[Xcb] some questions and remarks

Jamey Sharp jamey at minilop.net
Thu Sep 29 11:46:48 PDT 2005

On Sat, 2005-09-17 at 17:32 +0200, Vincent Torri wrote:
> Hey,

Hi Vincent! Sorry for the delay. Been reconstructing several servers
from scratch over here.

> I'm trying to port xcompmgr to xcb,


> 1) For the QueryTree stuff, there is no Next() or End() functions. Is it
> normal ?

I don't understand. There are XCBWINDOWNext and XCBWINDOWEnd functions,
which you should be able to use with the XCBWINDOWIter that you get from

> 2) for the damage extension, XCBDamageDAMAGE is just a CARD32, not a
> struct. And so, there is no New() function.

That would be a bug in the protocol description then. I assume from your
question that DAMAGE should have been declared as an xidtype, not a

> Also, XDamageReportNonEmpty is
> not ported in damage.h. I think it's missing

That's entirely possible. Is that function an actual part of the
protocol, or should it be an XCBAux thing or something?

> 3) Is there an equivalent of NextRequest in xcb ?

Yes... uh... (digging around) No. No, there isn't.

What do you need it for? Remember that the cookie returned by every
request contains the sequence number of that request.

> 4) In Xlib, XRenderFindVisualFormat returns iknformation for the format,
> the type and domething named 'direct'. With xcb, to get the format, I
> iterate on screen, depth, and visual iter variables, then I can get the
> format Id.
>  But type and direct can only be retrieved with forminfo, which is
> completely independant of the above iterations to get the format. Am I
> missing something ? any ideas ?

I don't entirely understand the question, but I'm pretty sure I've
written the code you want already. It's in
cairo/src/cairo-xcb-surface.c, in the functions format_from_visual and
_format_from_cairo (depending on how you want to select picture

That code is probably a good target for being put in a shared library.

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