add -color_cycle option to control automatic background color selection

Changes

@@ -3,6 +3,8 @@ Revision history for Perl extension Bio::Graphics.
 2.26
     - Support for normalizing quantitative plots across entire track.
     - Support for transparency within tracks, allowing features to overlap.
+    - Support for -color_series and -color_cycle options (see Bio::Graphics::Panel)
+      which cycle dynamically among a fixed series of background colors.
 
 2.25
     - Deprecate xyplot "histogram" subtype and default to "boxes".

lib/Bio/Graphics/FeatureFile.pm

@@ -440,7 +440,8 @@ END
     } else {
 	mkpath(dirname($cachefile));
 	my $parsed = $self->_new(@_);
-	lock_store($parsed,$cachefile);
+	eval {lock_store($parsed,$cachefile)};
+	warn $@ if $@;
 	return $parsed;
     }
 

lib/Bio/Graphics/Glyph/track.pm

@@ -35,9 +35,10 @@ sub draw {
   $self->normalize_track(@parts);
 
   # dynamic assignment of colors
-  if ($self->option('color_series')) {
-      my @color_series    = 
-	  qw(red blue green yellow orange brown aqua black fuchsia green lime maroon navy olive purple silver teal magenta);
+  if ($self->option('color_series') || $self->option('color_cycle')) {
+      my $series = $self->option('color_cycle');
+      $series ||= 'red blue green yellow orange brown aqua black fuchsia green lime maroon navy olive purple silver teal magenta';
+      my @color_series    = ref($series) eq 'ARRAY' ? @$series : split /\s+/,$series;
       my $index           = 0;
       my %color_cache;
       my $closure = sub {

lib/Bio/Graphics/Panel.pm

@@ -1961,10 +1961,14 @@ object to the panel.  This stylesheet will be called to determine both
 the glyph and the glyph options.  If both a stylesheet and direct
 options are provided, the latter take precedence.
 
-The B<-color_series> argument, if true, causes the track to ignore
-the -bgcolor setting and instead to assign glyphs a series of
-contrasting colors. This is usually used in combination with 
--bump=>'overlap' in order to create overlapping features.
+The B<-color_series> argument causes the track to ignore the -bgcolor
+setting and instead to assign glyphs a series of contrasting
+colors. This is usually used in combination with -bump=>'overlap' in
+order to create overlapping features. A true value activates the color
+series. You may adjust the default color series using the
+B<-color_cycle> option, which is either a reference to an array of
+Bio::Graphics color values, or a space-delimited string of color
+names/value.
 
 If successful, add_track() returns an Bio::Graphics::Glyph object.
 You can use this object to add additional features or to control the