[Octave-bug-tracker] [bug #43873] large image gets cropped if width/height exceeds OpenGL limit

[Dan Sebald]

Follow-up Comment #5, bug #43873 (project octave):

I made some clarifications on this topic at this bug report:

https://savannah.gnu.org/bugs/?44415

Basically, those folks seeing the partial image are using a system in which
Mesa's newer Gallium version of swrast_dri.so is used.  Here's an illustration
of the missing portion:

https://bugs.freedesktop.org/attachment.cgi?id=114714

I was able to do a crude patch that fixed the issue on a local build of Mesa,
as illustrated here:

https://bugs.freedesktop.org/attachment.cgi?id=114715

but what I did is not a valid fix, as I just commented out of the driver the
lines that impose the limit and by chance I think it worked.  (Mesa's layout
is to use the route of texture elements for laying out an image.)

Those folks seeing the vertical lines yet whole image have the legacy version
of swrast_dri.so (same name) on their systems, as illustrated here:

https://bugs.freedesktop.org/attachment.cgi?id=114712

There is now a patch that fixes those issues,

https://bugs.freedesktop.org/attachment.cgi?id=114713

but whether that makes it into the driver isn't certain as the developers
don't give much support to the legacy code.

BTW, I think many people with Nvidia hardware end up with the swrast software
implementation, and it may be that there are some vendor-specific drivers in
some cases that would override swrast.  So, those having a problem might want
to look for a vendor-specific driver solution to see if there is a quick
solution.

In any case, I don't think a work-around in Octave's gl-render.cc is a good
idea.  That would be a lot of work just to fix things for a particular
system/graphics card.  Instead, working with the Mesa developers would be more
productive.  I've created a bug report for the vertical lines issue of legacy
swrast here:

https://bugs.freedesktop.org/show_bug.cgi?id=89586

and a separate entry for the large image crop issue of Gallium swrast here:

https://bugs.freedesktop.org/show_bug.cgi?id=89622

Those wanting some help building Mesa can email me for details.


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