1# Based on the widget demo of Tcl/Tk8.5.2
2# The following is the original copyright text.
3#----------------------------------------------------------------------------
4# Copyright (C) 2008 Pat Thoyts <patthoyts@users.sourceforge.net>
5#
6#	Calculate a Knight's tour of a chessboard.
7#
8#	This uses Warnsdorff's rule to calculate the next square each
9#	time. This specifies that the next square should be the one that
10#	has the least number of available moves.
11#
12#	Using this rule it is possible to get to a position where
13#	there are no squares available to move into. In this implementation
14#	this occurs when the starting square is d6.
15#
16#	To solve this fault an enhancement to the rule is that if we
17#	have a choice of squares with an equal score, we should choose
18#	the one nearest the edge of the board.
19#
20#	If the call to the Edgemost function is commented out you can see
21#	this occur.
22#
23#	You can drag the knight to a specific square to start if you wish.
24#	If you let it repeat then it will choose random start positions
25#	for each new tour.
26#----------------------------------------------------------------------------
27require 'tk'
28
29class Knights_Tour
30  # Return a list of accessible squares from a given square
31  def valid_moves(square)
32    moves = []
33    [
34      [-1,-2], [-2,-1], [-2,1], [-1,2], [1,2], [2,1], [2,-1], [1,-2]
35    ].each{|col_delta, row_delta|
36      col = (square % 8) + col_delta
37      row = (square.div(8)) + row_delta
38      moves << (row * 8 + col) if row > -1 && row < 8 && col > -1 && col < 8
39    }
40    moves
41  end
42
43  # Return the number of available moves for this square
44  def check_square(square)
45    valid_moves(square).find_all{|pos| ! @visited.include?(pos)}.length
46  end
47
48  # Select the next square to move to. Returns -1 if there are no available
49  # squares remaining that we can move to.
50  def next_square(square)
51    minimum = 9
52    nxt = -1
53    valid_moves(square).each{|pos|
54      unless @visited.include?(pos)
55        cnt = check_square(pos)
56        if cnt < minimum
57          minimum = cnt
58          nxt = pos
59        elsif cnt == minimum
60          nxt = edgemost(nxt, pos)
61        end
62      end
63    }
64    nxt
65  end
66
67  # Select the square nearest the edge of the board
68  def edgemost(nxt, pos)
69    col_A = 3 - ((3.5 - nxt % 8).abs.to_i)
70    col_B = 3 - ((3.5 - pos % 8).abs.to_i)
71    row_A = 3 - ((3.5 - nxt.div(8)).abs.to_i)
72    row_B = 3 - ((3.5 - pos.div(8)).abs.to_i)
73    (col_A * row_A < col_B * row_B)? nxt : pos
74  end
75
76  # Display a square number as a standard chess square notation.
77  def _N(square)
78    '%c%d' % [(97 + square % 8), (square.div(8) + 1)]
79  end
80
81  # Perform a Knight's move and schedule the next move.
82  def move_piece(last, square)
83    @log.insert(:end, "#{@visited.length}. #{_N last} -> #{_N square}\n", '')
84    @log.see(:end)
85    @board.itemconfigure(1+last, :state=>:normal, :outline=>'black')
86    @board.itemconfigure(1+square, :state=>:normal, :outline=>'red')
87    @knight.coords(@board.coords(1+square)[0..1])
88    @visited << square
89    if (nxt = next_square(square)) != -1
90      @after_id = Tk.after(@delay.numeric){move_piece(square, nxt) rescue nil}
91    else
92      @start_btn.state :normal
93      if @visited.length == 64
94        if @initial == square
95          @log.insert :end, 'Closed tour!'
96        else
97          @log.insert :end, "Success\n", {}
98          Tk.after(@delay.numeric * 2){tour(rand(64))} if @continuous.bool
99        end
100      else
101        @log.insert :end, "FAILED!\n", {}
102      end
103    end
104  end
105
106  # Begin a new tour of the board given a random start position
107  def tour(square = nil)
108    @visited.clear
109    @log.clear
110    @start_btn.state :disabled
111    1.upto(64){|n|
112      @board.itemconfigure(n, :state=>:disabled, :outline=>'black')
113    }
114    unless square
115      square = @board.find_closest(*(@knight.coords << 0 << 65))[0].to_i - 1
116    end
117    @initial = square
118    Tk.after_idle{ move_piece(@initial, @initial) rescue nil }
119  end
120
121  def _stop
122    Tk.after_cancel(@after_id) rescue nil
123  end
124
125  def _exit
126    _stop
127    $knightstour.destroy
128  end
129
130  def set_delay(new)
131    @delay.numeric = new.to_i
132  end
133
134  def drag_start(w, x, y)
135    w.dtag('selected')
136    w.addtag('selected', :withtag, 'current')
137    @dragging = [x, y]
138  end
139
140  def drag_motion(w, x, y)
141    return unless @dragging
142    w.move('selected', x - @dragging[0], y - @dragging[1])
143    @dragging = [x, y]
144  end
145
146  def drag_end(w, x, y)
147    square = w.find_closest(x, y, 0, 65)
148    w.coords('selected', w.coords(square)[0..1])
