So, I was trying to create something similar to a furnace that runs on sunlight, so I copied the relevant Furnace classes (Container, Gui, and TileEntity) and renamed them. I've not yet added the furnace functionality, but I have huge slot problems, which I assume is from removing the fuel slot, lowering the count to 2 slots instead of 3. I lowered what I thought were the right values, but now it dups the items weirdly, adding them in every row.

 

Relevant files attached below, other stuff can be added if needed. Cannot access attachment upload path apparently.

 

Ahem: Files here. https://gist.github.com/kenzierocks/e4f92432c0e2520602fd.

Okay, this happens when your server and client don't sync: the server thinks you don't have a GUI open or something. To fix, I just implemented some stuff out of this: http://www.minecraftforum.net/topic/1949352-172164-custom-inventories-in-items-and-players/

Oh, and to make it run on sunlight, you might wanna take a look at the light detector thingy, or whatever its called.