ftp://ftp.sunet.se/pub/os/Linux/distributions/ultrapenguin/ultrapenguin-1.1/SRPMS...
[xscreensaver] / hacks / maze.c
index 22af1d6a848450fb7cf0bad3d21c8b0ea71a4908..aa2de92fcd36f337c76f687630415f28cf0b6153 100644 (file)
@@ -1,6 +1,9 @@
 /******************************************************************************
  * [ maze ] ...
  *
+ * modified:  [ 4-10-97 ]  Johannes Keukelaar <johannes@nada.kth.se>
+ *              Added multiple maze creators. Robustified solver.
+ *              Added bridge option.
  * modified:  [ 8-11-95 ] Ed James <james@mml.mmc.com>
  *              added fill of dead-end box to solve_maze while loop.
  * modified:  [ 3-7-93 ]  Jamie Zawinski <jwz@netscape.com>
@@ -81,6 +84,7 @@ static int solve_delay, pre_solve_delay, post_solve_delay;
 #define DOOR_OUT_BOTTOM        0x20
 #define DOOR_OUT_LEFT  0x10
 
+#define SOLVER_VISIT    0x4
 #define START_SQUARE   0x2
 #define END_SQUARE     0x1
 
@@ -113,13 +117,15 @@ static int maze_size_x, maze_size_y;
 static int sqnum, cur_sq_x, cur_sq_y, path_length;
 static int start_x, start_y, start_dir, end_x, end_y, end_dir;
 static int grid_width, grid_height;
+static int bw;
 
 static Display *dpy;
 static Window  win;
-static GC      gc, cgc, tgc, logo_gc;
+static GC      gc, cgc, tgc, logo_gc, erase_gc;
 static Pixmap  logo_map;
 
-static int     x = 0, y = 0, restart = 0, stop = 1, state = 1;
+static int     x = 0, y = 0, restart = 0, stop = 1, state = 1, max_length;
+static int      sync_p, bridge_p;
 
 static int
 check_events (void)                        /* X event handler [ rhess ] */
@@ -180,6 +186,8 @@ static void
 initialize_maze (void) /* draw the surrounding wall and start/end squares */
 {
   register int i, j, wall;
+  int logow = 1 + logo_width / grid_width;
+  int logoh = 1 + logo_height / grid_height;
   
   /* initialize all squares */
   for ( i=0; i<maze_size_x; i++) {
@@ -266,13 +274,11 @@ initialize_maze (void) /* draw the surrounding wall and start/end squares */
   end_dir = wall;
   
   /* set logo */
-  if ((maze_size_x > 15) && (maze_size_y > 15))
+  if ((maze_size_x-logow >= 6) && (maze_size_y-logoh >= 6))
     {
-      int logow = 1 + logo_width / grid_width;
-      int logoh = 1 + logo_height / grid_height;
       /* not closer than 3 grid units from a wall */
-      logo_x = get_random (maze_size_x - logow - 6) + 3;
-      logo_y = get_random (maze_size_y - logoh - 6) + 3;
+      logo_x = get_random (maze_size_x - logow - 5) + 3;
+      logo_y = get_random (maze_size_y - logoh - 5) + 3;
       for (i=0; i<logow; i++)
        for (j=0; j<logoh; j++)
          maze[logo_x + i][logo_y + j] |= DOOR_IN_TOP;
@@ -283,15 +289,626 @@ initialize_maze (void) /* draw the surrounding wall and start/end squares */
 
