Source:NetHack 3.2.0/vision.c

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Below is the full text to vision.c from the source code of NetHack 3.2.0. To link to a particular line, write [[NetHack 3.2.0/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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This content was modified from the original NetHack source code distribution (by splitting up NetHack content between wiki pages, and possibly further editing). See the page history for a list of who changed it, and on what dates.

1.    /*	SCCS Id: @(#)vision.c	3.2	96/02/14	*/
2.    /* Copyright (c) Dean Luick, with acknowledgements to Dave Cohrs, 1990.	*/
3.    /* NetHack may be freely redistributed.  See license for details.	*/
4.    
5.    #include "hack.h"
6.    
7.    /* Circles ==================================================================*/
8.    
9.    /*
10.    * These numbers are limit offsets for one quadrant of a circle of a given
11.    * radius (the first number of each line) from the source.  The number in
12.    * the comment is the element number (so pointers can be set up).  Each
13.    * "circle" has as many elements as its radius+1.  The radius is the number
14.    * of points away from the source that the limit exists.  The radius of the
15.    * offset on the same row as the source *is* included so we don't have to
16.    * make an extra check.  For example, a circle of radius 4 has offsets:
17.    *
18.    *				XXX	+2
19.    *				...X	+3
20.    *				....X	+4
21.    *				....X	+4
22.    *				@...X   +4
23.    *
24.    */
25.   char circle_data[] = {
26.   /*  0*/	 1, 1,
27.   /*  2*/	 2, 2, 1,
28.   /*  5*/	 3, 3, 2, 1,
29.   /*  9*/	 4, 4, 4, 3, 2,
30.   /* 14*/	 5, 5, 5, 4, 3, 2,
31.   /* 20*/	 6, 6, 6, 5, 5, 4, 2,
32.   /* 27*/	 7, 7, 7, 6, 6, 5, 4, 2,
33.   /* 35*/	 8, 8, 8, 7, 7, 6, 6, 4, 2,
34.   /* 44*/	 9, 9, 9, 9, 8, 8, 7, 6, 5, 3,
35.   /* 54*/	10,10,10,10, 9, 9, 8, 7, 6, 5, 3,
36.   /* 65*/	11,11,11,11,10,10, 9, 9, 8, 7, 5, 3,
37.   /* 77*/	12,12,12,12,11,11,10,10, 9, 8, 7, 5, 3,
38.   /* 90*/	13,13,13,13,12,12,12,11,10,10, 9, 7, 6, 3,
39.   /*104*/	14,14,14,14,13,13,13,12,12,11,10, 9, 8, 6, 3,
40.   /*119*/	15,15,15,15,14,14,14,13,13,12,11,10, 9, 8, 6, 3,
41.   /*135*/ 16 /* should be MAX_RADIUS+1; used to terminate range loops -dlc */
42.   };
43.   
44.   /*
45.    * These are the starting indexes into the circle_data[] array for a
46.    * circle of a given radius.
47.    */
48.   char circle_start[] = {
49.   /*  */	  0,	/* circles of radius zero are not used */
50.   /* 1*/    0,
51.   /* 2*/	  2,
52.   /* 3*/	  5,
53.   /* 4*/	  9,
54.   /* 5*/	 14,
55.   /* 6*/	 20,
56.   /* 7*/	 27,
57.   /* 8*/	 35,
58.   /* 9*/	 44,
59.   /*10*/	 54,
60.   /*11*/	 65,
61.   /*12*/	 77,
62.   /*13*/	 90,
63.   /*14*/	104,
64.   /*15*/	119,
65.   };
66.   
67.   
68.   /*===========================================================================*/
69.   /* Vision (arbitrary line of sight) =========================================*/
70.   
71.   /*------ global variables ------*/
72.   
73.   #if 0	/* (moved to decl.c) */
74.   /* True if we need to run a full vision recalculation. */
75.   boolean	vision_full_recalc = 0;
76.   
77.   /* Pointers to the current vision array. */
78.   char	**viz_array;
79.   #endif
80.   char	*viz_rmin, *viz_rmax;		/* current vision cs bounds */
81.   
82.   
83.   /*------ local variables ------*/
84.   
85.   
86.   static char could_see[2][ROWNO][COLNO];		/* vision work space */
87.   static char *cs_rows0[ROWNO], *cs_rows1[ROWNO];
88.   static char  cs_rmin0[ROWNO],  cs_rmax0[ROWNO];
89.   static char  cs_rmin1[ROWNO],  cs_rmax1[ROWNO];
90.   
91.   static char  viz_clear[ROWNO][COLNO];		/* vision clear/blocked map */
92.   static char *viz_clear_rows[ROWNO];
93.   
94.   static char  left_ptrs[ROWNO][COLNO];		/* LOS algorithm helpers */
95.   static char right_ptrs[ROWNO][COLNO];
96.   
97.   /* Forward declarations. */
98.   static void FDECL(fill_point, (int,int));
99.   static void FDECL(dig_point, (int,int));
100.  static void NDECL(view_init);
101.  static void FDECL(view_from,(int,int,char **,char *,char *,int,
102.  			     void (*)(int,int,genericptr_t),genericptr_t));
103.  static void FDECL(get_unused_cs, (char ***,char **,char **));
104.  #ifdef REINCARNATION
105.  static void FDECL(rogue_vision, (char **,char *,char *));
106.  #endif
107.  
108.  /* Macro definitions that I can't find anywhere. */
109.  #define sign(z) ((z) < 0 ? -1 : ((z) ? 1 : 0 ))
110.  #define v_abs(z)  ((z) < 0 ? -(z) : (z))	/* don't use abs -- it may exist */
111.  
112.  /*
113.   * vision_init()
114.   *
115.   * The one-time vision initialization routine.
116.   *
117.   * This must be called before mklev() is called in newgame() [allmain.c],
118.   * or before a game restore.   Else we die a horrible death.
119.   */
120.  void
121.  vision_init()
122.  {
123.      int i;
124.  
125.      /* Set up the pointers. */
126.      for (i = 0; i < ROWNO; i++) {
127.  	cs_rows0[i] = could_see[0][i];
128.  	cs_rows1[i] = could_see[1][i];
129.  	viz_clear_rows[i] = viz_clear[i];
130.      }
131.  
132.      /* Start out with cs0 as our current array */
133.      viz_array = cs_rows0;
134.      viz_rmin  = cs_rmin0;
135.      viz_rmax  = cs_rmax0;
136.  
137.      vision_full_recalc = 0;
138.      (void) memset((genericptr_t) could_see, 0, sizeof(could_see));
139.  
140.      /* Initialize the vision algorithm (currently C or D). */
141.      view_init();
142.  
143.  #ifdef VISION_TABLES
144.      /* Note:  this initializer doesn't do anything except guarantee that
145.  	      we're linked properly.
146.      */
147.      vis_tab_init();
148.  #endif
149.  }
150.  
151.  /*
152.   * does_block()
153.   *
154.   * Returns true if the level feature, object, or monster at (x,y) blocks
155.   * sight.
156.   */
157.  int
158.  does_block(x,y,lev)
159.      int x, y;
160.      register struct rm    *lev;
161.  {
162.      struct obj   *obj;
163.      struct monst *mon;
164.  
165.      /* Features that block . . */
166.      if (IS_ROCK(lev->typ) || (IS_DOOR(lev->typ) &&
167.  			    (lev->doormask & (D_CLOSED|D_LOCKED|D_TRAPPED) )))
168.  	return 1;
169.  
170.      if (lev->typ == CLOUD || lev->typ == WATER ||
171.  			(lev->typ == MOAT && Underwater))
172.  	return 1;
173.  
174.      /* Boulders block light. */
175.      for (obj = level.objects[x][y]; obj; obj = obj->nexthere)
176.  	if (obj->otyp == BOULDER) return 1;
177.  
178.      /* Mimics mimicing a door or boulder block light. */
179.      if ((mon = m_at(x,y)) && (!mon->minvis || See_invisible) &&
180.  	  ((mon->m_ap_type == M_AP_FURNITURE &&
181.  	  (mon->mappearance == S_hcdoor || mon->mappearance == S_vcdoor)) ||
182.  	  (mon->m_ap_type == M_AP_OBJECT && mon->mappearance == BOULDER)))
183.  	return 1;
184.  
185.      return 0;
186.  }
187.  
188.  /*
189.   * vision_reset()
190.   *
191.   * This must be called *after* the levl[][] structure is set with the new
192.   * level and the level monsters and objects are in place.
193.   */
194.  void
195.  vision_reset()
196.  {
197.      int y;
198.      register int x, i, dig_left, block;
199.      register struct rm    *lev;
200.  
201.      /* Start out with cs0 as our current array */
202.      viz_array = cs_rows0;
203.      viz_rmin  = cs_rmin0;
204.      viz_rmax  = cs_rmax0;
205.  
206.      (void) memset((genericptr_t) could_see, 0, sizeof(could_see));
207.  
208.      /* Reset the pointers and clear so that we have a "full" dungeon. */
209.      (void) memset((genericptr_t) viz_clear,        0, sizeof(viz_clear));
210.  
211.      /* Dig the level */
212.      for (y = 0; y < ROWNO; y++) {
213.  	dig_left = 0;
214.  	block = TRUE;	/* location (0,y) is always stone; it's !isok() */
215.  	lev = &levl[1][y];
216.  	for (x = 1; x < COLNO; x++, lev += ROWNO)
217.  	    if (block != (IS_ROCK(lev->typ) || does_block(x,y,lev))) {
218.  		if(block) {
219.  		    for(i=dig_left; i<x; i++) {
220.  			left_ptrs [y][i] = dig_left;
221.  			right_ptrs[y][i] = x-1;
222.  		    }
223.  		} else {
224.  		    i = dig_left;
225.  		    if(dig_left) dig_left--; /* point at first blocked point */
226.  		    for(; i<x; i++) {
227.  			left_ptrs [y][i] = dig_left;
228.  			right_ptrs[y][i] = x;
229.  			viz_clear[y][i] = 1;
230.  		    }
231.  		}
232.  		dig_left = x;
233.  		block = !block;
234.  	    }
235.  	/* handle right boundary; almost identical for blocked/unblocked */
236.  	i = dig_left;
237.  	if(!block && dig_left) dig_left--; /* point at first blocked point */
238.  	for(; i<COLNO; i++) {
239.  	    left_ptrs [y][i] = dig_left;
240.  	    right_ptrs[y][i] = (COLNO-1);
241.  	    viz_clear[y][i] = !block;
242.  	}
243.      }
244.  
245.      vision_full_recalc = 1;	/* we want to run vision_recalc() */
246.  }
247.  
248.  
249.  /*
250.   * get_unused_cs()
251.   *
252.   * Called from vision_recalc() and at least one light routine.  Get pointers
253.   * to the unused vision work area.
254.   */
255.  static void
256.  get_unused_cs(rows, rmin, rmax)
257.      char ***rows;
258.      char **rmin, **rmax;
259.  {
260.      register int  row;
261.      register char *nrmin, *nrmax;
262.  
263.      if (viz_array == cs_rows0) {
264.  	*rows = cs_rows1;
265.  	*rmin = cs_rmin1;
266.  	*rmax = cs_rmax1;
267.      } else {
268.  	*rows = cs_rows0;
269.  	*rmin = cs_rmin0;
270.  	*rmax = cs_rmax0;
271.      }
272.  
273.      /* return an initialized, unused work area */
274.      nrmin = *rmin;
275.      nrmax = *rmax;
276.  
277.      (void) memset((genericptr_t)**rows, 0, ROWNO*COLNO);  /* we see nothing */
278.      for (row = 0; row < ROWNO; row++) {		/* set row min & max */
279.  	*nrmin++ = COLNO-1;
280.  	*nrmax++ = 0;
281.      }
282.  }
283.  
284.  
285.  #ifdef REINCARNATION
286.  /*
287.   * rogue_vision()
288.   *
289.   * Set the "could see" and in sight bits so vision acts just like the old
290.   * rogue game:
291.   *
292.   *	+ If in a room, the hero can see to the room boundaries.
293.   *	+ The hero can always see adjacent squares.
294.   *
295.   * We set the in_sight bit here as well to escape a bug that shows up
296.   * due to the one-sided lit wall hack.
297.   */
298.  static void
299.  rogue_vision(next, rmin, rmax)
300.      char **next;	/* could_see array pointers */
301.      char *rmin, *rmax;
302.  {
303.      int rnum = levl[u.ux][u.uy].roomno - ROOMOFFSET; /* no SHARED... */
304.      int start, stop, in_door, xhi, xlo, yhi, ylo;
305.      register int zx, zy;
306.  
307.      /* If in a lit room, we are able to see to its boundaries. */
308.      /* If dark, set COULD_SEE so various spells work -dlc */
309.      if (rnum >= 0) {
310.  	for (zy = rooms[rnum].ly-1; zy <= rooms[rnum].hy+1; zy++) {
311.  	    rmin[zy] = start = rooms[rnum].lx-1;
312.  	    rmax[zy] = stop  = rooms[rnum].hx+1;
313.  
