1 files changed, 1340 insertions, 0 deletions

diff --git a/apps/plugins/puzzles/src/pegs.c b/apps/plugins/puzzles/src/pegs.c
new file mode 100644
index 0000000000..8286851954
--- /dev/null
+++ b/apps/plugins/puzzles/src/pegs.c
@@ -0,0 +1,1340 @@
+/*
+ * pegs.c: the classic Peg Solitaire game.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <ctype.h>
+#include <math.h>
+
+#include "puzzles.h"
+#include "tree234.h"
+
+#define GRID_HOLE 0
+#define GRID_PEG  1
+#define GRID_OBST 2
+
+#define GRID_CURSOR 10
+#define GRID_JUMPING 20
+
+enum {
+    COL_BACKGROUND,
+    COL_HIGHLIGHT,
+    COL_LOWLIGHT,
+    COL_PEG,
+    COL_CURSOR,
+    NCOLOURS
+};
+
+/*
+ * Grid shapes. I do some macro ickery here to ensure that my enum
+ * and the various forms of my name list always match up.
+ */
+#define TYPELIST(A) \
+    A(CROSS,Cross,cross) \
+    A(OCTAGON,Octagon,octagon) \
+    A(RANDOM,Random,random)
+#define ENUM(upper,title,lower) TYPE_ ## upper,
+#define TITLE(upper,title,lower) #title,
+#define LOWER(upper,title,lower) #lower,
+#define CONFIG(upper,title,lower) ":" #title
+
+enum { TYPELIST(ENUM) TYPECOUNT };
+static char const *const pegs_titletypes[] = { TYPELIST(TITLE) };
+static char const *const pegs_lowertypes[] = { TYPELIST(LOWER) };
+#define TYPECONFIG TYPELIST(CONFIG)
+
+#define FLASH_FRAME 0.13F
+
+struct game_params {
+    int w, h;
+    int type;
+};
+
+struct game_state {
+    int w, h;
+    int completed;
+    unsigned char *grid;
+};
+
+static game_params *default_params(void)
+{
+    game_params *ret = snew(game_params);
+
+    ret->w = ret->h = 7;
+    ret->type = TYPE_CROSS;
+
+    return ret;
+}
+
+static const struct game_params pegs_presets[] = {
+    {7, 7, TYPE_CROSS},
+    {7, 7, TYPE_OCTAGON},
+    {5, 5, TYPE_RANDOM},
+    {7, 7, TYPE_RANDOM},
+    {9, 9, TYPE_RANDOM},
+};
+
+static int game_fetch_preset(int i, char **name, game_params **params)
+{
+    game_params *ret;
+    char str[80];
+
+    if (i < 0 || i >= lenof(pegs_presets))
+        return FALSE;
+
+    ret = snew(game_params);
+    *ret = pegs_presets[i];
+
+    strcpy(str, pegs_titletypes[ret->type]);
+    if (ret->type == TYPE_RANDOM)
+        sprintf(str + strlen(str), " %dx%d", ret->w, ret->h);
+
+    *name = dupstr(str);
+    *params = ret;
+    return TRUE;
+}
+
+static void free_params(game_params *params)
+{
+    sfree(params);
+}
+
+static game_params *dup_params(const game_params *params)
+{
+    game_params *ret = snew(game_params);
+    *ret = *params;                    /* structure copy */
+    return ret;
+}
+
+static void decode_params(game_params *params, char const *string)
+{
+    char const *p = string;
+    int i;
+
+    params->w = atoi(p);
+    while (*p && isdigit((unsigned char)*p)) p++;
+    if (*p == 'x') {
+        p++;
+        params->h = atoi(p);
+        while (*p && isdigit((unsigned char)*p)) p++;
+    } else {
+        params->h = params->w;
+    }
+
+    for (i = 0; i < lenof(pegs_lowertypes); i++)
+        if (!strcmp(p, pegs_lowertypes[i]))
+            params->type = i;
+}
+
+static char *encode_params(const game_params *params, int full)
+{
+    char str[80];
+
+    sprintf(str, "%dx%d", params->w, params->h);
+    if (full) {
+        assert(params->type >= 0 && params->type < lenof(pegs_lowertypes));
+        strcat(str, pegs_lowertypes[params->type]);
+    }
+    return dupstr(str);
+}
+
+static config_item *game_configure(const game_params *params)
+{
+    config_item *ret = snewn(4, config_item);
+    char buf[80];
+
+    ret[0].name = "Width";
+    ret[0].type = C_STRING;
+    sprintf(buf, "%d", params->w);
+    ret[0].sval = dupstr(buf);
+    ret[0].ival = 0;
+
+    ret[1].name = "Height";
+    ret[1].type = C_STRING;
+    sprintf(buf, "%d", params->h);
+    ret[1].sval = dupstr(buf);
+    ret[1].ival = 0;
+
+    ret[2].name = "Board type";
+    ret[2].type = C_CHOICES;
+    ret[2].sval = TYPECONFIG;
+    ret[2].ival = params->type;
+
+    ret[3].name = NULL;
+    ret[3].type = C_END;
+    ret[3].sval = NULL;
+    ret[3].ival = 0;
+
+    return ret;
+}
+
+static game_params *custom_params(const config_item *cfg)
+{
+    game_params *ret = snew(game_params);
+
+    ret->w = atoi(cfg[0].sval);
+    ret->h = atoi(cfg[1].sval);
+    ret->type = cfg[2].ival;
+
+    return ret;
+}
+
+static char *validate_params(const game_params *params, int full)
+{
+    if (full && (params->w <= 3 || params->h <= 3))
+        return "Width and height must both be greater than three";
+
+    /*
+     * It might be possible to implement generalisations of Cross
+     * and Octagon, but only if I can find a proof that they're all
+     * soluble. For the moment, therefore, I'm going to disallow
+     * them at any size other than the standard one.
