[Mesa-dev] [Bug 30847] New: Serious rendering issues when drawing to front buffer with GL_LIGHTING enabled

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=30847

           Summary: Serious rendering issues when drawing to front buffer
                    with GL_LIGHTING enabled
           Product: Mesa
           Version: git
          Platform: x86-64 (AMD64)
        OS/Version: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: Mesa core
        AssignedTo: mesa-dev at lists.freedesktop.org
        ReportedBy: jpjokela.spam at gmail.com


Created an attachment (id=39421)
 --> (https://bugs.freedesktop.org/attachment.cgi?id=39421)
Testcase to reproduce the problem. Can be compiled by executing as shell
script.

Test code fails on 7.9~git20100924-0ubuntu2 version running on Ubuntu 10.10. I
haven't tested on other systems yet, and am not sure, in which component the
bug actually is.

Expected result:
When running the test program on my nvidia system, it draws same triangle (one
vertex at left, one right and third at the top, all centered) in various
(constant for all vertices) colors.

Actual result:
When running the same program on my Asus 1215N using the Intel chipset,
however, the first triangle is rendered ok, but next one (and all after that)
have one red vertex at top left, another red at bottom center, and white top
right.

This code works the same on both if I either:
1)Don't draw to front buffer
2)don't glEnable(GL_LIGHTING)

If glEnable(GL_DEPTH_TEST) line is uncommented, only the top line of upside
down triangle will be drawn.

While drawing to front buffer probably isn't too common, it can result in whole
program becoming useless, when rendering stops working.

The code itself doesn't make much sense, as it's based on bugles exetrace of a
lot bigger project, with functions that don't change the outcome removed.

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