Completely re-engineered version of Loopy, courtesy of Lambros

Lambrou. Now capable of handling triangular and hexagonal grids as
well as square ones, and then a number of semiregular plane tilings
and duals of semiregular ones. In fact, most of the solver code
supports an _arbitrary_ planar graph (well, provided both the graph
and its dual have no self-edges), so it could easily be extended
further with only a little more effort.

[originally from svn r8162]

1 files changed, 96 insertions, 0 deletions

diff --git a/grid.h b/grid.h
new file mode 100644
index 0000000..0116074
--- /dev/null
+++ b/grid.h
@@ -0,0 +1,96 @@
+/*
+ * (c) Lambros Lambrou 2008
+ *
+ * Code for working with general grids, which can be any planar graph
+ * with faces, edges and vertices (dots).  Includes generators for a few
+ * types of grid, including square, hexagonal, triangular and others.
+ */
+
+#ifndef PUZZLES_GRID_H
+#define PUZZLES_GRID_H
+
+/* Useful macros */
+#ifndef SQ
+#  define SQ(x) ( (x) * (x) )
+#endif
+
+/* ----------------------------------------------------------------------
+ * Grid structures:
+ * A grid is made up of faces, edges and dots.  These structures hold
+ * the incidence relationships between these types.  For example, an
+ * edge always joins two dots, and is adjacent to two faces.
+ * The "grid_xxx **" members are lists of pointers which are dynamically
+ * allocated during grid generation.
+ * A pointer to a face/edge/dot will always point somewhere inside one of the
+ * three lists of the main "grid" structure: faces, edges, dots.
+ * Could have used integer offsets into these lists, but using actual
+ * pointers instead gives us type-safety.
+ */
+
+/* Need forward declarations */
+typedef struct grid_face grid_face;
+typedef struct grid_edge grid_edge;
+typedef struct grid_dot grid_dot;
+
+struct grid_face {
+  int order; /* Number of edges, also the number of dots */
+  grid_edge **edges; /* edges around this face */
+  grid_dot **dots; /* corners of this face */
+};
+struct grid_edge {
+  grid_dot *dot1, *dot2;
+  grid_face *face1, *face2; /* Use NULL for the infinite outside face */
+};
+struct grid_dot {
+  int order;
+  grid_edge **edges;
+  grid_face **faces; /* A NULL grid_face* means infinite outside face */
+
+  /* Position in some fairly arbitrary (Cartesian) coordinate system.
+   * Use large enough values such that we can get away with
+   * integer arithmetic, but small enough such that arithmetic
+   * won't overflow. */
+  int x, y;
+};
+typedef struct grid {
+  /* These are (dynamically allocated) arrays of all the
+   * faces, edges, dots that are in the grid. */
+  int num_faces; grid_face *faces;
+  int num_edges; grid_edge *edges;
+  int num_dots;  grid_dot *dots;
+
+  /* Should be a face roughly near the middle of the grid.
+   * Used to seed path-generation, and also for nearest-edge
+   * detection. */
+  grid_face *middle_face;
+
+  /* Cache the bounding-box of the grid, so the drawing-code can quickly
+   * figure out the proper scaling to draw onto a given area. */
+  int lowest_x, lowest_y, highest_x, highest_y;
+
+  /* A measure of tile size for this grid (in grid coordinates), to help
+   * the renderer decide how large to draw the grid.
+   * Roughly the size of a single tile - for example the side-length
+   * of a square cell. */
+  int tilesize;
+
+  /* We really don't want to copy this monstrosity!
+   * A grid is immutable once generated.
+   */
+  int refcount;
+} grid;
+
+grid *grid_new_square(int width, int height);
+grid *grid_new_honeycomb(int width, int height);
+grid *grid_new_triangular(int width, int height);
+grid *grid_new_snubsquare(int width, int height);
+grid *grid_new_cairo(int width, int height);
+grid *grid_new_greathexagonal(int width, int height);
+grid *grid_new_octagonal(int width, int height);
+grid *grid_new_kites(int width, int height);
+
+void grid_free(grid *g);
+
+grid_edge *grid_nearest_edge(grid *g, int x, int y);
+
+#endif /* PUZZLES_GRID_H */