Bio::Graphics::Browser::Plugin -- Base class for gbrowse plugins.


     package Bio::Graphics::Browser::Plugin::MyPlugin;
     use Bio::Graphics::Browser::Plugin;
     use CGI ':standard';
     @ISA = 'Bio::Graphics::Browser::Plugin';
     # called by gbrowse to return name of plugin for popup menu
     sub name        { 'Example Plugin' }
     # called by gbrowse to return description of plugin
     sub description { 'This is an example plugin' }
     # called by gbrowse to return type of plugin
     sub type        { 'annotator' }
     # called by gbrowse to configure default settings for plugin
     sub config_defaults {
         my $self = shift;
         return {foo => $value1,
                 bar => $value2}
     # called by gbrowse to reconfigure plugin settings based on CGI parameters
     sub reconfigure {
       my $self = shift;
       my $current = $self->configuration;
       $current->{foo} = $self->config_param('foo');
       $current->{bar} = $self->config_param('bar');
     # called by gbrowse to create a <form> fragment for changing settings
     sub configure_form {
       my $self    = shift;
       my $current = $self->configuration;
       my $form = textfield(-name  => $self->config_name('foo'),
                            -value => $current->{foo})
                  textfield(-name  => $self->config_name('bar'),
                            -value => $current->{bar});
       return $form;
     # called by gbrowse to annotate the DNA, returning features
     sub annotate {
        my $self     = shift;
        my $segment  = shift;
        my $config   = $self->configuration;
        # do something with the sequence segment
        my @features = do_something();
        return \@features;


This is the base class for Generic Genome Browser plugins. Plugins are perl .pm files that are stored in the gbrowse.conf/plugins directory. Plugins are activated in the gbrowse.conf/ configuration file by including them on the list indicated by the ``plugins'' setting:

      plugins = BatchDumper FastaDumper GFFDumper
                OligoFinder RestrictionAnnotator

Site-specific plugins may be placed in one or more site-specific directories and added to the plugin search path using the plugin_path setting:

      plugin_path = /usr/local/gbrowse_plugins

GBrowse currently recognizes four distinct types of plugins:

  1. dumpers

    These plugins receive the genomic segment object and generate a dump -- the output can be text, html or some other specialized format. Example: GAME dumper.

  2. finders

    These plugins accept input from the user and return a list of genomic regions. The main browser displays the found regions and allows the user to select among them. Example: BLAST search.

  3. annotators

    These plugins receive the genomic segment object and return a list of features which are overlayed on top of the detailed view. Example: restriction site annotator.

  4. highlighters

    These plugins receive each feature in turn before it is rendered and can return a color name in order to highlight the background of the feature with that color.

  5. filters

    These plugins take filtering options from the user and are converted into a filter closure. Every feature from the track is passed to this closure. All features for which a true value is returned by the filter closure show up in the track.

All plug-ins inherit from Bio::Graphics::Browser::Plugin, which defines reasonable (but uninteresting) defaults for each of the methods. Specific behavior is then implemented by selectively overriding certain methods.

The best way to understand how this works is to look at the source code for some working plugins. Examples provided with the gbrowse distribution include:

A simple dumper which produces GFF format output representing the features of the currently-selected segment.

A more complex dumper that illustrates how to create and manage persistent user-modifiable settings.

Another dumper that shows how plugins interact with the Bio::SeqIO system.

A finder that searches for short oligos in the entire database. (Only works with Bio::DB::GFF databases.)

An annotator that finds restriction sites in the currently selected region of the genome. It creates a new track for each type of restriction site selected.

An example annotator that generates random gene-like structures in the currently displayed region of the genome. It's intended as a template for front-ends to gene prediction programs.

An example filter that filters the features from the 'ORFs' track (yeast example database). The user can pass options to filter the ORFs based on strand or length. Only those ORFs meeting the passed criteria are displayed.


The remainder of this document describes the methods available to the programmer.


The initialization methods establish the human-readable name, description, and basic operating parameters of the plugin. They should be overridden in each plugin you write.

$name = $self->name()

Return a short human-readable name for the plugin. This will be displayed to the user in a menu using one of the following forms:

            Dump <name>
            Find <name>
            Annotate <name>
$description = $self->description()

This method returns a longer description for the plugin. The text may contain HTML tags, and should describe what the plugin does and who wrote it. This text is displayed when the user presses the ``About...'' button.

$type = $self->type()

This tells gbrowse what the plugin's type is. It must return one of the scripts ``dumper,'' ``finder,'' ``annotator'' or ``highlighter'' as described in the introduction to this documentation. If the method is not overridden, type() will return ``dumper.''


This method is called before any methods are invoked and allows the plugin to do any run-time initialization it needs. The default is to do nothing. Ordinarily this method does not need to be implemented.


