Fix log playback for particle emitters

[jennuine]

🦟 Bug fix

Depends on #742

Summary

When playing back a recorded log with particle emitters, most of the time the change from the ParticleEmitterCmd component is not captured (occasionally it is captured). The fix was to call _ecm.SetChanged when the ParticleEmitterCmd emitting component was changed from the previous iteration.

Using this fog.sdf world:

fog.sdf

<?xml version="1.0" ?>
<sdf version="1.6">
<world name="fog">
  <plugin
    filename="ignition-gazebo-physics-system"
    name="ignition::gazebo::systems::Physics">
  </plugin>
  <plugin
    filename="ignition-gazebo-user-commands-system"
    name="ignition::gazebo::systems::UserCommands">
  </plugin>

  <plugin
    filename="ignition-gazebo-scene-broadcaster-system"
    name="ignition::gazebo::systems::SceneBroadcaster">
  </plugin>

  <include>
    <uri>
      https://fuel.ignitionrobotics.org/1.0/OpenRobotics/models/fog emitter
    </uri>
  </include>

</world>
</sdf>

1. ign gazebo -r --record-path ./fog_emitter --log-overwrite fog.sdf
2. ign topic -t "/model/fog_generator/particle_emitter/fog_generator" -m ignition.msgs.ParticleEmitter -p "emitting: {data: 1}"
3. Wait a couple of seconds then run: ign topic -t "/model/fog_generator/particle_emitter/fog_generator" -m ignition.msgs.ParticleEmitter -p "emitting: {data: 0}"
4. Let particles disappear then close Ignition
5. Playback recording: ign gazebo -r --playback ./fog_emitter

Before PR
In step 5 listed above, particles probably did not stop emitting (the particles should disappear when it reaches the end of playback). If they did stop emitting, run step 5 again.

Afrter PR
Particles will stop emitting and particles will disappear when it has reached the end of playback.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge

[codecov]

Codecov Report

Merging #745 (7814dc0) into ign-gazebo4 (302f5ed) will decrease coverage by 11.91%.
The diff coverage is 68.42%.

@@               Coverage Diff                @@
##           ign-gazebo4     #745       +/-   ##
================================================
- Coverage        77.37%   65.46%   -11.92%     
================================================
  Files              217      237       +20     
  Lines            12217    17277     +5060     
================================================
+ Hits              9453    11310     +1857     
- Misses            2764     5967     +3203     

Impacted Files	Coverage Δ
include/ignition/gazebo/EntityComponentManager.hh	100.00% <ø> (ø)
include/ignition/gazebo/rendering/SceneManager.hh	100.00% <ø> (ø)
src/Conversions.cc	82.03% <ø> (+0.13%)	⬆️
.../plugins/component_inspector/ComponentInspector.cc	7.29% <0.00%> (-1.32%)	⬇️
.../plugins/component_inspector/ComponentInspector.hh	28.57% <ø> (ø)
src/network/PeerTracker.hh	100.00% <ø> (ø)
src/systems/apply_joint_force/ApplyJointForce.hh	100.00% <ø> (ø)
src/systems/breadcrumbs/Breadcrumbs.hh	100.00% <ø> (ø)
src/systems/buoyancy/Buoyancy.hh	100.00% <ø> (ø)
src/systems/contact/Contact.hh	100.00% <ø> (ø)
... and 87 more

---

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[iche033]

after merging this branch with jennuine/ecm_changedstate, the particle emitter works in log playback as advertised