| AW: [platform-ui-dev] Difference between Action and Command |
Well I think the GEF team is not thinking of this but this is off-topic here. You can't use the Command framework from GEF or EMF here because the Eclipse platform can't depend on such specialized technology (EMF or GEF). The only possible solution is to create a new and complete undo/redo command framework integrated into the Eclipse platform, which can be reused by EMF and GEF. That means at least new package names ;) Cu, Gunnar -----Ursprüngliche Nachricht----- Von: Joseph Khalil [mailto:jkhalil@xxxxxxxxxx] Gesendet: Do 07.08.2003 06:45 An: platform-ui-dev@xxxxxxxxxxx Cc: Betreff: Re: [platform-ui-dev] Difference between Action and Command 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) ------------------------------------------------------------------------------------------- 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 ------------------------------------------------------------------------------------------- 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 _______________________________________________ platform-ui-dev mailing list platform-ui-dev@xxxxxxxxxxx http://dev.eclipse.org/mailman/listinfo/platform-ui-dev _______________________________________________ platform-ui-dev mailing list platform-ui-dev@xxxxxxxxxxx http://dev.eclipse.org/mailman/listinfo/platform-ui-dev _______________________________________________ platform-ui-dev mailing list platform-ui-dev@xxxxxxxxxxx http://dev.eclipse.org/mailman/listinfo/platform-ui-dev
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