SessionChangeManager - Need support for applying changes to a different
component than the immediate target, need for supporting ChangeMarker
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Key: TRINIDAD-1015
URL: https://issues.apache.org/jira/browse/TRINIDAD-1015
Project: MyFaces Trinidad
Issue Type: Improvement
Environment: Not applicable
Reporter: Prakash Udupa N
Component changes that are added to SessionChangeManager are applied while the
components are being created by the tag handlers. Specifically
UIXComponentELTag._applyChanges() and UIXComponentELTag.doEndTag() does this
job. Changes are applied only if the component was created newly during tag
execution. UIComponentELTag.getCreated() is consulted for this purpose.
There are certain type of changes that are registered on a particular target
component, but actually need to be applied on a different component to make the
change effective.
Consider example of a MoveComponentChange specialization that moves components
within the view tree. There are three participants in this change:
1. The component that is to be moved.
2. The parent at the destination of the move.
3. The neighboring sibling at the destination to be able to position the
component rightly after the move.
At the outset this seems to be a change to be recorded against the component
that is to be moved (i.e. #1). However, this change needs to be applied
actually on the nearest common root parent of the tree that #1 and #2 belongs
to.
During tag execution (createview/restoreview), the component for #1 gets
created, however the common root never gets created.
UIXComponentELTag.getCreated() returns false for the common root, as a result,
from the current behavior in UIXComponentELTag._applyChanges(), this type of
change never gets applied correctly.
Proposal is to:
a) Provide a ChangeMarker interface that clients could register against the
immediately apparent target component (In the above example it is component in
#1).
b) Improve UIXComponentELTag such that upon applying changes, if a ChangeMarker
is encountered instead of a Change, do not apply any change, but ask the
ChangeMarker for actual target. Subsequently mark the tag for the new target
component as forcibly needing change. This ensures that the Change is correctly
applied on the actual target at later point in time.
c) UIXComponentELTag, will consult getCreated() as well as check if a change
application is forced while applying change.
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