Message-ID: <02Nov93.114144@LoVerso.Southborough.MA.US>
From: John Robert LoVerso <John@LoVerso.Southborough.MA.US>
Organization: John & Sue's House, Southborough MA
Newsgroups: comp.lang.tcl
Subject: text widget wrapper

Below is a module I call "text.constrain.tcl" which wraps around the
text widget to change some of it's behavior.  Some of the code is
original to me; most of it I have collected from various sources
(which credit attributed as it is due).

Once you install this in your auto_path (with an appropriate update
to tclIndex), an application merely needs to call:

	text:Init

to pull in the new features.  This interposes on the "text" and "scrollbar"
commands as necessary to implement things.  It does not interpose on the
widget commands (this implies that changing a text widget's -yscrollcommand
or a scrollbar's -command will "break" this package).

The features added:
	- constrained scrolling and scanning
		This makes the scrollable text constrained ala an xterm.
		That is, the last line of the text cannot scroll up
		past bottom edge of the widget.  I find this a feature
		when I want to scan or scroll to the bottom of the text;
		I'd prefer not to end up with just one line displayed.

		I originally got this idea from a comp.lang.tcl posting,
		but I no longer know the author.  If the code in text:oldYview 
		is vaguely familiar, let me know.  However, Brent Welch
		took this and improved it, so I know include his version
		(with my variable names).

	- Paste or Scan via Button-2
		From Tom Phelps <phelps@ginkgo.CS.Berkeley.EDU>.

	- Use catch around all [selection get] to avoid errors

	- Allow selections to extend past displayed screen
		From code by Paul E. Raines <raines@cgibm1.SLAC.Stanford.EDU>
		as modified by Brent Welch <welch@parc.xerox.com>.
	
	- Provides binding for Next/Prior keys for scrolling by pages
		This works whether or not the text widget has a scrollbar.

Also included is a demonstration program, tkpage.  Usage: tkpage files...
It loads the contents of files into a text widget and then lets you page,
scan, or scroll over them.  It has a toggle button or two to enable/disable
some features of the text.constrain.tcl.

All this works with 7.0/3.3.  I make no statements about other Tcl/Tk releases.
I hope this is useful to someone.

John


Thu Mar 03 12:08:04 EST 1994

Addendum:

	The code for Prior/Next & the constrained scrollbar code 
	was used to "seed" the work that went into lib/widgetText.tcl
	in "exmh".  THAT version of the code may be more robust.

Also, "tkpage" is a testbed program that I've used for several purposes.
It is only a "demonstration" program and unworthly by itself.  Two other
things I've used it for is to aid in development of a set of vi-like
bindings for the text widget, and a MIME text/enriched decoder.
text.vi.tcl is still pending; I've abandoned enriched.tcl.  Brent Welch
has an excellent text/enriched decoder in exmh.