An implementation idea:
Component {
public final void configure()
{
if (!getFlag(FLAG_CONFIGURED))
{
setVisible_NoClientCode(isVisible()); //we only check the user
isVisible in here
onConfigure();
setFlag(FLAG_CONFIGURED, true);
}
}
}
On Tue, Nov 30, 2010 at 2:16 PM, Igor Vaynberg <igor.vaynb...@gmail.com>wrote:
> so how is it different if they can still override something that needs
> to be checked all the time?
>
> -igor
>
> On Tue, Nov 30, 2010 at 8:02 AM, Pedro Santos <pedros...@gmail.com> wrote:
> > I understand the concern about possible isVisible implementations like
> >
> > isVisible(return currentlyTime < 10:00:00;) //imagine this component
> being
> > rendered at 09:59:59
> > isVisible(return dao.list().size() > 0);// performance issues
> >
> > But maybe we can have the best from both approaches. This is an
> copy/paste
> > from java.awt.Component:
> >
> > public boolean isVisible() {
> > return isVisible_NoClientCode();
> > }
> > final boolean isVisible_NoClientCode() {
> > return visible;
> > }
> >
> > There are some points in the awt framework were the isVisible method is
> not
> > used in benefit of isVisible_NoClientCode
> > I'm in favor of create an final isVisible/Enabled version and change the
> > Wicket core to use it. Also maintain the hotspot to users provide their
> > isVisible/Enable implementations that will serve to feed the core
> component
> > state.
> >
> > On Mon, Nov 29, 2010 at 4:56 PM, Igor Vaynberg <igor.vaynb...@gmail.com
> >wrote:
> >
> >> ive run into plenty of weird problems with overrides, but maybe
> >> because this was in a high concurrency app where data changed
> >> frequently. the problems arise from the fact that the value returned
> >> from isvisible() can change while we are doing traversals, etc.
> >>
> >> eg we run a traversal for all visible components and put them in a
> >> list. later we iterate over the list and try to render these
> >> components. the render function also checks their visibility and if
> >> they are no longer visible it throws an exception.
> >>
> >> if isvisible() override depends on some external factor like the
> >> database there is a small window where the value can change and now
> >> you can have a weird exception: such as "tried to invoke a listener on
> >> a component that is not visible or not enabled". these are very
> >> intermittent and damn near impossible to reproduce.
> >>
> >> another problem is performance. isvisible() is called multiple times
> >> during the request and if it depends on the database it can be a
> >> performance problem. in fact a couple of users have complained about
> >> this on the list in the past. at least now we have an easy solution
> >> for them - use onconfigure().
> >>
> >> so as of right now the developers have two choices: override
> >> isvisible() and potentially suffer the consequences. or, override
> >> onconfigure() and set visibility there in a more deterministic
> >> fashion.
> >>
> >> -igor
> >>
> >>
> >>
> >> On Mon, Nov 29, 2010 at 10:21 AM, Eelco Hillenius
> >> <eelco.hillen...@gmail.com> wrote:
> >> > To expand, unless I'm missing something (new?), things are really only
> >> > problematic when both the mutable value and the override are mixed. In
> >> > a way, I think that using the override is 'more pure', as it's a
> >> > simple function that is executed when needed, whereas mutable state
> >> > can be harder to deal with when trying to figure out how it got to be
> >> > in that state. So, sorry Igor, but we disagree on this one.
> >> >
> >> > Eelco
> >> >
> >> >
> >> > On Mon, Nov 29, 2010 at 10:13 AM, Eelco Hillenius
> >> > <eelco.hillen...@gmail.com> wrote:
> >> >> Niether is evil. It has potential pitfalls, which you should just be
> >> >> aware of. We use such overrides all over the place and never have
> >> >> problems with them either. :-) Avoiding it is safer, but also more
> >> >> verbose (in 1.3.x at least).
> >> >>
> >> >> Eelco
> >> >>
> >> >> On Mon, Nov 29, 2010 at 9:49 AM, Igor Vaynberg <
> igor.vaynb...@gmail.com>
> >> wrote:
> >> >>> On Mon, Nov 29, 2010 at 9:35 AM, Sven Meier <s...@meiers.net>
> wrote:
> >> >>>> Hi Douglas,
> >> >>>>
> >> >>>> WICKET-3171 describes a problematic case, where visibility of a
> >> >>>> component changes while its form is being processed.
> >> >>>> In our projects we're overriding isVisible() where appropriate and
> >> never
> >> >>>> encountered a similar problem.
> >> >>>>
> >> >>>> I'd say WICKET-3171 is the rare 5% usecase. What's next, is
> overriding
> >> >>>> isEnabled() going to be declared evil too? ;)
> >> >>>
> >> >>> yes
> >> >>>
> >> >>> -igor
> >> >>>
> >> >>>>
> >> >>>> Sven
> >> >>>>
> >> >>>> On Mon, 2010-11-29 at 11:22 -0600, Douglas Ferguson wrote:
> >> >>>>
> >> >>>>> Can you explain why? We have done this all over the place.
> >> >>>>>
> >> >>>>> D/
> >> >>>>>
> >> >>>>> On Nov 29, 2010, at 10:00 AM, Martin Grigorov wrote:
> >> >>>>>
> >> >>>>> > The recommended way since a few 1.4 releases is to override
> >> onConfigure()
> >> >>>>> > and call setVisible(true|false) depending on your conditions.
> >> >>>>> >
> >> >>>>> > On Mon, Nov 29, 2010 at 4:49 PM, Douglas Ferguson <
> >> >>>>> > doug...@douglasferguson.us> wrote:
> >> >>>>> >
> >> >>>>> >> Igor posted a comment to this bug saying that overriding
> >> isVisible() is
> >> >>>>> >> "evil"
> >> >>>>> >>
> >> >>>>> >> https://issues.apache.org/jira/browse/WICKET-3171
> >> >>>>> >>
> >> >>>>> >> I was surprised by this and am curious to hear more.
> >> >>>>> >>
> >> >>>>> >> D/
> >> >>>>>
> >> >>>>
> >> >>>>
> >> >>>>
> >> >>>
> >> >>
> >> >
> >>
> >
> >
> >
> > --
> > Pedro Henrique Oliveira dos Santos
> >
>
--
Pedro Henrique Oliveira dos Santos
