Omnitool fix & Engi Omnitool qol (#95752)

## About The Pull Request
- Large tank welding tool is now merged with engi omnitool. The welding
tank is shared across both omnitools so no extra fuel or such. Gives you
greater versatility in switching between tools without requiring you to
return the welding tool back to storage or bringing another omnitool
into an extra module slot and frees up a storage slot in storage. Plus
it just makes sense, completes the full set of tools an engi omnitool
should be having.
- Examining an omnitool also displays the examine of the internal tool
it is using. So examining the engi-omnitool with the multitool selected
will reveal what's in its buffer & examining it with the welding tool
will display how much welding fuel is left etc

## Changelog
🆑
qol: merged large welding tool tank with engi omnitool for engiborg
fix: examining the omnitool will reveal details about its internal tool
such as multitool buffer, welding fuel left etc
/🆑

code/game/objects/items/robot/items/tools.dm

@@ -187,13 +187,20 @@
 	return ..()
 
 /obj/item/borg/cyborg_omnitool/add_context(atom/source, list/context, obj/item/held_item, mob/user)
-	. = ..()
+	. = NONE
 	if (!issilicon(user))
 		return
+
 	var/mob/living/silicon/robot/as_cyborg = user
 	if (!(src in as_cyborg.held_items))
 		context[SCREENTIP_CONTEXT_RMB] = "Select Tool"
-	return CONTEXTUAL_SCREENTIP_SET
+		return CONTEXTUAL_SCREENTIP_SET
+
+/obj/item/borg/cyborg_omnitool/examine(mob/user)
+	. = ..()
+	if(reference)
+		var/obj/item/tool = get_proxy_attacker_for(src, usr)
+		. += tool.examine(user)
 
 /**
  * Sets the new internal tool to be used
@@ -202,8 +209,6 @@
  * * obj/item/ref - typepath for the new internal omnitool
  */
 /obj/item/borg/cyborg_omnitool/proc/set_internal_tool(obj/item/tool)
-	SHOULD_NOT_OVERRIDE(TRUE)
-
 	for(var/obj/item/internal_tool as anything in omni_toolkit)
 		if(internal_tool == tool)
 			reference = internal_tool
@@ -237,11 +242,14 @@
 
 	//if all else fails just make a new one from scratch
 	tool = new reference(user)
+	//assign the upgraded toolspeed, if engi omnitool upgrade was applied.
+	tool.toolspeed = initial(tool.toolspeed) - upgraded * 0.3
 	//the internal tool is considered part of the tool itself, so don't let it be dropped.
 	tool.item_flags |= ABSTRACT
 	ADD_TRAIT(tool, TRAIT_NODROP, INNATE_TRAIT)
+	//store tool for future use
 	atoms[reference] = tool
-	tool.toolspeed = initial(tool.toolspeed) - upgraded * 0.3 //and finally assign the upgraded toolspeed, if any.
+
 	return tool
 
 /obj/item/borg/cyborg_omnitool/attack_self(mob/user)
@@ -270,7 +278,8 @@
 	var/mob/living/silicon/robot/user = usr
 	if (!(src in user.held_items))
 		attack_self(user)
-	return ..()
+	. = ..()
+	user.select_module(user.held_items.Find(src))
 
 /obj/item/borg/cyborg_omnitool/update_icon_state()
 	if (reference)
@@ -318,15 +327,77 @@
 		/obj/item/screwdriver/cyborg,
 		/obj/item/crowbar/cyborg,
 		/obj/item/multitool/cyborg,
+		/obj/item/weldingtool/largetank/cyborg,
 	)
 
+/obj/item/borg/cyborg_omnitool/engineering/Initialize(mapload)
+	. = ..()
+	RegisterSignal(src, COMSIG_SILICON_MODULE_ACTIVATION, PROC_REF(welder_toggle))
+
+/obj/item/borg/cyborg_omnitool/engineering/add_context(atom/source, list/context, obj/item/held_item, mob/user)
+	. = ..()
+	if (!issilicon(user) || tool_behaviour != TOOL_WELDER)
+		return
+
+	context[SCREENTIP_CONTEXT_CTRL_LMB] = "Toggle welder"
+	return CONTEXTUAL_SCREENTIP_SET
+
 /obj/item/borg/cyborg_omnitool/engineering/examine(mob/user)
 	. = ..()
+	if(tool_behaviour == TOOL_WELDER)
+		. += span_notice("Use [EXAMINE_HINT("Ctrl Click")] to toggle welder")
 
