From: Chris <c-soc-google@...>
Date: 2009-02-27T12:44:13+09:00
Subject: Ruby/Tk: how to get Scrollbar to stay scrolled on non-scroll widget?

Hello all,

I am trying to get a new grid control working (similar to a TreeView
without the tree) and my most recent problem is to get the Scrollbar
to respond to the changes it initiates in the grid.  I've tried a few
things, but nothing on the web seems to deal with getting a Scrollbar
to work with anything that isn't already inside Tk and has the correct
hooks.  The closest I've come is some allusions at
http://www.tkdocs.com/tutorial/onepage.html

The code I was trying includes this just after the widgets are setup:
	@v_scroll.command proc{|*args| self.yview(*args)}
#	self.yscrollcommand proc{|*args| @v_scroll.set(*args)}
	self.yscrollcommand proc{|*args| @v_scroll.set
(@y_scroll_start_fraction, @y_scroll_end_fraction)}
The scrollbar responds since I defined yview to send to internal
yviewMoveTo and yviewScroll methods (as I found somewhere else): the
move commands are sent to the correct methods.  However once the user
releases the scrollbar it always returns to the original position.

I tried defining it the same as in existing widgets, eg:
	def yscrollcommand block
		configure_cmd 'yscrollcommand', block
		self
	end
But even if I include TkConfigMethod and TkComm in the class, it can't
figure out what TkConfigMethod's path is (and I certainly don't
know).  I also tried some other things like using the standard *args
version above and have this definition of yscrollcommand:
	block.call(@y_scroll_start_fraction, @y_scroll_end_fraction)
But apparently I am missing some deeper understanding of what the
process is here.

Has anyone been successful at this, or otherwise knows what kind of
abstraction histrionics are required?


Thanks!

-Chris