% vim: set tw=72:

% Part of Hetris

\section{The user interface module (UI)}

The user interface is the most obvious case where multiple
implementations are sensible. User interfaces are one of the less well
developed areas in the Haskell community, but the new FFI allows us to
easily and portably define a Haskell interface to curses. We don't show
the actual interface here, but it should be easy to understand from the
C documentation; the \hsmodule{Curses} module exports it.

While as far as the game is concerned the user interface is a single
idea, the input and output aspects are really completely separate in
curses. We therefore split the functionality off into separate modules
which are both imported by \hsmodule{UI}. The initialisation and
shutdown functions come under neither category so we leave them in the
main module.

\begin{code}
module UI (init_ui, shutdown_ui, make_board, get_event, do_changes) where

import Data

import UI.HSCurses.Curses (initScr, cBreak, echo, keypad, cursSet, CursorVisibility(..), endWin)

import Input
import Output
\end{code}

The actual initialisation work is standard curses startup stuff: we
initialise the curses system, enter cbreak mode (disable line buffering
etc) and turn off echoing in common with the vast majority of curses
programs. We also enable the keypad mode so that we can use the arrow
keys to control the movement of the active piece. Finally we ask for the
cursor to be invisible.

The maximum board size depends on how the board is drawn, and the logic
for that is in the \hsmodule{Output} module. We therefore have that
module export a function that gives this maximum size and we return that
value.

\begin{code}

init_ui :: IO (Vector, Vector)
init_ui = do w <- initScr
             cBreak True
             echo False
             keypad w True
             cursSet CursorInvisible
             max_size
\end{code}

Shutting the interface down is rather simpler---we just call the
curses shutdown function.

\begin{code}
shutdown_ui :: IO ()
shutdown_ui = do _ <- endWin
                 return ()
\end{code}