Holomap Port

- Port of Holomaps from Virgo

code/_onclick/hud/hud.dm

@@ -14,7 +14,8 @@ var/list/global_huds = list(
 		global_hud.thermal,
 		global_hud.meson,
 		global_hud.science,
-		global_hud.material
+		global_hud.material,
+		global_hud.holomap
 		)
 
 /datum/hud/var/obj/screen/grab_intent
@@ -35,6 +36,7 @@ var/list/global_huds = list(
 	var/obj/screen/meson
 	var/obj/screen/science
 	var/obj/screen/material
+	var/obj/screen/holomap
 
 /datum/global_hud/proc/setup_overlay(var/icon_state)
 	var/obj/screen/screen = new /obj/screen()
@@ -84,6 +86,18 @@ var/list/global_huds = list(
 	science = setup_overlay("science_hud")
 	material = setup_overlay("material_hud")
 
+	// The holomap screen object is actually totally invisible.
+	// Station maps work by setting it as an images location before sending to client, not
+	// actually changing the icon or icon state of the screen object itself!
+	// Why do they work this way? I don't know really, that is how /vg designed them, but since they DO
+	// work this way, we can take advantage of their immutability by making them part of
+	// the global_hud (something we have and /vg doesn't) instead of an instance per mob.
+	holomap = new /obj/screen()
+	holomap.name = "holomap"
+	holomap.icon = null
+	holomap.screen_loc = ui_holomap
+	holomap.mouse_opacity = 0
+
 	var/obj/screen/O
 	var/i
 	//that nasty looking dither you  get when you're short-sighted