[Xcb] How can I increase the maximum request length?

Bart Massey bart at cs.pdx.edu
Sat Jan 19 01:39:50 UTC 2019

Offhand, looks like your bigger display is too big to use a single PutImage
request even with BIG-REQUESTS enabled. Looks like xcb_image_put() doesn't
break the request into pieces for you (maybe it should? pull requests
welcome) so you'll have to put the image a piece at a time: break it into
bands and use the y offset.

On Fri, Jan 18, 2019 at 2:29 PM paul ewing <pcewing at outlook.com> wrote:

> Hello,
> I am running into an issue with xcb_image_put failing. The cookie being
> returned has a sequence number of 0. After reading the following thread
> from
> this mailing list I believe it's due to my maximum request size being too
> low:
> https://lists.freedesktop.org/archives/xcb/2006-June/001687.html
> The reason I suspect this is that the code in question is being used to
> set the
> root pixmap (I.E. Set the wallpaper) and works on one machine where the
> display
> (And thus the image) is 1920x1080, but fails on another machine with a
> 3440x1440 display.
> As the documentation mentions, the request size is actually the number of 4
> byte blocks. The image data size should be the pixel count multiplied by
> the
> bytes per pixel (4 in my case), so it would make sense that the first case
> would succeed and the second would fail:
> - (1920*1080*4)/4 => 2073600 < 4194303  OKAY
> - (3440*1440*4)/4 => 4953600 > 4194303  ERROR
> I verified via xdpyinfo that the BIG-REQUESTS extension is present and also
> tried manually running xcb_big_requests_enable and
> xcb_big_requests_enable_reply, which returned without an error.
> Even still, the result of xcb_get_maximum_request_length is 4194303.
> Is there something I need to do to manually increase the maximum request
> length?
> Thanks,
> Paul Ewing
> _______________________________________________
> Xcb mailing list
> Xcb at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/xcb
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