+     */
+    if (full && (params->type == TYPE_CROSS || params->type == TYPE_OCTAGON)) {
+        if (params->w != 7 || params->h != 7)
+            return "This board type is only supported at 7x7";
+    }
+    return NULL;
+}
+
+/* ----------------------------------------------------------------------
+ * Beginning of code to generate random Peg Solitaire boards.
+ * 
+ * This procedure is done with no aesthetic judgment, no effort at
+ * symmetry, no difficulty grading and generally no finesse
+ * whatsoever. We simply begin with an empty board containing a
+ * single peg, and repeatedly make random reverse moves until it's
+ * plausibly full. This typically yields a scrappy haphazard mess
+ * with several holes, an uneven shape, and no redeeming features
+ * except guaranteed solubility.
+ *
+ * My only concessions to sophistication are (a) to repeat the
+ * generation process until I at least get a grid that touches
+ * every edge of the specified board size, and (b) to try when
+ * selecting moves to reuse existing space rather than expanding
+ * into new space (so that non-rectangular board shape becomes a
+ * factor during play).
+ */
+
+struct move {
+    /*
+     * x,y are the start point of the move during generation (hence
+     * its endpoint during normal play).
+     * 
+     * dx,dy are the direction of the move during generation.
+     * Absolute value 1. Hence, for example, x=3,y=5,dx=1,dy=0
+     * means that the move during generation starts at (3,5) and
+     * ends at (5,5), and vice versa during normal play.
+     */
+    int x, y, dx, dy;
+    /*
+     * cost is 0, 1 or 2, depending on how many GRID_OBSTs we must
+     * turn into GRID_HOLEs to play this move.
+     */
+    int cost;
+};
+
+static int movecmp(void *av, void *bv)
+{
+    struct move *a = (struct move *)av;
+    struct move *b = (struct move *)bv;
+
+    if (a->y < b->y)
+        return -1;
+    else if (a->y > b->y)
+        return +1;
+
+    if (a->x < b->x)
+        return -1;
+    else if (a->x > b->x)
+        return +1;
+
+    if (a->dy < b->dy)
+        return -1;
+    else if (a->dy > b->dy)
+        return +1;
+
+    if (a->dx < b->dx)
+        return -1;
+    else if (a->dx > b->dx)
+        return +1;
+
+    return 0;
+}
+
+static int movecmpcost(void *av, void *bv)
+{
+    struct move *a = (struct move *)av;
+    struct move *b = (struct move *)bv;
+
+    if (a->cost < b->cost)
+        return -1;
+    else if (a->cost > b->cost)
+        return +1;
+
+    return movecmp(av, bv);
+}
+
+struct movetrees {
+    tree234 *bymove, *bycost;
+};
+
+static void update_moves(unsigned char *grid, int w, int h, int x, int y,
+                         struct movetrees *trees)
+{
+    struct move move;
+    int dir, pos;
+
+    /*
+     * There are twelve moves that can include (x,y): three in each
+     * of four directions. Check each one to see if it's possible.
+     */
+    for (dir = 0; dir < 4; dir++) {
+        int dx, dy;
+
+        if (dir & 1)
+            dx = 0, dy = dir - 2;
+        else
+            dy = 0, dx = dir - 1;
+
+        assert(abs(dx) + abs(dy) == 1);
+
+        for (pos = 0; pos < 3; pos++) {
+            int v1, v2, v3;
+
+            move.dx = dx;
+            move.dy = dy;
+            move.x = x - pos*dx;
+            move.y = y - pos*dy;
+
+            if (move.x < 0 || move.x >= w || move.y < 0 || move.y >= h)
+                continue;              /* completely invalid move */
+            if (move.x+2*move.dx < 0 || move.x+2*move.dx >= w ||
+                move.y+2*move.dy < 0 || move.y+2*move.dy >= h)
+                continue;              /* completely invalid move */
+
+            v1 = grid[move.y * w + move.x];
+            v2 = grid[(move.y+move.dy) * w + (move.x+move.dx)];
+            v3 = grid[(move.y+2*move.dy)*w + (move.x+2*move.dx)];
+            if (v1 == GRID_PEG && v2 != GRID_PEG && v3 != GRID_PEG) {
+                struct move *m;
+
+                move.cost = (v2 == GRID_OBST) + (v3 == GRID_OBST);
+
+                /*
+                 * This move is possible. See if it's already in
+                 * the tree.
+                 */
+                m = find234(trees->bymove, &move, NULL);
+                if (m && m->cost != move.cost) {
+                    /*
+                     * It's in the tree but listed with the wrong
+                     * cost. Remove the old version.
+                     */
+#ifdef GENERATION_DIAGNOSTICS
+                    printf("correcting %d%+d,%d%+d at cost %d\n",
+                           m->x, m->dx, m->y, m->dy, m->cost);
+#endif
+                    del234(trees->bymove, m);
+                    del234(trees->bycost, m);
+                    sfree(m);
+                    m = NULL;
+                }
+                if (!m) {
+                    struct move *m, *m2;
+                    m = snew(struct move);
+                    *m = move;
+                    m2 = add234(trees->bymove, m);
+                    m2 = add234(trees->bycost, m);
+                    assert(m2 == m);
+#ifdef GENERATION_DIAGNOSTICS
+                    printf("adding %d%+d,%d%+d at cost %d\n",
+                           move.x, move.dx, move.y, move.dy, move.cost);
+#endif
+                } else {
+#ifdef GENERATION_DIAGNOSTICS
+                    printf("not adding %d%+d,%d%+d at cost %d\n",
+                           move.x, move.dx, move.y, move.dy, move.cost);
+#endif
+                }
+            } else {
+                /*
+                 * This move is impossible. If it is already in the
+                 * tree, delete it.
