[Engine-devel] Sorting in tabs

Fri Jun 28 06:45:17 UTC 2013

----- Original Message -----
> From: "Einav Cohen" <ecohen at redhat.com>
> To: "Lior Vernia" <lvernia at redhat.com>
> Cc: "Vojtech Szocs" <vszocs at redhat.com>, "Eli Mesika" <emesika at redhat.com>, engine-devel at ovirt.org, "Alexander Wels"
> <awels at redhat.com>, "Daniel Erez" <derez at redhat.com>, "Gilad Chaplik" <gchaplik at redhat.com>, "Alona Kaplan"
> <alkaplan at redhat.com>, "Tomas Jelinek" <tjelinek at redhat.com>
> Sent: Thursday, June 27, 2013 6:40:56 PM
> Subject: Re: [Engine-devel] Sorting in tabs
> 
> > ----- Original Message -----
> > From: "Lior Vernia" <lvernia at redhat.com>
> > Sent: Thursday, June 27, 2013 12:15:14 PM
> > 
> > 
> > 
> > On 27/06/13 18:15, Einav Cohen wrote:
> > >> ----- Original Message -----
> > >> From: "Lior Vernia" <lvernia at redhat.com>
> > >> Sent: Thursday, June 27, 2013 10:38:04 AM
> > >>
> > >>
> > >>
> > >> On 27/06/13 16:42, Einav Cohen wrote:
> > >>>> ----- Original Message -----
> > >>>> From: "Lior Vernia" <lvernia at redhat.com>
> > >>>> Sent: Thursday, June 27, 2013 8:53:59 AM
> > >>>>
> > >>>>
> > >>>>
> > >>>> On 27/06/13 15:37, Einav Cohen wrote:
> > >>>>>> ----- Original Message -----
> > >>>>>> From: "Eli Mesika" <emesika at redhat.com>
> > >>>>>> Sent: Thursday, June 27, 2013 6:46:58 AM
> > >>>>>>
> > >>>>>>
> > >>>>>> ----- Original Message -----
> > >>>>>>> From: "Lior Vernia" <lvernia at redhat.com>
> > >>>>>>> To: engine-devel at ovirt.org
> > >>>>>>> Sent: Thursday, June 27, 2013 10:12:33 AM
> > >>>>>>> Subject: [Engine-devel] Sorting in tabs
> > >>>>>>>
> > >>>>>>> Hello everyone (UI peeps in particular),
> > >>>>>>>
> > >>>>>>> I've pushed (not yet merged) a patch that would enable us to keep
> > >>>>>>> items
> > >>>>>>> in tabs (main/sub) sorted at all times by setting a comparator in
> > >>>>>>> SearchableListModel:
> > >>>>>>
> > >>>>>> But tabs includes only 100 records and supports paging , how you
> > >>>>>> deal
> > >>>>>> with
> > >>>>>> that ???
> > >>>>>
> > >>>>> if this is in the GUI level, then I assume that the comparator is
> > >>>>> simply
> > >>>>> comparing the
> > >>>>> items within the current page, and not "globally".
> > >>>>> so the sorting doesn't affect the set of items that is displayed in
> > >>>>> the
> > >>>>> page (it would
> > >>>>> be the same as before the sorting) - just their order.
> > >>>>
> > >>>> Yes, if I understand correctly how the paging works, Einav is correct
> > >>>> -
> > >>>> only the items passed to the UI are sorted.
> > >>>>
> > >>>>> also: @Lior - what happens when the search query contains a "sort by"
> > >>>>> part?
> > >>>>> there is a chance that the behaivor would be unexpected in this case;
> > >>>>
> > >>>> Yes, I thought about this case, and it may result in a confusing user
> > >>>> experience if developers aren't careful. Together with the issue of
> > >>>> paging, this probably makes this sorting mechanism a better candidate
> > >>>> for use within subtabs rather than main tabs.
> > >>>
> > >>> note that at some point, I think that we would want to introduce paging
> > >>> also to search-
> > >>> based sub-tabs - it will be useful especially for sub-tabs that
> > >>> potentially
> > >>> display a
> > >>> large number of results (e.g. Disks sub-tab in Storage main tab).
> > >>> In addition, at some point, we would want to get rid of the paging UI
> > >>> as
> > >>> it
> > >>> is now
> > >>> (i.e. "next"/"prev" buttons at the top panel) and move to paging
> > >>> triggered
> > >>> by scroll
> > >>> (i.e. have a very long grid, dynamically loaded as you continue to
> > >>> scroll
> > >>> -
> > >>> similar
> > >>> to the behavior of some e-mail web-clients, for example). In this case,
> > >>> sorting on
> > >>> the client side will make no sense at all (i.e. from the user
> > >>> perspective,
> > >>> only a
> > >>> portion of a very large grid will be sorted, the other portions won't
> > >>> be).
> > >>>
> > >>> So for now - yes, I think it makes sense to introduce your mechanism to
> > >>> all
> > >>> sub-tabs,
> > >>> however in the long-term - we would probably want the search-based
> > >>> sub-tabs
> > >>> (which
> > >>> will support paging) to move to search-based sorting, rather than
> > >>> GUI-based-sorting.
> > >>
> > >> Sounds good to me. Let me just re-iterate that it is not mandatory to
> > >> set a comparator, so in technical terms it's not even necessary to
> > >> introduce it at once to all sub-tabs, if they're already sorting their
> > >> items some other way. It could happen gradually, and only if developers
> > >> find it more convenient. In either case, dropping the GUI sorting once
> > >> search-based sorting is implemented shouldn't be difficult.
> > >>
> > >>> BTW (maybe the other GUI maintainers can help me with that one) - what
> > >>> about sub-tabs
> > >>> that are not search-based (i.e. display results from a "regular" query
> > >>> or
> > >>> even from a
> > >>> field within the selected item in the main grid, e.g. Applications in
> > >>> VM)
> > >>> -
> > >>> are these
