Re: GtkCanvas requirements?

[Benjamin Otte <otte gnome org>]

Carl Worth <cworth <at> cworth.org> writes:

> I'm quite convinced that using floating-point at the interface, and
> fixed-point internally as needed provides the right combination of
> performance and ease-of-use for cairo. I'd highly recommend any new
> canvas interfaces being proposed follow the same approach.
> 
A huge advantage that a cairo-like API has over a canvas is that it has far less
interaction using the interfaces. In cairo the interfacing goes like this:
-> create surface
-> draw
In a canvas it goes like this:
-> add item
<- query size
-> answer size request
<- allocate size
<- send event
-> answer event
...
So there's a lot more situations where you have to pass doubles.

That being said, I'll trust doubles being slow when I see the numbers. There
have been a lot of complaints about cairo's usage of doubles when it wasn't even
an issue. [1]

But the most important issue for a canvas is its API. If I have to know all
sorts of internal things (like what sort of fixed point magic to apply) to get a
canvas item coded, I'm not gonna code a canvas item. And without canvas items a
canvas is pretty boring. Noone cares about text entries and rectangles.

Benjamin


[1] http://blogs.gnome.org/view/xan/2006/11/06/0 - compare the green and the
blue bar