+                 * 
+                 * (We make use here of the fact that del234
+                 * doesn't have to be passed a pointer to the
+                 * _actual_ element it's deleting: it merely needs
+                 * one that compares equal to it, and it will
+                 * return the one it deletes.)
+                 */
+                struct move *m = del234(trees->bymove, &move);
+#ifdef GENERATION_DIAGNOSTICS
+                printf("%sdeleting %d%+d,%d%+d\n", m ? "" : "not ",
+                       move.x, move.dx, move.y, move.dy);
+#endif
+                if (m) {
+                    del234(trees->bycost, m);
+                    sfree(m);
+                }
+            }
+        }
+    }
+}
+
+static void pegs_genmoves(unsigned char *grid, int w, int h, random_state *rs)
+{
+    struct movetrees atrees, *trees = &atrees;
+    struct move *m;
+    int x, y, i, nmoves;
+
+    trees->bymove = newtree234(movecmp);
+    trees->bycost = newtree234(movecmpcost);
+
+    for (y = 0; y < h; y++)
+        for (x = 0; x < w; x++)
+            if (grid[y*w+x] == GRID_PEG)
+                update_moves(grid, w, h, x, y, trees);
+
+    nmoves = 0;
+
+    while (1) {
+        int limit, maxcost, index;
+        struct move mtmp, move, *m;
+
+        /*
+         * See how many moves we can make at zero cost. Make one,
+         * if possible. Failing that, make a one-cost move, and
+         * then a two-cost one.
+         * 
+         * After filling at least half the input grid, we no longer
+         * accept cost-2 moves: if that's our only option, we give
+         * up and finish.
+         */
+        mtmp.y = h+1;
+        maxcost = (nmoves < w*h/2 ? 2 : 1);
+        m = NULL;                      /* placate optimiser */
+        for (mtmp.cost = 0; mtmp.cost <= maxcost; mtmp.cost++) {
+            limit = -1;
+            m = findrelpos234(trees->bycost, &mtmp, NULL, REL234_LT, &limit);
+#ifdef GENERATION_DIAGNOSTICS
+            printf("%d moves available with cost %d\n", limit+1, mtmp.cost);
+#endif
+            if (m)
+                break;
+        }
+        if (!m)
+            break;
+
+        index = random_upto(rs, limit+1);
+        move = *(struct move *)index234(trees->bycost, index);
+
+#ifdef GENERATION_DIAGNOSTICS
+        printf("selecting move %d%+d,%d%+d at cost %d\n",
+               move.x, move.dx, move.y, move.dy, move.cost);
+#endif
+
+        grid[move.y * w + move.x] = GRID_HOLE;
+        grid[(move.y+move.dy) * w + (move.x+move.dx)] = GRID_PEG;
+        grid[(move.y+2*move.dy)*w + (move.x+2*move.dx)] = GRID_PEG;
+
+        for (i = 0; i <= 2; i++) {
+            int tx = move.x + i*move.dx;
+            int ty = move.y + i*move.dy;
+            update_moves(grid, w, h, tx, ty, trees);
+        }
+
+        nmoves++;
+    }
+
+    while ((m = delpos234(trees->bymove, 0)) != NULL) {
+        del234(trees->bycost, m);
+        sfree(m);
+    }
+    freetree234(trees->bymove);
+    freetree234(trees->bycost);
+}
+
+static void pegs_generate(unsigned char *grid, int w, int h, random_state *rs)
+{
+    while (1) {
+        int x, y, extremes;
+
+        memset(grid, GRID_OBST, w*h);
+        grid[(h/2) * w + (w/2)] = GRID_PEG;
+#ifdef GENERATION_DIAGNOSTICS
+        printf("beginning move selection\n");
+#endif
+        pegs_genmoves(grid, w, h, rs);
+#ifdef GENERATION_DIAGNOSTICS
+        printf("finished move selection\n");
+#endif
+
+        extremes = 0;
+        for (y = 0; y < h; y++) {
+            if (grid[y*w+0] != GRID_OBST)
+                extremes |= 1;
+            if (grid[y*w+w-1] != GRID_OBST)
+                extremes |= 2;
+        }
+        for (x = 0; x < w; x++) {
+            if (grid[0*w+x] != GRID_OBST)
+                extremes |= 4;
+            if (grid[(h-1)*w+x] != GRID_OBST)
+                extremes |= 8;
+        }
+
+        if (extremes == 15)
+            break;
+#ifdef GENERATION_DIAGNOSTICS
+        printf("insufficient extent; trying again\n");
+#endif
+    }
+#ifdef GENERATION_DIAGNOSTICS
+    fflush(stdout);
+#endif
+}
+
+/* ----------------------------------------------------------------------
+ * End of board generation code. Now for the client code which uses
+ * it as part of the puzzle.
