On 11/26/2020 09:22 AM, Brian Paul wrote:
On Wed, Nov 25, 2020 at 8:19 PM Ian Romanick <i...@freedesktop.org
<mailto:i...@freedesktop.org>> wrote:
I was looking at the dlist-beginend subtest test_illegal_begin_mode.
The test compiles a display list with GL_COMPILE_AND_EXECUTE mode. The
glBegin in the test uses an invalid mode. This should generate a
GL_INVALID_OPERATION error immediately. The test checks this, and that
GL_INVALID_ENUM, actually, but anyway..
seems correct.
The test then tries to execute the display list and checks for
GL_INVALID_OPERATION again. I believe this is incorrect. Section 5.4
("Display Lists") of the OpenGL 1.0 spec (this is a gl-1.0 test, after
all!) says:
If mode is COMPILE_AND_EXECUTE then commands are executed as they
are encountered, then placed in the display list.
Section 2.5 ("GL Errors") of the OpenGL 1.0 spec says:
In other cases, the command generating the error is ignored so that
it has no effect on GL state or framebuffer contents.
Unfortunately, the spec doesn't clearly define what's meant by "ignored"
here. That is, does it mean the command is not compiled into the
display list? My intuition is that even if a command has invalid args
at compile time, the command should still be compiled into the list. If
the spec doesn't spell out the answer, I'd opt to do whatever other
vendors do (hoping they're consistent).
While the section numbers and titles have changed, every later version
of the GL (compatibility profile) spec says the exact same thing.
To me, this indicates that the errant glBegin should not be included in
the display list. Assuming this test passes on other implementations, I
think it does so only by luck. The mis-matched glEnd in the display
list will generate the same error. Am I missing some spec language to
justify this test?
I haven't searched, but I suspect the spec doesn't explicitly describe
this situation.
I noticed this because I was adding a test that does
glNewList(list, GL_COMPILE_AND_EXECUTE);
glColor4fv(green);
glBegin(GL_QUADS);
glBegin(GL_QUADS);
glVertex2f(-1, -1);
glVertex2f( 1, -1);
glVertex2f( 1, 0);
glVertex2f(-1, 0);
glEnd();
glEndList();
I expected an error while compiling the list, but I expected glCallList
to not generate an error. Errors are generated in both places.
I guess my instinct is that errors should be generated both at list
compile and execute time. I wonder if there's any API function /
argument combinations that would be errant at compile time but not at
execute time, depending on some other state. If so, that would indicate
that calls should always be compiled into the list, even if they
generate an error at compile time.
I think it gets worse. There's a second part to this new subtest that
replaces the errant glBegin call with glReadPixels. glReadPixels is not
allowed between glBegin and glEnd, so it should generate an error in
GL_COMPILE_AND_EXECUTE mode. It does not.
Sound like a run of the mill bug.
These changes are in the top commit of:
https://gitlab.freedesktop.org/idr/piglit/-/commits/display-list-hell
<https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.freedesktop.org%2Fidr%2Fpiglit%2F-%2Fcommits%2Fdisplay-list-hell&data=04%7C01%7Cbrianp%40vmware.com%7C1bece8f6bb15456a704108d892278cef%7Cb39138ca3cee4b4aa4d6cd83d9dd62f0%7C0%7C0%7C637420045848819859%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=CGW3oxTFndTrF4fVU8EADRhSr1ORAODexsSgl4pYsjc%3D&reserved=0>
I don't have any systems currently available with closed-source drivers,
but I would be very interested to see the results of
gl-1.0-dlist-beginend from that branch on any closed source drivers (on
any platform).
I can check on Nvidia next week when I'm back. Maybe someone else can
test in the mean time.
Here's the results with Nvidia's 455.38 driver:
$ build-debug/bin/gl-1.0-dlist-beginend -auto
PIGLIT: {"enumerate subtests": ["glCallList inside glBegin-glEnd",
"nested glCallList inside glBegin-glEnd", "illegal glRect inside
glBegin-glEnd", "illegal glDrawArrays inside glBegin-glEnd", "illegal
glDrawArrays inside glBegin-glEnd (2)", "separate glBegin-glVertex-glEnd
lists", "illegal glBegin mode in display list"]}
PIGLIT: {"subtest": {"glCallList inside glBegin-glEnd" : "pass"}}
PIGLIT: {"subtest": {"nested glCallList inside glBegin-glEnd" : "pass"}}
PIGLIT: {"subtest": {"illegal glRect inside glBegin-glEnd" : "pass"}}
Probe color at (80,80)
Expected: 0.000000 1.000000 0.000000 1.000000
Observed: 1.000000 0.000000 0.000000 1.000000
PIGLIT: {"subtest": {"illegal glDrawArrays inside glBegin-glEnd" : "fail"}}
PIGLIT: {"subtest": {"illegal glDrawArrays inside glBegin-glEnd (2)" :
"pass"}}
PIGLIT: {"subtest": {"separate glBegin-glVertex-glEnd lists" : "pass"}}
PIGLIT: {"subtest": {"illegal glBegin mode in display list" : "pass"}}
PIGLIT: {"result": "fail" }
Looks like the subtest in question passes.
-Brian
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