Registry

class Registry(**properties: Any)

Superclasses: Object, InitiallyUnowned, Object

One registry holds the metadata of a set of plugins.

<emphasis role=”bold”>Design:</emphasis>

The Registry object is a list of plugins and some functions for dealing with them. Each Plugin is matched 1-1 with a file on disk, and may or may not be loaded at a given time.

The primary source, at all times, of plugin information is each plugin file itself. Thus, if an application wants information about a particular plugin, or wants to search for a feature that satisfies given criteria, the primary means of doing so is to load every plugin and look at the resulting information that is gathered in the default registry. Clearly, this is a time consuming process, so we cache information in the registry file. The format and location of the cache file is internal to gstreamer.

On startup, plugins are searched for in the plugin search path. The following locations are checked in this order:

  • location from –gst-plugin-path commandline option.

  • the GST_PLUGIN_PATH environment variable.

  • the GST_PLUGIN_SYSTEM_PATH environment variable.

  • default locations (if GST_PLUGIN_SYSTEM_PATH is not set). Those default locations are: $XDG_DATA_HOME/gstreamer-$GST_API_VERSION/plugins/ and $prefix/libs/gstreamer-$GST_API_VERSION/. $XDG_DATA_HOME defaults to $HOME/.local/share.

The registry cache file is loaded from $XDG_CACHE_HOME/gstreamer-$GST_API_VERSION/registry-$ARCH.bin (where $XDG_CACHE_HOME defaults to $HOME/.cache) or the file listed in the GST_REGISTRY env var. One reason to change the registry location is for testing.

For each plugin that is found in the plugin search path, there could be 3 possibilities for cached information:

  • the cache may not contain information about a given file.

  • the cache may have stale information.

  • the cache may have current information.

In the first two cases, the plugin is loaded and the cache updated. In addition to these cases, the cache may have entries for plugins that are not relevant to the current process. These are marked as not available to the current process. If the cache is updated for whatever reason, it is marked dirty.

A dirty cache is written out at the end of initialization. Each entry is checked to make sure the information is minimally valid. If not, the entry is simply dropped.

Implementation notes:

The “cache” and “registry” are different concepts and can represent different sets of plugins. For various reasons, at init time, the cache is stored in the default registry, and plugins not relevant to the current process are marked with the CACHED bit. These plugins are removed at the end of initialization.

Methods

class Registry
add_feature(feature: PluginFeature) → bool

Add the feature to the registry. The feature-added signal will be emitted.

feature’s reference count will be incremented, and any floating reference will be removed (see ref_sink())

Parameters:

feature – the feature to add

add_plugin(plugin: Plugin) → bool

Add the plugin to the registry. The plugin-added signal will be emitted.

plugin’s reference count will be incremented, and any floating reference will be removed (see ref_sink())

Parameters:

plugin – the plugin to add

check_feature_version(feature_name: str, min_major: int, min_minor: int, min_micro: int) → bool

Checks whether a plugin feature by the given name exists in registry and whether its version is at least the version required.

Parameters:

  • feature_name – the name of the feature (e.g. “oggdemux”)

  • min_major – the minimum major version number

  • min_minor – the minimum minor version number

  • min_micro – the minimum micro version number

feature_filter(filter: Callable[[...], bool], first: bool, *user_data: Any) → list[PluginFeature]

Runs a filter against all features of the plugins in the registry and returns a GList with the results. If the first flag is set, only the first match is returned (as a list with a single object).

Parameters:

  • filter – the filter to use

  • first – only return first match

  • user_data – user data passed to the filter function

find_feature(name: str, type: type) → PluginFeature | None

Find the pluginfeature with the given name and type in the registry.

Parameters:

  • name – the pluginfeature name to find

  • type – the pluginfeature type to find

find_plugin(name: str) → Plugin | None

Find the plugin with the given name in the registry. The plugin will be reffed; caller is responsible for unreffing.

Parameters:

name – the plugin name to find

fork_is_enabled() → bool

By default GStreamer will perform scanning and rebuilding of the registry file using a helper child process.

Applications might want to disable this behaviour with the fork_set_enabled() function, in which case new plugins are scanned (and loaded) into the application process.

fork_set_enabled(enabled: bool) → None

Applications might want to disable/enable spawning of a child helper process when rebuilding the registry. See fork_is_enabled() for more information.

Parameters:

enabled – whether rebuilding the registry can use a temporary child helper process.

get() → Registry

Retrieves the singleton plugin registry. The caller does not own a reference on the registry, as it is alive as long as GStreamer is initialized.

get_feature_list(type: type) → list[PluginFeature]

Retrieves a GList of PluginFeature of type.

Parameters:

type – a Type.

get_feature_list_by_plugin(name: str) → list[PluginFeature]

Retrieves a GList of features of the plugin with name name.

Parameters:

name – a plugin name.

Returns the registry’s feature list cookie. This changes every time a feature is added or removed from the registry.

get_plugin_list() → list[Plugin]

Get a copy of all plugins registered in the given registry. The refcount of each element in the list in incremented.

lookup(filename: str) → Plugin | None

Look up a plugin in the given registry with the given filename. If found, plugin is reffed.

Parameters:

filename – the name of the file to look up

lookup_feature(name: str) → PluginFeature | None

Find a PluginFeature with name in registry.

Parameters:

name – a PluginFeature name

plugin_filter(filter: Callable[[...], bool], first: bool, *user_data: Any) → list[Plugin]

Runs a filter against all plugins in the registry and returns a GList with the results. If the first flag is set, only the first match is returned (as a list with a single object). Every plugin is reffed; use list_free() after use, which will unref again.

Parameters:

  • filter – the filter to use

  • first – only return first match

  • user_data – user data passed to the filter function

remove_feature(feature: PluginFeature) → None

Remove the feature from the registry.

MT safe.

Parameters:

feature – the feature to remove

remove_plugin(plugin: Plugin) → None

Remove the plugin from the registry.

MT safe.

Parameters:

plugin – the plugin to remove

scan_path(path: str) → bool

Scan the given path for plugins to add to the registry. The syntax of the path is specific to the registry.

Parameters:

path – the path to scan

Signals

class Registry.signals
feature_added(feature: PluginFeature) → None

Signals that a feature has been added to the registry (possibly replacing a previously-added one by the same name)

Parameters:

feature – the feature that has been added

plugin_added(plugin: Plugin) → None

Signals that a plugin has been added to the registry (possibly replacing a previously-added one by the same name)

Parameters:

plugin – the plugin that has been added

Fields

class Registry
object
priv