# Use multiple layers to create a history of the current pattern.
# The "envelope" layer remembers all live cells.
# Author: Andrew Trevorrow (andrew@trevorrow.com), December 2006.
# Updated for better compatibility with envelope.pl, June 2007.
# Updated to use new setcolors command, September 2008.

import golly as g

if g.empty(): g.exit("There is no pattern.")

currindex = g.getlayer()
startindex = 0
envindex = 0
startname = "starting pattern"
envname = "envelope"

if currindex > 1 and g.getname(currindex - 1) == startname \
                 and g.getname(currindex - 2) == envname :
   # continue from where we left off
   startindex = currindex - 1
   envindex = currindex - 2

elif currindex + 2 < g.numlayers() \
                 and g.getname(currindex + 1) == startname \
                 and g.getname(currindex)     == envname :
   # switch from envelope layer to current layer and continue
   currindex += 2
   g.setlayer(currindex)
   startindex = currindex - 1
   envindex = currindex - 2

elif currindex + 1 < g.numlayers() \
                 and g.getname(currindex)     == startname \
                 and g.getname(currindex - 1) == envname :
   # switch from starting layer to current layer and continue
   currindex += 1
   g.setlayer(currindex)
   startindex = currindex - 1
   envindex = currindex - 2

else:
   # start a new envelope using pattern in current layer
   if g.numlayers() + 1 > g.maxlayers():
      g.exit("You need to delete a couple of layers.")
   if g.numlayers() + 2 > g.maxlayers():
      g.exit("You need to delete a layer.")
   
   # get current layer's starting pattern
   startpatt = g.getcells(g.getrect())
   
   envindex = g.addlayer()       # create layer for remembering all live cells
   g.setcolors([-1,100,100,100]) # set all states to darkish gray
   g.putcells(startpatt)         # copy starting pattern into this layer

   startindex = g.addlayer()     # create layer for starting pattern
   g.setcolors([-1,0,255,0])     # set all states to green
   g.putcells(startpatt)         # copy starting pattern into this layer

   # move currindex to above the envelope and starting pattern
   g.movelayer(currindex, envindex)
   g.movelayer(envindex, startindex)
   currindex = startindex
   startindex = currindex - 1
   envindex = currindex - 2
   
   # name the starting and envelope layers so user can run script
   # again and continue from where it was stopped
   g.setname(startname, startindex)
   g.setname(envname, envindex)

# ------------------------------------------------------------------------------

def envelope ():
   # draw stacked layers using same location and scale
   g.setoption("stacklayers", 1)
   
   g.show("Hit escape key to stop script...")
   while True:
      g.run(1)
      if g.empty():
         g.show("Pattern died out.")
         break
      
      # copy current pattern to envelope layer;
      # we temporarily disable event checking so thumb scrolling
      # and other mouse events won't cause confusing changes
      currpatt = g.getcells(g.getrect())
      g.check(0)
      g.setlayer(envindex)
      g.putcells(currpatt)
      g.setlayer(currindex)
      g.check(1)
      
      step = 1
      exp = g.getstep()
      if exp > 0:
         step = g.getbase()**exp
      if int(g.getgen()) % step == 0:
         # display all 3 layers (envelope, start, current)
         g.update()

# ------------------------------------------------------------------------------

# show status bar but hide layer & edit bars (faster, and avoids flashing)
oldstatus = g.setoption("showstatusbar", True)
oldlayerbar = g.setoption("showlayerbar", False)
oldeditbar = g.setoption("showeditbar", False)

try:
   envelope()
finally:
   # this code is always executed, even after escape/error;
   # restore original state of status/layer/edit bars
   g.setoption("showstatusbar", oldstatus)
   g.setoption("showlayerbar", oldlayerbar)
   g.setoption("showeditbar", oldeditbar)