New grid type: compass dodecagonal

A grid based on dodecagons with square symmetry. In between dodecagons
there are 4 triangles around 1 square, which resembles a compass rose.
https://en.wikipedia.org/wiki/3-4-3-12_tiling

grid.c

@@ -2747,7 +2747,7 @@ static grid *grid_new_greatgreatdodecagonal(int width, int height, const char *d
                 d = grid_get_dot(g, points, px + (2*a + 2*b), py - 2*a); grid_face_set_dot(g, d, 5);
             }
 
-            /* hexagon on bottom right  of dodecagon */
+            /* hexagon on bottom right of dodecagon */
             if ((y < height - 1) && (x < width - 1 || !(y % 2))) {
                 grid_face_add_new(g, 6);
                 d = grid_get_dot(g, points, px + (a + 2*b), py + (2*a + b)); grid_face_set_dot(g, d, 0);
@@ -2839,6 +2839,102 @@ static grid *grid_new_greatgreatdodecagonal(int width, int height, const char *d
     return g;
 }
 
+static void grid_size_compassdodecagonal(int width, int height,
+                                         int *tilesize, int *xextent, int *yextent)
+{
+    int a = DODEC_A;
+    int b = DODEC_B;
+
+    *tilesize = DODEC_TILESIZE;
+    *xextent = (4*a + 2*b) * width;
+    *yextent = (4*a + 2*b) * height;
+}
+
+static grid *grid_new_compassdodecagonal(int width, int height, const char *desc)
+{
+    int x, y;
+    /* Vector for side of triangle - ratio is close to sqrt(3) */
+    int a = DODEC_A;
+    int b = DODEC_B;
+
+    /* Upper bounds - don't have to be exact */
+    int max_faces = 6 * width * height;
+    int max_dots = 18 * width * height;
+
+    tree234 *points;
+
+    grid *g = grid_empty();
+    g->tilesize = DODEC_TILESIZE;
+    g->faces = snewn(max_faces, grid_face);
+    g->dots = snewn(max_dots, grid_dot);
+
+    points = newtree234(grid_point_cmp_fn);
+
+    for (y = 0; y < height; y++) {
+        for (x = 0; x < width; x++) {
+            grid_dot *d;
+            /* centre of dodecagon */
+            int px = (4*a + 2*b) * x;
+            int py = (4*a + 2*b) * y;
+
+            /* dodecagon */
+            grid_face_add_new(g, 12);
+            d = grid_get_dot(g, points, px + (  a    ), py - (2*a + b)); grid_face_set_dot(g, d, 0);
+            d = grid_get_dot(g, points, px + (  a + b), py - (  a + b)); grid_face_set_dot(g, d, 1);
+            d = grid_get_dot(g, points, px + (2*a + b), py - (  a    )); grid_face_set_dot(g, d, 2);
+            d = grid_get_dot(g, points, px + (2*a + b), py + (  a    )); grid_face_set_dot(g, d, 3);
+            d = grid_get_dot(g, points, px + (  a + b), py + (  a + b)); grid_face_set_dot(g, d, 4);
+            d = grid_get_dot(g, points, px + (  a    ), py + (2*a + b)); grid_face_set_dot(g, d, 5);
+            d = grid_get_dot(g, points, px - (  a    ), py + (2*a + b)); grid_face_set_dot(g, d, 6);
+            d = grid_get_dot(g, points, px - (  a + b), py + (  a + b)); grid_face_set_dot(g, d, 7);
+            d = grid_get_dot(g, points, px - (2*a + b), py + (  a    )); grid_face_set_dot(g, d, 8);
+            d = grid_get_dot(g, points, px - (2*a + b), py - (  a    )); grid_face_set_dot(g, d, 9);
+            d = grid_get_dot(g, points, px - (  a + b), py - (  a + b)); grid_face_set_dot(g, d, 10);
+            d = grid_get_dot(g, points, px - (  a    ), py - (2*a + b)); grid_face_set_dot(g, d, 11);
+
+            if (x < width - 1 && y < height - 1) {
+                /* north triangle */
+                grid_face_add_new(g, 3);
+                d = grid_get_dot(g, points, px + (2*a + b), py + (  a    )); grid_face_set_dot(g, d, 0);
+                d = grid_get_dot(g, points, px + (3*a + b), py + (  a + b)); grid_face_set_dot(g, d, 1);
+                d = grid_get_dot(g, points, px + (  a + b), py + (  a + b)); grid_face_set_dot(g, d, 2);
+
+                /* east triangle */
+                grid_face_add_new(g, 3);
+                d = grid_get_dot(g, points, px + (3*a + 2*b), py + (2*a + b)); grid_face_set_dot(g, d, 0);
+                d = grid_get_dot(g, points, px + (3*a +   b), py + (3*a + b)); grid_face_set_dot(g, d, 1);
+                d = grid_get_dot(g, points, px + (3*a +   b), py + (  a + b)); grid_face_set_dot(g, d, 2);
+
+                /* south triangle */
+                grid_face_add_new(g, 3);
+                d = grid_get_dot(g, points, px + (3*a + b), py + (3*a +   b)); grid_face_set_dot(g, d, 0);
+                d = grid_get_dot(g, points, px + (2*a + b), py + (3*a + 2*b)); grid_face_set_dot(g, d, 1);
+                d = grid_get_dot(g, points, px + (  a + b), py + (3*a +   b)); grid_face_set_dot(g, d, 2);
+
+                /* west triangle */
+                grid_face_add_new(g, 3);
+                d = grid_get_dot(g, points, px + (a + b), py + (  a + b)); grid_face_set_dot(g, d, 0);
+                d = grid_get_dot(g, points, px + (a + b), py + (3*a + b)); grid_face_set_dot(g, d, 1);
+                d = grid_get_dot(g, points, px + (a    ), py + (2*a + b)); grid_face_set_dot(g, d, 2);
+
+                /* square in center */
+                grid_face_add_new(g, 4);
+                d = grid_get_dot(g, points, px + (3*a + b), py + (  a + b)); grid_face_set_dot(g, d, 0);
+                d = grid_get_dot(g, points, px + (3*a + b), py + (3*a + b)); grid_face_set_dot(g, d, 1);
+                d = grid_get_dot(g, points, px + (  a + b), py + (3*a + b)); grid_face_set_dot(g, d, 2);
+                d = grid_get_dot(g, points, px + (  a + b), py + (  a + b)); grid_face_set_dot(g, d, 3);
+            }
+        }
+    }
+
+    freetree234(points);
+    assert(g->num_faces <= max_faces);
+    assert(g->num_dots <= max_dots);
+
+    grid_make_consistent(g);
+    return g;
+}
+
 typedef struct setface_ctx
 {
     int xmin, xmax, ymin, ymax;

