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Re: [albireo-dev] SWT size/layout management

Bruno Haible wrote:
Gordon Hirsch wrote:
In contrast, Swing's relayout mechanism climbs up to the next "validation root",
i.e. the next component in the ancestors list which is known to isolate size
changes in its children from its parent (i.e. which is known to have constant
size, regardless of its children).
I don't know of any analogous concept in SWT. It's up to the
application. In effect, eveything is a validation root.

You mean, by default, every Composite is a "validation root" (shields its parent component from size changes among its children)? And if a Composite does not want to behave that way, it overrides layout():

No, I mean that asking a parent widget to layout() does not generally happen. It's the user of the widgets rather than the widget implementations themselves that decide when to force a relayout.



This is why, in the RelayoutExample, the size on the SWT side did not update itself when one presses the Grow/Shrink buttons. You can play with these buttons and the "SWT-Layout" button to convince yourself that calling getParent().layout() is necessary for a good application behaviour.

getParent().layout() works, but it is not the right solution. It is also wrong in the one case I used it, and I feel a little guilty for leading us down the wrong path.


I think I can construct an example that will show why getParent().layout() is not adequate and why we will have to defer to the application in this case. I'll try to add it to our examples in the next day or two.