On Wed, 04 Oct 2006 13:38:03 +0200
Marc Weustink <[EMAIL PROTECTED]> wrote:
> Mattias Gaertner wrote:
> > On Wed, 04 Oct 2006 12:46:27 +0200
> > Marc Weustink <[EMAIL PROTECTED]> wrote:
> >
> >> Mattias Gaertner wrote:
> >>> On Wed, 04 Oct 2006 11:29:51 +0200
> >>> Marc Weustink <[EMAIL PROTECTED]> wrote:
> >>>
> >>>> Mattias Gaertner wrote:
> >>>>> On Wed, 4 Oct 2006 09:27:03 +0200
> >>>>> "Graeme Geldenhuys" <[EMAIL PROTECTED]> wrote:
> >>>>>
> >>>>>>>> Changing a property can change various others as well. For
> >>>>>>>> example changing the Width can change child controls,
> >>>>>>>> siblings and parent.
> >>>>>>> Yes, but applying this change to the child form should result
> >>>>>>> in exactly the same consequences, unless the affected
> >>>>>>> components were changed already... ?
> >>>>>>>
> >>>>>>> Michael.
> >>>>>> Mattias,
> >>>>>>
> >>>>>> This is where my implementation of the Observer using
> >>>>>> BeginUpdate and EndUpdate plays a roll. See the tiOPF code I
> >>>>>> sent you. Normally the Subject (FormA) would fire off the
> >>>>>> Notify method for every small change which could cause lots of
> >>>>>> screen redraws. BeginUpdate and EndUpdate allows you to make
> >>>>>> all those small changes and then fire off a single Notify call.
> >>>>> BeginUpdate can only be called for the IDE tools (OI, AE, ...).
> >>>>> The component editors will only call the Modified event.
> >>>>> But there is a solution:
> >>>>> We could call the update on Idle.
> >>>> Not really a nice option and hard to work with if some who knows
> >>>> future designer plugin needs the result of a modification (I'm
> >>>> just making things up here).
> >>> Then the plugin can force an update.
> >>>
> >>>
> >>>> But...
> >>>> component editors call Modified. This Modified method can use
> >>>> Begin/EndModification. If this is passed to the
> >>>> "derived form" observer, it knows whan all modifications are done
> >>>> (and can update itself)
> >>> Do you mean, all methods, that now call the Modified method should
> >>> be changed to call Begin/EndModification?
> >> No,
> >> Modified needs to be modified :)
> >>
> >> procedure Modified;
> >> begin
> >> SendBeginModificationToAllBeginEndObeservers;
> >> SendModifiedNotificationToAllModifiedObeservers;
> >> SendEndModificationToAllBeginEndObeservers;
> >> end;
> >
> > But then Begin/End is useless, isn't it? The modification took place
> > before 'Begin'. For example:
> >
> > NewToolButton.Parent:=CurToolBar;
> > Modified;
>
> Indeed, I was more thinking of controls reacting on the
> ModifiedNotification which would trigger more modifications.
>
> In your example, an editor sets the Parent and calls Modified. Why
> would setting the parent trigger other code which will call
> Modified ? Afterall, Modified is a Designer/Editor method, and
> should/can not be called from the component itself. So I see no chain
> of modified there.
There are some components, that call Modified. For example
changing the PageIndex of a TNoteBook. But this is very rare and can be
changed. Let's ignore these things.
More important is that we don't have a working Begin/End enclosement.
So, we can only react, but not prepare. Or in other words: Only a
OnModified event, but no OnChanging.
At the moment the solution is to swallow the bitter pill and implement
a dynamic property propagation system. The more information the
changer (e.g. OI) provides, the less the system will copy.
The OI can call BeginUpdate/ChangeProperty/EndUpdate, while others
can call Modified and the whole forms are scanned/copied.
Mattias
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