Re: [ve-dev] Question regarding Layouts

[Peter Walker <walkerp@xxxxxxxxxx>]

>My question is ,is there any way
i can add my layout type there in the drop down, in addition to the existing
ones,
>so everyone can see the existing
as well as new layouts when, they drop a shell or a composite


Although this is not documented anywhere
yet (another tutorial the VE team needs to write up ;-), there are APIs
and the capability to add your own layout in VE so it will show up in the
drop down list in the property sheet view for the 'layout' property...
and if even show up in the (optional) Customize Layout Window. I will attempt
to give you some pointers to classes and overrides to help you get started.

Overrides
The first place to look is the layout.override
file in the org.eclipse.ve.swt plugin. It's located in the overrides
directory. In your plugin, you will need to create an overrides
directory. The directory structure is the same as the package name for
the actual class. For example, layout.override is for the class
org.eclipse.swt.widgets and is in the directory ...override\org\eclipse\swt\widgets.
You will need to create an SWT layout.override file in your plugin
(with the same respective directory structure) and put your layout information
in the file. VE will automatically pickup this override and add the information
to VE's layout.override. BTW... look in the LayoutCellEditor
class if you want to see how it's done. The xmi format for the override
file varies depending on whether you are using VE 1.1 or the current (under
development) VE 1.2. If you use the 1.1 format, you will have to convert
it to 1.2 format using a migration tool later on when you move up to VE
1.2 (which is based on Eclipse 3.2). Either version there are key/value
pairs in the file and you need to add your layout here. Here's an example
of the xmi decorator for RowLayout (1.2 format):
   <objectsToAttach source="org.eclipse.ve.LayoutInfo"
xmi:id="_eAnnotations3" xsi:type="ecore:EAnnotation">
         
      <details key="org.eclipse.ve.internal.swt.layoutClass"
value="org.eclipse.swt.layout.RowLayout"/>
         
      <details key="org.eclipse.ve.internal.swt.layoutDisplayName"
value="RowLayout"/>
   </objectsToAttach>

There are two important keys defined
here:

1. org.eclipse.ve.internal.swt.layoutClass - the value is the actual class name (i.e. org.eclipse.swt.layout.RowLayout)
2. org.eclipse.ve.internal.swt.layoutDisplayName - the value is the display name in the property sheet view drop down list (i.e. RowLayout)

In addition to the layout.override file, you will also need to create
an override file for the actual layout you have developed and in it you
will point to the layout factory to be used by VE for your layout. Put
this also in the directory structure to what your layout path is. For example,
cool.layouts.MyCoolSWTLayout would be in ...overrides\cool\layouts\MyCoolSWTLayout.override.

A layout factory is an implementation
of the class ILayoutPolicyFactory
which has various getter methods that return things like the type of layout
policy to use in the graph viewer, the layout switcher to use when someone
selects your layout, a constraint class that is used if your layout
class uses layout data for the children (e.g. RowData for RowLayout), and
other methods as well... just check out the javadoc. Looking at an example
is the easiest way to find out how to write up your own. Here's the xmi
information for RowLayout.override (located in the ...override\org\eclipse\swt\layout
directory):
<objectsToAttach xmi:id="_eAnnotations"
xsi:type="org.eclipse.ve.internal.jcm:BeanDecorator">
   <keyedValues key="org.eclipse.ve.internal.java.visual.layoutpolicyfactoryclassnamekey"
  
   value="org.eclipse.ve.swt/org.eclipse.ve.internal.swt.RowLayoutPolicyFactory"
xsi:type="ecore:EStringToStringMapEntry"/>
</objectsToAttach>

The key here is "org.eclipse.ve.internal.java.visual.layoutpolicyfactoryclassnamekey"
and the value will be your own layout policy factory.


Policies
To actually use your layout in VE such
that you can create, move, delete, and manipulate the SWT controls with
a Composite, you will need to create your own edit policy, helper, and
container policy... or use some (or all) of the VE policies if they suit
your needs. These policies are used primarily to create and execute GEF
commands. VE uses commands so that operations can be undone and batched
together in a logical manner. 

Your layout factory will return the
layout policy and policy helper to be used for this purpose and you will
need to write these with the respective interfaces. You can use one of
the VE classes if you find it performs the behavior you want or you can
subclass one of them and just override the methods you need to. VE provides
a layout policy org.eclipse.ve.internal.swt.DefaultLayoutEditPolicy
which provides basic functions similar to RowLayout and FillLayout. This
provides a vertical or horizontal insertion line when dragging controls
in the graph viewer.

