Octave: dotted feval in DashboardWidgetRegistry.fromStruct breaks widget deserialization (dashboard load + detach)

[HanSur94]

Summary

DashboardWidgetRegistry.fromStruct deserializes widgets with a dotted-static-method feval:

% libs/Dashboard/DashboardWidgetRegistry.m:92
w = feval([className '.fromStruct'], s);

GNU Octave (a fully supported runtime per the project docs) does not resolve that form and throws:

feval: function 'FastSenseWidget.fromStruct' not found

MATLAB is unaffected.

Impact

Both code paths that deserialize a widget are broken under Octave:

1. Serialized dashboard load — DashboardEngine.load(jsonPath) / any fromStruct round-trip.
2. Detached mirrors — DashboardEngine.detachWidget → DetachedMirror.cloneWidget (libs/Dashboard/DetachedMirror.m:178) → the registry call above.

Programmatically-built dashboards (addWidget + render) work under Octave; only deserialization/detach hit this.

Reproduce (Octave 11)

install();
bx = linspace(0,1000,5000);
t1 = SensorTag('a','X',bx,'Y',sin(bx/7));
d  = DashboardEngine('Repro');
d.addWidget('fastsense','Title','A','Position',[1,1,12,2],'Tag',t1);
d.render();
d.detachWidget(d.activePageWidgets(){1});   % -> feval: function 'FastSenseWidget.fromStruct' not found

Suggested fix

Replace the string-concatenation feval with a handle Octave resolves:

fn = str2func([className '.fromStruct']);
w  = fn(s);

Verify str2func([className '.fromStruct']) actually resolves a static-method handle in Octave (test in Octave 11); if it doesn't, fall back to another portable dispatch (e.g. metaclass lookup). Confirm the fix in both MATLAB R2025b and Octave 11 by round-tripping a widget through toStruct/fromStruct and by exercising detachWidget, and run the widget-serialization / DashboardSerializer suites on both runtimes.

Context

Found while adding benchmarks/bench_detached_mirror_refresh.m (merged in #215), which currently guards with an Octave skip because of this. Once fixed, that skip can be removed. See the note in benchmarks/.reports/coverage.md.

🤖 Generated with Claude Code