[regression] Multi-monitor frame sync no longer works (not synchronized), and frames skip/jump/stutter

I guess now might be a good time to implement that parameterless frame sync algorithm I had in mind and abolish "frameno".

Bisected. The regression happened here:

------------------------------------------------------------
revno: 1398 [merge]
author: Alan Griffiths <email address hidden>
committer: Tarmac
branch nick: development-branch
timestamp: Fri 2014-02-14 19:14:15 +0000
message:
  compositor: non-blocking implementation of SwitchingBundle::client_acquire. Fixes: https://bugs.launchpad.net/bugs/1267323.

  Approved by PS Jenkins bot, Alexandros Frantzis, Andreas Pokorny, Kevin DuBois.
------------------------------------------------------------

Symptoms are fixed by lp:~raof/mir/nested-one-surface-per-crtc - am still investigating the exact mechanism.

Weird - as soon as I conclude there's no good reason for nested-one-surface-per-crtc to fix it I can reproduce the problem using it.

Note that this bug affects screencasting, i.e., the rendering speeds up beyond ~60FPS and becomes jumpy.

I guess this is to be expected, since our current implementation of screencasting works by recompositing the specified region, it's essentially like having an extra offscreen display.

Fix committed into lp:mir/devel at revision None, scheduled for release in mir, milestone Unknown

This wasn't just a sync bug, but caused bad frame ordering too. You could see bad frame ordering in mir_demo_client_egltriangle when it straddled multiple monitors. And today I saw the same scary frame ordering glitches in XMir --> bug 1291755

This bug was fixed in the package mir - 0.1.7+14.04.20140317.1-0ubuntu1

---------------
mir (0.1.7+14.04.20140317.1-0ubuntu1) trusty; urgency=medium

  [ Daniel van Vugt ]
  * New upstream release 0.1.7 (https://launchpad.net/mir/+milestone/0.1.7)
    - mirserver ABI bumped to 17
    - mirclient ABI unchanged, still at 7. Clients do not need rebuilding.
    - Server API changes (AKA why doesn't my code build any more?):
      . Class "CompositingCriteria" has been removed. It's replaced by the more
        flexible "Renderable" interface. This also resulted in parameter
        changes for the Renderer and scene filtering classes.
      . The function "DisplayConfiguration::configure_output()" has been
        removed. Instead, please use the new mutable version of
        "DisplayConfiguration::for_each_output()" with which you can modify
        the output structure passed in on each iteration.
      . Exposed formerly private class "GLRenderer" and demonstrated how
        to override its behaviour in demo-shell. This area is under
        construction and may experience further major changes.
    - Added initial support for hardware (HWC) overlays to accelerate
      rendering and reduce power consumption. Not complete yet.
    - Screen rotation: Added mouse cursor rotation support, so you can now
      still control things on a rotated screen. Still missing rotation of
      the cursor bitmap itself.
    - Lots of fixes to support nested Mir servers (see below).
    - Major simplification to how surface size/position/transformation
      interact, making transformations much easier to manage and work with.
    - Bugs fixed:
      . ./cross-compile-chroot.sh: line 83: popd: build-android-arm: invalid
        argument popd: usage: popd [-n] [+N | -N] (LP: #1287600)
      . Key events sent to the wrong client (and delayed) (LP: #1213804)
      . Nested servers never receive input events (in their filters)
        (LP: #1260612)
      . Software clients crash immediately on nested servers - what(): Failed
        to mmap buffer (LP: #1261286)
      . MirMotionEvent lacks local coordinates. Reports only screen
        coordinates. (LP: #1268819)
      . Nested Mir crashes with - what():
        MesaNativePlatform::create_internal_client is not implemented yet!
        (LP: #1279092)
      . clients fail to find some libraries if mir installed via "make install"
        (LP: #1285566)
      . Nested server hangs with multimonitor and internal clients.
        (LP: #1287282)
      . [regression] Multi-monitor frame sync no longer works (not
        synchronized), and frames skip/jump/stutter (LP: #1288570)
      . Mir FTBFS: /usr/bin/ld: cannot find -lmirtestdraw (when cmake ..
        -DMIR_ENABLE_TESTS=OFF) (LP: #1283951)
      . nested Mir library calls next_buffer() during startup (LP: #1284739)
      . Building Mir produces lots of warnings from GLM headers about
        deprecated degrees values vs radians (LP: #1286010)
      . [enhancement] screencast of a single window (LP: #1288478)
      . Nexus4 + mir_demo_client_eglplasma starts to stutter after a while
        (LP: #1189753)
      . --host-socket documented default argument isn't...