From: Hidetoshi NAGAI <nagai@...>
Date: 2004-04-30T13:52:22+09:00
Subject: Re: Ruby/Tk - TkComposite

Hi, 

From: mhm26@drexel.edu (matt)
Subject: Ruby/Tk - TkComposite
Date: Fri, 30 Apr 2004 10:19:02 +0900
Message-ID: <13383d7a.0404291715.4208c80c@posting.google.com>
> Are there any good pointers on where to learn how to make new Tk
> Widgets?  I'm not a Tk guy, and I've been using Ruby/Tk for only about
> a week and a half (so I'm making okay stuff, but not even near
> guru...)

There are some samples in 'ext/tk/sample' directory of Ruby source 
archive.
'tkmulticolumnlist.rb', 'tkmultilistbox.rb', tkmultilistframe.rb', 
and 'tktextframe.rb' use TkComposite module. 'tkalignbox.rb' and 
'tkballoonhelp.rb' don't use the module. 

When create a new widget class, you shold make it as a daughter 
class of TkWindow. If you want to use TkComposite module, note 
@path, @epath, and 'delegate' method. 

Each of @path and @epath keeps a Tk's widget path string. 
General widgets keep same string on both of @path and @epath. 
@path decides the receiver widget of method calls, and @epath 
(returned by 'epath' method) is used by geometry managers. 

A composite widget is a widget set layouted on a frame widget. 
So, @epath of the composite widget has to denote the frame widget. 
The composite widget's initializer overrided by TkComposite module 
create a frame widget (kept on @frame) as a container, and set 
@path and @epath to the path name of the frame widget. After that, 
the initializer calls 'initialize_composite' method. In the 
'initialize_composite' method, you will create widgets as parts 
of the composite widget and set @path to the pathname of one of 
the widgets. 

'delegate' method is used to make easier for controlling options 
of contained widgets. 1st argument of the method is a name of 
the widget option, and others are widgets to change the option 
simultaneously. For example, on 'tktextframe.rb', 
--------------------------------------------------------------
    delegate('DEFAULT', @text)
    delegate('background', @frame, @h_scroll, @v_scroll)
    delegate('activebackground', @h_scroll, @v_scroll)
    delegate('troughcolor', @h_scroll, @v_scroll)
    delegate('repeatdelay', @h_scroll, @v_scroll)
    delegate('repeatinterval', @h_scroll, @v_scroll)
    delegate('borderwidth', @frame)
    delegate('relief', @frame)
--------------------------------------------------------------
When the configure method of the composite widget is called 
(e.g. widget['troughcolor'] = 'yellow'), the option name is 
searched on the delegate table of the widget. If find it, 
configure all widgets of the list defined by 'delegate' method 
(e.g. configure 'troughcolor', both of @h_scroll and @v_scroll 
are changed about the option). If cannot find the definition, 
'DEFAULT' entry is used. 

When not include TkComposite module, note @path and 'epath' method. 
Although sample 'tkalignbox.rb' and 'tkballoonhelp.rb' override 
'initialize' method, you can define an initializer by overriding 
'create_self' method. The following is one of the simple examples.
--------------------------------------------------------------
require 'tk'

class Button_with_Frame < TkButton
  def create_self(keys)
    @frame = TkFrame.new('widgetname'=>@path, 'background'=>'yellow')
    install_win(@path) # create new @path which is a daughter of old @path
    super(keys)
    TkPack(@path, :padx=>7, :pady=>7)
    @epath = @frame.path
  end
  def epath
    @epath
  end
end

Button_with_Frame.new(:text=>'QUIT', :command=>proc{exit}) {
  pack(:padx=>15, :pady=>5)
}

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