Generating new vertices in a shader

We are using a UI effect that creates an outline around text by cloning existing vertices and displacing them slightly (by a given amount) to create an outline.

I was wondering whether this effect could actually be achieved using a shader?

*NOTE: we are targeting mobile platforms so this has to be compatible.

Can anyone point me in the right direction? what kind of shader type? what components / steps needed to be used in Unity for this ?

 

Generally for this you don't duplicate the verts, you just draw the mesh in two passes. One draws the outline (pushed verts, inverted normals) and the other draws the mesh itself as normal.

 

Is that favorable to duplicating (generating new vertices) ?

 

Yes, you can't duplicate vertices in a standard vertex shader (I should have mentioned that)