Re: GNOME/GTK canvas

[Federico Mena Quintero <federico nuclecu unam mx>]

>  You can only put selected number of items to canvas. For example,
>  a spline curve widget is not supported. Right?

The canvas allows you to create your own custom item types.  It is a
generic display engine, and several applications (like Gnumeric and
Gnomecal) define their own custom items and use the canvas as their
main rendering engine.

The line item in the canvas is supposed to support splines, but that
functionality is not finished.  You could also write your own spline
item, customized to your needs.  This should be really easy to do.

>  I would like to ask if it is possible to put a large drawing area
>  to canvas, and to put a second but smaller drawing area over the large
>  one? Both drawing areas should have their own callbacks.

You can do that.  I wouldn't think putting drawing areas inside the
canvas as being a very useful idea :-)  Just let the canvas do the
drawing for you.

>  Actually, putting two windows over each other should be so trivial that
>  it should be possible to implement without monsterous canvases.

If you think the canvas is monstrous, please do tell why.  I am always
interested in making it leaner.  It is very lean already.

>  Can I put any widget on the canvas? Overlapping or not?

Yes.

>  I'm not a GTK expert but I joined to gtk-devel list to ask more:
>  is it possible to write a general layer widget which would be
>  a container cabable of containing any other widget? Then I could
>  put a drawing area widget to one layer and second one to other layer.
>  Well, this kind of layer widget would make sense if widgets cannot
>  overlap at the moment. One could even use hbox/vbox functions to
>  build distinct systems to distinct layers.

I think you are rather confused on the way widgets and windows work.

  Federico