Discrepancies in xts results between master and xwayland-24.1

added Xwayland label

mentioned in merge request !1852

I will look into these this week.

Possibly a false alarm, looking into it…

We might want to consider expanding the XTS coverage in CI. Currently we're using piglit's xts-render profile, which runs only the Xlib9 subset of tests, which cover only drawing primitives, nothing related to input / window management / ...

My comment above applies even if so.

Yes, FWIW, this is something we also considered for libx11 in xorg/lib/libx11!264 (comment 2520519)

But not a blocker for xwayland-25.1

One thing to consider though is the time it takes, a full XTS run here takes roughly 1 hour on a pretty beefy laptop.

Right, there's a spectrum between what we're doing now and everything.

Anyway, I ran the piglit xts profile on Xwayland 24.1.5 and built from the current master branch, no regressions (actually 2 tests got fixed).

There's hundreds of pre-existing failures though, we'd need to either track (so we'll know when they get fixed) or exclude those.

a full XTS run here takes roughly 1 hour on a pretty beefy laptop.

I see two strategies for dealing with that:

Avoid long-running test cases. I notice mostly Xt* cases taking a long time, maybe we can just not run those for now.
Multiple CI jobs, which can run in parallel, each running a subset of test cases.

So, as it turns out, the build options were different and apparently, that does cause some discrepancies. For the record, I am using -Dxcsecurity=true -Dglamor=true -Ddri3=true to build locally.

With that, the number of differences between Xwayland build from xwayland-24.1 and master is more limited:

xts5/Xlib9/XDrawLines/XDrawLines (57/104): FAIL (was PASS)
xts5/Xlib13/XUngrabButton (1/6): UNRESOLVED (was PASS)
xts5/Xlib13/XUngrabButton (4/6): FAIL (was PASS)
xts5/Xlib13/XUngrabKey (1/7): UNRESOLVED (was PASS)
xts5/Xlib13/XUngrabKey (2/7): UNRESOLVED (was PASS)

Full logs xts-run-xwayland-24.1.log and xts-run-xwayland-master.log

First one:

xts5/Xlib9/XDrawLines/XDrawLines (57/104): FAIL (was PASS)

Is caused by:

530e80375ebbe825247646d5225e0ebb91f940cb is the first bad commit
commit 530e80375ebbe825247646d5225e0ebb91f940cb
Author: Jan Engelhardt <jengelh@inai.de>
Date:   Mon Dec 30 17:10:35 2024 +0100

    glamor: explicitly draw endpoints of line segments
    
    The OpenGL 4.6 specification §14.5.1 "Basic Line Rasterization"
    figure 14.2 says:
    
    """A diamond shaped region of height 1 is placed around each fragment
    center; those regions that the line segment **exits** cause
    rasterization to produce corresponding fragments."""
    
    As the line does not necessarily exit the last diamond,
    it is necessary to explicitly paint a pixel at line ends.
    
    Fixes: https://gitlab.freedesktop.org/xorg/xserver/-/issues/1434
    Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1755>

 glamor/glamor_lines.c | 1 +
 1 file changed, 1 insertion(+)

/cc @jengelh

I guess, let's revert and the submitter will address the test failure in a subsequent MR.

The rest are inconclusive unfortunately:

xts5/Xlib13/XUngrabButton (1/6): UNRESOLVED (was PASS)
xts5/Xlib13/XUngrabButton (4/6): FAIL (was PASS)
xts5/Xlib13/XUngrabKey (1/7): UNRESOLVED (was PASS)
xts5/Xlib13/XUngrabKey (2/7): UNRESOLVED (was PASS)

If I run those tests individually (rather than the full XTS suite), I get the same results with Xwayland build from the xwayland-24.1 branch and master, so

My guess is that some previous test changes the results of the later tests, as the Xserver is run with -noreset (required, otherwise xts-run fails to start as the xserver rests after xts-run spawns an initial xdpyinfo command!)

A possibility would be to run and compare the subsets of test cases separately.

mentioned in merge request !1755 (merged)

mentioned in commit p12tic/xserver@2d690a4d

mentioned in merge request !1858

Discrepancies in xts results between master and xwayland-24.1

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Discrepancies in xts results between master and xwayland-24.1

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