 static int choose_door (void);
 static int backup (void);
-static void draw_wall (int, int, int);
+static void draw_wall (int, int, int, GC);
 static void draw_solid_square (int, int, int, GC);
-static void enter_square (int);
+/*static void enter_square (int);*/
+static void build_wall (int, int, int);
+/*static void break_wall (int, int, int);*/
+
+static void join_sets(int, int);
+
+/* For set_create_maze. */
+/* The sets that our squares are in. */
+static int *sets = 0;
+/* The `list' of hedges. */
+static int *hedges = 0;
+
+#define DEBUG_SETS 0
+
+/* Initialise the sets. */
+static void 
+init_sets(void)
+{
+  int i, t, r, x, y;
+
+  if(sets)
+    free(sets);
+  sets = (int *)malloc(maze_size_x*maze_size_y*sizeof(int));
+  if(!sets)
+    abort();
+  for(i = 0; i < maze_size_x*maze_size_y; i++)
+    {
+      sets[i] = i;
+    }
+  
+  if(hedges)
+    free(hedges);
+  hedges = (int *)malloc(maze_size_x*maze_size_y*2*sizeof(int));
+  if(!hedges)
+    abort();
+  for(i = 0; i < maze_size_x*maze_size_y*2; i++)
+    {
+      hedges[i] = i;
+    }
+  /* Mask out outside walls. */
+  for(i = 0; i < maze_size_y; i++)
+    {
+      hedges[2*((maze_size_x)*i+maze_size_x-1)+1] = -1;
+    }
+  for(i = 0; i < maze_size_x; i++)
+    {
+      hedges[2*((maze_size_y-1)*maze_size_x+i)] = -1;
+    }
+  /* Mask out a possible logo. */
+  if(logo_x!=-1)
+    {
+      int logow = 1 + logo_width / grid_width;
+      int logoh = 1 + logo_height / grid_height;
+      int bridge_dir, bridge_c;
+
+      if(bridge_p && logoh>=3 && logow>=3)
+       {
+         bridge_dir = 1+random()%2;
+         if(bridge_dir==1)
+           {
+             bridge_c = logo_y+random()%(logoh-2)+1;
+           }
+         else
+           {
+             bridge_c = logo_x+random()%(logow-2)+1;
+           }
+       }
+      else
+       {
+         bridge_dir = 0;
+         bridge_c = -1;
+       }
+
+      for(x = logo_x; x < logo_x+logow; x++)
+       for(y = logo_y; y < logo_y+logoh; y++)
+         {
+           /* I should check for the bridge here, except that I join the
+             * bridge together below.
+             */
+           hedges[2*(x+maze_size_x*y)+1] = -1;
+           hedges[2*(x+maze_size_x*y)] = -1;
+         }
+      for(x = logo_x; x < logo_x+logow; x++)
+       {
+         if(!(bridge_dir==2 && x==bridge_c))
+           {
+             build_wall(x, logo_y, 0);
+             build_wall(x, logo_y+logoh, 0);
+           }
+         hedges[2*(x+maze_size_x*(logo_y-1))] = -1;
+         if(bridge_dir==1)
+           {
+             build_wall(x, bridge_c, 0);
+             build_wall(x, bridge_c, 2);
+           }
+       }
+      for(y = logo_y; y < logo_y+logoh; y++)
+       {
+         if(!(bridge_dir==1 && y==bridge_c))
+           {
+             build_wall(logo_x, y, 3);
+             build_wall(logo_x+logow, y, 3);
+           }
+         hedges[2*(logo_x-1+maze_size_x*y)+1] = -1;
+         if(bridge_dir==2)
+           {
+             build_wall(bridge_c, y, 1);
+             build_wall(bridge_c, y, 3);
+           }
+       }
+      /* Join the whole bridge together. */
+      if(bridge_p)
+       {
+         if(bridge_dir==1)
+           {
+             x = logo_x-1;
+             y = bridge_c;
+             for(i = logo_x; i < logo_x+logow+1; i++)
+               join_sets(x+y*maze_size_x, i+y*maze_size_x);
+           }
+         else
+           {
+             y = logo_y-1;
+             x = bridge_c;
+             for(i = logo_y; i < logo_y+logoh+1; i++)
+               join_sets(x+y*maze_size_x, x+i*maze_size_x);
+           }
+       }
+    }
+
+  for(i = 0; i < maze_size_x*maze_size_y*2; i++)
+    {
+      t = hedges[i];
+      r = random()%(maze_size_x*maze_size_y*2);
+      hedges[i] = hedges[r];
+      hedges[r] = t;
+    }
+}
+
+/* Get the representative of a set. */
+static int
+get_set(int num)
+{
+  int s;
+
+  if(sets[num]==num)
+    return num;
+  else
+    {
+      s = get_set(sets[num]);
+      sets[num] = s;
+      return s;
+    }
+}
 