 You'll may need a policy helper
as a common policy for both the beans viewer and the graph viewer. The
layout policy usually forwards requests onto the helper policy. The CompositeTreeEditPart.createLayoutPolicyHelper()
shows where the helper policy is created. The layout policy also instantiates
them. Or just use VE's UnknownLayoutPolicyHelper
which VE uses for layouts it doesn't know about.

Initially, you may want to just add
one of the VE default layout policies and helpers to get things working
in a generic way and then add your own layout policies. You will need to
override various functions (add, delete, move, create, etc.).  The
simplest layout to look at is probably FillLayout or RowLayout. GridLayout
and a null layout are much more complex because of the constraints and
feedback mechanisms in place.

Just a little background information
that might prove useful in understanding and debugging layout behavior
in the graph viewer, VE uses CompositeGraphicalEditPart as the general
purpose graphical editpart for Composites. In the createLayoutPolicy
method, it gets the 'layout' property and uses some VE utilities to get
the layout factory based on the layout. From the factory, it gets the layout
policy. 


Customize Layout Window
If you want to provide your own layout
and/or component page (for layout or layout data, respectively) in the
Customize Layout window, you will need to have your own layout policy
and point the customize layout window to your own pages. For RowLayout,
look in RowLayoutEditPolicy.activate(). At the end of the method
there is a statement that defines what page to use for the layout itself:
     CustomizeLayoutWindowAction.addLayoutCustomizationPage(getHost().getViewer(),
RowLayoutLayoutPage.class);
Whereas RowLayoutLayoutPage
is the GUI page for change RowLayout properties. If you write your own
you will need to extend VE's CustomizeLayoutPage.


If you have a page for the layout data
(for a child of the composite), you will need to add an additional statement
in the activate method of your layout policy. For example, in GridLayoutEditPolicy,
there is a page for the layout and the component:
  CustomizeLayoutWindowAction.addLayoutCustomizationPage(getHost().getViewer(),
GridLayoutLayoutPage.class);
       // for the layout itself
  CustomizeLayoutWindowAction.addComponentCustomizationPage(getHost().getViewer(),
GridLayoutComponentPage.class);
// for GridData of the child

This layout component page (GridLayoutComponentPage)
also extends VE's CustomizeLayoutPage.
Please pay particular attention to the
handleSelectionChanged(ISelection
oldSelection) method which is
called by the VE's Customize window to determine if your page needs to
be shown or not when selection changes in the graph or beans view.

In your layout policy, you also need
to implement the interface IActionFilter
which requires a method
     
public boolean testAttribute(Object target, String name, String value)
This is a basic test for actions on
the popup menu to determine if Customize Layout... should be added
when someone clicks MB2 over a composite with your layout. You will need
to add the statements:
        if
(name.startsWith(CustomizeLayoutPage.LAYOUT_POLICY_KEY) && value.equals(LAYOUT_ID))

         
      return true;
        return
false;

Whereas the LAYOUT_ID should be your
own unique ID for your layout (e.g. RowLayoutEditPolicy's LAYOUT_ID is
"org.eclipse.swt.layout.RowLayout").


Good luck and post here if you have
further questions.

Regards...

Peter Walker
-------------------------------------
Eclipse VE Development
919-254-1558

Ameet A Kulkarni/Durham/IBM@IBMUS
Sent by: ve-dev-bounces@xxxxxxxxxxx

11/03/2005 10:11 AM

Please respond to
Discussions people developing code for the Visual Editor project

To	Discussions people developing code for the Visual Editor project <ve-dev@xxxxxxxxxxx>
cc
Subject	[ve-dev] Question regarding Layouts

Hi 
       we are currently using the visual editor capabilities
in our project. So to extend that, with respect to layouts, that Visual
editor provides, like the null, form,grid etc, for the composite /shell
containers .We plan to add our own layout to the existing ones.

So when we create a shell or a composite or container, in the properties
tab, we see the layout property. It is a drop down containing the existing
layouts, My question is ,is there any way i can add my layout type there
in the drop down, in addition to the existing ones,so everyone can see
the existing as well as new layouts when, they drop a shell or a composite

I figured out a way to add my own property in the properties tab and use
it, I am not sure, if new additions can be done to the existing properties..
Thanks 
Regards,
Ameet
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