What is MOD_shapekey.c file?

Hi

I wanted to write a shapekey modifier and Is ee that there is already a MOD_shapekey.c file in the modifiers/intern. But the thing is that there is no shapekey modifier in Blender. Does anyone know what this file does actually? Is this really a deformer modifier?

Shape key is a modifier internally (one that always gets applied first), its just not exposed to the user as one.

ideasman42, thanks for the reply. That explains a lot, and in fact that was the main problem I had with the blend shape system before deciding to take a look at into the shapekey deformer. I do not want the shapekey deformer to be applied first. Since the blend shapes are applied first it makes it hard to combine morphing with other modifiers. So I am thinking that I either try to write a modifier, or create an option for the current modifier (after your reply).

In that system obivously one either has to use the shapekeys or use the new modifier. What is your take on a shapekey modifier that relies on the stack order? Is that something that can go well with the state of the mesh in Blender?