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Re: [platform-ui-dev] Difference between Action and Command
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Hi eclipse dev. team
I just want to mark something about the command framework
Please use the EMF command framework and not to invent your own command
framework
This problem already exists in GEF because they have their own command
framework , and they are thinking of moving to the EMF command framework in
the future.
so , please don't do the same mistake GEF did in the past
Best regards,
Joseph G.M. Khalil
Software Engineer
Business Integration Product Development
Cairo Technology Development Center (TDC)
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IBM Egypt
Address: 72 Gameat Al-Dowal Al-Arabia St., Fifth Floor, Mohandesseen, Giza
12311, Egypt
Phone: +202 761-7394
+202 761-7392
+202 761-7393, Ext.123
Email:jkhalil@xxxxxxxxxx
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Chris
McLaren/Ottawa/IBM@IBM To: platform-ui-dev@xxxxxxxxxxx
CA cc:
Sent by: Subject: Re: [platform-ui-dev] Difference between Action and
platform-ui-dev-admin@ Command
eclipse.org
06-08-2003 22:11
Please respond to
platform-ui-dev
yes. the command is just that: a classification id for a group of
semantically related actions. you are dead on that the name, description,
etc. was added to commands initially (solely, right now, in fact) to
support the key bindings preference page. as i mentioned, i'd like to see
these names and descriptions eventually being used other places as well,
like menus and toolbars for instance. i like the wording that a command
'identifies a common class of actions'.
as for scott's definition of 'action' (i think influenced by swing),
scott's 'action name' is equivalent to command ids. we build the
equivalent of swing's 'input map' by each plugin contributing keybindings
for command ids via the commands extension point. the equivalent of
swing's 'action map' is the workbench choosing the proper action for a
command. (which is basically 'retargeting')
the difference between swing and this mechanism is that we will probably
put commands on menus and toolbars rather than actions. this will decouple
menus and toolbars from actions in a way that swing cannot. which makes me
wonder if the word 'action' is too confusing, considering swing user's
think of it as the thing put on the menus and toolbars themselves. perhaps
'handler' might be a less confusing word than 'action'.?
also, back to undo/redo, i would expect that in an undo/redo mechanism, it
is the particular action itself that would choose to place undo objects on
an undo stack following execution. only the particular action knows how to
undo itself. that's why i felt undo/redo was really a side topic to this
notion of commands, but i agree the terminology is confusing here as well,
as this 'undo object' that an action would add to an undo stack is often
known as a 'command'.
as the commands extension point was put in in 2.1, it looks like that is
the only use of the term that is unchangable right now.
chris.
Randy Hudson/Raleigh/IBM@IBMUS
Sent by: platform-ui-dev-admin@xxxxxxxxxxx
08/06/2003 02:32 PM
Please respond to platform-ui-dev
To: platform-ui-dev@xxxxxxxxxxx
cc:
Subject: Re: [platform-ui-dev] Difference between Action and
Command
Sorry, I was a little confused and thought some new concept was brewing.
To clarify, a "command" is not an interface or java type anywhere, just an
extension point. In fact, it is nothing but an Action descriptor ID,
which is later used to identify a common "class" of Actions. But, since
the keybindings preference page needs a way to label/categorize/configure
the keybindings, there are a few more properties for a command extension
point.
Perhaps "Action Class" (meaning some group of related actions) is a term
which would help people understand commands as they are used here.
Sorry for the mix-up. It looks like eclipse.core has another meaning for
Command too ;-)
-Randy
"Chris McLaren" <Chris_McLaren@xxxxxxxxxx>
Sent by: platform-ui-dev-admin@xxxxxxxxxxx
08/06/2003 02:01 PM
Please respond to platform-ui-dev
To: platform-ui-dev@xxxxxxxxxxx
cc:
Subject: Re: [platform-ui-dev] Difference between Action
and Command
The definitions are close. The term 'command', introduced in 2.1 as part
of the commands extension point, is used to describe a request from a
user. I define an 'action' as the object which executes a command.
This distinction means:
1. Commands have unique ids, names (used in menu labels, etc),
descriptions (used in tooltips), help ids.
2. Commands can have keybindings assigned to them.
3. Commands can be bound to particular contexts.
4. Commands can have various images bound to them (for use in menus and
toolbars)
5. Commands, via the context mechanism, decide whether or not it should be
visible in the menus or toolbars.
6. Actions do the actual work for a command. Based on the active part,
perspective, etc, the workbench chooses the best action to which to
delegate the actual execution of the command.
7. The action that the workbench has chosen decides whether it is enabled
or not ('can be executed'), and affects the enabled state where commands
appear on menus and toolbars.
8. The action can optionally override the name, description, or help id to
provide more specific information than the command itself usually provides
in those places in the UI which accept these overrides, such as the menus
and toolbars. e.g. The current action for 'Copy' might override the name
to 'Copy Image', but should not override it to say 'Cut'. Other parts of
the UI would always use the proper name of the command. e.g. the names and
descriptions of the commands as presented in the keybindings UI should not
use any overridden names or descriptions provided by the current actions,
if any.
When I say 'command-centric' I'm thinking the following ideas:
1. That perhaps menus and toolbars should be explicitly defined in terms
of commands. Rather than have the action specify a menu or toolbar path,
the command should be bound to particular menus and toolbars, and the
action should only worry about handling command execution when it is
asked. I am currently exploring a 'menus' extension point to explicity
define reusable and compositable menus in terms of commands.
2. Keybindings and other means of command execution (i.e. scripting..)
should only be concerned with the command itself and not the action.
As far any naming confusion with an undo/redo mechanism, I'm not so
concerned. Perhaps we will see that ideas are one in the same when the
time comes to add a proper undo/redo stack to eclipse. The primary goal
right now is to unwind some of the more tangled knots in the current
action architecture. I am working on a 'Commands' proposal now, as well as
perhaps as separate proposal for a 'menus' extension point which should
help here.
Chris
Randy Hudson/Raleigh/IBM@IBMUS
Sent by: platform-ui-dev-admin@xxxxxxxxxxx
08/06/2003 01:21 PM
Please respond to platform-ui-dev
To: platform-ui-dev@xxxxxxxxxxx
cc:
Subject: [platform-ui-dev] Difference between Action and
Command
In the recently announced "contexts" proposal:
"As Eclipse moves from an action-centric model to command-centric model,
action sets would disappear entirely"
To me "action" and "command" are the same thing. What is the difference
here between a command and an action? Where can I read more on the new
"command" stuff?
Won't this be confusing since the term "command" is widely used to mean a
change which can be undone and redone? There is also a bugzilla open
tracking the proposal to add undo/redo to the workbench.
-Randy
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