The following methods give the plugin access to the environment, including the gbrowse page settings, the sequence features database, and the plugin's own configuration settings.

These methods do not generally need to be overridden.

$config = $self->configuration()

Call this method to retrieve the persistent configuration for this plugin. The configuration is a hashref containing the default configuration settings established by config_defaults(), possibly modified by the user. Due to cookie limitations, the values of the hashref must be scalars or array references.

See CONFIGURATION METHODS for instructions on how to create and maintain the plugin's persistent configuration information.

$database = $self->database

This method returns a copy of the sequence database. Depending on the data source chosen by the gbrowse administrator, this may be a Bio::DB::GFF database, a Bio::DB::Das::Chado database, a Bio::Das database, a Bio::DB::Das::BioSQL database, or any of the other Das-like databases that gbrowse supports.

@track_names = $self->selected_tracks

This method returns the list of track names that the user currently has turned on. Track names are the internal names identified in gbrowse configuration file stanzas, for example ``ORFs'' in the 01.yeast.conf example file.

@feature_types = $self->selected_features

This method returns the list of feature types that the user currently has turned on. Feature types are the feature identifiers indicated by the ``feature'' setting in each track in the gbrowse configuration file, for example ``ORF:sgd'' in the 01.yeast.conf [ORFs] track.

$gbrowse_settings = $self->page_settings

This method returns a big hash containing the current gbrowse persistent user settings. These settings are documented in the gbrowse executable source code. You will not ordinarily need to access the contents of this hash, and you should *not* change its values.

$browser_config = $self->browser_config

This method returns a copy of the Bio::Graphics::Browser object that drives gbrowse. This object allows you to interrogate (and change!) the values set in the current gbrowse configuration file.

The recommended use for this object is to recover plugin-specific settings from the gbrowse configuration file. These can be defined by the gbrowse administrator by placing the following type of stanza into the gbrowse config file:

          traverse_isa = 1
          use_server   =

``GOSearch'' is the package name of the plugin, and the ``:plugin'' part of the stanza name tells gbrowse that this is a plugin-private configuration section.

You can now access these settings from within the plugin by using the following idiom:

   my $browser_config = $self->browser_config; 
   my $traverse_isa = $browser_config->plugin_setting('traverse_isa');
   my $server       = $browser_config->plugin_setting('use_server');

This facility is intended to be used for any settings that should not be changed by the end user. Persistent user preferences should be stored in the hash returned by configuration().

$config_path = $self->config_path

This method returns the path to the directory in which gbrowse stores its configuration files. This is very useful for storing plugin-specific configuration files. See the sourcecode of RestrictionAnnotator for an exmaple of this.


All plugins that act as feature dumpers should override one or more of the methods described in this section.


Given a Bio::Das::SegmentI object, produce some output from its sequence and/or features. This can be used to dump something as simple as a FASTA file, or as complex as a motif analysis performed on the sequence.

As described in the Bio::Das::SegmentI manpage, the segment object represents the region of the genome currently on display in the gbrowse ``detail'' panel. You may call its seq() method to return the sequence as a string, or its features() method to return a list of all features that have been annotated onto this segment of the genome.

At the time that dump() is called, gbrowse will already have set up the HTTP header and performed other initialization. The dump() method merely needs to begin printing output using the appropriate MIME type. By default, the MIME type is text/plain, but this can be changed with the mime_type() method described next.

The following trivial example shows a dump() method that prints the name and length of the segment:

          sub dump {
             my $self = shift;
             my $segment = shift;
             print "name   = ",$segment->seq_id,"\n";
             print "length = ",$segment->length,"\n";
$type = $self->mime_type

Return the MIME type of the information produced by the plugin. By default, this method returns ``text/plain''. Override it to return another MIME type, such as ``text/xml''.


All finder plugins will need to override one or more of the methods described in this section.

$features = $self->find($segment);

The find() method will be passed a Bio::Das::SegmentI segment object, as described earlier for the dump() method. Your code should search the segment for features of interest, and return an arrayref of Bio::SeqFeatureI objects (see the Bio::SeqFeatureI manpage). These synthetic feature objects should indicate the position, name and type of the features found.

Depending on the type of find you are performing, you might search the preexisting features on the segment for matches, or create your own features from scratch in the way that the annotator plugins do. You may choose to ignore the passed segment and perform the search on the entire database, which you can obtain using the database() method call.

To create features from scratch I suggest you use either Bio::Graphics::Feature, or Bio::SeqFeature::Generic to generate the features. See their respective manual pages for details, and the plugin for an example of how to do this.

