home *** CD-ROM | disk | FTP | other *** search
- Newsgroups: comp.lang.tcl
- Path: sparky!uunet!eco.twg.com!twg.com!news
- From: "David Herron" <david@twg.com>
- Subject: Re: Wishes for TK listboxes & scrollbars
- Message-ID: <1992Jul29.211736.1744@twg.com>
- Sensitivity: Personal
- Encoding: 75 TEXT , 4 TEXT
- Sender: news@twg.com (USENET News System)
- Conversion: Prohibited
- Organization: The Wollongong Group, Inc., Palo Alto, CA
- Conversion-With-Loss: Prohibited
- Date: Wed, 29 Jul 1992 21:19:21 GMT
- Lines: 80
-
- Wolfgang Fischer sent me a private note asking a couple of questions and
- trying to explain why TK shouldn't have a viewport widget. At least that's
- what I think he was trying. In any case, I wrote a response but the mail
- bounced because of his address: Wolfgang Fischer <wf@athen.uucp>. This is
- not a proper domain name and I haven't the foggiest idea how to reach it.
-
- Since the reply is likely of general interest .....
-
- > This is a conceptual difference between Motif and tk. The scrollbar
- > is a entity in itself talking to the scrolled widget and beeing called
- > from the scrolled widget.
-
- you can do that in Motif as well. But it's more difficult to set up.
- Just like with TK, you must set up communication between the two widgets.
- In TK it's pretty trivial, while in Motif it isn't.
-
- > If a widget does not want a scrollbar, it does not configure one.
-
- NIT: It is not the widget which wants or not wants.. it is the programmer.
-
- With TK listbox+scrollbar situations the scrollbar is there all the time.
- Granted a programmer could set up code to detect the need for the scrollbar,
- but that is never done because it is hard to do.
-
- > If the contents of a window is to large in whatever direction, the
- > widget may configure one or two scrollbars.
-
- Again, in TK the widget cannot do this automatically. The programmer has to
- write code to do it (non-trivial).
-
-
- The advantage of XmScrolledWindow is its generality. It is useful for listboxes
- and editboxes to automatically pop scrollbars up and down on need. The equivalent
- in TK is to create one or two scrollbars, and set up mutual callbacks to update
- each others details. This works well with things which already support the
- `scrolling' idea.
-
- But a viewport window (that is, XmScrolledWindow) is much more generally
- usable than that. It can be used with any other widget, ones which don't
- normally support the scrolling idea. A scrolled button is a very real (and
- weird) possibility. The place where Motif makes really good use of this
- is on the XmMainWindow and XmPanedWindow widgets.
-
- Main windows can be set up so that resizing them to be too small will pop
- up scroll bars at the edges of the window. The user then has a viewport..
-
- Paned windows have the same effect as main windows, but there is one viewport
- per pane.
-
- > But why are you not posting your tk-procs to get the keyboard
- > commands?
-
- I did. (yesterday)
-
-
-
-
-
-
-
-
- While writing the above I remembered that the canvas widget (new in tk2.1)
- has a viewport facility in it. But that the viewport area is unable to
- hold regular TK widgets.
-
- It would be really nifty-keano if the viewport part would be spun off into its
- own widget and that it were able to manage any TK widget. It should support
- the yscrollcommand and xscrollcommand concept from the listboxes and edit boxes.
- Come to think of it.. there should already be code to do viewports in the
- listbox code already there.
-
- Like I was saying to Wolfgang.. having a viewport widget is a lot more
- flexibility since it allows the scrolling ability to be added to any other
- widget. The most useful will be to the window as a whole. It would be a
- step in the direction to having paned windows in tk. &c
-
- <- David Herron <david@twg.com>, Just: Another E-Mail hacker ...
- <-
- <- As for the prevalence of gratuitous stupidity in modern life, well,
- <- need I say more than "MS-DOS"? -- Bill Janssen
-