Refactor scissors, fix and finalize prefs, fix missing part definition for xion models, etc.

continued: Monitor changing verb will now only show a list of monitor
styles available for the monitor head brand you are using.

For example, if you chose any of the regular monitor heads (default
morpheus or anything suffixed with mtr.) you will get a list of IPC
standard monitor styles and nothing else.
However, if you chose the hesphiastos alt head (which is also a monitor,
but of a different style) the list will be populated with the monitor
styles suitable for that hesphiastos head, but none others (not even the
ipc standard ones, since those don't fit and hesphiastos alt. isn't in
the models_allowed list)

code/modules/client/preferences.dm

@@ -1496,23 +1496,35 @@ var/global/list/special_role_times = list( //minimum age (in days) for accounts
 									organ_data[second_limb] = "amputated"
 									rlimb_data[second_limb] = null
 						if("Prosthesis")
-							var/choice = input(user, "Which manufacturer do you wish to use for this limb?") as null|anything in chargen_robolimbs
+							var/choice
 							var/subchoice
 							var/datum/robolimb/R = new()
 							var/in_model
+							var/robolimb_companies = list()
+							for(var/limb_type in typesof(/datum/robolimb)) //This loop populates a list of companies that offer the limb the user selected previously as one of their cybernetic products.
+								R = new limb_type()
+								if(!R.unavailable_at_chargen)
+									if(limb in R.parts) //Ensures users can only choose companies that offer the parts they want.
+										robolimb_companies[R.company] = R //List only main brands that have the parts we're looking for.
+							R = new() //Re-initialize R.
+
+							choice = input(user, "Which manufacturer do you wish to use for this limb?") as null|anything in robolimb_companies //Choose from a list of companies that offer the part the user wants.
 							if(!choice)
 								return
 							R.company = choice
 							R = all_robolimbs[R.company]
-							if(R.has_subtypes == 1)
+							if(R.has_subtypes == 1) //If the company the user selected provides more than just one base model, lets handle it.
 								var/list/robolimb_models = list()
-								for(var/limb_type in typesof(R))
+								for(var/limb_type in typesof(R)) //Handling the different models of parts that manufacturers can provide.
 									var/datum/robolimb/L = new limb_type()
-									if(limb in L.parts)
+									if(limb in L.parts) //Make sure that only models that provide the parts the user needs populate the list.
 										robolimb_models[L.company] = L
-										if(second_limb in L.parts)
+										if(robolimb_models.len == 1) //If there's only one model available in the list, autoselect it to avoid having to bother the user with a dialog that provides only one option.
+											subchoice = L.company //If there ends up being more than one model populating the list, subchoice will be overwritten later anyway, so this isn't a problem.
+										if(second_limb in L.parts) //If the child limb of the limb the user selected is also present in the model's parts list, state it's been found so the second limb can be set later.
 											in_model = 1
-								subchoice = input(user, "Which model of [choice] [limb_name] do you wish to use?") as null|anything in robolimb_models
+								if(robolimb_models.len > 1) //If there's more than one model in the list that can provide the part the user wants, let them choose.
+									subchoice = input(user, "Which model of [choice] [limb_name] do you wish to use?") as null|anything in robolimb_models
 								if(subchoice)
 									choice = subchoice
 							if(limb == "head")

code/modules/mob/living/carbon/human/human.dm

@@ -1614,7 +1614,7 @@
 			var/list/hair = list()
 			for(var/i in hair_styles_list)
 				var/datum/sprite_accessory/hair/tmp_hair = hair_styles_list[i]
-				if(species.name in tmp_hair.species_allowed)
+				if((species.name in tmp_hair.species_allowed) && (robohead.company in tmp_hair.models_allowed)) //Populate the list of available monitor styles only with styles that the monitor-head is allowed to use.
 					hair += i
 
 			var/new_style = input(src, "Select a monitor display", "Monitor Display", h_style)  as null|anything in hair

code/modules/surgery/organs/robolimbs.dm

@@ -106,11 +106,13 @@ var/global/datum/robolimb/basic_robolimb
 /datum/robolimb/xion/alt1
 	company = "Xion Manufacturing Group alt."
 	icon = 'icons/mob/human_races/cyberlimbs/xion/xion_alt1.dmi'
+	parts = list("head")
 	has_subtypes = null
 
 /datum/robolimb/xion/monitor
 	company = "Xion Manufacturing Group mtr."
 	icon = 'icons/mob/human_races/cyberlimbs/xion/xion_monitor.dmi'
+	parts = list("head")
 	is_monitor = 1
 	has_subtypes = null