From: David Bailey <david.bailey@...>
Date: 2006-04-01T22:41:56+09:00
Subject: Re: Ruby/Tk (X,Y) Coordinate Question

unknown wrote:
> You could try "%X %Y" to get coordinates relative to the top left corner
> of the program.
> 
> There is also a "%W" that might be useful.  If I remember correctly, it
> returns the id of the widget the mouse clicked, but it might return the
> reference.

Um, just to try out these %X and %Y objects real quick, I added X, Y, %X 
and %Y to my argument list in the callback proc in the same form as the 
x, y, %x and %y objects to see what would happen, but got the following 
"dynamic constant assignment" and "formal argument" errors:

C:\Documents and Settings\dbailey1\Desktop\Ruby My Dear>ruby 
sudoku_treasury.rb
sudoku_treasury.rb:15: dynamic constant assignment
    @root.bind('Button', proc{|b,x,y,X,Y| mainCellClickedProc(b, x, y, 
X, Y)}, "%b %x %y %X %Y")
                                       ^
sudoku_treasury.rb:15: dynamic constant assignment
    @root.bind('Button', proc{|b,x,y,X,Y| mainCellClickedProc(b, x, y, 
X, Y)}, "%b %x %y %X %Y")
                                         ^
sudoku_treasury.rb:68: formal argument cannot be a constant
  def mainCellClickedProc(btn,x,y,X,Y)
                                   ^
sudoku_treasury.rb:68: formal argument cannot be a constant
  def mainCellClickedProc(btn,x,y,X,Y)
                                     ^
sudoku_treasury.rb:116: formal argument cannot be a constant
  def tell_it(btn, x, y, X, Y)
                          ^
sudoku_treasury.rb:116: formal argument cannot be a constant
  def tell_it(btn, x, y, X, Y)
                             ^
C:\Documents and Settings\dbailey1\Desktop\Ruby My Dear>

What are these %X and %Y objects, and where can I find some 
documentation on them?  But, more to the point, what does the "%" 
leading character on these object names mean?  I am looking through the 
pickaxe book, but I'm not finding any reference to "%" outside of the 
modulo operator.  Please excuse my ignorance of Ruby syntax and 
semantics!

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