Re: Static items (Was: Can this be done with goocanvas?)

[Damon Chaplin <damon karuna eclipse co uk>]

On Tue, 2008-10-28 at 19:16 +0000, Gustavo J. A. M. Carneiro wrote:

> Today I tried replacing connect with connect_after for the adjustment
> signals.  It does not solve the flicker, but it helps keep the static
> items more static.  Not sure whether you did the same thing, but I'd
> like to just drop this node.

I've just committed my code so you can try it out.

It is easy to use - just get the static root item and add items to it
like the normal root item:
  static_root = goo_canvas_get_static_root_item (canvas);

The demo shows a few static items.

Static items always use pixels for units at present. I don't know if we
want to support other units.

Also, static items are placed above normal items - I hope that is what
everyone wants.


> > (There is one way I tried which avoids flicker completely - redraw the
> > entire window when scrolling. Of course the problem then is performance,
> > but with only a few items on the canvas it works great.)
> 
> I see.  The performance would not be great, but for sure that is the
> only way this is ever going to work flicker free[1].  Maybe making this
> an option?  Those that want to draw static overlay items would activate
> the option, otherwise it would be disabled by default.

We could add this as an option. The code needed is very simple.


> [1] either that or draw the static items on another X11 window with
> alpha channel and let a compositing manager do basically the same work
> but in hardware accelerated opengl ;-)  

Using a shaped window might be an alternative as well. Though I don't
know how well they work in GTK. Too much work for me as well.

Damon