Re: [e4-dev] Proposal to replace the 'visible' flag

[Eric Moffatt <emoffatt@xxxxxxxxxx>]

David, I've been toying with the idea
of switching over to a dirty/refresh cycle for the synchronization of the
presentation and the model. If there were a method in the renderer ('synchUI')
then we could switch away from the current pattern (where discreet listeners
manage changes to their own particular attributes) and adopt a much simpler
approach. The general plan would be something like this:

- a global listener detects that some
UI-related attribute has changed and adds the element to the 'dirty' list.
(if it's not already there)
- if the change is containment related
(ADD/REMOVE) then the parent is added to the list
- at some point (in SWT likely using
asycnExec) we traverse the dirty list calling 'sychUI' on the elements
renderer and then clear it

This has a few advantages over the more
fine-grained approach we are currently using:

- Handles multiple attribute changes
to the same element (i.e. label, tooltip and icon) to be handled in a single
sych, right now we set each separately causing 3 updates in the UI).
- Allows at least the potential to optimize
sets of changes by examining the complete list of pending changes

The big advantage though is that it
makes the rendering simpler by removing the necessity for each discreet
renderer to create its own set of discreet listeners, all they would have
to do is to write the 'synchUI' merhod. Of course care should be taken
in 'synchUI' to minimize the impact on the rendered widget (i.e. Only call
'setText' on the widget if it's different from what's already there...).

From your experience do you have any
hints as to whether this is better/worse than the current state ?

Eric

From:	David Orme <djo@xxxxxxxxxxxxxxxxxxxxxxxxx>
To:	E4 Project developer mailing list <e4-dev@xxxxxxxxxxx>
Date:	10/21/2010 12:41 PM
Subject:	Re: [e4-dev] Proposal to replace the 'visible' flag
Sent by:	e4-dev-bounces@xxxxxxxxxxx

---

FWIW:

On Thu, Oct 21, 2010 at 10:17 AM, Tom Schindl <tom.schindl@xxxxxxxxxxxxxxx>
wrote:
visibility = NONE      (no widget)
visibility = TO_RENDER (widget created but not shown)
visibility = VISIBLE   (widget made visible)

I've found this be a common idiom in UI controls.

Similarly, updating/refreshing/redrawing a UI control often follows a similar
pattern: 

* Mark the widget as dirty or otherwise trigger a refresh
* Recalculate where everything has to go now
* Actually move stuff around/repaint

HTH.  :)


Regards,

Dave Orme
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