[SofaCore] Add new (simpler) DataEngine implementation

[marques-bruno]

Here's a simpler implementation of sofa::core::DataEngine. This implementation hides the code related to updating datafields and calling cleanDirty() in an attempt to reduce human errors.

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This PR:

• builds with SUCCESS for all platforms on the CI.
• does not generate new warnings.
• does not generate new unit test failures.
• does not generate new scene test failures.
• does not break API compatibility.
• is more than 1 week old (or has fast-merge label).

Reviewers will merge only if all these checks are true.

[epernod]

as it is more the behavior we want, maybe one of the current engine could already become a simpleDataEngine?
As an example and it would go through the CI tests

[epernod]

I'm not use to the dataTracker, if the data are added in the dataTracker, is it not possible to use it in the update method to check the data instead of calling the updateIfDirty?

[marques-bruno]

The datatracker is not influenced by the updateIfDirty() call. You can absolutely use the datatracker in the update() method if needed (to check which inputs have been changed, and to specific actions for each dirty data. The call to UpdateIfDirty() simply guarantees that all data have been accessed (thus updated upstream) before calling cleanDirty().

[epernod]

ok so the dataTracker just return dirty if on of its Data is dirty?

[marques-bruno]

yes, the dataTracker is not at all used in the internal mechanism of the DataEngine class actually. It's a helper object (one instance per dataEngine) that tracks data. It has a very simple interface, and you can just call
trackData(BaseData*) << sets a datafield in its map. for now on, its counter will be tracked
clean() / clean(BaseData*) << resets the data's counter
isDirty() : isDirty() << checks if the counter is up to date

You can then use this in your update() ( or doUpdate() now) method to see if a specific datafield is dirty or not.

[marques-bruno]

@epernod Good idea. I would suggest the TransformEngine, since it's a very basic engine (the most used also) so the feature would be more visible to users with minimal code change.

[guparan]

This PR was set to ready too soon. DataEngine_test doesn't compile ^^

[marques-bruno]

Waiting for CI but I think it's better now:
used enable_if<is_base_of> to compile or not the doUpdate / update methods in the test. should be clean enough

[guparan]

CI was missing disk space. I relaunch ;)
[ci-build][with-scene-tests]

[marques-bruno]

alright, that should fix the failing test. Although, the test doesn't reflect very well the behavior of the component. the SimpleDataEngine must exclusively be used in cases where the process performed the engine has to be applied no matter which datafield is set to dirty.
Currently, the engine would even be called if NO data is set to dirty, which is also the case in the core::DataEngine if there's no check performed on the DataTracker. I believe this is a mistake. I think that doUpdate() should be called iff at least 1 data field is dirty.
What do you think?

concretely, it means that in DataEngine_test.cpp, line 151 would assert FALSE

[marques-bruno]

Following our discussions:
SimpleDataEngine's update method now looks like this:

void update() final
{
   updateAllInputs() // a method that calls `updateIfDirty()` on all inputs: can be overridden, but rarely necessary
   DDGNode::cleanDirty() // same as cleanDirty(), but does NOT call m_datatracker->clean() so counters are still valid after
   doUpdate() // actual magic
   m_datatracker->clean() // cleaning the counters
}

To my understanding, DataTrackerDDGNode's cleanDirty() method becomes useless in DataEngines at this point, making the workflow much smoother for the user's impl of doUpdate().

I believe there would be no side effects (apart from being BRAKING...) if we would replace core::DataEngine with core::SimpleDataEngine, and rename all engine's udpate() methods to doUpdate()

[damienmarchal]

What about ?

void update() final
{
   updateAllInputs(); // a method that calls `updateIfDirty()` on all inputs: can be overridden, but rarely necessary
   cleanAllInputsDirty(); // same as cleanDirty(), but does NOT call m_datatracker->clean() so counters are still valid after
   doUpdate() // actual magic
   cleanAllInputsCounter() // cleaning the counters
}

[guparan]

I'm rebasing this before merge ;-)