If the plugin requires user input before it can perform its task, find() should return undef. Gbrowse will invoke configure_form() followed by reconfigure() in order to prompt the user for input. If nothing is found, the plugin should return an empty list. The following is an example of how to prompt the user for input -- in this case, a gene ontology term:

          sub find {
             my $self = shift;
             my $segment  = shift;  # we ignore this!
             my $config   = $self->configuration;
             my $query    = $config->{query} or return undef;  # PROMPT FOR INPUT
             my $database = $self->database;
             my @features = $database->features(-attributes=>{GO_Term => $query});
             return \@features; 
          sub configure_form {
             my $self = shift;
             return "Enter a GO Term: "
                    . textfield(-name=>$self->config_name('query'));
          sub reconfigure {
             my $self = shift;
             my $config = $self->configuration;
             $config->{query} = $self->config_param('query');

See the sections below for more description of the configure_form() and reconfigure() methods.

NOTE: If you need to use auxiliary files like BLAST files, you can store the location of those files in the gbrowse .conf file under the stanza [YourPlugin:plugin]:

           blast_path = /usr/local/blast/databases
           sub find {
              my $self = shift;
              my $segment = shift;  # ignored
              my $blast_path = $self->browser_config->plugin_setting('blast_path');
              # etc etc etc  


All annotator plugins will need to override the method described in this section.

$feature_file = $plugin->annotate($segment)

The annotate() method will be invoked with a Bio::Das::SegmentI segment representing the region of the genome currently on view in the gbrowse detail panel. The method should create one or more Bio::Graphics::Feature objects and add them to a Bio::Graphics::FeatureFile feature set. The latter acts as a container for a set of sequence features.

The reason that annotate() returns a Bio::Graphics::FeatureFile rather than an array of features the way that find() does is because Bio::Graphics::FeatureFile also allows you to set up how the features will be rendered; you can define tracks, assign different feature types to different tracks, and assign each feature type a glyph, color, and other options.

See the Bio::Graphics::FeatureFile manpage for details, and the plugin for an example.


All annotator plugins will need to override the method described in this section.

$color = $plugin->highlight($feature)

The highlight() method will be invoked with a Bio::Das::FeatureI object representing one of the features currently being rendered. The method must either return a color name or undef. In the former case, the feature will be rendered on top of a rectangular background of the indicated color. In the latter case no highlighting will be applied. See Bio::Graphics::Panel for a list of valid color names.

See the AttributeHiliter plugin for an example.


All filter plugins will need to override/implement the method described in this section.

$stanza = $plugin->name

The name() method must return the name (stanza) of the track which should be filtered.


This method is invoked by gbrowse in order to set the filter option. If desired, at the same time the 'key' option can be changed so that filtering (or failing) is clearly indicated.

See the FilterTest plugin for an example.


The following methods can be called to retrieve data about the environment in which the plugin is running. These methods are also used by gbrowse to change the plugin state.

$config = $self->config_defaults()

This method will be called once at plugin startup time to give the plugin a chance to set up its default configuration state. If you implement this method you should return the configuration as a hash reference in which the values of the hash are either scalar values or array references. The contents of this hash will be placed in a cookie in order to establish the state.

You will wish to implement this method if the plugin has user-modifiable settings.


This method will be called when the user presses the ``Configure plugin'' button. You should return the HTML for a fill-out form that allows the user to change the current settings. The HTML should contain the contents of an HTML <form> section, but not the actual <form> and </form> tags. These tags, along with the Submit and Cancel buttons, will be added automatically. Typically you will build up the HTML to return using a series of .= append operations.

It is highly recommended that you use the CGI module to generate the fill-out form. In order to avoid clashing with other parts of gbrowse, plugin fill-out forms must respect a namespacing convention in which the name of each form field is preceded by the plugin package name and a dot. The package name is the last component of the plugin's package; for example ``GoSearch'' is the package name for Bio::Graphics::Browser::Plugin::GoSearch. To represent the ``query'' field of the plugin named ``GOSearch'', the text field must be named ``GOSearch.query''.

To make this easier to do right, the Plugin module provides a method named config_name() which will add the prefix for you. Here is how to use it with the ``query'' example:

      $html .= textfield(-name  => $self->config_name('query'));

If you implement a configure_form() method, you must also implement a reconfigure() method. This method is called after the user submits the form and should be used to integrate the form values with the current configuration.

Remember that the form fields are namespaced. You may recover them using the CGI param() method by preceding them with the proper prefix. To make this easier to manage, this module provides a config_param() method that manages the namespaces transparently.

Here is a working example:

   sub reconfigure {
     my $self = shift;
     my $current_configuration = $self->configuration;
     $current_configuration->{query} = $self->config_param('query');

All this does is to retrieve the current configuration by calling the configuration() method. The value of the ``query'' key is then replaced by a fill-out form parameter named ``query'', using config_param() instead of the more familiar CGI module's param() function.


The Bio::Graphics::Browser manpage.


Please address support requests to


Lincoln Stein <>.

Copyright (c) 2003 Cold Spring Harbor Laboratory

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself. See DISCLAIMER.txt for disclaimers of warranty.