Re: [XaraXtreme-dev] Cairo Port

[Jonas Diemer <diemer@xxxxxx>]

Hi,

Thanks a lot for your reply!

Carl Worth schrieb:
> On Mon, 07 May 2007 22:08:14 +0200, Jonas Diemer wrote:
>   
> > 1. Carl created stubs for function calls to CDraw functions, which are
> > to be replaced by Cairo functions. Wouldn't it be easier to derive a new
> > GDrawContext instead? This has been done originally with GDrawAsm as a
> > C++ wrapper for the assemblerfunctions in GDRAW.DLL. I think this would
> > at least save passing around contexts, and would be more object
> > oriented, too.
> >     
>
> I have no idea on this point, (see above where I confess to zero
> experience with Xara). I just made the cut at at exactly the point
> where the code switched from GPL to non-GPL. If you've got a better
> place in the code to make the cut, go for it!
>   

Well, maybe some Xara folks can tell...

>   
> > 2. I am so far struggling with the very basic: I need to set up a cairo
> > context. To do this, I need a "drawable", i.e. some canvas I can draw
> > to. I have found examples on how to do this from GTK/GDK, and I guess
> > wxWidget is using a GTK backend...
> >     
>
> No, I don't think you actually want a window system "drawable".
>
> What the current CDraw library does is render things to a buffer of
> memory. The equivalent notion in cairo is cairo's image backend which
> you can get at with the cairo_image_surface_create_for_data function.
>
> One thing to figure out right away is whether the image format that
> Xara is using is compatible with any existing cairo image format.
>
> So after using cairo instead of CDraw to render content, the existing
> code within Xara that takes the content from the image buffer and
> pushed it out through wxWidget stuff should work just fine. And that's
> the right way to start, I think.
>   
> Yes, cairo does have other window-system-specific ways of drawing,
> such as cairo_xlib_surface_create and cairo_win32_surface_create.
> Moving to use those instead of cairo's image backend would be a fair
> amount of work, and would be more disruptive to the Xara code I
> think. So let's not so that as a first step.
>   
Yeah, thanks for explaining. I did not know how it worked in Xara, so I 
figured I'd have to use a window-system specific surface. Using a 
cairo_image_surface_create_for_data seems much easier, I will look into 
that.

> > PS: I will be on vacation starting May 7, so my mail responses may be slow.
> >     
>
> What's better to do on vacation than some fun hacking like this? :-)
>   

Well, from that point of view, I am on vacation already. But I will 
actually be travelling soon, so I won't be able to hack/email then :-)

Jonas