X-Git-Url: https://git.distorted.org.uk/~mdw/sgt/puzzles/blobdiff_plain/aabb03faff75f39e9ad21f62891a4fd146ccc2eb..HEAD:/devel.but

diff --git a/devel.but b/devel.but
index 8e35359..970a73a 100644
--- a/devel.but
+++ b/devel.but
@@ -856,7 +856,7 @@ producing new \c{game_state}s.
 \S{backend-interpret-move} \cw{interpret_move()}
 
 \c char *(*interpret_move)(game_state *state, game_ui *ui,
-\c                         game_drawstate *ds,
+\c                         const game_drawstate *ds,
 \c                         int x, int y, int button);
 
 This function receives user input and processes it. Its input
@@ -868,6 +868,11 @@ indicating an arrow or function key or a mouse event; when
 coordinates of the mouse pointer relative to the top left of the
 puzzle's drawing area.
 
+(The pointer to the \c{game_drawstate} is marked \c{const}, because
+\c{interpret_move} should not write to it. The normal use of that
+pointer will be to read the game's tile size parameter in order to
+divide mouse coordinates by it.)
+
 \cw{interpret_move()} may return in three different ways:
 
 \b Returning \cw{NULL} indicates that no action whatsoever occurred
@@ -1224,6 +1229,34 @@ a mine from the colour it uses when you complete the game. In order
 to achieve this, its \cw{flash_length()} function has to store a
 flag in the \c{game_ui} to indicate which flash type is required.)
 
+\S{backend-status} \cw{status()}
+
+\c int (*status)(game_state *state);
+
+This function returns a status value indicating whether the current
+game is still in play, or has been won, or has been conclusively lost.
+The mid-end uses this to implement \cw{midend_status()}
+(\k{midend-status}).
+
+The return value should be +1 if the game has been successfully
+solved. If the game has been lost in a situation where further play is
+unlikely, the return value should be -1. If neither is true (so play
+is still ongoing), return zero.
+
+Front ends may wish to use a non-zero status as a cue to proactively
+offer the option of starting a new game. Therefore, back ends should
+not return -1 if the game has been \e{technically} lost but undoing
+and continuing is still a realistic possibility.
+
+(For instance, games with hidden information such as Guess or Mines
+might well return a non-zero status whenever they reveal the solution,
+whether or not the player guessed it correctly, on the grounds that a
+player would be unlikely to hide the solution and continue playing
+after the answer was spoiled. On the other hand, games where you can
+merely get into a dead end such as Same Game or Inertia might choose
+to return 0 in that situation, on the grounds that the player would
+quite likely press Undo and carry on playing.)
+
 \S{backend-redraw} \cw{redraw()}
 
 \c void (*redraw)(drawing *dr, game_drawstate *ds,
@@ -1433,7 +1466,7 @@ them internally. (There are currently no puzzles which have a
 one-line ASCII representation, so there's no precedent yet for
 whether that should come with a newline or not.)
 
-\S{backend-wants-statusbar} \cw{wants_statusbar()}
+\S{backend-wants-statusbar} \cw{wants_statusbar}
 
 \c int wants_statusbar;
 
@@ -2686,14 +2719,12 @@ without closing the window...)
 
 Frees a mid-end structure and all its associated data.
 
-\H{midend-tilesize} 
+\H{midend-tilesize} \cw{midend_tilesize()}
 
 \c int midend_tilesize(midend *me);
 
 Returns the \cq{tilesize} parameter being used to display the
-current puzzle.
-
-\k{backend-preferred-tilesize}
+current puzzle (\k{backend-preferred-tilesize}).
 
 \H{midend-set-params} \cw{midend_set_params()}
 
@@ -2778,6 +2809,9 @@ to use scroll bars for large puzzles), you can pass dimensions of
 \cw{INT_MAX} as input to this function. You should probably not do
 that \e{and} set the \c{user_size} flag, though!
 
+The midend relies on the frontend calling \cw{midend_new_game()}
+(\k{midend-new-game}) before calling \cw{midend_size()}.
+
 \H{midend-new-game} \cw{midend_new_game()}
 
 \c void midend_new_game(midend *me);
@@ -2814,7 +2848,8 @@ undo list (so that an accidental restart can be undone).
 
 This function automatically causes a redraw, i.e. the front end can
 expect its drawing API to be called from \e{within} a call to this
-function.
+function. Some back ends require that \cw{midend_size()}
+(\k{midend-size}) is called before \cw{midend_restart_game()}.
 
 \H{midend-force-redraw} \cw{midend_force_redraw()}
 
@@ -2825,7 +2860,8 @@ discarding the current \c{game_drawstate} and creating a new one
 from scratch before calling the game's \cw{redraw()} function.
 
 The front end can expect its drawing API to be called from within a
-call to this function.
+call to this function. Some back ends require that \cw{midend_size()}
+(\k{midend-size}) is called before \cw{midend_force_redraw()}.
 
 \H{midend-redraw} \cw{midend_redraw()}
 
@@ -2836,7 +2872,8 @@ calling the game's \cw{redraw()} function. (That is, the only things
 redrawn will be things that have changed since the last redraw.)
 
 The front end can expect its drawing API to be called from within a
-call to this function.
+call to this function. Some back ends require that \cw{midend_size()}
+(\k{midend-size}) is called before \cw{midend_redraw()}.
 
 \H{midend-process-key} \cw{midend_process_key()}
 
@@ -3094,7 +3131,40 @@ user.
 
 The front end can expect its drawing API and/or
 \cw{activate_timer()} to be called from within a call to this
-function.
+function.  Some back ends require that \cw{midend_size()}
+(\k{midend-size}) is called before \cw{midend_solve()}.
+
+\H{midend-status} \cw{midend_status()}
+
+\c int midend_status(midend *me);
+
+This function returns +1 if the midend is currently displaying a game
+in a solved state, -1 if the game is in a permanently lost state, or 0
+otherwise. This function just calls the back end's \cw{status()}
+function. Front ends may wish to use this as a cue to proactively
+offer the option of starting a new game.
+
+(See \k{backend-status} for more detail about the back end's
+\cw{status()} function and discussion of what should count as which
+status code.)
+
+\H{midend-can-undo} \cw{midend_can_undo()}
+
+\c int midend_can_undo(midend *me);
+
+Returns \cw{TRUE} if the midend is currently in a state where the undo
+operation is meaningful (i.e. at least one position exists on the undo
+chain before the present one). Front ends may wish to use this to
+visually activate and deactivate an undo button.
+
+\H{midend-can-redo} \cw{midend_can_redo()}
+
+\c int midend_can_redo(midend *me);
+
+Returns \cw{TRUE} if the midend is currently in a state where the redo
+operation is meaningful (i.e. at least one position exists on the redo
+chain after the present one). Front ends may wish to use this to
+visually activate and deactivate a redo button.
 
 \H{midend-serialise} \cw{midend_serialise()}