+/* Join two sets together. */
 static void
-create_maze (void)    /* create a maze layout given the intiialized maze */
+join_sets(num1, num2)
+     int num1, num2;
+{
+  int s1, s2;
+
+  s1 = get_set(num1);
+  s2 = get_set(num2);
+  
+  if(s1<s2)
+    sets[s2] = s1;
+  else
+    sets[s1] = s2;
+}
+
+/* Exitialise the sets. */
+static void
+exit_sets(void)
+{
+  if(hedges)
+    free(hedges);
+  hedges = 0;
+  if(sets)
+    free(sets);
+  sets = 0;
+}
+
+#if DEBUG_SETS
+/* Temporary hack. */
+static void
+show_set(int num, GC gc)
+{
+  int x, y, set;
+
+  set = get_set(num);
+
+  for(x = 0; x < maze_size_x; x++)
+    for(y = 0; y < maze_size_y; y++)
+      {
+       if(get_set(x+y*maze_size_x)==set)
+         {
+           XFillRectangle(dpy, win, gc,  border_x + bw + grid_width * x, 
+                        border_y + bw + grid_height * y, 
+                        grid_width-2*bw , grid_height-2*bw);
+         }
+      }
+}
+#endif
+
+/* Second alternative maze creator: Put each square in the maze in a 
+ * separate set. Also, make a list of all the hedges. Randomize that list.
+ * Walk through the list. If, for a certain hedge, the two squares on both
+ * sides of it are in different sets, union the sets and remove the hedge.
+ * Continue until all hedges have been processed or only one set remains.
+ */
+static void
+set_create_maze(void)
+{
+  int i, h, x, y, dir, v, w;
+#if DEBUG_SETS
+  int cont = 0;
+  char c;
+#endif
+
+  /* Do almost all the setup. */
+  init_sets();
+
+  /* Start running through the hedges. */
+  for(i = 0; i < 2*maze_size_x*maze_size_y; i++)
+    { 
+      h = hedges[i];
+
+      /* This one is in the logo or outside border. */
+      if(h==-1)
+       continue;
+
+      dir = h%2?1:2;
+      x = (h>>1)%maze_size_x;
+      y = (h>>1)/maze_size_x;
+
+      v = x;
+      w = y;
+      switch(dir)
+       {
+       case 1:
+         v++;
+         break;
+       case 2:
+         w++;
+         break;
+       }
+
+#if DEBUG_SETS
+      show_set(x+y*maze_size_x, logo_gc);
+      show_set(v+w*maze_size_x, tgc);
+#endif
+      if(get_set(x+y*maze_size_x)!=get_set(v+w*maze_size_x))
+       {
+#if DEBUG_SETS
+         printf("Join!");
+#endif
+         join_sets(x+y*maze_size_x, v+w*maze_size_x);
+         /* Don't draw the wall. */
+       }
+      else
+       {
+#if DEBUG_SETS
+         printf("Build.");
+#endif
+         /* Don't join the sets. */
+         build_wall(x, y, dir); 
+       }
+#if DEBUG_SETS
+      if(!cont)
+       {
+         XSync(dpy, False);
+         c = getchar();
+         if(c=='c')
+           cont = 1;
+       }
+      show_set(x+y*maze_size_x, erase_gc);
+      show_set(v+w*maze_size_x, erase_gc);
+#endif
+    }
+
+  /* Free some memory. */
+  exit_sets();
+}
+
+/* First alternative maze creator: Pick a random, empty corner in the maze.
+ * Pick a random direction. Draw a wall in that direction, from that corner
+ * until we hit a wall. Option: Only draw the wall if it's going to be 
+ * shorter than a certain length. Otherwise we get lots of long walls.
+ */
+static void
+alt_create_maze(void)
+{
+  char *corners;
+  int *c_idx;
+  int i, j, height, width, open_corners, k, dir, x, y;
+
+  height = maze_size_y+1;
+  width = maze_size_x+1;
+
+  /* Allocate and clear some mem. */
+  corners = (char *)calloc(height*width, 1);
+  if(!corners)
+    return;
+
+  /* Set up the indexing array. */
+  c_idx = (int *)malloc(sizeof(int)*height*width);
+  if(!c_idx)
+    {
+      free(corners);
+      return;
+    }
+  for(i = 0; i < height*width; i++)
+    c_idx[i] = i;
+  for(i = 0; i < height*width; i++)
+    {
+      j = c_idx[i];
+      k = random()%(height*width);
+      c_idx[i] = c_idx[k];
+      c_idx[k] = j;
+    }
+
+  /* Set up some initial walls. */
+  /* Outside walls. */
+  for(i = 0; i < width; i++)
+    {
+      corners[i] = 1;
+      corners[i+width*(height-1)] = 1;
+    }
+  for(i = 0; i < height; i++)
+    {
+      corners[i*width] = 1;
+      corners[i*width+width-1] = 1;
+    }
+  /* Walls around logo. In fact, inside the logo, too. */
+  /* Also draw the walls. */
+  if(logo_x!=-1)
+    {
+      int logow = 1 + logo_width / grid_width;
+      int logoh = 1 + logo_height / grid_height;
+      int bridge_dir, bridge_c;
+
+      if(bridge_p && logoh>=3 && logow>=3)
+       {
+         bridge_dir = 1+random()%2;
+         if(bridge_dir==1)
+           {
+             bridge_c = logo_y+random()%(logoh-2)+1;
+           }
+         else
+           {
+             bridge_c = logo_x+random()%(logow-2)+1;
+           }
+       }
+      else
+       {
+         bridge_dir = 0;
+         bridge_c = -1;
+       }
+      for(i = logo_x; i <= logo_x + logow; i++)
+       {
+         for(j = logo_y; j <= logo_y + logoh; j++)
+           {
+             corners[i+width*j] = 1;
+           }
+       }
+      for(x = logo_x; x < logo_x+logow; x++)
+       {
+         if(!(bridge_dir==2 && x==bridge_c))
+           {
+             build_wall(x, logo_y, 0);
+             build_wall(x, logo_y+logoh, 0);
+           }
+         if(bridge_dir==1)
+           {
+             build_wall(x, bridge_c, 0);
+             build_wall(x, bridge_c, 2);
+           }
+       }
+      for(y = logo_y; y < logo_y+logoh; y++)
+       {
+         if(!(bridge_dir==1 && y==bridge_c))
+           {
