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

use strict;

g_exit("There is no pattern.") if g_empty();

my $currindex = g_getlayer();
my $startindex;
my $envindex;
my $startname = "starting pattern";
my $envname = "envelope";

if ($currindex > 1 and g_getname($currindex - 1) eq $startname
and g_getname($currindex - 2) eq $envname) {
    # continue from where we left off
    $startindex = $currindex - 1;
    $envindex = $currindex - 2;
}
elsif ($currindex + 2 < g_numlayers()
and g_getname($currindex + 1) eq $startname
and g_getname($currindex)     eq $envname) {
    # switch from envelope layer to current layer and continue
    $currindex += 2;
    g_setlayer($currindex);
    $startindex = $currindex - 1;
    $envindex = $currindex - 2;
}
elsif ($currindex + 1 < g_numlayers()
and g_getname($currindex)     eq $startname
and g_getname($currindex - 1) eq $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
    my $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);
}

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

sub envelope {
    # draw stacked layers using same location and scale
    g_setoption("stacklayers", 1);
    
    g_show("Hit escape key to stop script...");
    while (1) {
        g_run(1);
        if (g_empty()) {
            g_show("Pattern died out.");
            last;
        }
        
        # copy current pattern to envelope layer;
        # we temporarily disable event checking so thumb scrolling
        # and other mouse events won't cause confusing changes
        my $currpatt = g_getcells(g_getrect());
        g_check(0);
        g_setlayer($envindex);
        g_putcells($currpatt);
        g_setlayer($currindex);
        g_check(1);
        
        my $step = 1;
        my $expo = g_getstep();
        if ($expo > 0) {
            $step = g_getbase()**$expo;
        }
        if (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)
my $oldstatus = g_setoption("showstatusbar", 1);
my $oldlayerbar = g_setoption("showlayerbar", 0);
my $oldeditbar = g_setoption("showeditbar", 0);

envelope();

END {
    # 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);
}