149    w.dtag('selected')
150    @dragging = nil
151  end
152
153  def make_SeeDismiss
154    ## See Code / Dismiss
155    frame = Ttk::Frame.new($knightstour)
156    sep = Ttk::Separator.new(frame)
157    Tk.grid(sep, :columnspan=>4, :row=>0, :sticky=>'ew', :pady=>2)
158    TkGrid('x',
159           Ttk::Button.new(frame, :text=>'See Code',
160                           :image=>$image['view'], :compound=>:left,
161                           :command=>proc{showCode 'knightstour'}),
162           Ttk::Button.new(frame, :text=>'Dismiss',
163                           :image=>$image['delete'], :compound=>:left,
164                           :command=>proc{
165                             $knightstour.destroy
166                             $knightstour = nil
167                           }),
168           :padx=>4, :pady=>4)
169    frame.grid_columnconfigure(0, :weight=>1)
170    frame
171  end
172
173  def create_gui(parent = nil)
174    $knightstour.destroy rescue nil
175    $knightstour = Tk::Toplevel.new(parent, :title=>"Knight's tour")
176    $knightstour.withdraw
177    base_f = Ttk::Frame.new($knightstour)
178    @board = Tk::Canvas.new(base_f, :width=>240, :height=>240)
179    @log = Tk::Text.new(base_f, :width=>12, :height=>1,
180                        :font=>'Arial 8', :background=>'white')
181    scr = @log.yscrollbar(Ttk::Scrollbar.new(base_f))
182
183    @visited = []
184    @delay = TkVariable.new(600)
185    @continuous = TkVariable.new(false)
186
187    tool_f = Ttk::Frame.new($knightstour)
188    label = Ttk::Label.new(tool_f, :text=>'Speed')
189    scale = Ttk::Scale.new(tool_f, :from=>8, :to=>2000, :variable=>@delay,
190                           :command=>proc{|n| set_delay(n)})
191    check = Ttk::Checkbutton.new(tool_f, :text=>'Repeat',
192                                 :variable=>@continuous)
193    @start_btn = Ttk::Button.new(tool_f, :text=>'Start',
194                                 :command=>proc{tour()})
195    @exit_btn = Ttk::Button.new(tool_f, :text=>'Exit',
196                                :command=>proc{_exit()})
197
198    7.downto(0){|row|
199      0.upto(7){|col|
200        if ((col & 1) ^ (row & 1)).zero?
201          fill  = 'bisque'
202          dfill = 'bisque3'
203        else
204          fill  = 'tan3'
205          dfill = 'tan4'
206        end
207        coords = [col * 30 + 4, row * 30 + 4, col * 30 + 30, row * 30 + 30]
208        @board.create(TkcRectangle, coords,
209                      :fill=>fill, :disabledfill=>dfill,
210                      :width=>2, :state=>:disabled)
211      }
212    }
213
214    @knight_font = TkFont.new(:size=>-24)
215    @knight = TkcText.new(@board, 0, 0, :font=>@knight_font,
216                          :text=>Tk::UTF8_String.new('\u265e'),
217                          :anchor=>'nw', # :tags=>'knight',
218                          :fill=>'black', :activefill=>'#600000')
219    @knight.coords(@board.coords(rand(64)+1)[0..1])
220    @knight.bind('ButtonPress-1', '%W %x %y'){|w,x,y| drag_start(w,x,y)}
221    @knight.bind('Motion', '%W %x %y'){|w,x,y| drag_motion(w,x,y)}
222    @knight.bind('ButtonRelease-1', '%W %x %y'){|w,x,y| drag_end(w,x,y)}
223
224    Tk.grid(@board, @log, scr, :sticky=>'news')
225    base_f.grid_rowconfigure(0, :weight=>1)
226    base_f.grid_columnconfigure(0, :weight=>1)
227
228    Tk.grid(base_f, '-', '-', '-', '-', '-', :sticky=>'news')
229    widgets = [label, scale, check, @start_btn]
230    sg = nil
231    unless $RubyTk_WidgetDemo
232      widgets << @exit_btn
233      if Tk.windowingsystem != 'aqua'
234        #widgets.unshift(Ttk::SizeGrip.new(tool_f))
235        Ttk::SizeGrip.new(tool_f).pack(:side=>:right, :anchor=>'se')
236      end
237    end
238    Tk.pack(widgets, :side=>:right)
239    if Tk.windowingsystem == 'aqua'
240      TkPack.configure(widgets, :padx=>[4, 4], :pady=>[12, 12])
241      TkPack.configure(widgets[0], :padx=>[4, 24])
242      TkPack.configure(widgets[-1], :padx=>[16, 4])
243    end
244
245    Tk.grid(tool_f, '-', '-', '-', '-', '-', :sticky=>'ew')
246
247    if $RubyTk_WidgetDemo
248      Tk.grid(make_SeeDismiss(), '-', '-', '-', '-', '-', :sticky=>'ew')
249    end
250
251    $knightstour.grid_rowconfigure(0, :weight=>1)
252    $knightstour.grid_columnconfigure(0, :weight=>1)
253
254    $knightstour.bind('Control-F2'){TkConsole.show}
255    $knightstour.bind('Return'){@start_btn.invoke}
256    $knightstour.bind('Escape'){@exit_btn.invoke}
257    $knightstour.bind('Destroy'){ _stop }
258    $knightstour.protocol('WM_DELETE_WINDOW'){ _exit }
259
260    $knightstour.deiconify
261    $knightstour.tkwait_destroy
262  end
263
264  def initialize(parent = nil)
265    create_gui(parent)
266  end
267end
268
269Tk.root.withdraw unless $RubyTk_WidgetDemo
270Thread.new{Tk.mainloop} if __FILE__ == $0
271Knights_Tour.new
272