314.  	    for (zx = start; zx <= stop; zx++) {
315.  		if (rooms[rnum].rlit) {
316.  		    next[zy][zx] = COULD_SEE | IN_SIGHT;
317.  		    levl[zx][zy].seenv = SVALL;	/* see the walls */
318.  		} else
319.  		    next[zy][zx] = COULD_SEE;
320.  	    }
321.  	}
322.      }
323.  
324.      in_door = levl[u.ux][u.uy].typ == DOOR;
325.  
326.      /* Can always see adjacent. */
327.      ylo = max(u.uy - 1, 0);
328.      yhi = min(u.uy + 1, ROWNO - 1);
329.      xlo = max(u.ux - 1, 1);
330.      xhi = min(u.ux + 1, COLNO - 1);
331.      for (zy = ylo; zy <= yhi; zy++) {
332.  	if (xlo < rmin[zy]) rmin[zy] = xlo;
333.  	if (xhi > rmax[zy]) rmax[zy] = xhi;
334.  
335.  	for (zx = xlo; zx <= xhi; zx++) {
336.  	    next[zy][zx] = COULD_SEE | IN_SIGHT;
337.  	    /*
338.  	     * Yuck, update adjacent non-diagonal positions when in a doorway.
339.  	     * We need to do this to catch the case when we first step into
340.  	     * a room.  The room's walls were not seen from the outside, but
341.  	     * now are seen (the seen bits are set just above).  However, the
342.  	     * positions are not updated because they were already in sight.
343.  	     * So, we have to do it here.
344.  	     */
345.  	    if (in_door && (zx == u.ux || zy == u.uy)) newsym(zx,zy);
346.  	}
347.      }
348.  }
349.  #endif /* REINCARNATION */
350.  
351.  /*#define EXTEND_SPINE		/* possibly better looking wall-angle */
352.  
353.  #ifdef EXTEND_SPINE
354.  
355.  static int FDECL(new_angle, (struct rm *, unsigned char *, int, int));
356.  /*
357.   * new_angle()
358.   *
359.   * Return the new angle seen by the hero for this location.  The angle
360.   * bit is given in the value pointed at by sv.
361.   *
362.   * For T walls and crosswall, just setting the angle bit, even though
363.   * it is technically correct, doesn't look good.  If we can see the
364.   * next position beyond the current one and it is a wall that we can
365.   * see, then we want to extend a spine of the T to connect with the wall
366.   * that is beyond.  Example:
367.   *
368.   *	 Correct, but ugly			   Extend T spine
369.   *
370.   *		| ...					| ...
371.   *		| ...	<-- wall beyond & floor -->	| ...
372.   *		| ...					| ...
373.   * Unseen   -->   ...					| ...
374.   * spine	+-...	<-- trwall & doorway	-->	+-...
375.   *		| ...					| ...
376.   *
377.   *
378.   *		   @	<-- hero		-->	   @
379.   *
380.   *
381.   * We fake the above check by only checking if the horizontal &
382.   * vertical positions adjacent to the crosswall and T wall are
383.   * unblocked.  Then, _in general_ we can see beyond.  Generally,
384.   * this is good enough.
385.   *
386.   *	+ When this function is called we don't have all of the seen
387.   *	  information (we're doing a top down scan in vision_recalc).
388.   *	  We would need to scan once to set all IN_SIGHT and COULD_SEE
389.   *	  bits, then again to correctly set the seenv bits.
390.   *	+ I'm trying to make this as cheap as possible.  The display &
391.   *	  vision eat up too much CPU time.
392.   *	
393.   *
394.   * Note:  Even as I write this, I'm still not convinced.  There are too
395.   *	  many exceptions.  I may have to bite the bullet and do more
396.   *	  checks.	- Dean 2/11/93
397.   */
398.  static int
399.  new_angle(lev, sv, row, col)
400.      struct rm *lev;
401.      unsigned char *sv;
402.      int row, col;
403.  {
404.      register int res = *sv;
405.  
406.      /*
407.       * Do extra checks for crosswalls and T walls if we see them from
408.       * an angle.
409.       */
410.      if (lev->typ >= CROSSWALL && lev->typ <= TRWALL) {
411.  	switch (res) {
412.  	    case SV0:
413.  		if (col > 0	  && viz_clear[row][col-1]) res |= SV7;
414.  		if (row > 0	  && viz_clear[row-1][col]) res |= SV1;
415.  		break;
416.  	    case SV2:
417.  		if (row > 0	  && viz_clear[row-1][col]) res |= SV1;
418.  		if (col < COLNO-1 && viz_clear[row][col+1]) res |= SV3;
419.  		break;
420.  	    case SV4:
421.  		if (col < COLNO-1 && viz_clear[row][col+1]) res |= SV3;
422.  		if (row < ROWNO-1 && viz_clear[row+1][col]) res |= SV5;
423.  		break;
424.  	    case SV6:
425.  		if (row < ROWNO-1 && viz_clear[row+1][col]) res |= SV5;
426.  		if (col > 0	  && viz_clear[row][col-1]) res |= SV7;
427.  		break;
428.  	}
429.      }
430.      return res;
431.  }
432.  #else
433.  /*
434.   * new_angle()
435.   *
436.   * Return the new angle seen by the hero for this location.  The angle
437.   * bit is given in the value pointed at by sv.
438.   *
439.   * The other parameters are not used.
440.   */
441.  #define new_angle(lev, sv, row, col) (*sv)
442.  
443.  #endif
444.  
445.  
446.  /*
447.   * vision_recalc()
448.   *
449.   * Do all of the heavy vision work.  Recalculate all locations that could
450.   * possibly be seen by the hero --- if the location were lit, etc.  Note
451.   * which locations are actually seen because of lighting.  Then add to
452.   * this all locations that be seen by hero due to night vision and x-ray
453.   * vision.  Finally, compare with what the hero was able to see previously.
454.   * Update the difference.
455.   *
456.   * This function is usually called only when the variable 'vision_full_recalc'
457.   * is set.  The following is a list of places where this function is called,
458.   * with three valid values for the control flag parameter:
459.   *
460.   * Control flag = 0.  A complete vision recalculation.  Generate the vision
461.   * tables from scratch.  This is necessary to correctly set what the hero
462.   * can see.  (1) and (2) call this routine for synchronization purposes, (3)
463.   * calls this routine so it can operate correctly.
464.   *
465.   *	+ After the monster move, before input from the player. [moveloop()]
466.   *	+ At end of moveloop. [moveloop() ??? not sure why this is here]
467.   *	+ Right before something is printed. [pline()]
468.   *	+ Right before we do a vision based operation. [do_clear_area()]
469.   *	+ screen redraw, so we can renew all positions in sight. [docrt()]
470.   *
471.   * Control flag = 1.  An adjacent vision recalculation.  The hero has moved
472.   * one square.  Knowing this, it might be possible to optimize the vision
473.   * recalculation using the current knowledge.  This is presently unimplemented
474.   * and is treated as a control = 0 call.
475.   *
476.   *	+ Right after the hero moves. [domove()]
477.   *
478.   * Control flag = 2.  Turn off the vision system.  Nothing new will be
479.   * displayed, since nothing is seen.  This is usually done when you need
480.   * a newsym() run on all locations in sight, or on some locations but you
481.   * don't know which ones.
482.   *
483.   *	+ Before a screen redraw, so all positions are renewed. [docrt()]
484.   *	+ Right before the hero arrives on a new level. [goto_level()]
485.   *	+ Right after a scroll of light is read. [litroom()]
486.   *	+ After an option has changed that affects vision [parseoptions()]
487.   *	+ Right after the hero is swallowed. [gulpmu()]
488.   *	+ Just before bubbles are moved. [movebubbles()]
489.   */
490.  void
491.  vision_recalc(control)
492.      int control;
493.  {
494.      char **temp_array;	/* points to the old vision array */
495.      char **next_array;	/* points to the new vision array */
496.      char *next_row;	/* row pointer for the new array */
497.      char *old_row;	/* row pointer for the old array */
498.      char *next_rmin;	/* min pointer for the new array */
499.      char *next_rmax;	/* max pointer for the new array */
500.      char *ranges;	/* circle ranges -- used for xray & night vision */
501.      int row;		/* row counter (outer loop)  */
502.      int start, stop;	/* inner loop starting/stopping index */
503.      int dx, dy;		/* one step from a lit door or lit wall (see below) */
504.      register int col;	/* inner loop counter */
505.      register struct rm *lev;	/* pointer to current pos */
506.      struct rm *flev;	/* pointer to position in "front" of current pos */
507.      extern unsigned char seenv_matrix[3][3];	/* from display.c */
508.      static unsigned char colbump[COLNO+1];	/* cols to bump sv */
509.      unsigned char *sv;				/* ptr to seen angle bits */
510.      int oldseenv;				/* previous seenv value */
511.  
512.      vision_full_recalc = 0;			/* reset flag */
513.      if (in_mklev) return;
514.  
515.  #ifdef GCC_WARN
516.      row = 0;
517.  #endif
518.  
519.      /*
520.       * Either the light sources have been taken care of, or we must
521.       * recalculate them here.
522.       */
523.  
524.      /* Get the unused could see, row min, and row max arrays. */
525.      get_unused_cs(&next_array, &next_rmin, &next_rmax);
526.  
527.      /* You see nothing, nothing can see you --- if swallowed or refreshing. */
528.      if (u.uswallow || control == 2) {
529.  	/* do nothing -- get_unused_cs() nulls out the new work area */
530.  
531.      } else if (Blind) {
532.  	/*
533.  	 * Calculate the could_see array even when blind so that monsters
534.  	 * can see you, even if you can't see them.  Note that the current
535.  	 * setup allows:
536.  	 *
537.  	 *	+ Monsters to see with the "new" vision, even on the rogue
538.  	 *	  level.
539.  	 *
540.  	 *	+ Monsters can see you even when you're in a pit.
541.  	 */
542.  	view_from(u.uy, u.ux, next_array, next_rmin, next_rmax,
543.  					0,(void(*)())0,(genericptr_t)0);
544.  
545.  	/*
546.  	 * Our own version of the update loop below.  We know we can't see
547.  	 * anything, so we only need update positions we used to be able
548.  	 * to see.
549.  	 */
550.  	temp_array = viz_array;	/* set viz_array so newsym() will work */
551.  	viz_array = next_array;
552.  
553.  	for (row = 0; row < ROWNO; row++) {
554.  	    old_row = temp_array[row];
555.  
556.  	    /* Find the min and max positions on the row. */
557.  	    start = min(viz_rmin[row], next_rmin[row]);
558.  	    stop  = max(viz_rmax[row], next_rmax[row]);
559.  
560.  	    for (col = start; col <= stop; col++)
561.  		if (old_row[col] & IN_SIGHT) newsym(col,row);
562.  	}
563.  
564.  	/* skip the normal update loop */
565.  	goto skip;
566.      }
567.  #ifdef REINCARNATION
568.      else if (Is_rogue_level(&u.uz)) {
569.  	rogue_vision(next_array,next_rmin,next_rmax);
570.      }
571.  #endif
572.      else {
573.  	int has_night_vision = 1;	/* hero has night vision */
574.  
575.  	if (Underwater && !Is_waterlevel(&u.uz)) {
576.  	    /*
577.  	     * The hero is under water.  Only see surrounding locations if
578.  	     * they are also underwater.  This overrides night vision but
579.  	     * does not override x-ray vision.
580.  	     */
581.  	    has_night_vision = 0;
582.  
583.  	    for (row = u.uy-1; row <= u.uy+1; row++)
584.  		for (col = u.ux-1; col <= u.ux+1; col++) {
585.  		    if (!isok(col,row) || !is_pool(col,row)) continue;
586.  
587.  		    next_rmin[row] = min(next_rmin[row], col);
588.  		    next_rmax[row] = max(next_rmax[row], col);
589.  		    next_array[row][col] = IN_SIGHT;
590.  		}
591.  	}
592.  
593.  	/* if in a pit, just update for immediate locations */
594.  	else if (u.utrap && u.utraptype == TT_PIT) {
595.  	    for (row = u.uy-1; row <= u.uy+1; row++) {
596.  		if (row < 0) continue;	if (row >= ROWNO) break;
597.  
598.  		next_rmin[row] = max(      0, u.ux - 1);
599.  		next_rmax[row] = min(COLNO-1, u.ux + 1);
600.  		next_row = next_array[row];
601.  
602.  		for(col=next_rmin[row]; col <= next_rmax[row]; col++)
603.  		    next_row[col] = IN_SIGHT;
604.  	    }
605.  	} else
606.  	    view_from(u.uy, u.ux, next_array, next_rmin, next_rmax,
607.  					0,(void(*)())0,(genericptr_t)0);
608.  
609.  	/*
610.  	 * Set the IN_SIGHT bit for xray and night vision.
611.  	 */
612.  	if (u.xray_range >= 0) {
613.  	    if (u.xray_range) {
614.  		ranges = circle_ptr(u.xray_range);
615.  
616.  		for (row = u.uy-u.xray_range; row <= u.uy+u.xray_range; row++) {
617.  		    if (row < 0) continue;	if (row >= ROWNO) break;
618.  		    dy = v_abs(u.uy-row);	next_row = next_array[row];
619.  
620.  		    start = max(      0, u.ux - ranges[dy]);
621.  		    stop  = min(COLNO-1, u.ux + ranges[dy]);
622.  