+             build_wall(logo_x, y, 3);
+             build_wall(logo_x+logow, y, 3);
+           }
+         if(bridge_dir==2)
+           {
+             build_wall(bridge_c, y, 1);
+             build_wall(bridge_c, y, 3);
+           }
+       }
+      /* Connect one wall of the logo with an outside wall. */
+      if(bridge_p)
+       dir = (bridge_dir+1)%4;
+      else
+       dir = random()%4;
+      switch(dir)
+       {
+       case 0:
+         x = logo_x+(random()%(logow+1));
+         y = logo_y;
+         break;
+       case 1:
+         x = logo_x+logow;
+         y = logo_y+(random()%(logoh+1));
+         break;
+       case 2:
+         x = logo_x+(random()%(logow+1));
+         y = logo_y+logoh;
+         break;
+       case 3:
+         x = logo_x;
+         y = logo_y+(random()%(logoh+1));
+         break;
+       }
+      do
+       {
+         corners[x+width*y] = 1;
+         switch(dir)
+           {
+           case 0:
+             build_wall(x-1, y-1, 1);
+             y--;
+             break;
+           case 1:
+             build_wall(x, y, 0);
+             x++;
+             break;
+           case 2:
+             build_wall(x, y, 3);
+             y++;
+             break;
+           case 3:
+             build_wall(x-1, y-1, 2);
+             x--;
+             break;      
+           }
+       }
+      while(!corners[x+width*y]);
+      if(bridge_p)
+       {
+         dir = (dir+2)%4;
+         switch(dir)
+           {
+           case 0:
+             x = logo_x+(random()%(logow+1));
+             y = logo_y;
+             break;
+           case 1:
+             x = logo_x+logow;
+             y = logo_y+(random()%(logoh+1));
+             break;
+           case 2:
+             x = logo_x+(random()%(logow+1));
+             y = logo_y+logoh;
+             break;
+           case 3:
+             x = logo_x;
+             y = logo_y+(random()%(logoh+1));
+             break;
+           }
+         do
+           {
+             corners[x+width*y] = 1;
+             switch(dir)
+               {
+               case 0:
+                 build_wall(x-1, y-1, 1);
+                 y--;
+                 break;
+               case 1:
+                 build_wall(x, y, 0);
+                 x++;
+                 break;
+               case 2:
+                 build_wall(x, y, 3);
+                 y++;
+                 break;
+               case 3:
+                 build_wall(x-1, y-1, 2);
+                 x--;
+                 break;          
+               }
+           }
+         while(!corners[x+width*y]);
+       }
+    }
+
+  /* Count open gridpoints. */
+  open_corners = 0;
+  for(i = 0; i < width; i++)
+    for(j = 0; j < height; j++)
+      if(!corners[i+width*j])
+       open_corners++;
+
+  /* Now do actual maze generation. */
+  while(open_corners>0)
+    {
+      for(i = 0; i < width*height; i++)
+       {
+         if(!corners[c_idx[i]])
+           {
+             x = c_idx[i]%width;
+             y = c_idx[i]/width;
+             /* Choose a random direction. */
+             dir = random()%4;
+             
+             k = 0;
+             /* Measure the length of the wall we'd draw. */
+             while(!corners[x+width*y])
+               {
+                 k++;
+                 switch(dir)
+                   {
+                   case 0:
+                     y--;
+                     break;
+                   case 1:
+                     x++;
+                     break;
+                   case 2:
+                     y++;
+                     break;
+                   case 3:
+                     x--;
+                     break;
+                   }
+               }
+             
+             if(k<=max_length)
+               {
+                 x = c_idx[i]%width;
+                 y = c_idx[i]/width;
+                 
+                 /* Draw a wall until we hit something. */
+                 while(!corners[x+width*y])
+                   {
+                     open_corners--;
+                     corners[x+width*y] = 1;
+                     switch(dir)
+                       {
+                       case 0:
+                         build_wall(x-1, y-1, 1);
+                         y--;
+                         break;
+                       case 1:
+                         build_wall(x, y, 0);
+                         x++;
+                         break;
+                       case 2:
+                         build_wall(x, y, 3);
+                         y++;
+                         break;
+                       case 3:
+                         build_wall(x-1, y-1, 2);
+                         x--;
+                         break;
+                       }
+                   }
+               }
+           }
+       }
+    }
+
+  /* Free some memory we used. */
+  free(corners);
+  free(c_idx);
+}
+
+/* The original maze creator. Start somewhere. Take a step in a random 
+ * direction. Keep doing this until we hit a wall. Then, backtrack until
+ * we find a point where we can go in another direction.
+ */
+static void
+create_maze (void)    /* create a maze layout given the initialized maze */
 {
   register int i, newdoor = 0;
+  int logow = 1 + logo_width / grid_width;
+  int logoh = 1 + logo_height / grid_height;
   
