Aurora.3/code/modules/lighting/lighting_atom.dm

#define MINIMUM_USEFUL_LIGHT_RANGE 1.4

/atom
	var/light_power = 1 // Intensity of the light.
	var/light_range = 0 // Range in tiles of the light.
	var/light_color     // Hexadecimal RGB string representing the colour of the light.
	var/uv_intensity = 255	// How much UV light is being emitted by this object. Valid range: 0-255.
	var/light_wedge		// The angle that the light's emission should be restricted to. null for omnidirectional.

	var/tmp/datum/light_source/light // Our light source. Don't fuck with this directly unless you have a good reason!
	var/tmp/list/light_sources       // Any light sources that are "inside" of us, for example, if src here was a mob that's carrying a flashlight, that flashlight's light source would be part of this list.

// Nonesensical value for l_color default, so we can detect if it gets set to null.
#define NONSENSICAL_VALUE -99999

// The proc you should always use to set the light of this atom.
/atom/proc/set_light(var/l_range, var/l_power, var/l_color = NONSENSICAL_VALUE, var/uv = NONSENSICAL_VALUE, var/angle = NONSENSICAL_VALUE, var/no_update = FALSE)
	L_PROF(src, "atom_setlight")

	if(l_range > 0 && l_range < MINIMUM_USEFUL_LIGHT_RANGE)
		l_range = MINIMUM_USEFUL_LIGHT_RANGE	//Brings the range up to 1.4, which is just barely brighter than the soft lighting that surrounds players.
	if (l_power != null)
		light_power = l_power

	if (l_range != null)
		light_range = l_range

	if (l_color != NONSENSICAL_VALUE)
		light_color = l_color

	if (uv != NONSENSICAL_VALUE)
		set_uv(uv, no_update = TRUE)

	if (angle != NONSENSICAL_VALUE)
		light_wedge = angle

	if (no_update)
		return

	update_light()

#undef NONSENSICAL_VALUE

/atom/proc/set_uv(var/intensity, var/no_update)
	L_PROF(src, "atom_setuv")
	if (intensity < 0 || intensity > 255)
		intensity = min(max(intensity, 255), 0)

	uv_intensity = intensity

	if (no_update)
		return

	update_light()

// Will update the light (duh).
// Creates or destroys it if needed, makes it update values, makes sure it's got the correct source turf...
/atom/proc/update_light()
	set waitfor = FALSE
	if (QDELING(src))
		return

	L_PROF(src, "atom_update")

	if (!light_power || !light_range) // We won't emit light anyways, destroy the light source.
		QDEL_NULL(light)
	else
		if (!istype(loc, /atom/movable)) // We choose what atom should be the top atom of the light here.
			. = src
		else
			. = loc

		if (light) // Update the light or create it if it does not exist.
			light.update(.)
		else
			light = new/datum/light_source(src, .)

// If we have opacity, make sure to tell (potentially) affected light sources.
/atom/movable/Destroy()
	var/turf/T = loc
	if (opacity && istype(T))
		T.reconsider_lights()

	. = ..()

// Should always be used to change the opacity of an atom.
// It notifies (potentially) affected light sources so they can update (if needed).
/atom/proc/set_opacity(var/new_opacity)
	if (new_opacity == opacity)
		return

	L_PROF(src, "atom_setopacity")

	opacity = new_opacity
	var/turf/T = loc
	if (!isturf(T))
		return

	if (new_opacity == TRUE)
		T.has_opaque_atom = TRUE
		T.reconsider_lights()
	else
		var/old_has_opaque_atom = T.has_opaque_atom
		T.recalc_atom_opacity()
		if (old_has_opaque_atom != T.has_opaque_atom)
			T.reconsider_lights()


// This code makes the light be queued for update when it is moved.
// Entered() should handle it, however Exited() can do it if it is being moved to nullspace (as there would be no Entered() call in that situation).
/atom/Entered(var/atom/movable/Obj, var/atom/OldLoc) //Implemented here because forceMove() doesn't call Move()
	. = ..()

	if (Obj && OldLoc != src && Obj.light_sources && Obj.light_sources.len)
		for (var/datum/light_source/L in Obj.light_sources) // Cycle through the light sources on this atom and tell them to update.
			L.source_atom.update_light()

/atom/Exited(var/atom/movable/Obj, var/atom/newloc)
	. = ..()

	if (!newloc && Obj && newloc != src && Obj.light_sources && Obj.light_sources.len) // Incase the atom is being moved to nullspace, we handle queuing for a lighting update here.
		for (var/datum/light_source/L in Obj.light_sources) // Cycle through the light sources on this atom and tell them to update.
			L.source_atom.update_light()

/atom/set_dir(new_dir)
	. = ..()

	for (var/datum/light_source/L in src.light_sources)
		if (L.light_angle)
			L.source_atom.update_light()