[Laszlo-dev] About moving nodes...

[Rami Ojares / AMG]

 > I'd be interested in seeing an example of an application where views 
need to move.

I have as part of my application a tree structure.
Just like in classic filesystem where you have folders and files 
(although my nodes represent programs and program groups)
And I was about to implement a basic moving and copying of nodes under 
folders by drag and drop.

Now the basic way to implement a tree is to create a structure like
<view name="root">
    <view name="branch1">
       <view name="branch1.2">
          <view name="leaf1.2.1/>
          <view name="leaf1.2.2/>
          ...
       </view>
    </view>
    <view name="branch2">
    ...
    </view>
    ...
</view>

So moving these nodes around would naturally be implemented by moving 
the views around.
Now this can be done by destroying the old ones and creating the old 
ones but then I would have to copy all properties
of the old views to new ones. Attributes are easy, but if some other 
nodes/views have delegates listening to their events
that is a quite different ballgame. In a big application with complex 
links ... a practical impossibility.

For now I will try a different strategy with my tree like the following:

The tree is presented to laszlo object model like this
<view name="root">
    <view name="branch1" parent="root"/>
    <view name="branch1.2" parent="branch1">
    <view name="leaf1.2.1" parent="branch1.2"/>
    <view name="leaf1.2.2" parent="branch1.2"/>
    <view name="branch2" parent="root">
    ...
</view>

So all nodes are siblings that have enough of relatioship information 
for a treelayout to lay them out visually in a tree.
And moving is just a matter of updating those attributes. So no 
structural changes needed from laszlo's point of view.
I'll report if that works out well.

I quess if moving of nodes is to be implemented in laszlo one thing that 
nodes should have (internally) is a unique non-changing id
that is used always to make relationships between nodes. Then structural 
changes would not affect the links because they are based on a 
non-changing id.  

- rami