[platform-ui-dev] Adding "visibleWhen" Expression to every UI Element

[Jan-Hendrik Diederich <Jan-Hendrik.Diederich@xxxxxxxxx>]

Hello,
for enhancement https://bugs.eclipse.org/bugs/show_bug.cgi?id=201052, I 
want to add the expression "visibleWhen", with a property tester, to 
every "basic" UI element ("basic" should stand for Views, Editors, and 
similar things).
An example XML code:
  <visibleWhen>
     <test
          property="org.eclipse.rcpauth.expressions.rightsProperty"
          args="read"/>
  </visibleWhen>
I know there were already similar thoughts about this earlier, but they 
weren't realized. I had the impression it was a "nice to have feature" 
which hasn't enough people which needed it, so it was never done.

Now, I want to implement it, for the enhancement I mentioned above.

But I have a question: while it's quite easy to implement it, once you 
learned how the code in "org.eclipse.ui.internal.registry", 
"org.eclipse.ui.internal", "org.eclipse.ui", etc. works together, I have 
too much possibilities where I can implement my solution. The commands 
(ext.-point "org.eclipse.ui.commands"), have already the ability to 
process Expressions, i.e. to process them in all XML declarations which 
use their command declarations (via "commmandId"). Menus do this, for 
example. But views, editors and such things are another case: they are 
not commands, neither in their actual implementation nor in their 
abstract logic. So I implemented the logic to read and bind the 
visibleWhen Expression to a View, in the 
"org.eclipse.ui.internal.registry.ViewRegistryReader#readElement", and 
store the Expression in the "ViewDescriptor".
While the logic to read and store the Expressions for _commands_ is 
handled in "org.eclipse.ui.workbench.HandlerPersistence#read" (and 
stored in a global list). Although my solution works very good, I'm not 
sure what fits better to Eclipses (original?) Expressions concept:
Should the basic Expressions handling all be done in HandlerPersistence, 
or locale, in the Registry-Readers of the UI elements itself?

Or should there be a new standalone class and registry for all Expressions?


Thanks for any answers,
Jan Diederich

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