Tk read-only text box

[nornagon]

Another Tk question.

Perl/Tk has a widget called Tk::ROText, which acts just like a text
box, with the exception that the user cannot enter text into it.

I need something with the same functionality; I would like the user to
be able to select the text and scroll through it, but not edit it.
Also, I need to be able to change its contents dynamically.

Thanks,
--=20
- nornagon

 

[Hidetoshi NAGAI]

From: nornagon <[email protected]>
Subject: Tk read-only text box
Date: Tue, 24 May 2005 06:56:06 +0900

I need something with the same functionality; I would like the user to
be able to select the text and scroll through it, but not edit it.
Also, I need to be able to change its contents dynamically.

Hmmm.... Probably there are some ways.
One of the ways is "block Key events".
To do that, please use Tk.callback_break.
For example,
---------------------------------------------------
require 'tk'
t = TkText.new.pack
t.bindtags_unshift(b = TkBindTag.new)
b.bind('Key', proc{ Tk.callback_break })

t.insertend, "This is a test message.\n");

Tk.after(10000){t.insertend, "This is another test message.\n")}

Tk.mainloop

 

[nornagon]

From: nornagon <[email protected]>
Subject: Tk read-only text box
Date: Tue, 24 May 2005 06:56:06 +0900

=20
Hmmm.... Probably there are some ways.
One of the ways is "block Key events".
To do that, please use Tk.callback_break.
For example,
---------------------------------------------------
require 'tk'
t =3D TkText.new.pack
t.bindtags_unshift(b =3D TkBindTag.new)
b.bind('Key', proc{ Tk.callback_break })
=20
t.insertend, "This is a test message.\n");
=20
Tk.after(10000){t.insertend, "This is another test message.\n")}
=20
Tk.mainloop
---------------------------------------------------

Interesting. Could you tell me how that works, exactly? Like, what's
bindtags_unshift do? What's a BindTag, even?

Thanks a lot for your patience. ^_^

--=20
- nornagon

 

[Hidetoshi NAGAI]

From: nornagon <[email protected]>
Subject: Re: Tk read-only text box
Date: Tue, 24 May 2005 15:40:25 +0900

Interesting. Could you tell me how that works, exactly? Like, what's
bindtags_unshift do? What's a BindTag, even?

Each widget has a bindtag list to determine bindings which should be
appleid. The default value of the list is [<self>, <class of the
widget>, <toplevel which the widget is placed on>, 'all'].
When an event occurs on the widget, one or none of the procedures
binded to each bindtag is called. Of course, the event sequence of
the binding has to matche the event. Usually, the calling process is
done in order of the bindtag list. Tk.callback_break can break the
sequence and complete the operation for the event.

You can get/set the bindtag list by bindtags/bindtags= method. And can
add a new bindtag to the head of the list by bindtags_unshift method
(remove the head by bindtags_shift method).

If you remove <class of the widget> from a bindtag list of a widget,
the widget lose all bindings of the widget class. If add <class of the
widget> again, the widget gets the bindings of the widget class again.

Well, in the example case, a new bindtag is inserted at head of the
bindtag list of the text widget. The bindtag has a binding for all
"Key" events. And the binding is "Tk.callback_break", that is, "finish
the operation for the event".

The operataion "insert a key-pressed character" is one of the bindings
for a kind of "Key" event. And it is binded on <class of the widget>,
that is, "TkText".

However, on the example, all kind of "Key" events are blocked on the
new bindtag and aren't checked on "TkText" tag. So, keyboard events
cannot change the text widget.

# The reason of why don't remove "TkText" tag is to be able to accept
# mouse events.

 

[nornagon]

From: nornagon <[email protected]>
Subject: Tk read-only text box
Date: Tue, 24 May 2005 06:56:06 +0900

=20
Hmmm.... Probably there are some ways.
One of the ways is "block Key events".
To do that, please use Tk.callback_break.
For example,
---------------------------------------------------
require 'tk'
t =3D TkText.new.pack
t.bindtags_unshift(b =3D TkBindTag.new)
b.bind('Key', proc{ Tk.callback_break })
=20
t.insertend, "This is a test message.\n");
=20
Tk.after(10000){t.insertend, "This is another test message.\n")}
=20
Tk.mainloop
---------------------------------------------------

Hmm. I've been using this for a while and it works quite nicely.
However, I've noticed that it prevents you from copying from the text
box using Ctrl+C. Is there a way to fix this?

--=20
- nornagon

 

[Hidetoshi NAGAI]

From: nornagon <[email protected]>
Subject: Re: Tk read-only text box
Date: Wed, 25 May 2005 21:37:04 +0900

Hmm. I've been using this for a while and it works quite nicely.
However, I've noticed that it prevents you from copying from the text
box using Ctrl+C. Is there a way to fix this?

Here is an example.
----------------------------------------------------------------
require 'tk'
t = TkText.new.pack
t.bindtags_unshift(b = TkBindTag.new)
b.bind('Key', proc{ Tk.callback_break })
b.bind('Control-KeyPress-w',
proc{ Tk.callback_continue }) # continue to the next bindtag
b.bind('Control-KeyPress-y', proc{})
b.bind('Control-KeyPress-c', proc{t.insertend, "Press Ctrl-C !!\n")})
b.bind('Control-Alt-KeyPress-c', proc{exit})

t.insertend, "This is a test message.\n");

Tk.after(10000){t.insertend, "This is another test message.\n")}

Tk.mainloop

 

[Hidetoshi NAGAI]

From: Hidetoshi NAGAI <[email protected]>
Subject: Re: Tk read-only text box
Date: Wed, 25 May 2005 23:21:52 +0900

Here is an example.
----------------------------------------------------------------
require 'tk'
t = TkText.new.pack
t.bindtags_unshift(b = TkBindTag.new)
b.bind('Key', proc{ Tk.callback_break })
b.bind('Control-KeyPress-w',
proc{ Tk.callback_continue }) # continue to the next bindtag
b.bind('Control-KeyPress-y', proc{})
b.bind('Control-KeyPress-c', proc{t.insertend, "Press Ctrl-C !!\n")})
b.bind('Control-Alt-KeyPress-c', proc{exit})

t.insertend, "This is a test message.\n");

Tk.after(10000){t.insertend, "This is another test message.\n")}

Tk.mainloop
----------------------------------------------------------------

It goes without saying that the following is same to replace
the standard callback function of the text widget.