custom shaderGenerator not being used by registry

[gabr1gus]

osgEarth Version: 3.7.0 build 163

I was trying to use a custom shader generator so I would be able to create a different behavior for textures and shaderGen as the default is in conflict with the way that is used in my models, however, after creating this custom ShaderGenerator and using osgEarth::Registry::instance()->setShaderGenerator() to set this custom shadergen, I confirmed that no custom code was being called, even if using osgEarth::Registry::shaderGenerator().run(model) however, the custom code was being called if using the object directly, not through the registry.

For what I could find, this problem seem to be caused by osgEarth's use of ShaderGeneratorProxy.

All instances of registry that could return a instance of shaderGenerator, return instead an instance of shaderGenerator proxy, and in its constructor
ShaderGeneratorProxy(const ShaderGenerator* temp) : _instance( new ShaderGenerator(*temp, osg::CopyOp::SHALLOW_COPY) ) { }
It forces the creation of a new ShaderGenerator in specific, overruling any custom shadergenerator that may be passed to registry.

In my code I've "fixed" it by adding a function to shader generator:
virtual ShaderGenerator* getCopy(const osg::CopyOp& copy) const { return new ShaderGenerator(*this, copy); }
re-implementing this function in my custom ShaderGenerator as:
virtual ShaderGenerator* getCopy(const osg::CopyOp& copy) const { return new CustomShaderGenerator(*this, copy); }
and altering shaderGeneratorProxy constructor to:
ShaderGeneratorProxy(const ShaderGenerator* temp) : _instance( temp->getCopy( osg::CopyOp::SHALLOW_COPY) ) { }

[gwaldron]

You are probably the first one is history to try this :) so I am not surprised there are issues.
Can you please submit a PR and we'll integrate it? Thanks.