Thursday, May 11, 2017

A small Tetris-like clone using J and ncurses. Part 2

This is part two of our Tetris-like clone in J series. In this part we're going to see how the ncurses interface was created.

Creating the ncurses UI

To create the user interface we used the ncurses UI using the api/ncurses package. Sadly all interactions with this API makes the code look like straightforward imperative code.

Since we represented the game field using a matrix, we need a way to visualize this matrix. The next snippet shows how we used the wattr_on and mvwprintw functions to print each cell of the game field with the given color.

drawGame=: 3 : 0
matrix =. >{.}.y
win =. >{.y
cols =. }. $ matrix
rows =. {. $ matrix
for_row. i.rows do.
  for_col. i.cols do.
     value =. (<row, col) { matrix
     wattr_on_ncurses_ win;(COLOR_PAIR_ncurses_ (value+1));0
     mvwprintw_1_ncurses_ win; row; (2*col); (('  '))
  end.
end.
)

The game loop handles user interactions and game rules . Here's how it looks:

NB. Game loop
while. 1 do.
   c =. wgetch_ncurses_ vin 
   if. c = KEY_UP_ncurses_ do.
      game =: put_in_matrix (current*_1);k;j;game
      current =. rotate current
      needs_refresh =. 1
   elseif. c = KEY_RIGHT_ncurses_ do.
      game_tmp =. put_in_matrix (current*_1);k;j;game
      if. can_put_in_matrix current;k;(j + 1);game_tmp do.
         game =: game_tmp
         j =. j + 1
         needs_refresh =. 1
      end.
   elseif. c = KEY_LEFT_ncurses_ do.
      game_tmp =. put_in_matrix (current*_1);k;j;game
      if. can_put_in_matrix (current);k;(j - 1);game_tmp do.
         game =: game_tmp
         j =. j - 1
         needs_refresh =. 1
      end.
   elseif. 1 do. 
      if. ((seconds_from_start'') - timestamp) < 0.1 do.
         continue.
      else.
         timestamp =. seconds_from_start'' 
      end.
   
      if. automove = 0 do.
         game =: put_in_matrix (current*_1);k;j;game
         if. can_put_in_matrix (current);(k+1);j;game do.
            k =. k + 1
         else.
           game =: put_in_matrix (current);k;j;game
           k =. 0
           j =. 0
           if. can_put_in_matrix current;k;j;game do.
              current =. (?@$ tetriminos) {:: tetriminos
           else.
             mvwprintw_1_ncurses_ vin; 0; 0; ' Game over '
             nodelay_ncurses_ vin ;'0'
             wgetch_ncurses_ vin 
             exit''
          
           end.
         end.
         automove =. 2
         needs_refresh =. 1
      else.
          automove =. automove - 1
      end.
   end.
   unget_wch_ncurses_ c
   if. needs_refresh do.
      game =: put_in_matrix (current);k;j;game
      game =: remove_full_rows game
      drawGame vin; game
      wrefresh_ncurses_  vin
      needs_refresh =. 0
   end.
end.

The rest of the code is pure ncurses initialization which is not that interesting. Code for this post can be found here: : https://github.com/ldfallas/jcurtris .

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