+ return NULL;
+}
+
+static void decode_ui(game_ui *ui, char *encoding)
+{
+}
+
+static void game_changed_state(game_ui *ui, game_state *oldstate,
+ game_state *newstate)
+{
+ int c = newstate->c, r = newstate->r, cr = c*r;
+ /*
+ * We prevent pencil-mode highlighting of a filled square. So
+ * if the user has just filled in a square which we had a
+ * pencil-mode highlight in (by Undo, or by Redo, or by Solve),
+ * then we cancel the highlight.
+ */
+ if (ui->hx >= 0 && ui->hy >= 0 && ui->hpencil &&
+ newstate->grid[ui->hy * cr + ui->hx] != 0) {
+ ui->hx = ui->hy = -1;
+ }
+}
+
+struct game_drawstate {
+ int started;
+ int c, r, cr;
+ int tilesize;
+ digit *grid;
+ unsigned char *pencil;
+ unsigned char *hl;
+ /* This is scratch space used within a single call to game_redraw. */
+ int *entered_items;
+};
+
+static char *interpret_move(game_state *state, game_ui *ui, game_drawstate *ds,
+ int x, int y, int button)
+{
+ int c = state->c, r = state->r, cr = c*r;