623.  		    for (col = start; col <= stop; col++) {
624.  			next_row[col] |= IN_SIGHT;
625.  			levl[col][row].seenv = SVALL;	/* see all! */
626.  		    }
627.  
628.  		    next_rmin[row] = min(start, next_rmin[row]);
629.  		    next_rmax[row] = max(stop, next_rmax[row]);
630.  		}
631.  
632.  	    } else {	/* range is 0 */
633.  		next_array[u.uy][u.ux] |= IN_SIGHT;
634.  		levl[u.ux][u.uy].seenv = SVALL;
635.  		next_rmin[u.uy] = min(u.ux, next_rmin[u.uy]);
636.  		next_rmax[u.uy] = max(u.ux, next_rmax[u.uy]);
637.  	    }
638.  	}
639.  
640.  	if (has_night_vision && u.xray_range < u.nv_range) {
641.  	    if (!u.nv_range) {	/* range is 0 */
642.  		next_array[u.uy][u.ux] |= IN_SIGHT;
643.  		levl[u.ux][u.uy].seenv = SVALL;
644.  		next_rmin[u.uy] = min(u.ux, next_rmin[u.uy]);
645.  		next_rmax[u.uy] = max(u.ux, next_rmax[u.uy]);
646.  	    } else if (u.nv_range > 0) {
647.  		ranges = circle_ptr(u.nv_range);
648.  
649.  		for (row = u.uy-u.nv_range; row <= u.uy+u.nv_range; row++) {
650.  		    if (row < 0) continue;	if (row >= ROWNO) break;
651.  		    dy = v_abs(u.uy-row);	next_row = next_array[row];
652.  
653.  		    start = max(      0, u.ux - ranges[dy]);
654.  		    stop  = min(COLNO-1, u.ux + ranges[dy]);
655.  
656.  		    for (col = start; col <= stop; col++)
657.  			if (next_row[col]) next_row[col] |= IN_SIGHT;
658.  
659.  		    next_rmin[row] = min(start, next_rmin[row]);
660.  		    next_rmax[row] = max(stop, next_rmax[row]);
661.  		}
662.  	    }
663.  	}
664.      }
665.  
666.      /* Set the correct bits for all light sources. */
667.      do_light_sources(next_array);
668.  
669.  
670.      /*
671.       * Make the viz_array the new array so that cansee() will work correctly.
672.       */
673.      temp_array = viz_array;
674.      viz_array = next_array;
675.  
676.      /*
677.       * The main update loop.  Here we do two things:
678.       *
679.       *	    + Set the IN_SIGHT bit for places that we could see and are lit.
680.       *	    + Reset changed places.
681.       *
682.       * There is one thing that make deciding what the hero can see
683.       * difficult:
684.       *
685.       *  1.  Directional lighting.  Items that block light create problems.
686.       *      The worst offenders are doors.  Suppose a door to a lit room
687.       *      is closed.  It is lit on one side, but not on the other.  How
688.       *      do you know?  You have to check the closest adjacent position.
689.       *	    Even so, that is not entirely correct.  But it seems close
690.       *	    enough for now.
691.       */
692.      colbump[u.ux] = colbump[u.ux+1] = 1;
693.      for (row = 0; row < ROWNO; row++) {
694.  	dy = u.uy - row;                dy = sign(dy);
695.  	next_row = next_array[row];     old_row = temp_array[row];
696.  
697.  	/* Find the min and max positions on the row. */
698.  	start = min(viz_rmin[row], next_rmin[row]);
699.  	stop  = max(viz_rmax[row], next_rmax[row]);
700.  	lev = &levl[start][row];
701.  
702.  	sv = &seenv_matrix[dy+1][start < u.ux ? 0 : (start > u.ux ? 2:1)];
703.  
704.  	for (col = start; col <= stop;
705.  				lev += ROWNO, sv += (int) colbump[++col]) {
706.  	    if (next_row[col] & IN_SIGHT) {
707.  		/*
708.  		 * We see this position because of night- or xray-vision.
709.  		 */
710.  		oldseenv = lev->seenv;
711.  		lev->seenv |= new_angle(lev,sv,row,col); /* update seen angle */
712.  
713.  		/* Update pos if previously not in sight or new angle. */
714.  		if ( !(old_row[col] & IN_SIGHT) || oldseenv != lev->seenv)
715.  		    newsym(col,row);
716.  	    }
717.  
718.  	    else if (next_row[col] & COULD_SEE
719.  				&& (lev->lit || next_row[col] & TEMP_LIT)) {
720.  		/*
721.  		 * We see this position because it is lit.
722.  		 */
723.  		if (IS_DOOR(lev->typ) && !viz_clear[row][col]) {
724.  		    /*
725.  		     * Make sure doors, boulders or mimics don't show up
726.  		     * at the end of dark hallways.  We do this by checking
727.  		     * the adjacent position.  If it is lit, then we can see
728.  		     * the door, otherwise we can't.
729.  		     */
730.  		    dx = u.ux - col;	dx = sign(dx);
731.  		    flev = &(levl[col+dx][row+dy]);
732.  		    if (flev->lit || next_array[row+dy][col+dx] & TEMP_LIT) {
733.  			next_row[col] |= IN_SIGHT;	/* we see it */
734.  
735.  			oldseenv = lev->seenv;
736.  			lev->seenv |= new_angle(lev,sv,row,col);
737.  
738.  			/* Update pos if previously not in sight or new angle.*/
739.  			if (!(old_row[col] & IN_SIGHT) || oldseenv!=lev->seenv)
740.  			    newsym(col,row);
741.  		    } else
742.  			goto not_in_sight;	/* we don't see it */
743.  
744.  		} else {
745.  		    next_row[col] |= IN_SIGHT;	/* we see it */
746.  
747.  		    oldseenv = lev->seenv;
748.  		    lev->seenv |= new_angle(lev,sv,row,col);
749.  
750.  		    /* Update pos if previously not in sight or new angle. */
751.  		    if ( !(old_row[col] & IN_SIGHT) || oldseenv != lev->seenv)
752.  			newsym(col,row);
753.  		}
754.  	    } else if (next_row[col] & COULD_SEE && lev->waslit) {
755.  		/*
756.  		 * If we make it here, the hero _could see_ the location,
757.  		 * but doesn't see it (location is not lit).
758.  		 * However, the hero _remembers_ it as lit (waslit is true).
759.  		 * The hero can now see that it is not lit, so change waslit
760.  		 * and update the location.
761.  		 */
762.  		lev->waslit = 0; /* remember lit condition */
763.  		newsym(col,row);
764.  	    }
765.  	    /*
766.  	     * At this point we know that the row position is *not* in
767.  	     * sight.  If the old one *was* in sight, then clean up the
768.  	     * position.
769.  	     */
770.  	    else {
771.  not_in_sight:
772.  		if (old_row[col] & IN_SIGHT) newsym(col,row);
773.  	    }
774.  
775.  	} /* end for col . . */
776.      }	/* end for row . .  */
777.      colbump[u.ux] = colbump[u.ux+1] = 0;
778.  
779.  skip:
780.      newsym(u.ux,u.uy);		/* Make sure the hero shows up! */
781.  
782.      /* Set the new min and max pointers. */
783.      viz_rmin  = next_rmin;
784.      viz_rmax = next_rmax;
785.  }
786.  
787.  
788.  /*
789.   * block_point()
790.   *
791.   * Make the location opaque to light.
792.   */
793.  void
794.  block_point(x,y)
795.      int x, y;
796.  {
797.      fill_point(y,x);
798.  
799.      /* recalc light sources here? */
800.  
801.      /*
802.       * We have to do a full vision recalculation if we "could see" the
803.       * location.  Why? Suppose some monster opened a way so that the
804.       * hero could see a lit room.  However, the position of the opening
805.       * was out of night-vision range of the hero.  Suddenly the hero should
806.       * see the lit room.
807.       */
808.      if (viz_array[y][x]) vision_full_recalc = 1;
809.  }
810.  
811.  /*
812.   * unblock_point()
813.   *
814.   * Make the location transparent to light.
815.   */
816.  void
817.  unblock_point(x,y)
818.      int x, y;
819.  {
820.      dig_point(y,x);
821.  
822.      /* recalc light sources here? */
823.  
824.      if (viz_array[y][x]) vision_full_recalc = 1;
825.  }
826.  
827.  
828.  /*===========================================================================*\
829.   |									     |
830.   |	Everything below this line uses (y,x) instead of (x,y) --- the	     |
831.   |	algorithms are faster if they are less recursive and can scan	     |
832.   |	on a row longer.						     |
833.   |									     |
834.  \*===========================================================================*/
835.  
836.  
837.  /* ========================================================================= *\
838.  			Left and Right Pointer Updates
839.  \* ========================================================================= */
840.  
841.  /*
842.   *			LEFT and RIGHT pointer rules
843.   *
844.   *
845.   * **NOTE**  The rules changed on 4/4/90.  This comment reflects the
846.   * new rules.  The change was so that the stone-wall optimization
847.   * would work.
848.   *
849.   * OK, now the tough stuff.  We must maintain our left and right
850.   * row pointers.  The rules are as follows:
851.   *
852.   * Left Pointers:
853.   * ______________
854.   *
855.   * + If you are a clear spot, your left will point to the first
856.   *   stone to your left.  If there is none, then point the first
857.   *   legal position in the row (0).
858.   *
859.   * + If you are a blocked spot, then your left will point to the
860.   *   left-most blocked spot to your left that is connected to you.
861.   *   This means that a left-edge (a blocked spot that has an open
862.   *   spot on its left) will point to itself.
863.   *
864.   *
865.   * Right Pointers:
866.   * ---------------
867.   * + If you are a clear spot, your right will point to the first
868.   *   stone to your right.  If there is none, then point the last
869.   *   legal position in the row (COLNO-1).
870.   *
871.   * + If you are a blocked spot, then your right will point to the
872.   *   right-most blocked spot to your right that is connected to you.
873.   *   This means that a right-edge (a blocked spot that has an open
874.   *    spot on its right) will point to itself.
875.   */
876.  static void
877.  dig_point(row,col)
878.      int row,col;
879.  {
880.      int i;
881.  
882.      if (viz_clear[row][col]) return;		/* already done */
883.  
884.      viz_clear[row][col] = 1;
885.  
886.      /*
887.       * Boundary cases first.
888.       */
889.      if (col == 0) {				/* left edge */
890.  	if (viz_clear[row][1]) {
891.  	    right_ptrs[row][0] = right_ptrs[row][1];
892.  	} else {
893.  	    right_ptrs[row][0] = 1;
894.  	    for (i = 1; i <= right_ptrs[row][1]; i++)
895.  		left_ptrs[row][i] = 1;
896.  	}
897.      } else if (col == (COLNO-1)) {		/* right edge */
898.  
899.  	if (viz_clear[row][COLNO-2]) {
900.  	    left_ptrs[row][COLNO-1] = left_ptrs[row][COLNO-2];
901.  	} else {
902.  	    left_ptrs[row][COLNO-1] = COLNO-2;
903.  	    for (i = left_ptrs[row][COLNO-2]; i < COLNO-1; i++)
904.  		right_ptrs[row][i] = COLNO-2;
905.  	}
906.      }
907.  
908.      /*
909.       * At this point, we know we aren't on the boundaries.
910.       */
911.      else if (viz_clear[row][col-1] && viz_clear[row][col+1]) {
912.  	/* Both sides clear */
913.  	for (i = left_ptrs[row][col-1]; i <= col; i++) {
914.  	    if (!viz_clear[row][i]) continue;	/* catch non-end case */
915.  	    right_ptrs[row][i] = right_ptrs[row][col+1];
916.  	}
917.  	for (i = col; i <= right_ptrs[row][col+1]; i++) {
918.  	    if (!viz_clear[row][i]) continue;	/* catch non-end case */
919.  	    left_ptrs[row][i] = left_ptrs[row][col-1];
920.  	}
921.  
922.      } else if (viz_clear[row][col-1]) {
923.  	/* Left side clear, right side blocked. */
924.  	for (i = col+1; i <= right_ptrs[row][col+1]; i++)
925.  	    left_ptrs[row][i] = col+1;
926.  
927.  	for (i = left_ptrs[row][col-1]; i <= col; i++) {
928.  	    if (!viz_clear[row][i]) continue;	/* catch non-end case */
929.  	    right_ptrs[row][i] = col+1;
930.  	}
931.  	left_ptrs[row][col] = left_ptrs[row][col-1];
932.  
933.      } else if (viz_clear[row][col+1]) {
934.  	/* Right side clear, left side blocked. */
935.  	for (i = left_ptrs[row][col-1]; i < col; i++)
936.  	    right_ptrs[row][i] = col-1;
937.  
938.  	for (i = col; i <= right_ptrs[row][col+1]; i++) {
939.  	    if (!viz_clear[row][i]) continue;	/* catch non-end case */
940.  	    left_ptrs[row][i] = col-1;
941.  	}
942.  	right_ptrs[row][col] = right_ptrs[row][col+1];
943.  
944.      } else {
945.  	/* Both sides blocked */
946.  	for (i = left_ptrs[row][col-1]; i < col; i++)
947.  	    right_ptrs[row][i] = col-1;
948.  
