Various fixes and improvements for OpenFX filters

[ddennedy]

No description provided.

[Copilot]

Pull request overview

This PR improves the OpenFX host integration in MLT by extending supported parameter types, improving clip preference handling, and adding infrastructure for better threading and render-scale behavior when running OpenFX filters.

Changes:

• Added support for additional OpenFX parameter shapes (Integer2D/3D and Double2D/3D handling improvements) and sync-back of plugin-set parameter values to MLT filter properties.
• Implemented render-scale propagation into OFX actions and clip image properties, plus improved clip-preferences priming/caching.
• Added optional “frame-threaded” execution by creating per-frame OFX instances when the plugin’s declared thread-safety allows it, plus a Natron format compatibility helper.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
src/modules/openfx/mlt_openfx.h	Extends property type enum and exposes new OpenFX helper APIs (render scale + threading query).
src/modules/openfx/mlt_openfx.c	Implements new param handling, logging, clip preference priming/apply, render-scale plumbing, and threading-safety query.
src/modules/openfx/filter_openfx.c	Updates filter execution to use render-scale, improved pre-render action ordering, optional per-frame instances, and Natron format compatibility.

Comments suppressed due to low confidence (3)

src/modules/openfx/mlt_openfx.c:924

• In the Double3D branch, status is overwritten on each component read. If reading index 0/1 fails but index 2 succeeds, status becomes OK and the fallback-to-defaults block will be skipped, potentially returning an unset/stale X or Y.

        OfxStatus status
            = propGetDouble((OfxPropertySetHandle) param_props, "MltOfxParamValue", 0, X);
        status = propGetDouble((OfxPropertySetHandle) param_props, "MltOfxParamValue", 1, Y);
        status = propGetDouble((OfxPropertySetHandle) param_props, "MltOfxParamValue", 2, Z);

src/modules/openfx/mlt_openfx.c:940

• In the Integer3D branch, status is overwritten on each component read. A failure to read X or Y can be masked by a successful Z read, which skips the fallback and can return partially undefined values.

        OfxStatus status = propGetInt((OfxPropertySetHandle) param_props, "MltOfxParamValue", 0, X);
        status = propGetInt((OfxPropertySetHandle) param_props, "MltOfxParamValue", 1, Y);
        status = propGetInt((OfxPropertySetHandle) param_props, "MltOfxParamValue", 2, Z);

src/modules/openfx/mlt_openfx.c:908

• In the Integer2D branch, status is overwritten on the second propGetInt() call. A failure to read index 0 can be masked by a successful index 1 read, causing partial/undefined values and skipping the default fallback.

        OfxStatus status = propGetInt((OfxPropertySetHandle) param_props, "MltOfxParamValue", 0, X);
        status = propGetInt((OfxPropertySetHandle) param_props, "MltOfxParamValue", 1, Y);