+ */
+
+static char *new_game_desc(const game_params *params, random_state *rs,
+                           char **aux, int interactive)
+{
+    int w = params->w, h = params->h;
+    unsigned char *grid;
+    char *ret;
+    int i;
+
+    grid = snewn(w*h, unsigned char);
+    if (params->type == TYPE_RANDOM) {
+        pegs_generate(grid, w, h, rs);
+    } else {
+        int x, y, cx, cy, v;
+
+        for (y = 0; y < h; y++)
+            for (x = 0; x < w; x++) {
+                v = GRID_OBST;         /* placate optimiser */
+                switch (params->type) {
+                  case TYPE_CROSS:
+                    cx = abs(x - w/2);
+                    cy = abs(y - h/2);
+                    if (cx == 0 && cy == 0)
+                        v = GRID_HOLE;
+                    else if (cx > 1 && cy > 1)
+                        v = GRID_OBST;
+                    else
+                        v = GRID_PEG;
+                    break;
+                  case TYPE_OCTAGON:
+                    cx = abs(x - w/2);
+                    cy = abs(y - h/2);
+                    if (cx + cy > 1 + max(w,h)/2)
+                        v = GRID_OBST;
+                    else
+                        v = GRID_PEG;
+                    break;
+                }
+                grid[y*w+x] = v;
+            }
+
+        if (params->type == TYPE_OCTAGON) {
+            /*
+             * The octagonal (European) solitaire layout is
+             * actually _insoluble_ with the starting hole at the
+             * centre. Here's a proof:
+             * 
+             * Colour the squares of the board diagonally in
+             * stripes of three different colours, which I'll call
+             * A, B and C. So the board looks like this:
+             * 
+             *     A B C
+             *   A B C A B
+             * A B C A B C A
+             * B C A B C A B
+             * C A B C A B C
+             *   B C A B C
+             *     A B C
+             * 
+             * Suppose we keep running track of the number of pegs
+             * occuping each colour of square. This colouring has
+             * the property that any valid move whatsoever changes
+             * all three of those counts by one (two of them go
+             * down and one goes up), which means that the _parity_
+             * of every count flips on every move.
+             * 
+             * If the centre square starts off unoccupied, then
+             * there are twelve pegs on each colour and all three
+             * counts start off even; therefore, after 35 moves all
+             * three counts would have to be odd, which isn't
+             * possible if there's only one peg left. []
+             * 
+             * This proof works just as well if the starting hole
+             * is _any_ of the thirteen positions labelled B. Also,
+             * we can stripe the board in the opposite direction
+             * and rule out any square labelled B in that colouring
+             * as well. This leaves:
+             * 
+             *     Y n Y
+             *   n n Y n n
+             * Y n n Y n n Y
+             * n Y Y n Y Y n
+             * Y n n Y n n Y
+             *   n n Y n n
+             *     Y n Y
+             * 
+             * where the ns are squares we've proved insoluble, and
+             * the Ys are the ones remaining.
+             * 
+             * That doesn't prove all those starting positions to
+             * be soluble, of course; they're merely the ones we
+             * _haven't_ proved to be impossible. Nevertheless, it
+             * turns out that they are all soluble, so when the
+             * user requests an Octagon board the simplest thing is
+             * to pick one of these at random.
+             * 
+             * Rather than picking equiprobably from those twelve
+             * positions, we'll pick equiprobably from the three
+             * equivalence classes
+             */
+            switch (random_upto(rs, 3)) {
+              case 0:
+                /* Remove a random corner piece. */
+                {
+                    int dx, dy;
+
+                    dx = random_upto(rs, 2) * 2 - 1;   /* +1 or -1 */
+                    dy = random_upto(rs, 2) * 2 - 1;   /* +1 or -1 */
+                    if (random_upto(rs, 2))
+                        dy *= 3;
+                    else
+                        dx *= 3;
+                    grid[(3+dy)*w+(3+dx)] = GRID_HOLE;
+                }
+                break;
+              case 1:
+                /* Remove a random piece two from the centre. */
+                {
+                    int dx, dy;
+                    dx = 2 * (random_upto(rs, 2) * 2 - 1);
+                    if (random_upto(rs, 2))
+                        dy = 0;
+                    else
+                        dy = dx, dx = 0;
+                    grid[(3+dy)*w+(3+dx)] = GRID_HOLE;
+                }
+                break;
+              default /* case 2 */:
+                /* Remove a random piece one from the centre. */
+                {
+                    int dx, dy;
+                    dx = random_upto(rs, 2) * 2 - 1;
+                    if (random_upto(rs, 2))
+                        dy = 0;
+                    else
+                        dy = dx, dx = 0;
+                    grid[(3+dy)*w+(3+dx)] = GRID_HOLE;
+                }
+                break;
+            }
+        }
+    }
+
+    /*
+     * Encode a game description which is simply a long list of P
+     * for peg, H for hole or O for obstacle.
+     */
+    ret = snewn(w*h+1, char);
+    for (i = 0; i < w*h; i++)
+        ret[i] = (grid[i] == GRID_PEG ? 'P' :
+                  grid[i] == GRID_HOLE ? 'H' : 'O');
+    ret[w*h] = '\0';
+
+    sfree(grid);
+
+    return ret;
+}
+
+static char *validate_desc(const game_params *params, const char *desc)
+{
+    int len = params->w * params->h;
+
+    if (len != strlen(desc))
+        return "Game description is wrong length";
+    if (len != strspn(desc, "PHO"))
