On Thu, 4 Dec 2003, Callum Prentice wrote:
> > I think you've misinterpreted this. Aside from corruption of
> > the ximage data structure, the only time BadValue is returned
> > is if your source rectangle passed to XShmPutImage lies outside
> > of the XImage (or if you pass junk for the send_event). Check
> > your dimensions passed to XShmPutImage.
>
> that's odd then - if a rearrange my code so i call create 1 then write 1 then create 2 then
> write 2 it works perfectly.
>
> if i call create 1 create 2 write 1 write 2 it fails with the X error i mentioned.
>
> (where 'create' does all the shm stuff and creation of the ximage and 'write' does the
> 'XShmPutImage'
>
> so i don't need to save/restone any of the XShmSegmentInfo then ?
Looking through the code, it looks like Xlib stores a pointer
to the shminfo. I didn't realize it did that. That would imply
that each XImage needs a XShmSegmentInfo that sticks around for the
life of the XImage.
It impresses me that it is a mistake that it did this rather
than copying the contents of the XShmSegmentInfo. I'm not sure
why it was implemented that way. I don't think we have any
XShm man pages. If we did, hopefully, they would mention something
like that.
The error must be that the first XImage ends up with the second
XImage's data and subsequently the operation appears to be addressing
outside of the shared memory segment, so the BadValue error happens.
Mark.
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