RE: [platform-ui-dev] Proposal for CommandStack in JFace

[Scott Stanchfield <scott@xxxxxxxxxxxx>]

You're correct in that Swing's implementation only requires undo/redo methods and not an execute method. That could be overcome by subclassing to add an execute. Alternatively, because the "redo" is quite often the exact same code as the execute, the convention could be to just use the redo when executing, and if the command needed to do something different for a "real" redo, it could keep track of whether it is being "done" or "redone".

 

From what I can see, the Swing edit classes/interfaces aren't specific to text editing; there are some implementations/subclasses that add specific support, as that's pretty much the only area that Swing uses the command pattern.

 

RE changes performed by the widget; what you're seeing is poor implementation of the undo support interfaces being used by the text widgets. I totally agree that the command itself should make the model changes. However, I don't see anything in the interfaces that require this approach. I think they could be used in exactly the same way as the GEF/EMF commands...

 

Check out the javax.swing.undo.UndoManager class too -- you should be able to add commands to the undo manager that indicate when the user saved, and you can undo/redo to that point, as well as check if the last significant edit (command) was a Save, which would indicate the editor is clean as well.

 

So...

 

Based on what I'm hearing/seeing so far, I'd stand by my suggestion.

 

I'd definitely like to hear if I missed something else though, and I'd like to hear from some of the EMF folks as well...

 

-- Scott 

==============================================================
Scott Stanchfield    scott@xxxxxxxxxxxx    http://javadude.com

Lead author of "Effective VisualAge for Java, Version 3"
                                      http://javadude.com/evaj

VisualAge for Java Tips and Tricks     http://javadude.com/vaj

AWT & Swing FAQ Manager, jGuru.com
Visit for Java Enlightenment!             http://www.jguru.com
==============================================================

-----Original Message-----
From: platform-ui-dev-admin@xxxxxxxxxxx [mailto:platform-ui-dev-admin@xxxxxxxxxxx]On Behalf Of Randy Hudson
Sent: Sunday, January 05, 2003 8:37 PM
To: platform-ui-dev@xxxxxxxxxxx
Subject: RE: [platform-ui-dev] Proposal for CommandStack in JFace

Scott--
I'll start off by answering your first response. I knew about Swing's undo support but have never looked at it until now. I think the main difference between our approach and the Swing approach is that Swing is missing the execute portion of the command.  Swing's UndoableEdit is designed for a text widget, where the change to the "model" is handled internally by the widget, and the change is simply *documented* on the undo stack. UndoableEdit does NOT make the change itself.

Our command has a .execute().  It is intended that the model be changed only by the command.  However, there are still cases like the ones Swing designed for (for example, continuous typing).  Editors like Page Designer (an HTML editor) can still achieve the Swing behavior by making execute() a no-op.

Our CommandStack offers a little more.  It now contains a mechanism for marking the save point, and then detecting when the User has undone the stack to the save point, indicating the Editor is "clean".

Finally, Swing lets you label (and therfore translate) the command in both directions.  I recommended this at one point, but none of our translators have identified situations where this is necessary.

Swing's classes are not a suitable alternative.

Frank--
I don't think this is something unique to Graphical or EMF-based editors, so I don't think you are arguing that they should stay in GEF/EMF.
1)Are arguing that they need to be in Core or some plugin higher-up?
2)What is missing in the proposed API that cannot be achieved in subclasses?

UI Team--
The TextEditor could benefit from better undo support.  Lots of cool stuff has been added to AutoIndentStrategies, but some of these features result in two or more "edits" to the StyledText widget.  The result is that a single keystroke requires multiple undos.  For an example, type a Javadoc header '/**' in front of a method and press ENTER, then undo the change.

-Randy

Scott Stanchfield <scott@xxxxxxxxxxxx> Sent by: platform-ui-dev-admin@xxxxxxxxxxx 01/04/2003 02:18 PM Please respond to platform-ui-dev

To:        platform-ui-dev@xxxxxxxxxxx         cc:        platform-ui-dev-admin@xxxxxxxxxxx         Subject:        RE: [platform-ui-dev] Proposal for CommandStack in JFace

This is the type of thing that would make me suggest switching both
implementations to the Swing undo framework. It's very similar (from what I
see so far), and doesn't have any dependency on UI code (despite being under
javax.swing.undo).

Because it's in the Java core, both EMF and GEF (as well as anything else
that wants undo support) could use it without depending on other plugins.

Thoughts?
-- Scott

==============================================================
Scott Stanchfield    scott@xxxxxxxxxxxx    http://javadude.com

Lead author of "Effective VisualAge for Java, Version 3"
                                     http://javadude.com/evaj

VisualAge for Java Tips and Tricks     http://javadude.com/vaj
Visit for Java Enlightenment!             http://www.jguru.com
==============================================================

> -----Original Message-----
> From: platform-ui-dev-admin@xxxxxxxxxxx
> [mailto:platform-ui-dev-admin@xxxxxxxxxxx]On Behalf Of frankb@xxxxxxxxxx
> Sent: Saturday, January 04, 2003 2:12 PM
> To: platform-ui-dev@xxxxxxxxxxx
> Cc: platform-ui-dev@xxxxxxxxxxx; platform-ui-dev-admin@xxxxxxxxxxx
> Subject: Re: [platform-ui-dev] Proposal for CommandStack in JFace
>
>
> This proposal isn't acceptable for EMF. EMF's common commands are UI
> independent - they can't have a dependency on JFace. The proposed API is
> also not sufficient.
>
> Frank.
>
>
>
>
>
>
>                       Randy
>
>                       Hudson/Raleigh/IBM@IBM        To:
> platform-ui-dev@xxxxxxxxxxx
>
>                       US                            cc:
>
>                       Sent by:                      Subject:
> [platform-ui-dev] Proposal for CommandStack in JFace
>
>                       platform-ui-dev-admin@
>
>                       eclipse.org
>
>
>
>
>
>                       01/03/2003 06:11 PM
>
>                       Please respond to
>
>                       platform-ui-dev
>
>
>
>
>
>
>
>
>
>
> GEF provides a Command and CommandStack implementation. This should be
> moved into JFace (which was proposed _too_ late during the 2.0
> developement
> cycle).
>
> Other technologies such as EMF [Edit] also require their own Command and
> CommandStack. We have both invented the wheel. When plugins
> combine GEF and
> EMF, it becomes difficult to deal with multiple definitions of the same
> concept/classes.
>
> Attached is a proposal for a Command and CommandStack implementation.
> Moving them into JFace will simplify future WSAD releases as well as the
> work of others who are combining the "Tools" plugins mentioned above.
>
> We are considering one more feature for the CommandStack (the ability to
> append to an executing command), but the code itself it pretty simple and
> stable ;-)
>
> -Randy
>
>
>
>
> #### JFaceCommands.jar has been removed from this note on January 04 2003
> by Frank Budinsky
>
>
> _______________________________________________
> platform-ui-dev mailing list
> platform-ui-dev@xxxxxxxxxxx
> http://dev.eclipse.org/mailman/listinfo/platform-ui-dev
>


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