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List:       kde-devel
Subject:    handling complex logic to enable/disable actions
From:       Stefano Crocco <stefano.crocco () alice ! it>
Date:       2009-06-23 12:42:48
Message-ID: 200906231442.49002.stefano.crocco () alice ! it
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Hello to everyone,

I'm developing an application for KDE, and I'm usingthe XML GUI framework to 
enable and disable actions. I know how to do it for simple situations. For 
example, if I have an action which starts an external process and one which 
stops it, I can write:

<State name="process_started">
  <enable>
    <Action name="stop_process"/>
  </enable>
  <disable>
    <Action name="start_process/>
  </disable>
</State>

This way, when I set the "process_started" state, the "stop_process" action 
will be enabled and the "start_process" will be disabled.

The problem arises if I need a more complex logic to find out whether an 
action should be enabled or not. For example, suppose that I have an action 
called "action1" which needs to be enabled only if there are both an open 
project and an open document. A first attempt would then be
<State name="project_exists">
  <enable>
    <Action name="action1"/>
  </enable>
</State>
<State name="document_exists">
  <enable>
    <Action name="action1"/>
  </enable>
</State>
Of course, this won't work: as soon as the "project_exists" state is set, the 
action will be activated, even if the "document_exists" state isn't set.

My question is: is it possible to use the XML GUI framework also to handle 
these more complex situations? If, that's impossible, what would be the best 
approach? I tried searching the KDE API documentation and google for hints, 
but found nothing. I also thought of looking at the source code of some 
application which could have the same problem, but I could think of none.

Any suggestions are welcome

Thanks in advance

Stefano
 
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