1. Roger Gammans
  2. Mystery Machine


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Mystery Machine / DeveloperInformation

Information for Developers

Extension Mechanism

This primary way of adding non-core features to MysteryMachine.

To add feature you can do this by writing one (or more) Extensions . Each Extension has a mm-plugin file which describes what Features are offered by the plugin, and a python file which is imported if the plugin is loaded.

The MysteryMachine context will only load plugins which are trusted. A SHA hash of the plugins python file is stored in the users configuration file and the MysteryMachine will only load plugins whose hash is known.

Features are connected to 'Points' which describe the API exposed by the plugin, each plugin can lost a set of 'features' it exposes on each 'Point' . Both a 'Point' and a feature , are simple textual names·

The plugin system is based on Yapsy, and The mm-plugin file is a simple ini-file format file , the usual yapsy format.

Extension Points

Currently there are four defined extension points. Each extension point is a comma separated list.

Attribute Types

To implement a new Attribute type a plugin need to provide features on two complementary points. As both the internal MysteryMachine type name for the new Attribute type needs to be advertised, and also the typename of any python object which should be auto converted to the appropriate type.

To define the MysteryMachine typename which will trigger loaded of the module list the on the 'AttributeValueMMType' point, and the python type names on the 'AttributeValuePyType' point.

Loading a plugin which advertises any names on these points should cause the plugin to register it's types with MysteryMachine.schema.MMAttributeValue.register_value_type . After that they can be referenced by the core engine.

The register class should be a subclass of MMAttributeValue .

Store Types

The other extension point currently implemented is 'StoreScheme'. The features advertised on this point should be the name of MysteryMachine store backends. Again a when the plugin is loaded in should register it's stores with the MysteryMachine.store.RegisterStore function.

A store class should derive from or a least implement MysteryMachine.store.Base

Packfile helpers

An extension point named 'PackFileDescriptor' also exists , this is to allow extension to loaded with Packfile, and have directives which control the pack files. This is of use mainly to Store extensions.

The implementation of this though is subject to change. Please refer the source for the time being. And let me know if you use it. That way I can see how you need and I can try to avoid breaking your extension with updates.

Future Points

The following places need extension points defined for threm in the core, but currently lack and code for it.

  1. Error handling. Some error will be able to resolved if it is known that the System follows certain conventions. By adding error handler's the aiding the users experience with an appropriate Convention module becomes possible.
  2. Policies
  3. UI Menu entries. These entries allow actions like batch email sending. And insertion of complex MysteryMachine expansions, show in a way that doesn't force the user to learn more than necessary about the internal syntax of MysteryMachine.
  4. UI Panel objects. Currently if you add a new type, there is No way to extend the wx UI to correctly allow editing of you new type. This will need and extension point as well.