"Performers" can handle melodies

shared/instrument.lua

@@ -0,0 +1,31 @@
+instrument=klass()
+function instrument:init(callback)
+ self.callback=callback
+ self.volume=1.0
+end
+
+function instrument:spackle(track,channel,t0,t1,note,verbs)
+ -- a one-indexed table of note data
+ -- (one-indexed because Lua kind of sucks)
+ local nflagses,keep_silence=self.callback(t1-t0,note,instrument_split_verbs(verbs))
+ for i,nflags in pairs(nflagses) do
+  if nflags.v>0 or keep_silence then
+   nflags = nflags:clone()  -- avoid breaking instrument
+
+   local min_v=0
+   if (nflags.v>0) min_v = 1
+   nflags.v = mid(flr(nflags.v * self.volume + 0.5),min_v,7)
+
+   track:plot(channel,t0+i-1,nflags)
+  end
+ end
+end
+
+instrument_split_verbs=function(x)
+ if (not x) return {}
+ local t={}
+ for i in all(split(x)) do
+  t[i]=true
+ end
+ return t
+end

shared/nflags.lua

@@ -9,6 +9,10 @@ function nflags:init(o)
  self:validate()
 end
 
+function nflags:clone()
+ return nflags:new(self)
+end
+
 function nflags:validate()
  local c,e,v,w,p
   =self.c,self.e,self.v,self.w,self.p

shared/performer.lua

@@ -0,0 +1,28 @@
+performer=klass()
+function performer:init(track,channel,instrument,time,roots)
+ assert_range(#roots,1,33,"#roots")
+
+ self.track=track
+ self.channel=channel
+ self.instrument=instrument
+ self.time=time
+ self.roots=roots
+ self.selected_root=1
+end
+
+function performer:root(root)
+ assert_range(root,1,#self.roots,"root")
+ self.selected_root=root
+end
+function performer:play(duration,note,verbs)
+ local base=self.roots[self.selected_root]
+ local note=base+note
+ local t0=self.time
+ local t1=t0+duration
+ self.time+=duration
+ self.instrument:spackle(self.track,self.channel,t0,t1,note,verbs)
+end
+function performer:rest(duration)
+ self.time+=duration
+end
+

shared/track.lua

@@ -31,13 +31,13 @@ function track:pattern(channel,offset)
  return self.frames[offset+1][channel+1]
 end
 
-function track:plot(channel,offset,inst)
+function track:plot(channel,offset,ndata)
  assert_range(channel,0,4,"channel")
  assert_range(offset,0,self.next_frame_start,"offset")
  local tup=self.ix_to_frame[offset]
  assert(tup)  -- should be unable to fail
  local frame,offset=unpack(tup)
- self.frames[frame+1][channel+1]:plot(offset,inst)
+ self.frames[frame+1][channel+1]:plot(offset,ndata)
 end
 
 function track:build(
@@ -73,6 +73,6 @@ function track:build(
   for i=0,3 do
    poke(fmaddr+i,map_to_real_pattern(self.frames[frame][i+1]))
   end
-  fmaddr+=1
+  fmaddr+=4
  end
 end