Provided by: tcllib_1.15-dfsg-2_all 
NAME
pluginmgr - Manage a plugin
SYNOPSIS
package require Tcl 8.4
package require pluginmgr ?0.3?
::pluginmgr objectName ?option value...?
::pluginmgr::paths objectName name...
objectName method ?arg arg ...?
objectName clone
objectName configure
objectName configure option
objectName configure -option value...
objectName cget -option
objectName destroy
objectName do arg...
objectName interpreter
objectName plugin
objectName load string
objectName unload
objectName list
objectName path path
objectName paths
_________________________________________________________________
DESCRIPTION
This package provides commands and objects for the generic management of plugins which can
be loaded into an application.
To avoid the implementation of yet another system to locate Tcl code the system provides
by this package is built on top of the regular package management system. Each plugin is
considered as a package and a simple invokation of package require is enough to locate and
load it, if it exists. The only time we will need additional paths is when a plugin
manager is part of a wrapped application and has to be able to search for plugins existing
outside of that application. For this situation the package provides a command to create a
general set of such paths based on names for the plugin manager and/or application in
question.
The main contribution of this package is a generic framework which allows the easy
declaration of
[1] How to translate a plugin name to the name of the package implementing it, and vice
versa.
[2] The list of commands a plugin has to provide as API, and also of more complex
checks as code.
[3] The list of commands expected by the plugin from the environment.
This then allows the easy generation of plugin managers customized to particular types of
plugins for an application.
It should be noted that all plugin code is considered untrusted and will always be
executed within a safe interpreter. The interpreter is enabled enough to allow plugins the
loading of all additional packages they may need.
PUBLIC API
PACKAGE COMMANDS
::pluginmgr objectName ?option value...?
This command creates a new plugin manager object with an associated Tcl command
whose name is objectName. This object command is explained in full detail in the
sections OBJECT COMMAND and OBJECT METHODS. The object command will be created
under the current namespace if the objectName is not fully qualified, and in the
specified namespace otherwise.
The options and their values coming after the name of the object are used to set
the initial configuration of the mamager object, specifying the applicable plugins
and their API.
::pluginmgr::paths objectName name...
This utility command adds a set of paths to the specified object, based on the
given names. It will search for:
[1] The environment variable name_PLUGINS. Its contents will be interpreted as a
list of package paths. The entries have to be separated by either : (unix)
or ; (windows).
The name will be converted to upper-case letters.
[2] The registry entry "HKEY_LOCAL_MACHINE\SOFTWARE\name\PLUGINS". Its contents
will be interpreted as a list of package paths. The entries have to be
separated by ;. This item is considered only when on Windows (tm).
The casing of letters is not changed.
[3] The registry entry "HKEY_CURRENT_USER\SOFTWARE\name\PLUGINS". Its contents
will be interpreted as a list of package paths. The entries have to be
separated by ;. This item is considered only when on Windows (tm).
The casing of letters is not changed.
[4] The directory "~/.name/plugin".
[5] The directory "~/.name/plugins".
The casing of letters is not changed.
and add all the paths found that way to the list of package paths maintained by the
object.
If name is namespaced each item in the list will be repeated per prefix of name, with
conversion of :-sequences into the proper separator (underscore for environment variables,
backslash for registry entries, and / for directories).
Examples:
::pluginmgr::paths ::obj docidx
=> env DOCIDX_PLUGINS
reg HKEY_LOCAL_MACHINE\SOFTWARE\docidx\PLUGINS
reg HKEY_CURRENT_USER\SOFTWARE\docidx\PLUGINS
path ~/.docidx/plugins
::pluginmgr::paths ::obj doctools::idx
=> env DOCTOOLS_PLUGINS
env DOCTOOLS_IDX_PLUGINS
reg HKEY_LOCAL_MACHINE\SOFTWARE\doctools\PLUGINS
reg HKEY_LOCAL_MACHINE\SOFTWARE\doctools\idx\PLUGINS
reg HKEY_CURRENT_USER\SOFTWARE\doctools\PLUGINS
reg HKEY_CURRENT_USER\SOFTWARE\doctools\idx\PLUGINS
path ~/.doctools/plugin
path ~/.doctools/idx/plugin
OBJECT COMMAND
All commands created by the command ::pluginmgr (See section PACKAGE COMMANDS) have the
following general form and may be used to invoke various operations on their plugin
manager object.
objectName method ?arg arg ...?
The method method and its arg'uments determine the exact behavior of the command.
See section OBJECT METHODS for the detailed specifications.
OBJECT METHODS
objectName clone
This method creates a new plugin management object and returns the associated
object command. The generated object is a clone of the object the method was
invoked on. I.e. the new object will have the same configuration as the current
object. With regard to state, if the current object has a plugin loaded then this
plugin and all associated state is moved to the generated clone and the current
object is reset into the base state (no plugin loaded). In this manner a configured
plugin manager is also a factory for loaded plugins.
objectName configure
The method returns a list of all known options and their current values when called
without any arguments.
objectName configure option
The method behaves like the method cget when called with a single argument and
returns the value of the option specified by said argument.
objectName configure -option value...
