Re: [platform-swt-dev] Adding/removing components from a composite at ru

[Steve Northover <Steve_Northover@xxxxxxxxxx>]

Unfortunately, a control cannot exist
without a parent.  Therefore you can't add and remove it, you have
to create and dispose.

I don't think I understand "breaks
the current layout".  We fixed the bug that your snippet uncovered
(That's what the "Fixed >" thing was about).  Get the
latest and try it.  I think you need to read the article http://eclipse.org/articles/Understanding%20Layouts/Understanding%20Layouts.htm
to see how layout are supposed to work.  The summary is that you need
to call layout() when you add or
remove a control and any other time
where you change a property that can affect the preferred size.  

Here are some details:

Layouts only position and resize controls
when the parent is resized. The problem with doing it automatically elsewhere
is that it's not possible to predict which features of a control affect
the preferred size and multiple layouts cause flashing and performance
problems. For example, I know that Label.setText() affects the preferred
size of a control but what about controls other people write?  In
order to support automatic layout when controls are added or removed some
kind of deferred layout strategy would be needed, like the painting strategy.
 Of course, once you have a deferred strategy, you also need a way
to defeat it and force layouts.  All of this is getting farther away
from what the operating systems provide, causing problems porting and maintenance
problems.

Hope this helps.

"Brad O'Hearne" <brado@xxxxxxxxxxxxx> Sent by: platform-swt-dev-admin@xxxxxxxxxxx 10/23/2003 09:30 AM Please respond to platform-swt-dev

To:        "SWT-Dev" <platform-swt-dev@xxxxxxxxxxx>         cc:                 Subject:        [platform-swt-dev] Adding/removing components from a composite at runtime

In the wake of a previous thread stating that a Control's
setParent() method
is not supported on all platforms, and even on platforms it is supported
on,
using it breaks the current layout, is there any way to add/remove child
components from a composite at runtime, and if so, does this operation
maintain the function of the current layout?  I see no add/remove
methods
available.

Thanks in advance for your help,

BradO

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