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+/* penrose-legacy.h: legacy Penrose tiling functions.
+ *
+ * Provides an interface with which to generate Penrose tilings
+ * by recursive subdivision of an initial tile of choice (one of the
+ * four sets of two pairs kite/dart, or thin/thick rhombus).
+ *
+ * You supply a callback function and a context pointer, which is
+ * called with each tile in turn: you choose how many times to recurse.
+ *
+ * This method of generating Penrose tiling fragments is superseded by
+ * the completely different algorithm in penrose.c. We keep the legacy
+ * algorithm around only for interpreting Loopy game IDs generated by
+ * older versions of the code.
+ */
+
+#ifndef PUZZLES_PENROSE_LEGACY_H
+#define PUZZLES_PENROSE_LEGACY_H
+
+#ifndef PHI
+#define PHI 1.6180339887
+#endif
+
+typedef struct vector vector;
+
+double penrose_legacy_vx(vector *vs, int i);
+double penrose_legacy_vy(vector *vs, int i);
+
+typedef struct penrose_legacy_state penrose_legacy_state;
+
+/* Return non-zero to clip the tree here (i.e. not recurse
+ * below this tile).
+ *
+ * Parameters are state, vector array, npoints, depth.
+ * ctx is inside state.
+ */
+typedef int (*tile_callback)(penrose_legacy_state *, vector *, int, int);
+
+struct penrose_legacy_state {
+    int start_size;  /* initial side length */
+    int max_depth;      /* Recursion depth */
+
+    tile_callback new_tile;
+    void *ctx;          /* for callback */
+};
+
+#ifndef PENROSE_ENUM_DEFINED
+#define PENROSE_ENUM_DEFINED
+enum { PENROSE_P2, PENROSE_P3 };
+#endif
+
+extern int penrose_legacy(penrose_legacy_state *state, int which, int angle);
+
+/* Returns the side-length of a penrose tile at recursion level
+ * gen, given a starting side length. */
+extern double penrose_legacy_side_length(double start_size, int depth);
+
+/* Calculate start size and recursion depth required to produce a
+ * width-by-height sized patch of penrose tiles with the given tilesize */
+extern void penrose_legacy_calculate_size(
+    int which, int tilesize, int w, int h,
+    double *required_radius, int *start_size, int *depth);
+
+#endif