+        return "Invalid character in game description";
+
+    return NULL;
+}
+
+static game_state *new_game(midend *me, const game_params *params,
+                            const char *desc)
+{
+    int w = params->w, h = params->h;
+    game_state *state = snew(game_state);
+    int i;
+
+    state->w = w;
+    state->h = h;
+    state->completed = 0;
+    state->grid = snewn(w*h, unsigned char);
+    for (i = 0; i < w*h; i++)
+        state->grid[i] = (desc[i] == 'P' ? GRID_PEG :
+                          desc[i] == 'H' ? GRID_HOLE : GRID_OBST);
+
+    return state;
+}
+
+static game_state *dup_game(const game_state *state)
+{
+    int w = state->w, h = state->h;
+    game_state *ret = snew(game_state);
+
+    ret->w = state->w;
+    ret->h = state->h;
+    ret->completed = state->completed;
+    ret->grid = snewn(w*h, unsigned char);
+    memcpy(ret->grid, state->grid, w*h);
+
+    return ret;
+}
+
+static void free_game(game_state *state)
+{
+    sfree(state->grid);
+    sfree(state);
+}
+
+static char *solve_game(const game_state *state, const game_state *currstate,
+                        const char *aux, char **error)
+{
+    return NULL;
+}
+
+static int game_can_format_as_text_now(const game_params *params)
+{
+    return TRUE;
+}
+
+static char *game_text_format(const game_state *state)
+{
+    int w = state->w, h = state->h;
+    int x, y;
+    char *ret;
+
+    ret = snewn((w+1)*h + 1, char);
+
+    for (y = 0; y < h; y++) {
+        for (x = 0; x < w; x++)
+            ret[y*(w+1)+x] = (state->grid[y*w+x] == GRID_HOLE ? '-' :
+                              state->grid[y*w+x] == GRID_PEG ? '*' : ' ');
+        ret[y*(w+1)+w] = '\n';
+    }
+    ret[h*(w+1)] = '\0';
+
+    return ret;
+}
+
+struct game_ui {
+    int dragging;                      /* boolean: is a drag in progress? */
+    int sx, sy;                        /* grid coords of drag start cell */
+    int dx, dy;                        /* pixel coords of current drag posn */
+    int cur_x, cur_y, cur_visible, cur_jumping;
+};
+
+static game_ui *new_ui(const game_state *state)
+{
+    game_ui *ui = snew(game_ui);
+    int x, y, v;
+
+    ui->sx = ui->sy = ui->dx = ui->dy = 0;
+    ui->dragging = FALSE;
+    ui->cur_visible = ui->cur_jumping = 0;
+
+    /* make sure we start the cursor somewhere on the grid. */
+    for (x = 0; x < state->w; x++) {
+        for (y = 0; y < state->h; y++) {
+            v = state->grid[y*state->w+x];
+            if (v == GRID_PEG || v == GRID_HOLE) {
+                ui->cur_x = x; ui->cur_y = y;
+                goto found;
+            }
+        }
+    }
+    assert(!"new_ui found nowhere for cursor");
+found:
+
+    return ui;
+}
+
+static void free_ui(game_ui *ui)
+{
+    sfree(ui);
+}
+
+static char *encode_ui(const game_ui *ui)
+{
+    return NULL;
+}
+
+static void decode_ui(game_ui *ui, const char *encoding)
+{
+}
+
+static void game_changed_state(game_ui *ui, const game_state *oldstate,
+                               const game_state *newstate)
+{
+    /*
+     * Cancel a drag, in case the source square has become
+     * unoccupied.
+     */
+    ui->dragging = FALSE;
+}
+
+#define PREFERRED_TILE_SIZE 33
+#define TILESIZE (ds->tilesize)
+#define BORDER (TILESIZE / 2)
+
+#define HIGHLIGHT_WIDTH (TILESIZE / 16)
+
+#define COORD(x)     ( BORDER + (x) * TILESIZE )
+#define FROMCOORD(x) ( ((x) + TILESIZE - BORDER) / TILESIZE - 1 )
+
+struct game_drawstate {
+    int tilesize;
+    blitter *drag_background;
+    int dragging, dragx, dragy;
+    int w, h;
+    unsigned char *grid;
+    int started;
+    int bgcolour;
+};
+
+static char *interpret_move(const game_state *state, game_ui *ui,
+                            const game_drawstate *ds,
+                            int x, int y, int button)
+{
+    int w = state->w, h = state->h;
+    char buf[80];
+
+    if (button == LEFT_BUTTON) {
+        int tx, ty;
+
+        /*
+         * Left button down: we attempt to start a drag.
+         */
+        
+        /*
+         * There certainly shouldn't be a current drag in progress,
+         * unless the midend failed to send us button events in
+         * order; it has a responsibility to always get that right,
+         * so we can legitimately punish it by failing an
+         * assertion.
+         */
+        assert(!ui->dragging);
+
+        tx = FROMCOORD(x);
+        ty = FROMCOORD(y);
+        if (tx >= 0 && tx < w && ty >= 0 && ty < h &&
+            state->grid[ty*w+tx] == GRID_PEG) {
+            ui->dragging = TRUE;
+            ui->sx = tx;
+            ui->sy = ty;
+            ui->dx = x;
+            ui->dy = y;
+            ui->cur_visible = ui->cur_jumping = 0;
+            return "";                 /* ui modified */
+        }
+    } else if (button == LEFT_DRAG && ui->dragging) {
+        /*
+         * Mouse moved; just move the peg being dragged.
+         */
+        ui->dx = x;
+        ui->dy = y;
+        return "";                     /* ui modified */
+    } else if (button == LEFT_RELEASE && ui->dragging) {
+        int tx, ty, dx, dy;
+
+        /*
+         * Button released. Identify the target square of the drag,
+         * see if it represents a valid move, and if so make it.
+         */
+        ui->dragging = FALSE;          /* cancel the drag no matter what */
+        tx = FROMCOORD(x);
+        ty = FROMCOORD(y);
+        if (tx < 0 || tx >= w || ty < 0 || ty >= h)
+            return "";                 /* target out of range */
+        dx = tx - ui->sx;
+        dy = ty - ui->sy;
+        if (max(abs(dx),abs(dy)) != 2 || min(abs(dx),abs(dy)) != 0)
+            return "";                 /* move length was wrong */
+        dx /= 2;
+        dy /= 2;
+
+        if (state->grid[ty*w+tx] != GRID_HOLE ||
+            state->grid[(ty-dy)*w+(tx-dx)] != GRID_PEG ||
+            state->grid[ui->sy*w+ui->sx] != GRID_PEG)
+            return "";                 /* grid contents were invalid */
+
+        /*
+         * We have a valid move. Encode it simply as source and
+         * destination coordinate pairs.