+  /* Maybe we should make a bridge? */
+  if(bridge_p && logo_x>=0 && logow>=3 && logoh>=3)
+    {
+      int bridge_dir, bridge_c;
+
+      bridge_dir = 1+random()%2;
+      if(bridge_dir==1)
+       {
+         if(logoh>=3)
+           bridge_c = logo_y+random()%(logoh-2)+1;
+         else
+           bridge_c = logo_y+random()%logoh;
+       }
+      else
+       {
+         if(logow>=3)
+           bridge_c = logo_x+random()%(logow-2)+1;
+         else
+           bridge_c = logo_x+random()%logow;
+       }
+
+      if(bridge_dir==1)
+       {
+         for(i = logo_x; i < logo_x+logow; i++)
+           {
+             maze[i][bridge_c] &= ~DOOR_IN_TOP;
+           }
+       }
+      else
+       {
+         for(i = logo_y; i < logo_y+logoh; i++)
+           {
+             maze[bridge_c][i] &= ~DOOR_IN_TOP;
+           }
+       }
+    }
+
   do {
     move_list[sqnum].x = cur_sq_x;
     move_list[sqnum].y = cur_sq_y;
@@ -353,7 +970,7 @@ choose_door (void)                                   /* pick a new path */
   if ( maze[cur_sq_x][cur_sq_y - 1] & DOOR_IN_ANY ) {
     maze[cur_sq_x][cur_sq_y] |= WALL_TOP;
     maze[cur_sq_x][cur_sq_y - 1] |= WALL_BOTTOM;
-    draw_wall(cur_sq_x, cur_sq_y, 0);
+    draw_wall(cur_sq_x, cur_sq_y, 0, gc);
     goto rightwall;
   }
   candidates[num_candidates++] = 0;
@@ -369,7 +986,7 @@ choose_door (void)                                   /* pick a new path */
   if ( maze[cur_sq_x + 1][cur_sq_y] & DOOR_IN_ANY ) {
     maze[cur_sq_x][cur_sq_y] |= WALL_RIGHT;
     maze[cur_sq_x + 1][cur_sq_y] |= WALL_LEFT;
-    draw_wall(cur_sq_x, cur_sq_y, 1);
+    draw_wall(cur_sq_x, cur_sq_y, 1, gc);
     goto bottomwall;
   }
   candidates[num_candidates++] = 1;
@@ -385,7 +1002,7 @@ choose_door (void)                                   /* pick a new path */
   if ( maze[cur_sq_x][cur_sq_y + 1] & DOOR_IN_ANY ) {
     maze[cur_sq_x][cur_sq_y] |= WALL_BOTTOM;
     maze[cur_sq_x][cur_sq_y + 1] |= WALL_TOP;
-    draw_wall(cur_sq_x, cur_sq_y, 2);
+    draw_wall(cur_sq_x, cur_sq_y, 2, gc);
     goto leftwall;
   }
   candidates[num_candidates++] = 2;
@@ -401,7 +1018,7 @@ choose_door (void)                                   /* pick a new path */
   if ( maze[cur_sq_x - 1][cur_sq_y] & DOOR_IN_ANY ) {
     maze[cur_sq_x][cur_sq_y] |= WALL_LEFT;
     maze[cur_sq_x - 1][cur_sq_y] |= WALL_RIGHT;
-    draw_wall(cur_sq_x, cur_sq_y, 3);
+    draw_wall(cur_sq_x, cur_sq_y, 3, gc);
     goto donewall;
   }
   candidates[num_candidates++] = 3;
@@ -482,7 +1099,7 @@ draw_maze_border (void)                         /* draw the maze outline */
 