949.  	for (i = col+1; i <= right_ptrs[row][col+1]; i++)
950.  	    left_ptrs[row][i] = col+1;
951.  
952.  	left_ptrs[row][col]  = col-1;
953.  	right_ptrs[row][col] = col+1;
954.      }
955.  }
956.  
957.  static void
958.  fill_point(row,col)
959.      int row, col;
960.  {
961.      int i;
962.  
963.      if (!viz_clear[row][col]) return;
964.  
965.      viz_clear[row][col] = 0;
966.  
967.      if (col == 0) {
968.  	if (viz_clear[row][1]) {			/* adjacent is clear */
969.  	    right_ptrs[row][0] = 0;
970.  	} else {
971.  	    right_ptrs[row][0] = right_ptrs[row][1];
972.  	    for (i = 1; i <= right_ptrs[row][1]; i++)
973.  		left_ptrs[row][i] = 0;
974.  	}
975.      } else if (col == COLNO-1) {
976.  	if (viz_clear[row][COLNO-2]) {		/* adjacent is clear */
977.  	    left_ptrs[row][COLNO-1] = COLNO-1;
978.  	} else {
979.  	    left_ptrs[row][COLNO-1] = left_ptrs[row][COLNO-2];
980.  	    for (i = left_ptrs[row][COLNO-2]; i < COLNO-1; i++)
981.  		right_ptrs[row][i] = COLNO-1;
982.  	}
983.      }
984.  
985.      /*
986.       * Else we know that we are not on an edge.
987.       */
988.      else if (viz_clear[row][col-1] && viz_clear[row][col+1]) {
989.  	/* Both sides clear */
990.  	for (i = left_ptrs[row][col-1]+1; i <= col; i++)
991.  	    right_ptrs[row][i] = col;
992.  
993.  	if (!left_ptrs[row][col-1])		/* catch the end case */
994.  	    right_ptrs[row][0] = col;
995.  
996.  	for (i = col; i < right_ptrs[row][col+1]; i++)
997.  	    left_ptrs[row][i] = col;
998.  
999.  	if (right_ptrs[row][col+1] == COLNO-1)	/* catch the end case */
1000. 	    left_ptrs[row][COLNO-1] = col;
1001. 
1002.     } else if (viz_clear[row][col-1]) {
1003. 	/* Left side clear, right side blocked. */
1004. 	for (i = col; i <= right_ptrs[row][col+1]; i++)
1005. 	    left_ptrs[row][i] = col;
1006. 
1007. 	for (i = left_ptrs[row][col-1]+1; i < col; i++)
1008. 	    right_ptrs[row][i] = col;
1009. 
1010. 	if (!left_ptrs[row][col-1])		/* catch the end case */
1011. 	    right_ptrs[row][i] = col;
1012. 
1013. 	right_ptrs[row][col] = right_ptrs[row][col+1];
1014. 
1015.     } else if (viz_clear[row][col+1]) {
1016. 	/* Right side clear, left side blocked. */
1017. 	for (i = left_ptrs[row][col-1]; i <= col; i++)
1018. 	    right_ptrs[row][i] = col;
1019. 
1020. 	for (i = col+1; i < right_ptrs[row][col+1]; i++)
1021. 	    left_ptrs[row][i] = col;
1022. 
1023. 	if (right_ptrs[row][col+1] == COLNO-1)	/* catch the end case */
1024. 	    left_ptrs[row][i] = col;
1025. 
1026. 	left_ptrs[row][col] = left_ptrs[row][col-1];
1027. 
1028.     } else {
1029. 	/* Both sides blocked */
1030. 	for (i = left_ptrs[row][col-1]; i <= col; i++)
1031. 	    right_ptrs[row][i] = right_ptrs[row][col+1];
1032. 
1033. 	for (i = col; i <= right_ptrs[row][col+1]; i++)
1034. 	    left_ptrs[row][i] = left_ptrs[row][col-1];
1035.     }
1036. }
1037. 
1038. 
1039. /*===========================================================================*/
1040. /*===========================================================================*/
1041. /* Use either algorithm C or D.  See the config.h for more details. =========*/
1042. 
1043. /*
1044.  * Variables local to both Algorithms C and D.
1045.  */
1046. static int  start_row;
1047. static int  start_col;
1048. static int  step;
1049. static char **cs_rows;
1050. static char *cs_left;
1051. static char *cs_right;
1052. 
1053. static void FDECL((*vis_func), (int,int,genericptr_t));
1054. static genericptr_t varg;
1055. 
1056. /*
1057.  * Both Algorithms C and D use the following macros.
1058.  *
1059.  *      good_row(z)	  - Return TRUE if the argument is a legal row.
1060.  *      set_cs(rowp,col)  - Set the local could see array.
1061.  *      set_min(z)	  - Save the min value of the argument and the current
1062.  *			      row minimum.
1063.  *      set_max(z)	  - Save the max value of the argument and the current
1064.  *			      row maximum.
1065.  *
1066.  * The last three macros depend on having local pointers row_min, row_max,
1067.  * and rowp being set correctly.
1068.  */
1069. #define set_cs(rowp,col) (rowp[col] = COULD_SEE)
1070. #define good_row(z) ((z) >= 0 && (z) < ROWNO)
1071. #define set_min(z) if (*row_min > (z)) *row_min = (z)
1072. #define set_max(z) if (*row_max < (z)) *row_max = (z)
1073. #define is_clear(row,col) viz_clear_rows[row][col]
1074. 
1075. /*
1076.  * clear_path()		expanded into 4 macros/functions:
1077.  *
1078.  *	q1_path()
1079.  *	q2_path()
1080.  *	q3_path()
1081.  *	q4_path()
1082.  *
1083.  * "Draw" a line from the start to the given location.  Stop if we hit
1084.  * something that blocks light.  The start and finish points themselves are
1085.  * not checked, just the points between them.  These routines do _not_
1086.  * expect to be called with the same starting and stopping point.
1087.  *
1088.  * These routines use the generalized integer Bresenham's algorithm (fast
1089.  * line drawing) for all quadrants.  The algorithm was taken from _Procedural
1090.  * Elements for Computer Graphics_, by David F. Rogers.  McGraw-Hill, 1985.
1091.  */
1092. #ifdef MACRO_CPATH	/* quadrant calls are macros */
1093. 
1094. /*
1095.  * When called, the result is in "result".
1096.  * The first two arguments (srow,scol) are one end of the path.  The next
1097.  * two arguments (row,col) are the destination.  The last argument is
1098.  * used as a C language label.  This means that it must be different
1099.  * in each pair of calls.
1100.  */
1101. 
1102. /*
1103.  *  Quadrant I (step < 0).
1104.  */
1105. #define q1_path(srow,scol,y2,x2,label)			\
1106. {							\
1107.     int dx, dy;						\
1108.     register int k, err, x, y, dxs, dys;		\
1109. 							\
1110.     x  = (scol);	y  = (srow);			\
1111.     dx = (x2) - x;	dy = y - (y2);			\
1112. 							\
1113.     result = 0;		 /* default to a blocked path */\
1114. 							\
1115.     dxs = dx << 1;	   /* save the shifted values */\
1116.     dys = dy << 1;					\
1117.     if (dy > dx) {					\
1118. 	err = dxs - dy;					\
1119. 							\
1120. 	for (k = dy-1; k; k--) {			\
1121. 	    if (err >= 0) {				\
1122. 		x++;					\
1123. 		err -= dys;				\
1124. 	    }						\
1125. 	    y--;					\
1126. 	    err += dxs;					\
1127. 	    if (!is_clear(y,x)) goto label;/* blocked */\
1128. 	}						\
1129.     } else {						\
1130. 	err = dys - dx;					\
1131. 							\
1132. 	for (k = dx-1; k; k--) {			\
1133. 	    if (err >= 0) {				\
1134. 		y--;					\
1135. 		err -= dxs;				\
1136. 	    }						\
1137. 	    x++;					\
1138. 	    err += dys;					\
1139. 	    if (!is_clear(y,x)) goto label;/* blocked */\
1140. 	}						\
1141.     }							\
1142. 							\
1143.     result = 1;						\
1144. }
1145. 
1146. /*
1147.  * Quadrant IV (step > 0).
1148.  */
1149. #define q4_path(srow,scol,y2,x2,label)			\
1150. {							\
1151.     int dx, dy;						\
1152.     register int k, err, x, y, dxs, dys;		\
1153. 							\
1154.     x  = (scol);	y  = (srow);			\
1155.     dx = (x2) - x;	dy = (y2) - y;			\
1156. 							\
1157.     result = 0;		 /* default to a blocked path */\
1158. 							\
1159.     dxs = dx << 1;	   /* save the shifted values */\
1160.     dys = dy << 1;					\
1161.     if (dy > dx) {					\
1162. 	err = dxs - dy;					\
1163. 							\
1164. 	for (k = dy-1; k; k--) {			\
1165. 	    if (err >= 0) {				\
1166. 		x++;					\
1167. 		err -= dys;				\
1168. 	    }						\
1169. 	    y++;					\
1170. 	    err += dxs;					\
1171. 	    if (!is_clear(y,x)) goto label;/* blocked */\
1172. 	}						\
1173. 							\
1174.     } else {						\
1175. 	err = dys - dx;					\
1176. 							\
1177. 	for (k = dx-1; k; k--) {			\
1178. 	    if (err >= 0) {				\
1179. 		y++;					\
1180. 		err -= dxs;				\
1181. 	    }						\
1182. 	    x++;					\
1183. 	    err += dys;					\
1184. 	    if (!is_clear(y,x)) goto label;/* blocked */\
1185. 	}						\
1186.     }							\
1187. 							\
1188.     result = 1;						\
1189. }
1190. 
1191. /*
1192.  * Quadrant II (step < 0).
1193.  */
1194. #define q2_path(srow,scol,y2,x2,label)			\
1195. {							\
1196.     int dx, dy;						\
1197.     register int k, err, x, y, dxs, dys;		\
1198. 							\
1199.     x  = (scol);	y  = (srow);			\
1200.     dx = x - (x2);	dy = y - (y2);			\
1201. 							\
1202.     result = 0;		 /* default to a blocked path */\
1203. 							\
1204.     dxs = dx << 1;	   /* save the shifted values */\
1205.     dys = dy << 1;					\
1206.     if (dy > dx) {					\
1207. 	err = dxs - dy;					\
1208. 							\
1209. 	for (k = dy-1; k; k--) {			\
1210. 	    if (err >= 0) {				\
1211. 		x--;					\
1212. 		err -= dys;				\
1213. 	    }						\
1214. 	    y--;					\
1215. 	    err += dxs;					\
1216. 	    if (!is_clear(y,x)) goto label;/* blocked */\
1217. 	}						\
1218.     } else {						\
1219. 	err = dys - dx;					\
1220. 							\
1221. 	for (k = dx-1; k; k--) {			\
1222. 	    if (err >= 0) {				\
1223. 		y--;					\
1224. 		err -= dxs;				\
1225. 	    }						\
1226. 	    x--;					\
1227. 	    err += dys;					\
1228. 	    if (!is_clear(y,x)) goto label;/* blocked */\
1229. 	}						\
1230.     }							\
1231. 							\
1232.     result = 1;						\
1233. }
1234. 
1235. /*
1236.  * Quadrant III (step > 0).
1237.  */
1238. #define q3_path(srow,scol,y2,x2,label)			\
1239. {							\
1240.     int dx, dy;						\
1241.     register int k, err, x, y, dxs, dys;		\
1242. 							\
1243.     x  = (scol);	y  = (srow);			\
1244.     dx = x - (x2);	dy = (y2) - y;			\
1245. 							\
1246.     result = 0;		 /* default to a blocked path */\
1247. 							\
1248.     dxs = dx << 1;	   /* save the shifted values */\
1249.     dys = dy << 1;					\
1250.     if (dy > dx) {					\
1251. 	err = dxs - dy;					\
1252. 							\
1253. 	for (k = dy-1; k; k--) {			\
1254. 	    if (err >= 0) {				\
1255. 		x--;					\
1256. 		err -= dys;				\
1257. 	    }						\
1258. 	    y++;					\
1259. 	    err += dxs;					\
1260. 	    if (!is_clear(y,x)) goto label;/* blocked */\
1261. 	}						\
1262. 							\
1263.     } else {						\
1264. 	err = dys - dx;					\
1265. 							\
1266. 	for (k = dx-1; k; k--) {			\
1267. 	    if (err >= 0) {				\
1268. 		y++;					\
1269. 		err -= dxs;				\
1270. 	    }						\
1271. 	    x--;					\
1272. 	    err += dys;					\
1273. 	    if (!is_clear(y,x)) goto label;/* blocked */\
1274. 	}						\
1275.     }							\
1276. 							\
1277.     result = 1;						\
1278. }
1279. 
1280. #else   /* quadrants are really functions */
1281. 
1282. static int FDECL(_q1_path, (int,int,int,int));
1283. static int FDECL(_q2_path, (int,int,int,int));
1284. static int FDECL(_q3_path, (int,int,int,int));
1285. static int FDECL(_q4_path, (int,int,int,int));
1286. 