> > >>> managed via SearchableListModel as well? since the comparator mechanism
> > >>> *is* relevant
> > >>> for them.
> > >>
> > >> As far as I've seen, some are managed via SearchableListModel and some
> > >> aren't. Those that aren't are those that display non-trivial behaviour
> > >> upon receipt of the items to display (setItems() method) - often this
> > >> non-trivial behaviour is exactly sorting :) And if it's doing its job,
> > >> then there's no necessity to change it either. But anyway, I don't know
> > >> all of them, so I'd also love to hear GUI maintainers.
> > >>
> > >>> Also: Worth mentioning "Bug 893999 - webadmin: please allow column
> > >>> sorting", which
> > >>> requests to enable sorting when clicking on a grid-column header; when
> > >>> implementing
> > >>> column-sorting, probably worth attaching your mechanism to it somehow
> > >>> (i.e.
> > >>> clicking on
> > >>> a column header should set the relevant comparator in the relevant
> > >>> SearchableListModel).
> > >>
> > >> I didn't want to say it, because if we upgrade to a newer version of GWT
> > >> then we could probably use their table column sorting. But this
> > >> mechanism could allow us to achieve this without upgrading, and it was
> > >> definitely sitting in the back of my head when I implemented it. All
> > >> that's needed is, as you said, to listen to table header clicks in the
> > >> view, and then appropriately set the comparator in the model.
> > >>
> > > 
> > > [Vojtech/GUI-maintainers - your input would be appreciated here]
> > > 
> > > we are actually planning on upgrading the GWT version *really* soon (to
> > > GWT
> > > 2.5),
> > > so my question is: should we wait until the new GWT is introduced, and
> > > implement
> > > client-sorting based on the GWT-grid-widget built-in mechanism (assuming
> > > there is
> > > one)?
> > > also, not sure if it is better to utilize the widget default-built-in
> > > sorting mechanism
> > > (which doesn't manipulate the uicommon model data at all), or if it is
> > > better to utilize
> > > your comparator mechanism, which manipulates the uicommon model data, and
> > > the GUI-widget
> > > just reflects this data at any given time.
> > > thoughts?
> > 
> > I'll just give my two cents concerning this and then let others have the
> > stage: I don't think it really matters.
> > 
> > Manipulating the models directly is supposedly more portable in case we
> > ever move away from GWT, but we'd still have the pain of adding new
> > listeners to the new framework's table headers which could be just as
> > bad as using its sorting mechanism.
> > 
> > Graphically, the UI might look tighter if we use GWT's mechanism.
> > However, we could probably mimic everything using GWT's graphics (once
> > we upgrade) even if we perform the actual sorting using the tab model
> > and not their mechanism.
> > 
> > My gut feeling actually says to use GWT's built-in mechanism, mainly
> > because it will force us to put all sorting logic in the same place and
> > to always use the same sorting mechanism (whereas currently the sorting
> > logic is scattered and works differently in different places, even if we
> > use this tab mechanism other widgets will differ). But it shouldn't stop
> > us from setting a comparator for a tab where convenient.
> 
> [again, GUI maintainers - your input would be appreciated]
> 
> Thanks, Lior. Need to keep in mind several things:
> 
> - we are now talking only about client-sorting, which generally we would like
> to apply only to grids that display none-"pagable"-results; for grids that
> would
> display pagable-results, we would want to use search-based (i.e. server)
> sorting.
> [so the sorting logic across the application would be somewhat-scattered
> anyway].
> 
> - I think that if we are choosing to utilize GWT's built-in mechanism, then
> using
> a comparator would makes sense in case you want your results to be initially
> displayed
> in a specific order that would not be obtainable using the column-header
> sorting.
> 
> e.g. (dumb example, for demonstration only) if you would want your VMs to be
> displayed
> by default sorted alphabetically according to the VM's description (and keep
> in mind
> that description is NOT one of the columns in the VMs grid), then you would
> probably
> want to do that via the comparator.
> 
> Or (perhaps a better example), if you would want your Templates to be ordered
> by default
> in a way that "Blank" would appear first, and the rest would appear sorted
> alphabetically
> by name, utilizing the comparator can be a good idea.
> [After the initial load of the grid, if the user chooses to sort by name, he
> can click on
> the "Name" column header, which will sort the Templates alphabetically
> "regularly" (i.e.
> not taking "Blank" into special consideration)]
> 
> But - if, by default, we would want, for example, to sort VMs alphabetically
> by name,
> I think that we should imitate a mouse-click on the "Name" column-header,
> rather than
> utilize a comparator for that (the exact same result shouldn't be achieved by
> two different
> implementations).