 
 static void
-draw_wall(int i, int j, int dir)                      /* draw a single wall */
+draw_wall(int i, int j, int dir, GC gc)                /* draw a single wall */
 {
   switch (dir) {
   case 0:
@@ -514,9 +1131,78 @@ draw_wall(int i, int j, int dir)                      /* draw a single wall */
              border_y + grid_height * (j+1));
     break;
   }
+  if(sync_p)
+    XSync(dpy, False);
 }
 
-static int bw;
+/* Actually build a wall. */
+static void
+build_wall(i, j, dir)
+     int i, j, dir;
+{
+  /* Draw it on the screen. */
+  draw_wall(i, j, dir, gc);
+  /* Put it in the maze. */
+  switch(dir)
+    {
+    case 0:
+      maze[i][j] |= WALL_TOP;
+      if(j>0)
+       maze[i][j-1] |= WALL_BOTTOM;
+      break;
+    case 1:
+      maze[i][j] |= WALL_RIGHT;
+      if(i<maze_size_x-1)
+       maze[i+1][j] |= WALL_LEFT;
+      break;
+    case 2:
+      maze[i][j] |= WALL_BOTTOM;
+      if(j<maze_size_y-1)
+       maze[i][j+1] |= WALL_TOP;
+      break;
+    case 3:
+      maze[i][j] |= WALL_LEFT;
+      if(i>0)
+       maze[i-1][j] |= WALL_RIGHT;
+      break;
+    }
+}
+
+/* Break out a wall. */
+#if 0
+static void
+break_wall(i, j, dir)
+     int i, j, dir;
+{
+  /* Draw it on the screen. */
+  draw_wall(i, j, dir, erase_gc);
+  /* Put it in the maze. */
+  switch(dir)
+    {
+    case 0:
+      maze[i][j] &= ~WALL_TOP;
+      if(j>0)
+       maze[i][j-1] &= ~WALL_BOTTOM;
+      break;
+    case 1:
+      maze[i][j] &= ~WALL_RIGHT;
+      if(i<maze_size_x-1)
+       maze[i+1][j] &= ~WALL_LEFT;
+      break;
+    case 2:
+      maze[i][j] &= ~WALL_BOTTOM;
+      if(j<maze_size_y-1)
+       maze[i][j+1] &= ~WALL_BOTTOM;
+      break;
+    case 3:
+      maze[i][j] &= ~WALL_LEFT;
+      if(i>0)
+       maze[i-1][j] &= ~WALL_RIGHT;
+      break;
+    }
+}
+#endif /* 0 */
+
 