+         */
+        sprintf(buf, "%d,%d-%d,%d", ui->sx, ui->sy, tx, ty);
+        return dupstr(buf);
+    } else if (IS_CURSOR_MOVE(button)) {
+        if (!ui->cur_jumping) {
+            /* Not jumping; move cursor as usual, making sure we don't
+             * leave the gameboard (which may be an irregular shape) */
+            int cx = ui->cur_x, cy = ui->cur_y;
+            move_cursor(button, &cx, &cy, w, h, 0);
+            ui->cur_visible = 1;
+            if (state->grid[cy*w+cx] == GRID_HOLE ||
+                state->grid[cy*w+cx] == GRID_PEG) {
+                ui->cur_x = cx;
+                ui->cur_y = cy;
+            }
+            return "";
+        } else {
+            int dx, dy, mx, my, jx, jy;
+
+            /* We're jumping; if the requested direction has a hole, and
+             * there's a peg in the way, */
+            assert(state->grid[ui->cur_y*w+ui->cur_x] == GRID_PEG);
+            dx = (button == CURSOR_RIGHT) ? 1 : (button == CURSOR_LEFT) ? -1 : 0;
+            dy = (button == CURSOR_DOWN) ? 1 : (button == CURSOR_UP) ? -1 : 0;
+
+            mx = ui->cur_x+dx; my = ui->cur_y+dy;
+            jx = mx+dx; jy = my+dy;
+
+            ui->cur_jumping = 0; /* reset, whatever. */
+            if (jx >= 0 && jy >= 0 && jx < w && jy < h &&
+                state->grid[my*w+mx] == GRID_PEG &&
+                state->grid[jy*w+jx] == GRID_HOLE) {
+                /* Move cursor to the jumped-to location (this felt more
+                 * natural while playtesting) */
+                sprintf(buf, "%d,%d-%d,%d", ui->cur_x, ui->cur_y, jx, jy);
+                ui->cur_x = jx; ui->cur_y = jy;
+                return dupstr(buf);
+            }
+            return "";
+        }
+    } else if (IS_CURSOR_SELECT(button)) {
+        if (!ui->cur_visible) {
+            ui->cur_visible = 1;
+            return "";
+        }
+        if (ui->cur_jumping) {
+            ui->cur_jumping = 0;
+            return "";
+        }
+        if (state->grid[ui->cur_y*w+ui->cur_x] == GRID_PEG) {
+            /* cursor is on peg: next arrow-move wil jump. */
+            ui->cur_jumping = 1;
+            return "";
+        }
+        return NULL;
+    }
+
+    return NULL;
+}
+
+static game_state *execute_move(const game_state *state, const char *move)
+{
+    int w = state->w, h = state->h;
+    int sx, sy, tx, ty;
+    game_state *ret;
+
+    if (sscanf(move, "%d,%d-%d,%d", &sx, &sy, &tx, &ty) == 4) {
+        int mx, my, dx, dy;
+
+        if (sx < 0 || sx >= w || sy < 0 || sy >= h)
+            return NULL;               /* source out of range */
+        if (tx < 0 || tx >= w || ty < 0 || ty >= h)
+            return NULL;               /* target out of range */
+
+        dx = tx - sx;
+        dy = ty - sy;
+        if (max(abs(dx),abs(dy)) != 2 || min(abs(dx),abs(dy)) != 0)
+            return NULL;               /* move length was wrong */
+        mx = sx + dx/2;
+        my = sy + dy/2;
+
+        if (state->grid[sy*w+sx] != GRID_PEG ||
+            state->grid[my*w+mx] != GRID_PEG ||
+            state->grid[ty*w+tx] != GRID_HOLE)
+            return NULL;               /* grid contents were invalid */
+
+        ret = dup_game(state);
+        ret->grid[sy*w+sx] = GRID_HOLE;
+        ret->grid[my*w+mx] = GRID_HOLE;
+        ret->grid[ty*w+tx] = GRID_PEG;
+
+        /*
+         * Opinion varies on whether getting to a single peg counts as
+         * completing the game, or whether that peg has to be at a
+         * specific location (central in the classic cross game, for
+         * instance). For now we take the former, rather lax position.
+         */
+        if (!ret->completed) {
+            int count = 0, i;
+            for (i = 0; i < w*h; i++)
+                if (ret->grid[i] == GRID_PEG)
+                    count++;
+            if (count == 1)
+                ret->completed = 1;
+        }
+
+        return ret;
+    }
+    return NULL;
+}
+
+/* ----------------------------------------------------------------------
+ * Drawing routines.
