This shader needs to use the same interface as the OCIO shader. On Linux
and Windows this seems to be the case. On MacOS however there is a
mismatch that makes the overlay texture to be completely black when
switching to workbench in the Shader workspace.
This is just a temporarily work-around as this should be solved. Due to
the poor GPU debugging facilities on Mac we haven't been able to
pin-point the root cause.
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