 static void
 draw_solid_square(int i, int j,          /* draw a solid square in a square */
@@ -552,8 +1238,9 @@ static void
 solve_maze (void)                     /* solve it with graphical feedback */
 {
   int i;
-  
-  
+  int step_x[4] = { 0, 1, 0, -1 };
+  int step_y[4] = { -1, 0, 1, 0 };
+    
   /* plug up the surrounding wall */
   maze[start_x][start_y] |= (WALL_TOP >> start_dir);
   maze[end_x][end_y] |= (WALL_TOP >> end_dir);
@@ -563,6 +1250,7 @@ solve_maze (void)                     /* solve it with graphical feedback */
   path[i].x = end_x;
   path[i].y = end_y;
   path[i].dir = -1;
+  maze[end_x][end_y] |= SOLVER_VISIT;
   
   /* do it */
   while (1) {
@@ -572,15 +1260,23 @@ solve_maze (void)                     /* solve it with graphical feedback */
                     border_y + bw + grid_height * (int)(path[i].y),
                     grid_width - (bw+bw), grid_height - (bw+bw));
       i--;
+      if(i<0) /* Can't solve this maze. */
+       {
+         printf("Unsolvable maze.\n");
+         return;
+       }
       draw_solid_square( (int)(path[i].x), (int)(path[i].y), 
                        (int)(path[i].dir), cgc);
     }
-    else if ( ! (maze[path[i].x][path[i].y] & 
-                (WALL_TOP >> path[i].dir))  && 
-            ( (i == 0) || ( (path[i].dir != 
-                             (int)(path[i-1].dir+2)%4) ) ) ) {
-      enter_square(i);
+    else if ( (! (maze[path[i].x][path[i].y] & (WALL_TOP >> path[i].dir))) && 
+            (!( maze[path[i].x+step_x[path[i].dir]]
+                   [path[i].y+step_y[path[i].dir]]&SOLVER_VISIT)) ) {
+      path[i+1].x = path[i].x+step_x[path[i].dir];
+      path[i+1].y = path[i].y+step_y[path[i].dir];
+      path[i+1].dir = -1;
+      draw_solid_square(path[i].x, path[i].y, path[i].dir, tgc);
       i++;
+      maze[path[i].x][path[i].y] |= SOLVER_VISIT;
       if ( maze[path[i].x][path[i].y] & START_SQUARE ) {
        return;
       }
@@ -592,6 +1288,7 @@ solve_maze (void)                     /* solve it with graphical feedback */
 } 
 
 
+#if 0
 static void
 enter_square (int n)                      /* move into a neighboring square */
 {
@@ -614,6 +1311,7 @@ enter_square (int n)                      /* move into a neighboring square */
     break;
   }
 }
+#endif /* 0 */
 
