 		    set_min(lim_min);
2355. 		}
2356. 		return;
2357. 	    }
2358. 	    /* Check if we can see any spots in the opening. */
2359. 	    if (right <= left_edge) {
2360. 		right = left_edge;
2361. 		continue;
2362. 	    }
2363. 	}
2364. 
2365. 	/* Find the left side. */
2366. 	if (left_mark > left_edge) {
2367. 	    for (left = left_mark; left >= left_edge; --left) {
2368. 		if (step < 0) {
2369. 		    q2_path(start_row,start_col,row,left,lside2);
2370. 		} else {
2371. 		    q3_path(start_row,start_col,row,left,lside2);
2372. 		}
2373. lside2:					/* used if q?_path() is a macro */
2374. 		if (!result) break;
2375. 	    }
2376. 	    left++;	/* get rid of the last decrement */
2377. 	}
2378. 	else
2379. 	    left = left_edge;
2380. 
2381. 	if (left <= right) {
2382. 	    /* An ugly special case. */
2383. 	    if (left == right && right == start_col &&
2384. 			    start_col > 0 && !is_clear(row,start_col-1))
2385. 		left = start_col-1;
2386. 
2387. 	    if(left < lim_min) left = lim_min;
2388. 	    if(vis_func)
2389. 		for (i = left; i <= right; i++) (*vis_func)(i, row, varg);
2390. 	    else {
2391. 		for (i = left; i <= right; i++) set_cs(rowp,i);
2392. 		set_min(left);      set_max(right);
2393. 	    }
2394. 
2395. 	    /* Recurse */
2396. 	    if (deeper) left_side(nrow,left,right,limits);
2397. 	    right = left - 1; /* no limit check necessary */
2398. 	}
2399.     }
2400. }
2401. 
2402. 
2403. /*
2404.  * Calculate all possible visible locations from the given location
2405.  * (srow,scol).  NOTE this is (y,x)!  Mark the visible locations in the
2406.  * array provided.
2407.  */
2408. static void
2409. view_from(srow, scol, loc_cs_rows, left_most, right_most, range, func, arg)
2410.     int  srow, scol;	/* starting row and column */
2411.     char **loc_cs_rows;	/* pointers to the rows of the could_see array */
2412.     char *left_most;	/* min mark on each row */
2413.     char *right_most;	/* max mark on each row */
2414.     int range;		/* 0 if unlimited */
2415.     void FDECL((*func), (int,int,genericptr_t));
2416.     genericptr_t arg;
2417. {
2418.     register int i;		/* loop counter */
2419.     char         *rowp;		/* optimization for setting could_see */
2420.     int		 nrow;		/* the next row */
2421.     int		 left;		/* the left-most visible column */
2422.     int		 right;		/* the right-most visible column */
2423.     char	 *limits;	/* range limit for next row */
2424. 
2425.     /* Set globals for q?_path(), left_side(), and right_side() to use. */
2426.     start_col = scol;
2427.     start_row = srow;
2428.     cs_rows   = loc_cs_rows;	/* 'could see' rows */
2429.     cs_left   = left_most;
2430.     cs_right  = right_most;
2431.     vis_func = func;
2432.     varg = arg;
2433. 
2434.     /*
2435.      * Determine extent of sight on the starting row.
2436.      */
2437.     if (is_clear(srow,scol)) {
2438. 	left =  left_ptrs[srow][scol];
2439. 	right = right_ptrs[srow][scol];
2440.     } else {
2441. 	/*
2442. 	 * When in stone, you can only see your adjacent squares, unless
2443. 	 * you are on an array boundary or a stone/clear boundary.
2444. 	 */
2445. 	left  = (!scol) ? 0 :
2446. 		(is_clear(srow,scol-1) ? left_ptrs[srow][scol-1] : scol-1);
2447. 	right = (scol == COLNO-1) ? COLNO-1 :
2448. 		(is_clear(srow,scol+1) ? right_ptrs[srow][scol+1] : scol+1);
2449.     }
2450. 
