-static char *interpret_move(game_state *state, game_ui *ui, game_drawstate *ds,
+static char *interpret_move(game_state *state, game_ui *ui, const game_drawstate *ds,
int x, int y, int button)
{
int w = state->w, h = state->h;
int x, int y, int button)
{
int w = state->w, h = state->h;
(bgcolour != ds->bgcolour || /* always redraw when flashing */
v != ds->grid[y*w+x])) {
draw_tile(dr, ds, COORD(x), COORD(y), v, bgcolour);
(bgcolour != ds->bgcolour || /* always redraw when flashing */
v != ds->grid[y*w+x])) {
draw_tile(dr, ds, COORD(x), COORD(y), v, bgcolour);
- return state->completed;
+ /*
+ * 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;
FALSE, FALSE, game_print_size, game_print,
FALSE, /* wants_statusbar */
FALSE, game_timing_state,
FALSE, FALSE, game_print_size, game_print,
FALSE, /* wants_statusbar */
FALSE, game_timing_state,