1287. #define q1_path(sy,sx,y,x,dummy) result = _q1_path(sy,sx,y,x)
1288. #define q2_path(sy,sx,y,x,dummy) result = _q2_path(sy,sx,y,x)
1289. #define q3_path(sy,sx,y,x,dummy) result = _q3_path(sy,sx,y,x)
1290. #define q4_path(sy,sx,y,x,dummy) result = _q4_path(sy,sx,y,x)
1291. 
1292. /*
1293.  * Quadrant I (step < 0).
1294.  */
1295. static int
1296. _q1_path(srow,scol,y2,x2)
1297.     int scol, srow, y2, x2;
1298. {
1299.     int dx, dy;
1300.     register int k, err, x, y, dxs, dys;
1301. 
1302.     x  = scol;		y  = srow;
1303.     dx = x2 - x;	dy = y - y2;
1304. 
1305.     dxs = dx << 1;	   /* save the shifted values */
1306.     dys = dy << 1;
1307.     if (dy > dx) {
1308. 	err = dxs - dy;
1309. 
1310. 	for (k = dy-1; k; k--) {
1311. 	    if (err >= 0) {
1312. 		x++;
1313. 		err -= dys;
1314. 	    }
1315. 	    y--;
1316. 	    err += dxs;
1317. 	    if (!is_clear(y,x)) return 0; /* blocked */
1318. 	}
1319.     } else {
1320. 	err = dys - dx;
1321. 
1322. 	for (k = dx-1; k; k--) {
1323. 	    if (err >= 0) {
1324. 		y--;
1325. 		err -= dxs;
1326. 	    }
1327. 	    x++;
1328. 	    err += dys;
1329. 	    if (!is_clear(y,x)) return 0;/* blocked */
1330. 	}
1331.     }
1332. 
1333.     return 1;
1334. }
1335. 
1336. /*
1337.  * Quadrant IV (step > 0).
1338.  */
1339. static int
1340. _q4_path(srow,scol,y2,x2)
1341.     int scol, srow, y2, x2;
1342. {
1343.     int dx, dy;
1344.     register int k, err, x, y, dxs, dys;
1345. 
1346.     x  = scol;		y  = srow;
1347.     dx = x2 - x;	dy = y2 - y;
1348. 
1349.     dxs = dx << 1;	   /* save the shifted values */
1350.     dys = dy << 1;
1351.     if (dy > dx) {
1352. 	err = dxs - dy;
1353. 
1354. 	for (k = dy-1; k; k--) {
1355. 	    if (err >= 0) {
1356. 		x++;
1357. 		err -= dys;
1358. 	    }
1359. 	    y++;
1360. 	    err += dxs;
1361. 	    if (!is_clear(y,x)) return 0; /* blocked */
1362. 	}
1363.     } else {
1364. 	err = dys - dx;
1365. 
1366. 	for (k = dx-1; k; k--) {
1367. 	    if (err >= 0) {
1368. 		y++;
1369. 		err -= dxs;
1370. 	    }
1371. 	    x++;
1372. 	    err += dys;
1373. 	    if (!is_clear(y,x)) return 0;/* blocked */
1374. 	}
1375.     }
1376. 
1377.     return 1;
1378. }
1379. 
1380. /*
1381.  * Quadrant II (step < 0).
1382.  */
1383. static int
1384. _q2_path(srow,scol,y2,x2)
1385.     int scol, srow, y2, x2;
1386. {
1387.     int dx, dy;
1388.     register int k, err, x, y, dxs, dys;
1389. 
1390.     x  = scol;		y  = srow;
1391.     dx = x - x2;	dy = y - y2;
1392. 
1393.     dxs = dx << 1;	   /* save the shifted values */
1394.     dys = dy << 1;
1395.     if (dy > dx) {
1396. 	err = dxs - dy;
1397. 
1398. 	for (k = dy-1; k; k--) {
1399. 	    if (err >= 0) {
1400. 		x--;
1401. 		err -= dys;
1402. 	    }
1403. 	    y--;
1404. 	    err += dxs;
1405. 	    if (!is_clear(y,x)) return 0; /* blocked */
1406. 	}
1407.     } else {
1408. 	err = dys - dx;
1409. 
1410. 	for (k = dx-1; k; k--) {
1411. 	    if (err >= 0) {
1412. 		y--;
1413. 		err -= dxs;
1414. 	    }
1415. 	    x--;
1416. 	    err += dys;
1417. 	    if (!is_clear(y,x)) return 0;/* blocked */
1418. 	}
1419.     }
1420. 
1421.     return 1;
1422. }
1423. 
1424. /*
1425.  * Quadrant III (step > 0).
1426.  */
1427. static int
1428. _q3_path(srow,scol,y2,x2)
1429.     int scol, srow, y2, x2;
1430. {
1431.     int dx, dy;
1432.     register int k, err, x, y, dxs, dys;
1433. 
1434.     x  = scol;		y  = srow;
1435.     dx = x - x2;	dy = y2 - y;
1436. 
1437.     dxs = dx << 1;	   /* save the shifted values */
1438.     dys = dy << 1;
1439.     if (dy > dx) {
1440. 	err = dxs - dy;
1441. 
1442. 	for (k = dy-1; k; k--) {
1443. 	    if (err >= 0) {
1444. 		x--;
1445. 		err -= dys;
1446. 	    }
1447. 	    y++;
1448. 	    err += dxs;
1449. 	    if (!is_clear(y,x)) return 0; /* blocked */
1450. 	}
1451.     } else {
1452. 	err = dys - dx;
1453. 
1454. 	for (k = dx-1; k; k--) {
1455. 	    if (err >= 0) {
1456. 		y++;
1457. 		err -= dxs;
1458. 	    }
1459. 	    x--;
1460. 	    err += dys;
1461. 	    if (!is_clear(y,x)) return 0;/* blocked */
1462. 	}
1463.     }
1464. 
1465.     return 1;
1466. }
1467. 
1468. #endif	/* quadrants are functions */
1469. 
1470. /*
1471.  * Use vision tables to determine if there is a clear path from
1472.  * (col1,row1) to (col2,row2).  This is used by:
1473.  *		m_cansee()
1474.  *		m_canseeu()
1475.  *		do_light_sources()
1476.  */
1477. boolean
1478. clear_path(col1,row1,col2,row2)
1479.     int col1, row1, col2, row2;
1480. {
1481.     int result;
1482. 
1483.     if(col1 < col2) {
1484. 	if(row1 > row2) {
1485. 	    q1_path(row1,col1,row2,col2,cleardone);
1486. 	} else {
1487. 	    q4_path(row1,col1,row2,col2,cleardone);
1488. 	}
1489.     } else {
1490. 	if(row1 > row2) {
1491. 	    q2_path(row1,col1,row2,col2,cleardone);
1492. 	} else if(row1 == row2 && col1 == col2) {
1493. 	    result = 1;
1494. 	} else {
1495. 	    q3_path(row1,col1,row2,col2,cleardone);
1496. 	}
1497.     }
1498. cleardone:
1499.     return((boolean)result);
1500. }
1501. 
1502. #ifdef VISION_TABLES
1503. /*===========================================================================*\
1504. 			    GENERAL LINE OF SIGHT
1505. 				Algorithm D
1506. \*===========================================================================*/
1507. 
1508. 
1509. /*
1510.  * Indicate caller for the shadow routines.
1511.  */
1512. #define FROM_RIGHT 0
1513. #define FROM_LEFT  1
1514. 
1515. 
1516. /*
1517.  * Include the table definitions.
1518.  */
1519. #include "vis_tab.h"
1520. 
1521. 
1522. /* 3D table pointers. */
1523. static close2d *close_dy[CLOSE_MAX_BC_DY];
1524. static far2d   *far_dy[FAR_MAX_BC_DY];
1525. 
1526. static void FDECL(right_side, (int,int,int,int,int,int,int,char*));
1527. static void FDECL(left_side, (int,int,int,int,int,int,int,char*));
1528. static int FDECL(close_shadow, (int,int,int,int));
1529. static int FDECL(far_shadow, (int,int,int,int));
1530. 
1531. /*
1532.  * Initialize algorithm D's table pointers.  If we don't have these,
1533.  * then we do 3D table lookups.  Verrrry slow.
1534.  */
1535. static void
1536. view_init()
1537. {
1538.     int i;
1539. 
1540.     for (i = 0; i < CLOSE_MAX_BC_DY; i++)
1541. 	close_dy[i] = &close_table[i];
1542. 
1543.     for (i = 0; i < FAR_MAX_BC_DY; i++)
1544. 	far_dy[i] = &far_table[i];
1545. }
1546. 
1547. 
1548. /*
1549.  * If the far table has an entry of OFF_TABLE, then the far block prevents
1550.  * us from seeing the location just above/below it.  I.e. the first visible
1551.  * location is one *before* the block.
1552.  */
1553. #define OFF_TABLE 0xff
1554. 
1555. static int
1556. close_shadow(side,this_row,block_row,block_col)
1557.     int side,this_row,block_row,block_col;
1558. {
1559.     register int sdy, sdx, pdy, offset;
1560. 
1561.     /*
1562.      * If on the same column (block_row = -1), then we can see it.
1563.      */
1564.     if (block_row < 0) return block_col;
1565. 
1566.     /* Take explicit absolute values.  Adjust. */
1567.     if ((sdy = (start_row-block_row)) < 0) sdy = -sdy; --sdy;	/* src   dy */
1568.     if ((sdx = (start_col-block_col)) < 0) sdx = -sdx;		/* src   dx */
1569.     if ((pdy = (block_row-this_row))  < 0) pdy = -pdy;		/* point dy */
1570. 
1571.     if (sdy < 0 || sdy >= CLOSE_MAX_SB_DY || sdx >= CLOSE_MAX_SB_DX ||
1572. 						    pdy >= CLOSE_MAX_BC_DY) {
1573. 	impossible("close_shadow:  bad value");
1574. 	return block_col;
1575.     }
1576.     offset = close_dy[sdy]->close[sdx][pdy];
1577.     if (side == FROM_RIGHT)
1578. 	return block_col + offset;
1579. 
1580.     return block_col - offset;
1581. }
1582. 
1583. 
1584. static int
1585. far_shadow(side,this_row,block_row,block_col)
1586.     int side,this_row,block_row,block_col;
1587. {
1588.     register int sdy, sdx, pdy, offset;
1589. 
1590.     /*
1591.      * Take care of a bug that shows up only on the borders.
1592.      *
1593.      * If the block is beyond the border, then the row is negative.  Return
1594.      * the block's column number (should be 0 or COLNO-1).
1595.      *
1596.      * Could easily have the column be -1, but then wouldn't know if it was
1597.      * the left or right border.
1598.      */
1599.     if (block_row < 0) return block_col;
1600. 
1601.     /* Take explicit absolute values.  Adjust. */
1602.     if ((sdy = (start_row-block_row)) < 0) sdy = -sdy;		/* src   dy */
1603.     if ((sdx = (start_col-block_col)) < 0) sdx = -sdx; --sdx;	/* src   dx */
1604.     if ((pdy = (block_row-this_row))  < 0) pdy = -pdy; --pdy;	/* point dy */
1605. 
1606.     if (sdy >= FAR_MAX_SB_DY || sdx < 0 || sdx >= FAR_MAX_SB_DX ||
1607. 					    pdy < 0 || pdy >= FAR_MAX_BC_DY) {
1608. 	impossible("far_shadow:  bad value");
1609. 	return block_col;
1610.     }
1611.     if ((offset = far_dy[sdy]->far_q[sdx][pdy]) == OFF_TABLE) offset = -1;
1612.     if (side == FROM_RIGHT)
1613. 	return block_col + offset;
1614. 
1615.     return block_col - offset;
1616. }
1617. 
1618. 
1619. /*
1620.  * right_side()
1621.  *
1622.  * Figure out what could be seen on the right side of the source.
1623.  */
1624. static void
1625. right_side(row, cb_row, cb_col, fb_row, fb_col, left, right_mark, limits)
1626.     int row;		/* current row */
1627.     int	cb_row, cb_col;	/* close block row and col */
1628.     int	fb_row, fb_col;	/* far block row and col */
1629.     int left;		/* left mark of the previous row */
1630.     int	right_mark;	/* right mark of previous row */
1631.     char *limits;	/* points at range limit for current row, or NULL */
1632. {
1633.     register int  i;
1634.     register char *rowp;
1635.     int  hit_stone = 0;
1636.     int  left_shadow, right_shadow, loc_right;
1637.     int  lblock_col;		/* local block column (current row) */
1638.     int  nrow, deeper;
1639.     char *row_min;		/* left most */
1640.     char *row_max;		/* right most */
1641.     int		  lim_max;	/* right most limit of circle */
1642. 
1643.     nrow    = row + step;
1644.     deeper  = good_row(nrow) && (!limits || (*limits >= *(limits+1)));
1645.     if(!vis_func) {
1646. 	rowp    = cs_rows[row];
1647. 	row_min = &cs_left[row];
1648. 	row_max = &cs_right[row];
1649.     }
1650.     if(limits) {
1651. 	lim_max = start_col + *limits;
1652. 	if(lim_max > COLNO-1) lim_max = COLNO-1;
1653. 	if(right_mark > lim_max) right_mark = lim_max;
1654. 	limits++; /* prepare for next row */
1655.     } else
1656. 	lim_max = COLNO-1;
1657. 