2451.     if(range) {
2452. 	if(range > MAX_RADIUS || range < 1)
2453. 	    panic("view_from called with range %d", range);
2454. 	limits = circle_ptr(range) + 1; /* start at next row */
2455. 	if(left < scol - range) left = scol - range;
2456. 	if(right > scol + range) right = scol + range;
2457.     } else
2458. 	limits = (char*) 0;
2459. 
2460.     if(func) {
2461. 	for (i = left; i <= right; i++) (*func)(i, srow, arg);
2462.     } else {
2463. 	/* Row pointer optimization. */
2464. 	rowp = cs_rows[srow];
2465. 
2466. 	/* We know that we can see our row. */
2467. 	for (i = left; i <= right; i++) set_cs(rowp,i);
2468. 	cs_left[srow]  = left;
2469. 	cs_right[srow] = right;
2470.     }
2471. 
2472.     /*
2473.      * Check what could be seen in quadrants.  We need to check for valid
2474.      * rows here, since we don't do it in the routines right_side() and
2475.      * left_side() [ugliness to remove extra routine calls].
2476.      */
2477.     if ( (nrow = srow+1) < ROWNO ) {	/* move down */
2478. 	step =  1;
2479. 	if (scol < COLNO-1) right_side(nrow, scol, right, limits);
2480. 	if (scol)	    left_side (nrow, left,  scol, limits);
2481.     }
2482. 
2483.     if ( (nrow = srow-1) >= 0 ) {	/* move up */
2484. 	step = -1;
2485. 	if (scol < COLNO-1) right_side(nrow, scol, right, limits);
2486. 	if (scol)	    left_side (nrow, left,  scol, limits);
2487.     }
2488. }
2489. 
2490. #endif	/*===== End of algorithm C =====*/
2491. 
2492. /*
2493.  * AREA OF EFFECT "ENGINE"
2494.  *
2495.  * Calculate all possible visible locations as viewed from the given location
2496.  * (srow,scol) within the range specified. Perform "func" with (x, y) args and
2497.  * additional argument "arg" for each square.
2498.  *
2499.  * If not centered on the hero, just forward arguments to view_from(); it
2500.  * will call "func" when necessary.  If the hero is the center, use the
2501.  * vision matrix and reduce extra work.
2502.  */
2503. void
2504. do_clear_area(scol,srow,range,func,arg)
2505.     int scol, srow, range;
2506.     void FDECL((*func), (int,int,genericptr_t));
2507.     genericptr_t arg;
2508. {
2509. 	/* If not centered on hero, do the hard work of figuring the area */
2510. 	if (scol != u.ux || srow != u.uy)
2511. 	    view_from(srow, scol, (char **)0, NULL, NULL, range, func, arg);
2512. 	else {
2513. 	    register int x;
2514. 	    int y, min_x, max_x, max_y, offset;
2515. 	    char *limits;
2516. 
2517. 	    if (range > MAX_RADIUS || range < 1)
2518. 		panic("do_clear_area:  illegal range %d", range);
2519. 	    if(vision_full_recalc)
2520. 		vision_recalc(0);	/* recalc vision if dirty */
2521. 	    limits = circle_ptr(range);
2522. 	    if ((max_y = (srow + range)) >= ROWNO) max_y = ROWNO-1;
2523. 	    if ((y = (srow - range)) < 0) y = 0;
2524. 	    for (; y <= max_y; y++) {
2525. 		offset = limits[abs(y-srow)];
2526. 		if((min_x = (scol - offset)) < 0) min_x = 0;
2527. 		if((max_x = (scol + offset)) >= COLNO) max_x = COLNO-1;
2528. 		for (x = min_x; x <= max_x; x++)
2529. 		    if (couldsee(x, y))
2530. 			(*func)(x, y, arg);
2531. 	    }
2532. 	}
2533. }
2534. 
2535. /*vision.c*/

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