+ */
+
+static void game_compute_size(const game_params *params, int tilesize,
+                              int *x, int *y)
+{
+    /* Ick: fake up `ds->tilesize' for macro expansion purposes */
+    struct { int tilesize; } ads, *ds = &ads;
+    ads.tilesize = tilesize;
+
+    *x = TILESIZE * params->w + 2 * BORDER;
+    *y = TILESIZE * params->h + 2 * BORDER;
+}
+
+static void game_set_size(drawing *dr, game_drawstate *ds,
+                          const game_params *params, int tilesize)
+{
+    ds->tilesize = tilesize;
+
+    assert(TILESIZE > 0);
+
+    assert(!ds->drag_background);      /* set_size is never called twice */
+    ds->drag_background = blitter_new(dr, TILESIZE, TILESIZE);
+}
+
+static float *game_colours(frontend *fe, int *ncolours)
+{
+    float *ret = snewn(3 * NCOLOURS, float);
+
+    game_mkhighlight(fe, ret, COL_BACKGROUND, COL_HIGHLIGHT, COL_LOWLIGHT);
+
+    ret[COL_PEG * 3 + 0] = 0.0F;
+    ret[COL_PEG * 3 + 1] = 0.0F;
+    ret[COL_PEG * 3 + 2] = 1.0F;
+
+    ret[COL_CURSOR * 3 + 0] = 0.5F;
+    ret[COL_CURSOR * 3 + 1] = 0.5F;
+    ret[COL_CURSOR * 3 + 2] = 1.0F;
+
+    *ncolours = NCOLOURS;
+    return ret;
+}
+
+static game_drawstate *game_new_drawstate(drawing *dr, const game_state *state)
+{
+    int w = state->w, h = state->h;
+    struct game_drawstate *ds = snew(struct game_drawstate);
+
+    ds->tilesize = 0;                  /* not decided yet */
+
+    /* We can't allocate the blitter rectangle for the drag background
+     * until we know what size to make it. */
+    ds->drag_background = NULL;
+    ds->dragging = FALSE;
+
+    ds->w = w;
+    ds->h = h;
+    ds->grid = snewn(w*h, unsigned char);
+    memset(ds->grid, 255, w*h);
+
+    ds->started = FALSE;
+    ds->bgcolour = -1;
+
+    return ds;
+}
+
+static void game_free_drawstate(drawing *dr, game_drawstate *ds)
+{
+    if (ds->drag_background)
+        blitter_free(dr, ds->drag_background);
+    sfree(ds->grid);
+    sfree(ds);
+}
+
+static void draw_tile(drawing *dr, game_drawstate *ds,
+                      int x, int y, int v, int bgcolour)
+{
+    int cursor = 0, jumping = 0, bg;
+
+    if (bgcolour >= 0) {
+        draw_rect(dr, x, y, TILESIZE, TILESIZE, bgcolour);
+    }
+    if (v >= GRID_JUMPING) {
+        jumping = 1; v -= GRID_JUMPING;
+    }
+    if (v >= GRID_CURSOR) {
+        cursor = 1; v -= GRID_CURSOR;
+    }
+
+    if (v == GRID_HOLE) {
+        bg = cursor ? COL_HIGHLIGHT : COL_LOWLIGHT;
+        assert(!jumping); /* can't jump from a hole! */
+        draw_circle(dr, x+TILESIZE/2, y+TILESIZE/2, TILESIZE/4,
+                    bg, bg);
+    } else if (v == GRID_PEG) {
+        bg = (cursor || jumping) ? COL_CURSOR : COL_PEG;
+        draw_circle(dr, x+TILESIZE/2, y+TILESIZE/2, TILESIZE/3,
+                    bg, bg);
+        bg = (!cursor || jumping) ? COL_PEG : COL_CURSOR;
+        draw_circle(dr, x+TILESIZE/2, y+TILESIZE/2, TILESIZE/4,
+                    bg, bg);
+    }
+
+    draw_update(dr, x, y, TILESIZE, TILESIZE);
+}
+
+static void game_redraw(drawing *dr, game_drawstate *ds,
+                        const game_state *oldstate, const game_state *state,
+                        int dir, const game_ui *ui,
+                        float animtime, float flashtime)
+{
+    int w = state->w, h = state->h;
+    int x, y;
+    int bgcolour;
+
+    if (flashtime > 0) {
+        int frame = (int)(flashtime / FLASH_FRAME);
+        bgcolour = (frame % 2 ? COL_LOWLIGHT : COL_HIGHLIGHT);
+    } else
+        bgcolour = COL_BACKGROUND;
+
+    /*
+     * Erase the sprite currently being dragged, if any.
+     */
+    if (ds->dragging) {
+        assert(ds->drag_background);
+        blitter_load(dr, ds->drag_background, ds->dragx, ds->dragy);
+        draw_update(dr, ds->dragx, ds->dragy, TILESIZE, TILESIZE);
+        ds->dragging = FALSE;
+    }
+
+    if (!ds->started) {
+        draw_rect(dr, 0, 0,
+                  TILESIZE * state->w + 2 * BORDER,
+                  TILESIZE * state->h + 2 * BORDER, COL_BACKGROUND);
+
+        /*
+         * Draw relief marks around all the squares that aren't
+         * GRID_OBST.
+         */
+        for (y = 0; y < h; y++)
+            for (x = 0; x < w; x++)
+                if (state->grid[y*w+x] != GRID_OBST) {
+                    /*
+                     * First pass: draw the full relief square.
+                     */
+                    int coords[6];
+                    coords[0] = COORD(x+1) + HIGHLIGHT_WIDTH - 1;
+                    coords[1] = COORD(y) - HIGHLIGHT_WIDTH;
+                    coords[2] = COORD(x) - HIGHLIGHT_WIDTH;
+                    coords[3] = COORD(y+1) + HIGHLIGHT_WIDTH - 1;
+                    coords[4] = COORD(x) - HIGHLIGHT_WIDTH;
+                    coords[5] = COORD(y) - HIGHLIGHT_WIDTH;
+                    draw_polygon(dr, coords, 3, COL_HIGHLIGHT, COL_HIGHLIGHT);
+                    coords[4] = COORD(x+1) + HIGHLIGHT_WIDTH - 1;
+                    coords[5] = COORD(y+1) + HIGHLIGHT_WIDTH - 1;
+                    draw_polygon(dr, coords, 3, COL_LOWLIGHT, COL_LOWLIGHT);
+                }
+        for (y = 0; y < h; y++)
+            for (x = 0; x < w; x++)
+                if (state->grid[y*w+x] != GRID_OBST) {
+                    /*
+                     * Second pass: draw everything but the two
+                     * diagonal corners.
+                     */
+                    draw_rect(dr, COORD(x) - HIGHLIGHT_WIDTH,
+                              COORD(y) - HIGHLIGHT_WIDTH,
+                              TILESIZE + HIGHLIGHT_WIDTH,
+                              TILESIZE + HIGHLIGHT_WIDTH, COL_HIGHLIGHT);
+                    draw_rect(dr, COORD(x),
+                              COORD(y),
+                              TILESIZE + HIGHLIGHT_WIDTH,
+                              TILESIZE + HIGHLIGHT_WIDTH, COL_LOWLIGHT);
+                }
+        for (y = 0; y < h; y++)
+            for (x = 0; x < w; x++)
+                if (state->grid[y*w+x] != GRID_OBST) {
+                    /*
+                     * Third pass: draw a trapezium on each edge.