1658.     /*
1659.      * Get the left shadow from the close block.  This value could be
1660.      * illegal.
1661.      */
1662.     left_shadow = close_shadow(FROM_RIGHT,row,cb_row,cb_col);
1663. 
1664.     /*
1665.      * Mark all stone walls as seen before the left shadow.  All this work
1666.      * for a special case.
1667.      *
1668.      * NOTE.  With the addition of this code in here, it is now *required*
1669.      * for the algorithm to work correctly.  If this is commented out,
1670.      * change the above assignment so that left and not left_shadow is the
1671.      * variable that gets the shadow.
1672.      */
1673.     while (left <= right_mark) {
1674. 	loc_right = right_ptrs[row][left];
1675. 	if(loc_right > lim_max) loc_right = lim_max;
1676. 	if (viz_clear_rows[row][left]) {
1677. 	    if (loc_right >= left_shadow) {
1678. 		left = left_shadow;	/* opening ends beyond shadow */
1679. 		break;
1680. 	    }
1681. 	    left = loc_right;
1682. 	    loc_right = right_ptrs[row][left];
1683. 	    if(loc_right > lim_max) loc_right = lim_max;
1684. 	    if (left == loc_right) return;	/* boundary */
1685. 
1686. 	    /* Shadow covers opening, beyond right mark */
1687. 	    if (left == right_mark && left_shadow > right_mark) return;
1688. 	}
1689. 
1690. 	if (loc_right > right_mark)	/* can't see stone beyond the mark */
1691. 	    loc_right = right_mark;
1692. 
1693. 	if(vis_func) {
1694. 	    for (i = left; i <= loc_right; i++) (*vis_func)(i, row, varg);
1695. 	} else {
1696. 	    for (i = left; i <= loc_right; i++) set_cs(rowp,i);
1697. 	    set_min(left);	set_max(loc_right);
1698. 	}
1699. 
1700. 	if (loc_right == right_mark) return;	/* all stone */
1701. 	if (loc_right >= left_shadow) hit_stone = 1;
1702. 	left = loc_right + 1;
1703.     }
1704. 
1705.     /*
1706.      * At this point we are at the first visible clear spot on or beyond
1707.      * the left shadow, unless the left shadow is an illegal value.  If we
1708.      * have "hit stone" then we have a stone wall just to our left.
1709.      */
1710. 
1711.     /*
1712.      * Get the right shadow.  Make sure that it is a legal value.
1713.      */
1714.     if ((right_shadow = far_shadow(FROM_RIGHT,row,fb_row,fb_col)) >= COLNO)
1715. 	right_shadow = COLNO-1;
1716.     /*
1717.      * Make vertical walls work the way we want them.  In this case, we
1718.      * note when the close block blocks the column just above/beneath
1719.      * it (right_shadow < fb_col [actually right_shadow == fb_col-1]).  If
1720.      * the location is filled, then we want to see it, so we put the
1721.      * right shadow back (same as fb_col).
1722.      */
1723.     if (right_shadow < fb_col && !viz_clear_rows[row][fb_col])
1724. 	right_shadow = fb_col;
1725.     if(right_shadow > lim_max) right_shadow = lim_max;
1726. 
1727.     /*
1728.      * Main loop.  Within the range of sight of the previous row, mark all
1729.      * stone walls as seen.  Follow open areas recursively.
1730.      */
1731.     while (left <= right_mark) {
1732. 	/* Get the far right of the opening or wall */
1733. 	loc_right = right_ptrs[row][left];
1734. 	if(loc_right > lim_max) loc_right = lim_max;
1735. 
1736. 	if (!viz_clear_rows[row][left]) {
1737. 	    hit_stone = 1;	/* use stone on this row as close block */
1738. 	    /*
1739. 	     * We can see all of the wall until the next open spot or the
1740. 	     * start of the shadow caused by the far block (right).
1741. 	     *
1742. 	     * Can't see stone beyond the right mark.
1743. 	     */
1744. 	    if (loc_right > right_mark) loc_right = right_mark;
1745. 
1746. 	    if(vis_func) {
1747. 		for (i = left; i <= loc_right; i++) (*vis_func)(i, row, varg);
1748. 	    } else {
1749. 		for (i = left; i <= loc_right; i++) set_cs(rowp,i);
1750. 		set_min(left);	set_max(loc_right);
1751. 	    }
1752. 
1753. 	    if (loc_right == right_mark) return;	/* hit the end */
1754. 	    left = loc_right + 1;
1755. 	    loc_right = right_ptrs[row][left];
1756. 	    if(loc_right > lim_max) loc_right = lim_max;
1757. 	    /* fall through... we know at least one position is visible */
1758. 	}
1759. 
1760. 	/*
1761. 	 * We are in an opening.
1762. 	 *
1763. 	 * If this is the first open spot since the could see area  (this is
1764. 	 * true if we have hit stone), get the shadow generated by the wall
1765. 	 * just to our left.
1766. 	 */
1767. 	if (hit_stone) {
1768. 	    lblock_col = left-1;	/* local block column */
1769. 	    left = close_shadow(FROM_RIGHT,row,row,lblock_col);
1770. 	    if (left > lim_max) break;		/* off the end */
1771. 	}
1772. 
1773. 	/*
1774. 	 * Check if the shadow covers the opening.  If it does, then
1775. 	 * move to end of the opening.  A shadow generated on from a
1776. 	 * wall on this row does *not* cover the wall on the right
1777. 	 * of the opening.
1778. 	 */
1779. 	if (left >= loc_right) {
1780. 	    if (loc_right == lim_max) {		/* boundary */
1781. 		if (left == lim_max) {
1782. 		    if(vis_func) (*vis_func)(lim_max, row, varg);
1783. 		    else {
1784. 			set_cs(rowp,lim_max);	/* last pos */
1785. 			set_max(lim_max);
1786. 		    }
1787. 		}
1788. 		return;					/* done */
1789. 	    }
1790. 	    left = loc_right;
1791. 	    continue;
1792. 	}
1793. 
1794. 	/*
1795. 	 * If the far wall of the opening (loc_right) is closer than the
1796. 	 * shadow limit imposed by the far block (right) then use the far
1797. 	 * wall as our new far block when we recurse.
1798. 	 *
1799. 	 * If the limits are the the same, and the far block really exists
1800. 	 * (fb_row >= 0) then do the same as above.
1801. 	 *
1802. 	 * Normally, the check would be for the far wall being closer OR EQUAL
1803. 	 * to the shadow limit.  However, there is a bug that arises from the
1804. 	 * fact that the clear area pointers end in an open space (if it
1805. 	 * exists) on a boundary.  This then makes a far block exist where it
1806. 	 * shouldn't --- on a boundary.  To get around that, I had to
1807. 	 * introduce the concept of a non-existent far block (when the
1808. 	 * row < 0).  Next I have to check for it.  Here is where that check
1809. 	 * exists.
1810. 	 */
1811. 	if ((loc_right < right_shadow) ||
1812. 				(fb_row >= 0 && loc_right == right_shadow)) {
1813. 	    if(vis_func) {
1814. 		for (i = left; i <= loc_right; i++) (*vis_func)(i, row, varg);
1815. 	    } else {
1816. 		for (i = left; i <= loc_right; i++) set_cs(rowp,i);
1817. 		set_min(left);	set_max(loc_right);
1818. 	    }
1819. 
1820. 	    if (deeper) {
1821. 		if (hit_stone)
1822. 		    right_side(nrow,row,lblock_col,row,loc_right,
1823. 							left,loc_right,limits);
1824. 		else
1825. 		    right_side(nrow,cb_row,cb_col,row,loc_right,
1826. 							left,loc_right,limits);
1827. 	    }
1828. 
1829. 	    /*
1830. 	     * The following line, setting hit_stone, is needed for those
1831. 	     * walls that are only 1 wide.  If hit stone is *not* set and
1832. 	     * the stone is only one wide, then the close block is the old
1833. 	     * one instead one on the current row.  A way around having to
1834. 	     * set it here is to make left = loc_right (not loc_right+1) and
1835. 	     * let the outer loop take care of it.  However, if we do that
1836. 	     * then we then have to check for boundary conditions here as
1837. 	     * well.
1838. 	     */
1839. 	    hit_stone = 1;
1840. 
1841. 	    left = loc_right+1;
1842. 	}
1843. 	/*
1844. 	 * The opening extends beyond the right mark.  This means that
1845. 	 * the next far block is the current far block.
1846. 	 */
1847. 	else {
1848. 	    if(vis_func) {
1849. 		for (i=left; i <= right_shadow; i++) (*vis_func)(i, row, varg);
1850. 	    } else {
1851. 		for (i = left; i <= right_shadow; i++) set_cs(rowp,i);
1852. 		set_min(left);	set_max(right_shadow);
1853. 	    }
1854. 
1855. 	    if (deeper) {
1856. 		if (hit_stone)
1857. 		    right_side(nrow,   row,lblock_col,fb_row,fb_col,
1858. 						     left,right_shadow,limits);
1859. 		else
1860. 		    right_side(nrow,cb_row,    cb_col,fb_row,fb_col,
1861. 						     left,right_shadow,limits);
1862. 	    }
1863. 
1864. 	    return;	/* we're outta here */
1865. 	}
1866.     }
1867. }
1868. 
1869. 
1870. /*
1871.  * left_side()
1872.  *
1873.  * This routine is the mirror image of right_side().  Please see right_side()
1874.  * for blow by blow comments.
1875.  */
1876. static void
1877. left_side(row, cb_row, cb_col, fb_row, fb_col, left_mark, right, limits)
1878.     int row;		/* the current row */
1879.     int	cb_row, cb_col;	/* close block row and col */
1880.     int	fb_row, fb_col;	/* far block row and col */
1881.     int	left_mark;	/* left mark of previous row */
1882.     int right;		/* right mark of the previous row */
1883.     char *limits;
1884. {
1885.     register int  i;
1886.     register char *rowp;
1887.     int  hit_stone = 0;
1888.     int  left_shadow, right_shadow, loc_left;
1889.     int  lblock_col;		/* local block column (current row) */
1890.     int  nrow, deeper;
1891.     char *row_min;		/* left most */
1892.     char *row_max;		/* right most */
1893.     int		  lim_min;
1894. 
1895.     nrow    = row + step;
1896.     deeper  = good_row(nrow) && (!limits || (*limits >= *(limits+1)));
1897.     if(!vis_func) {
1898. 	rowp    = cs_rows[row];
1899. 	row_min = &cs_left[row];
1900. 	row_max = &cs_right[row];
1901.     }
1902.     if(limits) {
1903. 	lim_min = start_col - *limits;
1904. 	if(lim_min < 0) lim_min = 0;
1905. 	if(left_mark < lim_min) left_mark = lim_min;
1906. 	limits++; /* prepare for next row */
1907.     } else
1908. 	lim_min = 0;
1909. 
1910.     /* This value could be illegal. */
1911.     right_shadow = close_shadow(FROM_LEFT,row,cb_row,cb_col);
1912. 
1913.     while ( right >= left_mark ) {
1914. 	loc_left = left_ptrs[row][right];
1915. 	if(loc_left < lim_min) loc_left = lim_min;
1916. 	if (viz_clear_rows[row][right]) {
1917. 	    if (loc_left <= right_shadow) {
1918. 		right = right_shadow;	/* opening ends beyond shadow */
1919. 		break;
1920. 	    }
1921. 	    right = loc_left;
1922. 	    loc_left = left_ptrs[row][right];
1923. 	    if(loc_left < lim_min) loc_left = lim_min;
1924. 	    if (right == loc_left) return;	/* boundary */
1925. 	}
1926. 
1927. 	if (loc_left < left_mark)	/* can't see beyond the left mark */
1928. 	    loc_left = left_mark;
1929. 
1930. 	if(vis_func) {
1931. 	    for (i = loc_left; i <= right; i++) (*vis_func)(i, row, varg);
1932. 	} else {
1933. 	    for (i = loc_left; i <= right; i++) set_cs(rowp,i);
1934. 	    set_min(loc_left);	set_max(right);
1935. 	}
1936. 
1937. 	if (loc_left == left_mark) return;	/* all stone */
1938. 	if (loc_left <= right_shadow) hit_stone = 1;
1939. 	right = loc_left - 1;
1940.     }
1941. 
1942.     /* At first visible clear spot on or beyond the right shadow. */
1943. 
1944.     if ((left_shadow = far_shadow(FROM_LEFT,row,fb_row,fb_col)) < 0)
1945. 	left_shadow = 0;
1946. 
1947.     /* Do vertical walls as we want. */
1948.     if (left_shadow > fb_col && !viz_clear_rows[row][fb_col])
1949. 	left_shadow = fb_col;
1950.     if(left_shadow < lim_min) left_shadow = lim_min;
1951. 
1952.     while (right >= left_mark) {
1953. 	loc_left = left_ptrs[row][right];
1954. 
1955. 	if (!viz_clear_rows[row][right]) {
1956. 	    hit_stone = 1;	/* use stone on this row as close block */
1957. 