-	if(tool_behaviour == TOOL_MULTITOOL)
-		for(var/obj/item/multitool/tool in atoms)
-			. += "Its multitool buffer contains [tool.buffer]"
-			break
+/obj/item/borg/cyborg_omnitool/engineering/update_overlays()
+	. = ..()
+	if(tool_behaviour == TOOL_WELDER)
+		var/obj/item/weldingtool/tool = atoms[/obj/item/weldingtool/largetank/cyborg]
+		if(tool?.welding)
+			. |= tool.update_overlays()
+
+/obj/item/borg/cyborg_omnitool/engineering/set_internal_tool(obj/item/tool)
+	if(tool_behaviour == TOOL_WELDER)
+		welder_toggle(src, FALSE)
+
+	. = ..()
+
+	if(tool_behaviour == TOOL_WELDER)
+		welder_toggle(src, TRUE)
+
+/obj/item/borg/cyborg_omnitool/engineering/item_ctrl_click(mob/user)
+	. = NONE
+	if(tool_behaviour == TOOL_WELDER)
+		var/mob/living/silicon/robot/borgy = loc
+		if(!istype(borgy) || borgy.module_active != src)
+			return
+
+		welder_toggle(src, null)
+		return CLICK_ACTION_SUCCESS
+
+///Reflects internal welder icon onto the omnitool
+/obj/item/borg/cyborg_omnitool/engineering/proc/welder_update(source)
+	PRIVATE_PROC(TRUE)
+	SIGNAL_HANDLER
+
+	update_appearance(UPDATE_OVERLAYS)
+
+///Toggles welder on/off when module slot is selected/deselected
+/obj/item/borg/cyborg_omnitool/engineering/proc/welder_toggle(datum/omnitool, state)
+	PRIVATE_PROC(TRUE)
+	SIGNAL_HANDLER
+
+	if(tool_behaviour == TOOL_WELDER)
+		var/obj/item/weldingtool/tool = get_proxy_attacker_for(src, usr)
+		if(isnull(state))
+			state = !tool.welding
+		if(state == tool.welding)
+			return
+
+		if(state)
+			RegisterSignal(tool, COMSIG_ATOM_UPDATE_APPEARANCE, PROC_REF(welder_update))
+			tool.switched_on(usr)
+		else
+			tool.switched_off()
+			UnregisterSignal(tool, COMSIG_ATOM_UPDATE_APPEARANCE)
 
 /obj/item/borg/cyborg_omnitool/botany
 	name = "botanical omni-toolset"

code/game/objects/items/robot/robot_upgrades.dm

@@ -459,10 +459,6 @@
 	if(!.)
 		return .
 	ADD_TRAIT(cyborg, TRAIT_FASTMED, REF(src))
-	for(var/obj/item/borg/cyborg_omnitool/medical/omnitool_upgrade in cyborg.model.modules)
-		if(omnitool_upgrade.upgraded)
-			to_chat(user, span_warning("This unit is already equipped with an omnitool upgrade!"))
-			return FALSE
 	for(var/obj/item/borg/cyborg_omnitool/medical/omnitool in cyborg.model.modules)
 		omnitool.set_upgraded(TRUE)
 
@@ -471,7 +467,7 @@
 	if(!.)
 		return .
 	REMOVE_TRAIT(cyborg, TRAIT_FASTMED, REF(src))
-	for(var/obj/item/borg/cyborg_omnitool/omnitool in cyborg.model.modules)
+	for(var/obj/item/borg/cyborg_omnitool/medical/omnitool in cyborg.model.modules)
 		omnitool.set_upgraded(FALSE)
 
 /obj/item/borg/upgrade/engineering_omnitool
@@ -486,24 +482,16 @@
 /obj/item/borg/upgrade/engineering_omnitool/action(mob/living/silicon/robot/cyborg, mob/living/user = usr)
 	. = ..()
 	if(!.)
-		return .
-	for(var/obj/item/borg/cyborg_omnitool/engineering/omnitool_upgrade in cyborg.model.modules)
-		if(omnitool_upgrade.upgraded)
-			to_chat(user, span_warning("This unit is already equipped with an omnitool upgrade!"))
-			return FALSE
+		return
 	for(var/obj/item/borg/cyborg_omnitool/engineering/omnitool in cyborg.model.modules)
 		omnitool.set_upgraded(TRUE)
-	for(var/obj/item/weldingtool/largetank/cyborg/welder in cyborg.model.modules)
-		welder.toolspeed = initial(welder.toolspeed) - 0.3
 
 /obj/item/borg/upgrade/engineering_omnitool/deactivate(mob/living/silicon/robot/cyborg, mob/living/user = usr)
 	. = ..()
 	if(!.)
-		return .
-	for(var/obj/item/borg/cyborg_omnitool/omnitool in cyborg.model.modules)
+		return
+	for(var/obj/item/borg/cyborg_omnitool/engineering/omnitool in cyborg.model.modules)
 		omnitool.set_upgraded(FALSE)
-	for(var/obj/item/weldingtool/largetank/cyborg/welder in cyborg.model.modules)
-		welder.toolspeed = initial(welder.toolspeed)
 
 /obj/item/borg/upgrade/defib
 	name = "medical cyborg defibrillator"

code/game/objects/items/tools/engineering/weldingtool.dm

@@ -261,13 +261,13 @@
 			START_PROCESSING(SSobj, src)
 		else
 			balloon_alert(user, "no fuel!")
-			switched_off(user)
+			switched_off()
 	else
 		playsound(loc, deactivation_sound, 50, TRUE)
-		switched_off(user)
+		switched_off()
 
 /// Switches the welder off
-/obj/item/weldingtool/proc/switched_off(mob/user)
+/obj/item/weldingtool/proc/switched_off()
 	set_welding(FALSE)
 
 	force = 3