The method reconfigures the specified options of the object, setting them to the
associated values, when called with an even number of arguments, at least two.
The legal options are described in the section OBJECT CONFIGURATION.
objectName cget -option
This method expects a legal configuration option as argument and will return the
current value of that option for the object the method was invoked for.
The legal configuration options are described in section OBJECT CONFIGURATION.
objectName destroy
This method destroys the object it is invoked for.
objectName do arg...
This method interprets its list of arguments as the words of a command and invokes
this command in the execution context of the plugin. The result of the invoked
command is made the result of the method. The call will fail with an error if no
valid plugin has been loaded into the manager object.
objectName interpreter
This method returns the handle of the safe interpreter the current plugin is loaded
into. An empty string as return value signals that the manager currently has no
valid plugin loaded.
objectName plugin
This method returns the name of the plugin currently loaded. An empty string as
return value signals that the manager currently has no valid plugin loaded.
objectName load string
This method loads, validates, and initializes a named plugin into the manager
object.
The algorithm to locate and load the plugin employed is:
[1] If the string contains the path to an existing file then this file is taken
as the implementation of the plugin.
[2] Otherwise the plugin name is translated into a package name via the value of
the option -pattern and then loaded through the regular package management.
[3] The load fails.
The algorithm to validate and initialize the loaded code is:
[1] If the option -api is non-empty introspection commands are used to ascertain
that the plugin provides the listed commands.
[2] If the option -check is non-empty the specified command prefix is called.
[3] If either of the above fails the candidate plugin is unloaded again
[4] Otherwise all the commands specified via the option -cmds are installed in
the plugin.
A previously loaded plugin is discarded, but only if the new plugin was found and
sucessfully validated and initialized. Note that there will be no intereference between
old and new plugin as both will be put into separate safe interpreters.
objectName unload
This method unloads the currently loaded plugin. It returns the empty string. The
call will be silently ignored if no plugin is loaded at all.
objectName list
This method uses the contents of the option -pattern to find all packages which can
be plugins under the purview of this manager object. It translates their names into
plugin names and returns a list containing them.
objectName path path
This methods adds the specified path to the list of additional package paths to
look at when searching for a plugin. It returns the empty string. Duplicate paths
are ignored, i.e. each path is added only once. Paths are made absolute, but are
not normalized.
objectName paths
This method returns a list containing all additional paths which have been added to
the plugin manager object since its creation.
OBJECT CONFIGURATION
All plugin manager objects understand the following configuration options:
-pattern string
The value of this option is a glob pattern which has to contain exactly one
'*'-operator. All packages whose names match this pattern are the plugins
recognized by the manager object. And vice versa, the replacement of the
'*'-operator with a plugin name will yield the name of the package implementing
that plugin.
This option has no default, except if option -name was set. It has to be set
before attempting to load a plugin, either directly, or through option -name.
-api list
The value of this option is a list of command names, and any plugin loaded has to
provide these commands. Names which are not fully qualified are considered to be
rooted in the global namespace. If empty no expectations are made on the plugin.
The default value is the empty list.
-check cmdprefix
The value of this option is interpreted as a command prefix. Its purpose is to
perform complex checks on a loaded plugin package to validate it, which go beyond a
simple list of provided commands.
It is called with the manager object command as the only argument and has to return
a boolean value. A value of true will be interpreted to mean that the candidate
plugin passed the test. The call will happen if and only if the candidate plugin
already passed the basic API check specified through the option -api.
The default value is the empty list, which causes the manager object to suppress
the call and to assume the candidate plugin passes.
-cmds dict
The value of this option is a dictionary. It specifies the commands which will be
made available to the plugin (as keys), and the trusted commands in the environment
which implement them (as values). The trusted commands will be executed in the
interpreter specified by the option -cmdip. The default value is the empty
dictionary.
-cmdip ipspec
The value of this option is the path of the interpreter where the trusted commands
given to the plugin will be executed in. The default is the empty string,
referring to the current interpreter.
-setup cmdprefix
The value of this option is interpreted as a command prefix.
It is called whenever a new safe interpreter for a plugin has been created, but
before a plugin is loaded. It is provided with the manager object command and the
interpreter handle as its only arguments. Any return value will be ignored.
Its purpose is give a user of the plugin management the ability to define commands,
packages, etc. a chosen plugin may need while being loaded.
BUGS, IDEAS, FEEDBACK
This document, and the package it describes, will undoubtedly contain bugs and other
problems. Please report such in the category pluginmgr of the Tcllib SF Trackers
[http://sourceforge.net/tracker/?group_id=12883]. Please also report any ideas for
enhancements you may have for either package and/or documentation.
KEYWORDS
plugin management, plugin search
CATEGORY
Programming tools
COPYRIGHT
Copyright (c) 2005 Andreas Kupries <andreas_kupries@users.sourceforge.net>