Emissive Materials are not applied when rendering entities in the player's inventory
Version: Canvas-mc116-1.0.1267 Mc: 1.16.4 (dev environment) Fabric: 0.30.0+1.16 Loader: 0.10.6+build.214 No other mods are included that mess with rendering
Glowy:

Not Glowy:

I did check and my code does correctly set the material when rendering in the inventory.
This can be classified as #189, because it only applies shaders to worlds.
Yeah, Canvas only apply post processing effects to the world. Material shader is still applied to GUI items but not post processing like bloom. I dunno if it can be a feature or not, could be a performance issue or design restrictions such as not letting buggy shader mess with the rest of the GUI.
I doubt that it would lag because there are not that many pixels in that very small window
Mojang's GUI rendering is problematic, so would not get too optimistic about this.