Instrument tweaks

The piano will stop playing once you walk away from it or get stunned.

The song BPM of the piano and violin will generally speaking be wrong because of discrepancies between the sleep between notes and world.tick_lag. I've solved this by locking BPM to points where the stated BPM will actually be the case because tempo == world.tick_lag.

Example
Current:
song @ 5 tempo - 120 BPM: c, c/2, c -> note -> sleep(5) -> 6 ticks (5.4 time passes) -> note -> sleep(2.5) -> 3 ticks (2.7 time passes) -> note.

With this PR:
song @ 5.4 tempo - 111 BPM: c, c/2, c -> note -> sleep(5.4) -> 6 ticks (5.4 time passes) -> note/2 -> sleep(2.7) -> 3 ticks (2.7 time passes) -> note.

I was hoping this would make the damn things sound better but then I realized it wasn't actually messing anything up. Oh well.

code/game/objects/structures/musician.dm

@@ -3,7 +3,7 @@
 /datum/song
 	var/name = "Untitled"
 	var/list/lines = new()
-	var/tempo = 5
+	var/tempo = 5			// delay between notes
 
 	var/playing = 0			// if we're playing
 	var/help = 0			// if help is open
@@ -16,6 +16,7 @@
 	var/obj/instrumentObj = null	// the associated obj playing the sound
 
 /datum/song/New(dir, obj)
+	tempo = sanitize_tempo(tempo)
 	instrumentDir = dir
 	instrumentObj = obj
 
@@ -63,8 +64,10 @@
 /datum/song/proc/updateDialog(mob/user as mob)
 	instrumentObj.updateDialog()		// assumes it's an object in world, override if otherwise
 
-/datum/song/proc/shouldStopPlaying()
+/datum/song/proc/shouldStopPlaying(mob/user)
 	if(instrumentObj)
+		if(!user.canUseTopic(instrumentObj))
+			return 1
 		return !instrumentObj.anchored		// add special cases to stop in subclasses
 	else
 		return 1
@@ -84,7 +87,7 @@
 				var/list/notes = text2list(beat, "/")
 				for(var/note in text2list(notes[1], "-"))
 					//world << "note: [note]"
-					if(!playing || shouldStopPlaying())//If the instrument is playing, or special case
+					if(!playing || shouldStopPlaying(user))//If the instrument is playing, or special case
 						playing = 0
 						return
 					if(lentext(note) == 0)
@@ -104,7 +107,7 @@
 							cur_oct[cur_note] = text2num(ni)
 					playnote(cur_note, cur_acc[cur_note], cur_oct[cur_note])
 				if(notes.len >= 2 && text2num(notes[2]))
-					sleep(tempo / text2num(notes[2]))
+					sleep(sanitize_tempo(tempo / text2num(notes[2])))
 				else
 					sleep(tempo)
 		repeat--
@@ -136,10 +139,8 @@
 		dat += "<B><A href='?src=\ref[src];edit=1'>Hide Editor</A></B>"
 		dat += " <A href='?src=\ref[src];newsong=1'>Start a New Song</A>"
 		dat += " <A href='?src=\ref[src];import=1'>Import a Song</A><BR><BR>"
-		var/calctempo = round(600 / tempo)
-		var/calcstep = tempo - 600 / (calctempo+1)
-		var/calcstep_b = tempo - 600 / (calctempo+10)
-		dat += "Tempo: <A href='?src=\ref[src];tempo=[calcstep_b]'>-</A><A href='?src=\ref[src];tempo=[calcstep]'>-</A> [calctempo] BPM <A href='?src=\ref[src];tempo=-[calcstep]'>+</A><A href='?src=\ref[src];tempo=-[calcstep_b]'>+</A><BR><BR>"
+		var/bpm = round(600 / tempo)
+		dat += "Tempo: <A href='?src=\ref[src];tempo=[world.tick_lag]'>-</A> [bpm] BPM <A href='?src=\ref[src];tempo=-[world.tick_lag]'>+</A><BR><BR>"
 		var/linecount = 0
 		for(var/line in lines)
 			linecount += 1
@@ -183,7 +184,7 @@
 
 	if(href_list["newsong"])
 		lines = new()
-		tempo = 5 // default 120 BPM
+		tempo = sanitize_tempo(5) // default 120 BPM
 		name = ""
 
 	else if(href_list["import"])
@@ -203,10 +204,10 @@
 		spawn()
 			lines = text2list(t, "\n")
 			if(copytext(lines[1],1,6) == "BPM: ")
-				tempo = 600 / max(1, text2num(copytext(lines[1],6)))
+				tempo = sanitize_tempo(600 / text2num(copytext(lines[1],6)))
 				lines.Cut(1,2)
 			else
-				tempo = 5 // default 120 BPM
+				tempo = sanitize_tempo(5) // default 120 BPM
 			if(lines.len > 50)
 				usr << "Too many lines!"
 				lines.Cut(51)
@@ -235,11 +236,7 @@
 			repeat = max_repeats
 
 	else if(href_list["tempo"])
-		tempo += text2num(href_list["tempo"])
-		if(tempo < 1)
-			tempo = 1
-		if(tempo > 600)
-			tempo = 600
+		tempo = sanitize_tempo(tempo + text2num(href_list["tempo"]))
 
 	else if(href_list["play"])
 		playing = 1
@@ -279,6 +276,9 @@
 	updateDialog(usr)
 	return
 
+/datum/song/proc/sanitize_tempo(new_tempo)
+	new_tempo = abs(new_tempo)
+	return max(round(new_tempo, world.tick_lag), world.tick_lag)
 
 // subclass for handheld instruments, like violin
 /datum/song/handheld
@@ -322,6 +322,10 @@
 	song = null
 	..()
 
+/obj/structure/piano/initialize()
+	song.tempo = song.sanitize_tempo(song.tempo) // tick_lag isn't set when the map is loaded
+	..()
+
 /obj/structure/piano/attack_hand(mob/user as mob)
 	if(!user.IsAdvancedToolUser())
 		user << "<span class='danger'>You don't have the dexterity to do this!</span>"