Re: Future of Canvas on GTK+ (and probably GNOME)

[Fabrício Barros Cabral <fxcabral yahoo com br>]

On Fri, 2005-02-11 at 15:21 -0500, Havoc Pennington wrote:

Hi all,

> An important question is what a canvas widget is for. In the GNOME 1.x
> days, GnomeCanvas was used to implement a lot of custom widgets.
> However, in GNOME 2.x that is very uncommon; because of accessibility
> concerns and because GTK+ itself provides anti-flicker capabilities.

Basically, I think, a canvas widget allows a customized drawing. For
example, imagine that I want to make a program which draw polygons. How
can I do it with GNOME 2.x *without* using an especialized (external)
widget, like libgnomecanvas?

> So it would be interesting to map where the canvas is still used. I'd
> assume gnome-games and nautilus for example.

There are a lot of programs using gnome-canvas or an own canvas system.
What I'd like see is a unified basic canvas system (preferably, in
GTK+), flexible and powerful that could be used by all programs which
need a canvas support.

> On some level a canvas widget is a kind of alternate widget system
> inside GTK+, provided to work around some of the limitations of GTK+
> core. Certainly in GNOME 1.x that was one of the main reasons it was
> used.

So, what should I use in GNOME 2.x (and GNOME 3.x) to do a customized
drawing?

> In XUL you can imagine that there's no need for a canvas since you can
> use SVG and HTML and so forth;

I don't know the XUL stuff, but I think that they pretend implement a
canvas support:

http://wiki.mozilla.org/index.php/XUL:Canvas_Tag
http://www.xulplanet.com/ndeakin/article/231/

(please, correct me if I'm wrong)

> in Microsoft's Longhorn stuff I'm not as
> sure how it plays out but the "canvas" type functionality does seem to
> be more designed in to the overall toolkit.

Well, I don't know the MS Longhorn stuff too. But I know what you said
some time ago (please, correct me if I'm wrong):

1) "It's possible in the future, the GTK+ widgets will be able canvas
elements, using Cairo support for it";

2) "If I was redesign the canvas support in GNOME, I will do something
similar to Java 2D API"

Because these (and others) I ask to myself *every single day*: What's
the future of canvas in GTK+? :)

> Have to get a handle on the target use cases of the canvas I think in
> order to design it correctly.

I agree with you and I think that is time to think about the future of
canvas in GTK+.


Thanks for your attention,


--Fabr�o