Re: [platform-ui-dev] Question about JFace, wrapped objects, and objectC

[Michael Valenta <Michael_Valenta@xxxxxxxxxx>]

Dirk,

I'm not sure why you say that all JDT
actions needs to be adaptable and not just those that are objectContributions.
I think perhaps you are addressing a broader problem than I was describing.
Currently, if I put a java model element in one of my views and register
my context menu with the workbench, I will only get the objectContributions
showing up in my popup menu (I assume that Brian has tried this and got
a subset of the JDT actions). Any JDT actions that are not objectContributions
will not appear. These object contributions that do appear shouldn't have
any requirements on the view from which they originated (although they
could I suppose). With the new support for objectContribution adaptability
added in 3.1, you could add the adaptable=true flag to the JDT objectContributions
and they should appear on the wrappedObjects as long as they adapt to a
Java model element (this won't work in 3.0 or prior as only adaptablilty
of IResource was supported).

Anyway, I wasn't mentioning this as
the most viable solution. I actually think it is one we sould avoid if
possible because there are many pitfalls (i.e. how do you deal with mappings
that are not one-to-one). My prefered solutions would be to use the approach
Markus suggested (which I didn't know about. Thank's for the tip Markus).
This seems like the intended mechanism for this case. Of course, it is
possible that Brian would want access to the additional JDT actions but
I'll leave that to him to discuss.

Michael

Dirk Baeumer <dirk_baeumer@xxxxxxxxxx>
Sent by: platform-ui-dev-bounces@xxxxxxxxxxx

24/08/2005 11:17 AM

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Subject	Re: [platform-ui-dev] Question about JFace, wrapped objects,        and        objectContributions

Hi Brian, Hi Michael,

it's not JDT's object contributions that have to be adaptable it's all
JDT
actions. We looked into this during the 3.0 time frame and postponed it
(lots of actions, every action implementor as to think about it, not
possible to only do the conversion once). Instead we use two different
approaches depending on whether the selection should only contain the
unwrapped elements or if the wrapped elements are needed as well:

Only unwrapped elements:
======================
We use a special selection provider which does the conversion. You may
want
to look at the call hierarchy to see how this works.


Both wrapped and unwrapped elements
==================================
All JDT actions take an IViewSite to access the selection. We have a
special view site (ViewSiteDecorator) which is responsible for converting
the selection. We pass the special view site to the actions which need
the
unwrapped elements instead of the one provided by the view itself. The
problem with this approach is that it uses internal API. However we are
working with Platform/UI on an officially supported solution.

HTH

Dirk


                    
                     
                     
          
             Michael Valenta    
                     
                    
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  Subject 
             24.08.2005 15:59    
     Re: [platform-ui-dev] Question      
                    
                  about JFace,
wrapped objects,       
                    
                  and  
objectContributions           
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Brian,

The only other option I can think of is for JDT to make their
objectComntributions adaptable. I can't comment on whether they would agree
to do this and it wouldn't help you in the short term anyway. Other than
that, I think 2 would be your best option (although there may be some
gotchas that I don't know about).

The thing that is getting you here is the need to show the same model
object multiple times. If you could get ride of that requirement, you could
just implement a custom content provider (i.e. the intended way to handle
this situation).

Michael


                    
                     
                     
          
 Brian de Alwis                
                     
                     
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  Subject 
 22/08/2005 04:54 PM                
  [platform-ui-dev] Question about    
                    
                  JFace, wrapped
objects,        and  
                    
                  objectContributions
                
     Please respond to            
                     
                  
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Hi everybody.  I have a question about the interaction of
objectContributions and selections when dealing with custom models
managed through JFace.  My apologies if this isn't seen as appropriate
for this list, but it seemed that there is a deeper issue here.

I'm using a JFace TreeViewer to provide a view on a model.  As my
model doesn't directly correspond to a tree, I've created a projection
of the model using a structure similar to the TreeParent / TreeObject
as provided by the JFace generated templates.  I've modified my
LabelProvider to unwrap these objects appropriately.

My problem is this: although my wrappers are an internal thing,
meant only to impose a structure, they are bleeding through, becoming
the actual objects exposed to the workbench.  As a result, some of
the workbench's objectContributions are not being properly applied,
such as when building context menus.

For example, some of my model objects are actually JDT IJavaElements.
But because the JDT objectContributions don't specify "adaptable=true"
(e.g. org.eclipse.jdt.internal.ui.compare.JavaReplaceActions and
org.eclipse.jdt.internal.ui.compare.JavaCompareActions), they never
appear in the context menus, even when the wrappers can be adapted.
I think they should apply as my wrapper objects exist only to
support imposing a viewing structure; the `real' objects are the
model objects.

I can't return the actual model objects (e.g. the IJavaElements),
as they may occur multiple places in my model (which causes problems
with implementing ITreeContentProvider.getParent()).

I see three solutions to this problem, but I'm hoping there is a
better way?

1. My hacked solution for the moment is to explicitly call
   ObjectActionContributorManager.contributeObjectActions() in in
   my menuAboutToShow(IMenuManager) callback and provide an
   explicitly unwrapped selection.  This solves the immediate
   problem, but it's an undesirable, short-term solution.

2. Subclass TreeViewer and override the getSelection() to do the
   rewrapping.  This seems the better immediate option, but I'm
   not sure about the consequences, and the same problem will occur
   with other types of structured viewers.

3. Add another level of indirection with an additional method to
   IStructuredContentProvider.getModelObject(), called appropriately?

I apologize if this has been discussed before, but I couldn't find
anything appropriate.

Brian.

--
 Brian de Alwis | Software Practices Lab | UBC | http://www.cs.ubc.ca/~bsd/
"There is much pleasure to be gained in useless knowledge." -
Bertrand
Russell
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