Filter fuel input

[kryojenik]

TL;DR

Ability to place a filter on the input of fuel to furnaces. Primarily to inhibit consuming recipe ingredients that have a fuel value as fuel.

What ?

As added reference viewtopic.php?p=552365#p552365

In addition to the fix done here, it would also be nice to have a tic box (or other mechanism) to not use recipe ingredients as fuel. In the case of the regular furnace without a set recipe, maybe a disallow filter? Could accept that the filter only came for furnaces that allow a recipe to be set.

Why ?

The furnaces will continue to use the fuel that is initially placed in the fuel inventory. As long as you never have an interruption in supply, this is fine. If this rare situation that never happens in factorio occurs and you have a slump in your intended fuel supply, the furnace will start using ingredients as fuel. The you have to manually run to all furnaces, stop the ingredient supply, make sure inserters aren't holding any, remove the fuel, place the correct fuel, then hook everything back up. Rinse, repeat.

This is more impactful with items that have low fuel value where the consumption as fuel would outstrip their need as an ingredient.

[mrvn]

For situations like this I place a wire on the fuel and ingredients belt at the input to the factory part. Stop the ingredients when the fuel belt is not backed up. The fuel easily last long enough to consume all the ingredients left on the belt and new ones won't flow into until the fuel is back in all units.

Note: To detect when fuel is backed up split the belt in two, read content on the two belts and merge them back. If the count is < 10 (yellow belt) then the fuel is still flowing.