[Pixman] Make pixman compatible with big image

[Søren Sandmann]

LE GARREC Vincent <legarrec.vincent at gmail.com> writes:

> So, what should I do ? Is it okay to make a cast for every multiplication
> of stride by height ?

There are a couple of things that have to be kept in mind:

- The stride can be negative (this corresponds to the lines of the image
  being stored upside down), so storing or casting the stride to size_t
  probably won't work.

- Even if you fix the multiplication issues, has limitations in other
  places that prevents access to large images working well. See

        https://bugs.freedesktop.org/show_bug.cgi?id=46277

  for example. Fixing the multiplications may still be worthwhile
  though, since we may some day get large images working.

> I'm asking because I don't want to work on a patch that will be denied
> because my solution is wrong.

I don't know what the best way to do it is, but requiring all rowstride
multiplications to have a cast probably isn't going to be maintainable,
because people will forget about it when writing new code.


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