Hi Lior,

fist of all, I would be really careful about introducing something to UiCommon which could
potentially cause class cast exceptions - not that your approach would be incorrect but the 
UiCommon has lot's of hidden expectations and it is hard to keep tract who expects the
ListModel.getItems will be a list. I would be double careful about this kind of change right
before the freeze. Maybe create a SortedSearchableListModel as a child of SearchableListModel 
would be a much more safe approach.

About the GWT built-in vs Comparator - 
I would also go with the GWT's built in approach.
If we are using a framework we should make use of it and not
try to decouple too much to make it simpler to migrate to a different one.

So I agree with Lior that we should go with GWT's built in approach.
AFAIK Vojtech is already working on the GWT2.5 integration...

Also I would say that we should have the same user experience regardless the table is paged or not
e.g. the user needs to have the same button to click on and the result must make sense after he clicked
it everywhere. So I would say we will have to integrate this GUI sorting with server side sorting for paged tables.

But maybe this integration (however a ideal target) is a bit out of the scope of your initial intention ;)

If you have a good reason to have something always sorted and it is not a paged table, I'm not against. 
Just please be a bit more careful in changing return types in a non-generic code like UiCommon.

> 
> > 
> > >>>>
> > >>>>>
> > >>>>> I believe that the correct thing to do is to "attach" the GUI sorting
> > >>>>> mechanism
> > >>>>> to the one in the search mechanism.
> > >>>>>
> > >>>>> thoughts?
> > >>>>
> > >>>> This can be done, however I'm not sure there's much utility in it.
> > >>>> Main
> > >>>> tabs are always sorted according to some default ordering even if one
> > >>>> was not entered in the search panel, and this sorting is also
> > >>>> performed
> > >>>> consistently with respect to paging. So maybe the right thing to do
> > >>>> would be to just "block" the GUI sorting mechanism for main tabs (i.e.
> > >>>> override the setter method and make it no-op)?
> > >>>
> > >>> yes, and related to what I mentioned above - at some point in the
> > >>> future,
> > >>> we'd might want
> > >>> to block it for search-based sub-tabs as well.
> > >>>
> > >>>>
> > >>>>>>
> > >>>>>>
> > >>>>>>>
> > >>>>>>> http://gerrit.ovirt.org/#/c/15846/
> > >>>>>>>
> > >>>>>>> If a comparator isn't set, then everything should behave as before.
> > >>>>>>> If
> > >>>>>>> a
> > >>>>>>> comparator is set, then from that moment on the tab items will be
> > >>>>>>> kept
> > >>>>>>> in a SortedSet, so that even if an item is added in a way that
> > >>>>>>> doesn't
> > >>>>>>> trigger an event (e.g. getItems().add()) the items will be kept
> > >>>>>>> sorted
> > >>>>>>> according to the given comparator. If the comparator is set to
> > >>>>>>> null,
> > >>>>>>> from that moment on the tab should revert to its old behaviour.
> > >>>>>>>
> > >>>>>>> You're most welcome to have a look and let me know if this might
> > >>>>>>> break
> > >>>>>>> something (remember though that it's not obligatory to set a
> > >>>>>>> comparator,
> > >>>>>>> so only possible breakage should be in generic flows).
> > >>>>>>>
> > >>>>>>> Feel free to use it once it's merged; along with SortedListModel,
> > >>>>>>> this
> > >>>>>>> should make sorting less painful. Just keep in mind that once you
> > >>>>>>> set
> > >>>>>>> a
> > >>>>>>> comparator, you can't cast getItems() to a List. This shouldn't be
> > >>>>>>> a
> > >>>>>>> problem in general, as mostly it's as useful (and probably more
> > >>>>>>> correct)
> > >>>>>>> to cast to a Collection.
> > >>>>>>>
> > >>>>>>> Lior.
> > >>>>>>> _______________________________________________
> > >>>>>>> Engine-devel mailing list
> > >>>>>>> Engine-devel at ovirt.org
> > >>>>>>> http://lists.ovirt.org/mailman/listinfo/engine-devel
> > >>>>>>>
> > >>>>>> _______________________________________________
> > >>>>>> Engine-devel mailing list
> > >>>>>> Engine-devel at ovirt.org
> > >>>>>> http://lists.ovirt.org/mailman/listinfo/engine-devel
> > >>>>>>
> > >>>>
> > >>
> > 
> 