From: Hidetoshi NAGAI <nagai@...>
Date: 2004-12-03T23:23:33+09:00
Subject: Re: Tk mouse events and keys

Hi, 

From: "R. Mark Volkmann" <mark@ociweb.com>
Subject: Tk mouse events and keys
Date: Fri, 3 Dec 2004 21:05:09 +0900
Message-ID: <01be01c4d930$52e58e50$0200a8c0@MarkDesktop>
> I'm using the following code to detect a left mouse click.
> 
>     canvas.bind('1', proc {|event| doPress(event)})
> 
> Inside my doPress method, is there a way I can ask the event object whether
> the ctrl key was down when the mouse button was pressed?

Please see Tcl/Tk's "bind" manual. :-)
Modifiers of event sequence are required.
When a widget has 'Shift-Button-1' and 'Button-1' binding and 
the button 1 is pressed *WITHOUT* Shift-key on the widget, 
both of the sequences can mathe the event.
Then, the binding which is called for the event is decided 
based on the following rules.

  Rule1: Only one binding is called on each bindtag (NOT each widget).
  Rule2: More detailed sequence description  has higher priority.
  Rule3: The binding defined at last has highest priority. 

The following is a test script. I think the script will help you.
-------------------------------------------------------------------
#!/usr/bin/env ruby
require 'tk'

root = Tk.root

$ctrl_st  = false
$shift_st = false
$alt_st   = false

def p_st(btn, x, y, ctrl, shift, alt)
    puts "btn#{btn}(#{x},#{y}) ctrl=>[#{$ctrl_st},#{ctrl}] shift=>[#{$shift_st},#{shift}] alt=>[#{$alt_st},#{alt}]"
end

root.bind('KeyPress-Control_L', proc{puts 'press ctrl'; $ctrl_st = true})
root.bind('KeyRelease-Control_L', proc{puts 'release ctrl'; $ctrl_st = false})
root.bind('KeyPress-Control_R', proc{puts 'press ctrl'; $ctrl_st = true})
root.bind('KeyRelease-Control_R', proc{puts 'release ctrl'; $ctrl_st = false})

root.bind('KeyPress-Shift_L', proc{puts 'press shift'; $shift_st = true})
root.bind('KeyRelease-Shift_L', proc{puts 'release shift'; $shift_st = false})
root.bind('KeyPress-Shift_R', proc{puts 'press shift'; $shift_st = true})
root.bind('KeyRelease-Shift_R', proc{puts 'release shift'; $shift_st = false})

root.bind('KeyPress-Alt_L', proc{puts 'press alt'; $alt_st = true})
root.bind('KeyRelease-Alt_L', proc{puts 'release alt'; $alt_st = false})
root.bind('KeyPress-Alt_R', proc{puts 'press alt'; $alt_st = true})
root.bind('KeyRelease-Alt_R', proc{puts 'release alt'; $alt_st = false})

root.bind('Button', 
          proc{|b, x, y| p_st(b, x, y, false, false, false) }, '%b', '%x','%y')
root.bind('Control-Button', 
          proc{|b, x, y| p_st(b, x, y, true, false, false) }, '%b', '%x','%y')
root.bind('Shift-Button', 
          proc{|b, x, y| p_st(b, x, y, false, true, false) }, '%b', '%x','%y')
root.bind('Alt-Button', 
          proc{|b, x, y| p_st(b, x, y, false, false, true) }, '%b', '%x','%y')
root.bind('Shift-Alt-Button', 
          proc{|b, x, y| p_st(b, x, y, false, true, true) }, '%b', '%x','%y')
root.bind('Control-Alt-Button', 
          proc{|b, x, y| p_st(b, x, y, true, false, true) }, '%b', '%x','%y')
root.bind('Control-Shift-Button', 
          proc{|b, x, y| p_st(b, x, y, true, true, false) }, '%b', '%x','%y')
root.bind('Control-Shift-Alt-Button', 
          proc{|b, x, y| p_st(b, x, y, true, true, true) }, '%b', '%x','%y')

Tk.mainloop
-------------------------------------------------------------------
-- 
                                  Hidetoshi NAGAI (nagai@ai.kyutech.ac.jp)