 
 /*
@@ -633,6 +1331,10 @@ char *defaults[] = {
   "*postDelay: 4000000",
   "*liveColor: green",
   "*deadColor: red",
+  "*generator:  -1",
+  "*maxLength:  5",
+  "*syncDraw:   False",
+  "*bridge:     False",
 #ifdef XROGER
   "*logoColor: red3",
 #endif
@@ -646,6 +1348,10 @@ XrmOptionDescRec options[] = {
   { "-post-delay",     ".postDelay",   XrmoptionSepArg, 0 },
   { "-live-color",     ".liveColor",   XrmoptionSepArg, 0 },
   { "-dead-color",     ".deadColor",   XrmoptionSepArg, 0 },
+  { "-generator",       ".generator",   XrmoptionSepArg, 0 },
+  { "-max-length",      ".maxLength",   XrmoptionSepArg, 0 },
+  { "-bridge",          ".bridge",      XrmoptionNoArg, "True" },
+  { "-no-bridge",       ".bridge",      XrmoptionNoArg, "False" },
   { 0, 0, 0, 0 }
 };
 
@@ -657,7 +1363,7 @@ void
 screenhack(Display *display, Window window)
 {
   Pixmap gray;
-  int size, root;
+  int size, root, generator, this_gen;
   XWindowAttributes xgwa;
   unsigned long bg, fg, pfg, pbg, lfg;
 
@@ -666,6 +1372,9 @@ screenhack(Display *display, Window window)
   solve_delay = get_integer_resource ("solveDelay", "Integer");
   pre_solve_delay = get_integer_resource ("preDelay", "Integer");
   post_solve_delay = get_integer_resource ("postDelay", "Integer");
+  generator = get_integer_resource("generator", "Integer");
+  max_length = get_integer_resource("maxLength", "Integer");
+  bridge_p = get_boolean_resource("bridge", "Boolean");
 
   if (size < 2) size = 7 + (random () % 30);
   grid_width = grid_height = size;
@@ -687,6 +1396,7 @@ screenhack(Display *display, Window window)
   cgc = XCreateGC(dpy, win, 0, 0);
   tgc = XCreateGC(dpy,win,0,0);
   logo_gc = XCreateGC(dpy, win, 0, 0);
+  erase_gc = XCreateGC(dpy, win, 0, 0);
   
   gray = XCreateBitmapFromData (dpy,win,gray1_bits,gray1_width,gray1_height);
 
@@ -710,6 +1420,8 @@ screenhack(Display *display, Window window)
   XSetBackground (dpy, tgc, bg);
   XSetForeground (dpy, logo_gc, lfg);
   XSetBackground (dpy, logo_gc, bg);
+  XSetForeground (dpy, erase_gc, bg);
+  XSetBackground (dpy, erase_gc, bg);
 
   XSetStipple (dpy, cgc, gray);
   XSetFillStyle (dpy, cgc, FillOpaqueStippled);
@@ -741,10 +1453,11 @@ screenhack(Display *display, Window window)
     }
 #endif
   XMapRaised(dpy, win);
-  srandom(getpid());
 
   restart = root;
 
+  sync_p = !(random() % 10);
+
   while (1) {                            /* primary execution loop [ rhess ] */
     if (check_events()) continue ;
     if (restart || stop) goto pop;
@@ -757,7 +1470,22 @@ screenhack(Display *display, Window window)
       draw_maze_border();
       break;
     case 3:
-      create_maze();
+      this_gen = generator;
+      if(this_gen<0 || this_gen>2)
+       this_gen = random()%3;
+
+      switch(this_gen)
+       {
+       case 0:
+         create_maze();
+         break;
+       case 1:
+         alt_create_maze();
+         break;
+       case 2:
+         set_create_maze();
+         break;
+       }
       break;
     case 4:
       XSync (dpy, False);
@@ -786,6 +1514,7 @@ screenhack(Display *display, Window window)
        set_maze_sizes (wattr.width, wattr.height);
        XClearWindow (dpy, win);
        XSync (dpy, False);
+       sync_p = !(random() % 10);
       }
   }
 }