cross-platform devel libs?

[Mathieu Fenniak <laotzu pobox com>]

I'm interested in creating a program that I'd like to develop for linux,
mac, and windows operating systems. Now, I've seen lots of libraries
that are GTK wrappers or such, and provide a common interface for several
OSes. However, do any of these support complex things? For example, were
I to program this purely in linux, it would be based primarily on a
widget derived from canvas widget, because I need to display text and 
graphics together in a scrolling window. So I'd create a widget to do
what I need to do.. but would any of these cross-platform development
libraries allow me to do something like this, or even use a canvas widget
at all?

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Mathieu Fenniak
laotzu@pobox.com