1958. 	    /* We can only see walls until the left mark */
1959. 	    if (loc_left < left_mark) loc_left = left_mark;
1960. 
1961. 	    if(vis_func) {
1962. 		for (i = loc_left; i <= right; i++) (*vis_func)(i, row, varg);
1963. 	    } else {
1964. 		for (i = loc_left; i <= right; i++) set_cs(rowp,i);
1965. 		set_min(loc_left);	set_max(right);
1966. 	    }
1967. 
1968. 	    if (loc_left == left_mark) return;	/* hit end */
1969. 	    right = loc_left - 1;
1970. 	    loc_left = left_ptrs[row][right];
1971. 	    if (loc_left < lim_min) loc_left = lim_min;
1972. 	    /* fall through...*/
1973. 	}
1974. 
1975. 	/* We are in an opening. */
1976. 	if (hit_stone) {
1977. 	    lblock_col = right+1;	/* stone block (local) */
1978. 	    right = close_shadow(FROM_LEFT,row,row,lblock_col);
1979. 	    if (right < lim_min) return;	/* off the end */
1980. 	}
1981. 
1982. 	/*  Check if the shadow covers the opening. */
1983. 	if (right <= loc_left) {
1984. 	    /*  Make a boundary condition work. */
1985. 	    if (loc_left == lim_min) {	/* at boundary */
1986. 		if (right == lim_min) {
1987. 		    if(vis_func) (*vis_func)(lim_min, row, varg);
1988. 		    else {
1989. 			set_cs(rowp,lim_min);	/* caught the last pos */
1990. 			set_min(lim_min);
1991. 		    }
1992. 		}
1993. 		return;			/* and break out the loop */
1994. 	    }
1995. 
1996. 	    right = loc_left;
1997. 	    continue;
1998. 	}
1999. 
2000. 	/* If the far wall of the opening is closer than the shadow limit. */
2001. 	if ((loc_left > left_shadow) ||
2002. 				    (fb_row >= 0 && loc_left == left_shadow)) {
2003. 	    if(vis_func) {
2004. 		for (i = loc_left; i <= right; i++) (*vis_func)(i, row, varg);
2005. 	    } else {
2006. 		for (i = loc_left; i <= right; i++) set_cs(rowp,i);
2007. 		set_min(loc_left);	set_max(right);
2008. 	    }
2009. 
2010. 	    if (deeper) {
2011. 		if (hit_stone)
2012. 		    left_side(nrow,row,lblock_col,row,loc_left,
2013. 							loc_left,right,limits);
2014. 		else
2015. 		    left_side(nrow,cb_row,cb_col,row,loc_left,
2016. 							loc_left,right,limits);
2017. 	    }
2018. 
2019. 	    hit_stone = 1;	/* needed for walls of width 1 */
2020. 	    right = loc_left-1;
2021. 	}
2022. 	/*  The opening extends beyond the left mark. */
2023. 	else {
2024. 	    if(vis_func) {
2025. 		for (i=left_shadow; i <= right; i++) (*vis_func)(i, row, varg);
2026. 	    } else {
2027. 		for (i = left_shadow; i <= right; i++) set_cs(rowp,i);
2028. 		set_min(left_shadow);	set_max(right);
2029. 	    }
2030. 
2031. 	    if (deeper) {
2032. 		if (hit_stone)
2033. 		    left_side(nrow,row,lblock_col,fb_row,fb_col,
2034. 						     left_shadow,right,limits);
2035. 		else
2036. 		    left_side(nrow,cb_row,cb_col,fb_row,fb_col,
2037. 						     left_shadow,right,limits);
2038. 	    }
2039. 
2040. 	    return;	/* we're outta here */
2041. 	}
2042. 
2043.     }
2044. }
2045. 
2046. /*
2047.  * view_from
2048.  *
2049.  * Calculate a view from the given location.  Initialize and fill a
2050.  * ROWNOxCOLNO array (could_see) with all the locations that could be
2051.  * seen from the source location.  Initialize and fill the left most
2052.  * and right most boundaries of what could be seen.
2053.  */
2054. static void
2055. view_from(srow,scol,loc_cs_rows,left_most,right_most, range, func, arg)
2056.     int  srow, scol;			/* source row and column */
2057.     char **loc_cs_rows;			/* could_see array (row pointers) */
2058.     char *left_most, *right_most;	/* limits of what could be seen */
2059.     int range;		/* 0 if unlimited */
2060.     void FDECL((*func), (int,int,genericptr_t));
2061.     genericptr_t arg;
2062. {
2063.     register int i;
2064.     char	 *rowp;
2065.     int		 nrow, left, right, left_row, right_row;
2066.     char	 *limits;
2067. 
2068.     /* Set globals for near_shadow(), far_shadow(), etc. to use. */
2069.     start_col = scol;
2070.     start_row = srow;
2071.     cs_rows   = loc_cs_rows;
2072.     cs_left   = left_most;
2073.     cs_right  = right_most;
2074.     vis_func = func;
2075.     varg = arg;
2076. 
2077.     /*  Find the left and right limits of sight on the starting row. */
2078.     if (viz_clear_rows[srow][scol]) {
2079. 	left  = left_ptrs[srow][scol];
2080. 	right = right_ptrs[srow][scol];
2081.     } else {
2082. 	left  = (!scol) ? 0 :
2083. 	    (viz_clear_rows[srow][scol-1] ?  left_ptrs[srow][scol-1] : scol-1);
2084. 	right = (scol == COLNO-1) ? COLNO-1 :
2085. 	    (viz_clear_rows[srow][scol+1] ? right_ptrs[srow][scol+1] : scol+1);
2086.     }
2087. 
2088.     if(range) {
2089. 	if(range > MAX_RADIUS || range < 1)
2090. 	    panic("view_from called with range %d", range);
2091. 	limits = circle_ptr(range) + 1; /* start at next row */
2092. 	if(left < scol - range) left = scol - range;
2093. 	if(right > scol + range) right = scol + range;
2094.     } else
2095. 	limits = (char*) 0;
2096. 
2097.     if(func) {
2098. 	for (i = left; i <= right; i++) (*func)(i, srow, arg);
2099.     } else {
2100. 	/* Row optimization */
2101. 	rowp = cs_rows[srow];
2102. 
2103. 	/* We know that we can see our row. */
2104. 	for (i = left; i <= right; i++) set_cs(rowp,i);
2105. 	cs_left[srow]  = left;
2106. 	cs_right[srow] = right;
2107.     }
2108. 
2109.     /* The far block has a row number of -1 if we are on an edge. */
2110.     right_row = (right == COLNO-1) ? -1 : srow;
2111.     left_row  = (!left)		   ? -1 : srow;
2112. 
2113.     /*
2114.      *  Check what could be seen in quadrants.
2115.      */
2116.     if ( (nrow = srow+1) < ROWNO ) {
2117. 	step =  1;	/* move down */
2118. 	if (scol<COLNO-1)
2119. 	    right_side(nrow,-1,scol,right_row,right,scol,right,limits);
2120. 	if (scol)
2121. 	    left_side(nrow,-1,scol,left_row, left, left, scol,limits);
2122.     }
2123. 
2124.     if ( (nrow = srow-1) >= 0 ) {
2125. 	step = -1;	/* move up */
2126. 	if (scol<COLNO-1)
2127. 	    right_side(nrow,-1,scol,right_row,right,scol,right,limits);
2128. 	if (scol)
2129. 	    left_side(nrow,-1,scol,left_row, left, left, scol,limits);
2130.     }
2131. }
2132. 
2133. 
2134. #else	/*===== End of algorithm D =====*/
2135. 
2136. 
2137. /*===========================================================================*\
2138. 			    GENERAL LINE OF SIGHT
2139. 				Algorithm C
2140. \*===========================================================================*/
2141. 
2142. /*
2143.  * Defines local to Algorithm C.
2144.  */
2145. static void FDECL(right_side, (int,int,int,char*));
2146. static void FDECL(left_side, (int,int,int,char*));
2147. 
2148. /* Initialize algorithm C (nothing). */
2149. static void
2150. view_init()
2151. {
2152. }
2153. 
2154. /*
2155.  * Mark positions as visible on one quadrant of the right side.  The
2156.  * quadrant is determined by the value of the global variable step.
2157.  */
2158. static void
2159. right_side(row, left, right_mark, limits)
2160.     int row;		/* current row */
2161.     int left;		/* first (left side) visible spot on prev row */
2162.     int right_mark;	/* last (right side) visible spot on prev row */
2163.     char *limits;	/* points at range limit for current row, or NULL */
2164. {
2165.     int		  right;	/* right limit of "could see" */
2166.     int		  right_edge;	/* right edge of an opening */
2167.     int		  nrow;		/* new row (calculate once) */
2168.     int		  deeper;	/* if TRUE, call self as needed */
2169.     int		  result;	/* set by q?_path() */
2170.     register int  i;		/* loop counter */
2171.     register char *rowp;	/* row optimization */
2172.     char	  *row_min;	/* left most  [used by macro set_min()] */
2173.     char	  *row_max;	/* right most [used by macro set_max()] */
2174.     int		  lim_max;	/* right most limit of circle */
2175. 
2176. #ifdef GCC_WARN
2177.     rowp = row_min = row_max = 0;
2178. #endif
2179.     nrow    = row + step;
2180.     /*
2181.      * Can go deeper if the row is in bounds and the next row is within
2182.      * the circle's limit.  We tell the latter by checking to see if the next
2183.      * limit value is the start of a new circle radius (meaning we depend
2184.      * on the structure of circle_data[]).
2185.      */
2186.     deeper  = good_row(nrow) && (!limits || (*limits >= *(limits+1)));
2187.     if(!vis_func) {
2188. 	rowp    = cs_rows[row];	/* optimization */
2189. 	row_min = &cs_left[row];
2190. 	row_max = &cs_right[row];
2191.     }
2192.     if(limits) {
2193. 	lim_max = start_col + *limits;
2194. 	if(lim_max > COLNO-1) lim_max = COLNO-1;
2195. 	if(right_mark > lim_max) right_mark = lim_max;
2196. 	limits++; /* prepare for next row */
2197.     } else
2198. 	lim_max = COLNO-1;
2199. 
2200.     while (left <= right_mark) {
2201. 	right_edge = right_ptrs[row][left];
2202. 	if(right_edge > lim_max) right_edge = lim_max;
2203. 
2204. 	if (!is_clear(row,left)) {
2205. 	    /*
2206. 	     * Jump to the far side of a stone wall.  We can set all
2207. 	     * the points in between as seen.
2208. 	     *
2209. 	     * If the right edge goes beyond the right mark, check to see
2210. 	     * how much we can see.
2211. 	     */
2212. 	    if (right_edge > right_mark) {
2213. 		/*
2214. 		 * If the mark on the previous row was a clear position,
2215. 		 * the odds are that we can actually see part of the wall
2216. 		 * beyond the mark on this row.  If so, then see one beyond
2217. 		 * the mark.  Otherwise don't.  This is a kludge so corners
2218. 		 * with an adjacent doorway show up in nethack.
2219. 		 */
2220. 		right_edge = is_clear(row-step,right_mark) ?
2221. 						    right_mark+1 : right_mark;
2222. 	    }
2223. 	    if(vis_func) {
2224. 		for (i = left; i <= right_edge; i++) (*vis_func)(i, row, varg);
2225. 	    } else {
2226. 		for (i = left; i <= right_edge; i++) set_cs(rowp,i);
2227. 		set_min(left);      set_max(right_edge);
2228. 	    }
2229. 	    left = right_edge + 1; /* no limit check necessary */
2230. 	    continue;
2231. 	}
2232. 
2233. 	/* No checking needed if our left side is the start column. */
2234. 	if (left != start_col) {
2235. 	    /*
2236. 	     * Find the left side.  Move right until we can see it or we run
2237. 	     * into a wall.
2238. 	     */
2239. 	    for (; left <= right_edge; left++) {
2240. 		if (step < 0) {
2241. 		    q1_path(start_row,start_col,row,left,rside1);
2242. 		} else {
2243. 		    q4_path(start_row,start_col,row,left,rside1);
2244. 		}
2245. rside1:					/* used if q?_path() is a macro */
2246. 		if (result) break;
2247. 	    }
2248. 
2249. 	    /*
2250. 	     * Check for boundary conditions.  We *need* check (2) to break
2251. 	     * an infinite loop where:
2252. 	     *
2253. 	     *		left == right_edge == right_mark == lim_max.
2254. 	     *
2255. 	     */
2256. 	    if (left > lim_max) return;	/* check (1) */
2257. 	    if (left == lim_max) {	/* check (2) */
2258. 		if(vis_func) (*vis_func)(lim_max, row, varg);
2259. 		else {
2260. 		    set_cs(rowp,lim_max);
2261. 		    set_max(lim_max);
2262. 		}
2263. 		return;
2264. 	    }
2265. 	    /*
2266. 	     * Check if we can see any spots in the opening.  We might
2267. 	     * (left == right_edge) or might not (left == right_edge+1) have
2268. 	     * been able to see the far wall.  Make sure we *can* see the
2269. 	     * wall (remember, we can see the spot above/below this one)
2270. 	     * by backing up.