+                     */
+                    int coords[8];
+                    int dx, dy, s, sn, c;
+
+                    for (dx = 0; dx < 2; dx++) {
+                        dy = 1 - dx;
+                        for (s = 0; s < 2; s++) {
+                            sn = 2*s - 1;
+                            c = s ? COL_LOWLIGHT : COL_HIGHLIGHT;
+
+                            coords[0] = COORD(x) + (s*dx)*(TILESIZE-1);
+                            coords[1] = COORD(y) + (s*dy)*(TILESIZE-1);
+                            coords[2] = COORD(x) + (s*dx+dy)*(TILESIZE-1);
+                            coords[3] = COORD(y) + (s*dy+dx)*(TILESIZE-1);
+                            coords[4] = coords[2] - HIGHLIGHT_WIDTH * (dy-sn*dx);
+                            coords[5] = coords[3] - HIGHLIGHT_WIDTH * (dx-sn*dy);
+                            coords[6] = coords[0] + HIGHLIGHT_WIDTH * (dy+sn*dx);
+                            coords[7] = coords[1] + HIGHLIGHT_WIDTH * (dx+sn*dy);
+                            draw_polygon(dr, coords, 4, c, c);
+                        }
+                    }
+                }
+        for (y = 0; y < h; y++)
+            for (x = 0; x < w; x++)
+                if (state->grid[y*w+x] != GRID_OBST) {
+                    /*
+                     * Second pass: draw everything but the two
+                     * diagonal corners.
+                     */
+                    draw_rect(dr, COORD(x),
+                              COORD(y),
+                              TILESIZE,
+                              TILESIZE, COL_BACKGROUND);
+                }
+
+        ds->started = TRUE;
+
+        draw_update(dr, 0, 0,
+                    TILESIZE * state->w + 2 * BORDER,
+                    TILESIZE * state->h + 2 * BORDER);
+    }
+
+    /*
+     * Loop over the grid redrawing anything that looks as if it
+     * needs it.
+     */
+    for (y = 0; y < h; y++)
+        for (x = 0; x < w; x++) {
+            int v;
+
+            v = state->grid[y*w+x];
+            /*
+             * Blank the source of a drag so it looks as if the
+             * user picked the peg up physically.
+             */
+            if (ui->dragging && ui->sx == x && ui->sy == y && v == GRID_PEG)
+                v = GRID_HOLE;
+
+            if (ui->cur_visible && ui->cur_x == x && ui->cur_y == y)
+                v += ui->cur_jumping ? GRID_JUMPING : GRID_CURSOR;
+
+            if (v != GRID_OBST &&
+                (bgcolour != ds->bgcolour || /* always redraw when flashing */
+                 v != ds->grid[y*w+x])) {
+                draw_tile(dr, ds, COORD(x), COORD(y), v, bgcolour);
+                ds->grid[y*w+x] = v;
+            }
+        }
+
+    /*
+     * Draw the dragging sprite if any.
+     */
+    if (ui->dragging) {
+        ds->dragging = TRUE;
+        ds->dragx = ui->dx - TILESIZE/2;
+        ds->dragy = ui->dy - TILESIZE/2;
+        blitter_save(dr, ds->drag_background, ds->dragx, ds->dragy);
+        draw_tile(dr, ds, ds->dragx, ds->dragy, GRID_PEG, -1);
+    }
+
+    ds->bgcolour = bgcolour;
+}
+
+static float game_anim_length(const game_state *oldstate,
+                              const game_state *newstate, int dir, game_ui *ui)
+{
+    return 0.0F;
+}
+
+static float game_flash_length(const game_state *oldstate,
+                               const game_state *newstate, int dir, game_ui *ui)
+{
+    if (!oldstate->completed && newstate->completed)
+        return 2 * FLASH_FRAME;
+    else
+        return 0.0F;
+}
+
+static int game_status(const game_state *state)
+{
+    /*
+     * Dead-end situations are assumed to be rescuable by Undo, so we
+     * don't bother to identify them and return -1.
+     */
+    return state->completed ? +1 : 0;
+}
+
+static int game_timing_state(const game_state *state, game_ui *ui)
+{
+    return TRUE;
+}
+
+static void game_print_size(const game_params *params, float *x, float *y)
+{
+}
+
+static void game_print(drawing *dr, const game_state *state, int tilesize)
+{
+}
+
+#ifdef COMBINED
+#define thegame pegs
+#endif
+
+const struct game thegame = {
+    "Pegs", "games.pegs", "pegs",
+    default_params,
+    game_fetch_preset, NULL,
+    decode_params,
+    encode_params,
+    free_params,
+    dup_params,
+    TRUE, game_configure, custom_params,
+    validate_params,
+    new_game_desc,
+    validate_desc,
+    new_game,
+    dup_game,
+    free_game,
+    FALSE, solve_game,
+    TRUE, game_can_format_as_text_now, game_text_format,
+    new_ui,
+    free_ui,
+    encode_ui,
+    decode_ui,
+    game_changed_state,
+    interpret_move,
+    execute_move,
+    PREFERRED_TILE_SIZE, game_compute_size, game_set_size,
+    game_colours,
+    game_new_drawstate,
+    game_free_drawstate,
+    game_redraw,
+    game_anim_length,
+    game_flash_length,
+    game_status,
+    FALSE, FALSE, game_print_size, game_print,
+    FALSE,                             /* wants_statusbar */
+    FALSE, game_timing_state,
+    0,                                 /* flags */
+};
+
+/* vim: set shiftwidth=4 tabstop=8: */