Resizing child windows

[matthew.garman at gmail.com]

If I have a parent window with one or more child windows, and the
parent window's size is changed (either by the user, due to
application design/behavior, whatever), what's the typical generic
method of making sure the children get updated accordingly?

E.g., how do widget toolkits based on X11 (gtk, qt, etc) tell child
widgets to resize?

I'm not looking for exact code, just a general idea.

I looked through the gtk/gdk sources a bit... it looks like there is
some kind of queueing going on with size requests and actual size
allocations... but it wasn't clear to me where these requests are
first routed, and the path they take through the window hierarhcy.
Also the queueing/event mechanism wasn't obvious (at a glance
anyway).

Any tips would be much appreciated,
Thank you,
Matt