Open Effects Proposal for Standard Change

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Standard Change Workflow

• Create proposal as issue (you're doing this now!)
• Tag this issue with standard change tag
• Identify subcommittee: at least one plug-in vendor, and at least one host
• Discuss the idea in this issue
• Write new or updated code and doc
• Publish updates as a pull request (ideally on a feature/PROPOSAL-NAME branch)
  • Make sure that PR references this issue number to keep them in sync
  • Discuss and review code in the PR
  • Meet all requirements below for accepting PR
• When subcommittee signs off and other members don't have any further review comments,
  maintainer merges PR to master which closes PR and issue

Requirements for accepting a standard change:

• Header files updated
• Documentation updated
• Release notes added
• Compatibility review completed
• Working code demonstrated with at least one host and one plugin
• At least two members sign off
• No further changes requested from membership

Summary

Currently a host may or may not call instanceChanged after loading a saved project. This means plugins do not get an opportunity to update the enabled status of params or take other actions based on the input clips and/or param values. This proposal would require conforming hosts to call kOfxActionInstanceChanged after loading a project containing OpenFX plugin instances. This call would be with type=kOfxTypeClip. kOfxTypeParameter would also make sense but I suggest we just use Clip, and plugins can do whatever they need to.

As for kOfxPropChangeReason, should we recomend kOfxChangeUserEdited since loading a project is a user-initiated action? We could add a new reason, kOfxChangeProjectLoaded if that is needed, to distinguish these events from others, but since some hosts are already doing this, I don't think we need to make them change their behavior.

Motivation

Without this, plugins can't set their param enabledness or some overlay features because nothing is called after createInstance. A plugin has no way to know it's been updated (clip connected, params modified) after the instance was created.

Problem

This would enable plugins to show proper param status after a project is loaded.

Impact

This should have no impact on existing plugins, since some hosts already call instanceChanged after loading a project, and a plugin should respond to instanceChanged whenever it happens.

It does impact hosts, because any conforming host will need to make this call, if it doesn't already.

Documentation Impact

This is primarily (or entirely) a documentation/standard change. No change to the existing API.

Stakeholders

Both plugins and hosts will benefit from this by improving UI behavior.

Discussion