grid.h

@@ -107,6 +107,7 @@ typedef struct grid {
   A(DODECAGONAL,dodecagonal) \
   A(GREATDODECAGONAL,greatdodecagonal) \
   A(GREATGREATDODECAGONAL,greatgreatdodecagonal) \
+  A(COMPASSDODECAGONAL,compassdodecagonal) \
   A(PENROSE_P2,penrose_p2_kite) \
   A(PENROSE_P3,penrose_p3_thick)
 

loopy.c

@@ -279,6 +279,7 @@ static void check_caches(const solver_state* sstate);
     A("Penrose (rhombs)",PENROSE_P3,3,3)                        \
     A("Great-Great-Dodecagonal",GREATGREATDODECAGONAL,2,2)      \
     A("Kagome",KAGOME,3,3)                                      \
+    A("Compass-Dodecagonal",COMPASSDODECAGONAL,2,2)             \
     /* end of list */
 
 #define GRID_NAME(title,type,amin,omin) title,
@@ -552,6 +553,7 @@ static const game_params loopy_presets_more[] = {
     {  3,  3, DIFF_HARD,   LOOPY_GRID_DODECAGONAL },
     {  3,  3, DIFF_HARD,   LOOPY_GRID_GREATDODECAGONAL },
     {  3,  2, DIFF_HARD,   LOOPY_GRID_GREATGREATDODECAGONAL },
+    {  3,  3, DIFF_HARD,   LOOPY_GRID_COMPASSDODECAGONAL },
 #else
     { 10, 10, DIFF_HARD,   LOOPY_GRID_HONEYCOMB },
     {  5,  4, DIFF_HARD,   LOOPY_GRID_GREATHEXAGONAL },
@@ -561,6 +563,7 @@ static const game_params loopy_presets_more[] = {
     {  5,  4, DIFF_HARD,   LOOPY_GRID_DODECAGONAL },
     {  5,  4, DIFF_HARD,   LOOPY_GRID_GREATDODECAGONAL },
     {  5,  3, DIFF_HARD,   LOOPY_GRID_GREATGREATDODECAGONAL },
+    {  5,  4, DIFF_HARD,   LOOPY_GRID_COMPASSDODECAGONAL },
 #endif
 };