2271. 	     */
2272. 	    if (left >= right_edge) {
2273. 		left = right_edge;	/* for the case left == right_edge+1 */
2274. 		continue;
2275. 	    }
2276. 	}
2277. 
2278. 	/*
2279. 	 * Find the right side.  If the marker from the previous row is
2280. 	 * closer than the edge on this row, then we have to check
2281. 	 * how far we can see around the corner (under the overhang).  Stop
2282. 	 * at the first non-visible spot or we actually hit the far wall.
2283. 	 *
2284. 	 * Otherwise, we know we can see the right edge of the current row.
2285. 	 *
2286. 	 * This must be a strict less than so that we can always see a
2287. 	 * horizontal wall, even if it is adjacent to us.
2288. 	 */
2289. 	if (right_mark < right_edge) {
2290. 	    for (right = right_mark; right <= right_edge; right++) {
2291. 		if (step < 0) {
2292. 		    q1_path(start_row,start_col,row,right,rside2);
2293. 		} else {
2294. 		    q4_path(start_row,start_col,row,right,rside2);
2295. 		}
2296. rside2:					/* used if q?_path() is a macro */
2297. 		if (!result) break;
2298. 	    }
2299. 	    --right;	/* get rid of the last increment */
2300. 	}
2301. 	else
2302. 	    right = right_edge;
2303. 
2304. 	/*
2305. 	 * We have the range that we want.  Set the bits.  Note that
2306. 	 * there is no else --- we no longer handle splinters.
2307. 	 */
2308. 	if (left <= right) {
2309. 	    /*
2310. 	     * An ugly special case.  If you are adjacent to a vertical wall
2311. 	     * and it has a break in it, then the right mark is set to be
2312. 	     * start_col.  We *want* to be able to see adjacent vertical
2313. 	     * walls, so we have to set it back.
2314. 	     */
2315. 	    if (left == right && left == start_col &&
2316. 			start_col < (COLNO-1) && !is_clear(row,start_col+1))
2317. 		right = start_col+1;
2318. 
2319. 	    if(right > lim_max) right = lim_max;
2320. 	    /* set the bits */
2321. 	    if(vis_func)
2322. 		for (i = left; i <= right; i++) (*vis_func)(i, row, varg);
2323. 	    else {
2324. 		for (i = left; i <= right; i++) set_cs(rowp,i);
2325. 		set_min(left);      set_max(right);
2326. 	    }
2327. 
2328. 	    /* recursive call for next finger of light */
2329. 	    if (deeper) right_side(nrow,left,right,limits);
2330. 	    left = right + 1; /* no limit check necessary */
2331. 	}
2332.     }
2333. }
2334. 
2335. 
2336. /*
2337.  * This routine is the mirror image of right_side().  See right_side() for
2338.  * extensive comments.
2339.  */
2340. static void
2341. left_side(row, left_mark, right, limits)
2342.     int row, left_mark, right;
2343.     char *limits;
2344. {
2345.     int		  left, left_edge, nrow, deeper, result;
2346.     register int  i;
2347.     register char *rowp;
2348.     char	  *row_min, *row_max;
2349.     int		  lim_min;
2350. 
2351. #ifdef GCC_WARN
2352.     rowp = row_min = row_max = 0;
2353. #endif
2354.     nrow    = row+step;
2355.     deeper  = good_row(nrow) && (!limits || (*limits >= *(limits+1)));
2356.     if(!vis_func) {
2357. 	rowp    = cs_rows[row];
2358. 	row_min = &cs_left[row];
2359. 	row_max = &cs_right[row];
2360.     }
2361.     if(limits) {
2362. 	lim_min = start_col - *limits;
2363. 	if(lim_min < 0) lim_min = 0;
2364. 	if(left_mark < lim_min) left_mark = lim_min;
2365. 	limits++; /* prepare for next row */
2366.     } else
2367. 	lim_min = 0;
2368. 
2369.     while (right >= left_mark) {
2370. 	left_edge = left_ptrs[row][right];
2371. 	if(left_edge < lim_min) left_edge = lim_min;
2372. 
2373. 	if (!is_clear(row,right)) {
2374. 	    /* Jump to the far side of a stone wall. */
2375. 	    if (left_edge < left_mark) {
2376. 		/* Maybe see more (kludge). */
2377. 		left_edge = is_clear(row-step,left_mark) ?
2378. 						    left_mark-1 : left_mark;
2379. 	    }
2380. 	    if(vis_func) {
2381. 		for (i = left_edge; i <= right; i++) (*vis_func)(i, row, varg);
2382. 	    } else {
2383. 		for (i = left_edge; i <= right; i++) set_cs(rowp,i);
2384. 		set_min(left_edge); set_max(right);
2385. 	    }
2386. 	    right = left_edge - 1; /* no limit check necessary */
2387. 	    continue;
2388. 	}
2389. 
2390. 	if (right != start_col) {
2391. 	    /* Find the right side. */
2392. 	    for (; right >= left_edge; right--) {
2393. 		if (step < 0) {
2394. 		    q2_path(start_row,start_col,row,right,lside1);
2395. 		} else {
2396. 		    q3_path(start_row,start_col,row,right,lside1);
2397. 		}
2398. lside1:					/* used if q?_path() is a macro */
2399. 		if (result) break;
2400. 	    }
2401. 
2402. 	    /* Check for boundary conditions. */
2403. 	    if (right < lim_min) return;
2404. 	    if (right == lim_min) {
2405. 		if(vis_func) (*vis_func)(lim_min, row, varg);
2406. 		else {
2407. 		    set_cs(rowp,lim_min);
2408. 		    set_min(lim_min);
2409. 		}
2410. 		return;
2411. 	    }
2412. 	    /* Check if we can see any spots in the opening. */
2413. 	    if (right <= left_edge) {
2414. 		right = left_edge;
2415. 		continue;
2416. 	    }
2417. 	}
2418. 
2419. 	/* Find the left side. */
2420. 	if (left_mark > left_edge) {
2421. 	    for (left = left_mark; left >= left_edge; --left) {
2422. 		if (step < 0) {
2423. 		    q2_path(start_row,start_col,row,left,lside2);
2424. 		} else {
2425. 		    q3_path(start_row,start_col,row,left,lside2);
2426. 		}
2427. lside2:					/* used if q?_path() is a macro */
2428. 		if (!result) break;
2429. 	    }
2430. 	    left++;	/* get rid of the last decrement */
2431. 	}
2432. 	else
2433. 	    left = left_edge;
2434. 
2435. 	if (left <= right) {
2436. 	    /* An ugly special case. */
2437. 	    if (left == right && right == start_col &&
2438. 			    start_col > 0 && !is_clear(row,start_col-1))
2439. 		left = start_col-1;
2440. 
2441. 	    if(left < lim_min) left = lim_min;
2442. 	    if(vis_func)
2443. 		for (i = left; i <= right; i++) (*vis_func)(i, row, varg);
2444. 	    else {
2445. 		for (i = left; i <= right; i++) set_cs(rowp,i);
2446. 		set_min(left);      set_max(right);
2447. 	    }
2448. 
2449. 	    /* Recurse */
2450. 	    if (deeper) left_side(nrow,left,right,limits);
2451. 	    right = left - 1; /* no limit check necessary */
2452. 	}
2453.     }
2454. }
2455. 
2456. 
2457. /*
2458.  * Calculate all possible visible locations from the given location
2459.  * (srow,scol).  NOTE this is (y,x)!  Mark the visible locations in the
2460.  * array provided.
2461.  */
2462. static void
2463. view_from(srow, scol, loc_cs_rows, left_most, right_most, range, func, arg)
2464.     int  srow, scol;	/* starting row and column */
2465.     char **loc_cs_rows;	/* pointers to the rows of the could_see array */
2466.     char *left_most;	/* min mark on each row */
2467.     char *right_most;	/* max mark on each row */
2468.     int range;		/* 0 if unlimited */
2469.     void FDECL((*func), (int,int,genericptr_t));
2470.     genericptr_t arg;
2471. {
2472.     register int i;		/* loop counter */
2473.     char         *rowp;		/* optimization for setting could_see */
2474.     int		 nrow;		/* the next row */
2475.     int		 left;		/* the left-most visible column */
2476.     int		 right;		/* the right-most visible column */
2477.     char	 *limits;	/* range limit for next row */
2478. 
2479.     /* Set globals for q?_path(), left_side(), and right_side() to use. */
2480.     start_col = scol;
2481.     start_row = srow;
2482.     cs_rows   = loc_cs_rows;	/* 'could see' rows */
2483.     cs_left   = left_most;
2484.     cs_right  = right_most;
2485.     vis_func = func;
2486.     varg = arg;
2487. 
2488.     /*
2489.      * Determine extent of sight on the starting row.
2490.      */
2491.     if (is_clear(srow,scol)) {
2492. 	left =  left_ptrs[srow][scol];
2493. 	right = right_ptrs[srow][scol];
2494.     } else {
2495. 	/*
2496. 	 * When in stone, you can only see your adjacent squares, unless
2497. 	 * you are on an array boundary or a stone/clear boundary.
2498. 	 */
2499. 	left  = (!scol) ? 0 :
2500. 		(is_clear(srow,scol-1) ? left_ptrs[srow][scol-1] : scol-1);
2501. 	right = (scol == COLNO-1) ? COLNO-1 :
2502. 		(is_clear(srow,scol+1) ? right_ptrs[srow][scol+1] : scol+1);
2503.     }
2504. 
2505.     if(range) {
2506. 	if(range > MAX_RADIUS || range < 1)
2507. 	    panic("view_from called with range %d", range);
2508. 	limits = circle_ptr(range) + 1; /* start at next row */
2509. 	if(left < scol - range) left = scol - range;
2510. 	if(right > scol + range) right = scol + range;
2511.     } else
2512. 	limits = (char*) 0;
2513. 
2514.     if(func) {
2515. 	for (i = left; i <= right; i++) (*func)(i, srow, arg);
2516.     } else {
2517. 	/* Row pointer optimization. */
2518. 	rowp = cs_rows[srow];
2519. 
2520. 	/* We know that we can see our row. */
2521. 	for (i = left; i <= right; i++) set_cs(rowp,i);
2522. 	cs_left[srow]  = left;
2523. 	cs_right[srow] = right;
2524.     }
2525. 
2526.     /*
2527.      * Check what could be seen in quadrants.  We need to check for valid
2528.      * rows here, since we don't do it in the routines right_side() and
2529.      * left_side() [ugliness to remove extra routine calls].
2530.      */
2531.     if ( (nrow = srow+1) < ROWNO ) {	/* move down */
2532. 	step =  1;
2533. 	if (scol < COLNO-1) right_side(nrow, scol, right, limits);
2534. 	if (scol)	    left_side (nrow, left,  scol, limits);
2535.     }
2536. 
2537.     if ( (nrow = srow-1) >= 0 ) {	/* move up */
2538. 	step = -1;
2539. 	if (scol < COLNO-1) right_side(nrow, scol, right, limits);
2540. 	if (scol)	    left_side (nrow, left,  scol, limits);
2541.     }
2542. }
2543. 
2544. #endif	/*===== End of algorithm C =====*/
2545. 
2546. /*
2547.  * AREA OF EFFECT "ENGINE"
2548.  *
2549.  * Calculate all possible visible locations as viewed from the given location
2550.  * (srow,scol) within the range specified. Perform "func" with (x, y) args and
2551.  * additional argument "arg" for each square.
2552.  *
2553.  * If not centered on the hero, just forward arguments to view_from(); it
2554.  * will call "func" when necessary.  If the hero is the center, use the
2555.  * vision matrix and reduce extra work.
2556.  */
2557. void
2558. do_clear_area(scol,srow,range,func,arg)
2559.     int scol, srow, range;
2560.     void FDECL((*func), (int,int,genericptr_t));
2561.     genericptr_t arg;
2562. {
2563. 	/* If not centered on hero, do the hard work of figuring the area */
2564. 	if (scol != u.ux || srow != u.uy)
2565. 	    view_from(srow, scol, (char **)0, (char *)0, (char *)0,
2566. 							range, func, arg);
2567. 	else {
2568. 	    register int x;
2569. 	    int y, min_x, max_x, max_y, offset;
2570. 	    char *limits;
2571. 
2572. 	    if (range > MAX_RADIUS || range < 1)
2573. 		panic("do_clear_area:  illegal range %d", range);
2574. 	    if(vision_full_recalc)
2575. 		vision_recalc(0);	/* recalc vision if dirty */
2576. 	    limits = circle_ptr(range);
2577. 	    if ((max_y = (srow + range)) >= ROWNO) max_y = ROWNO-1;
2578. 	    if ((y = (srow - range)) < 0) y = 0;
2579. 	    for (; y <= max_y; y++) {
2580. 		offset = limits[v_abs(y-srow)];
2581. 		if((min_x = (scol - offset)) < 0) min_x = 0;
2582. 		if((max_x = (scol + offset)) >= COLNO) max_x = COLNO-1;
2583. 		for (x = min_x; x <= max_x; x++)
2584. 		    if (couldsee(x, y))
2585. 			(*func)(x, y, arg);
2586. 	    }
2587. 	}
2588. }
2589. 
2590. /*vision.c*/