[libavg-devel] Plugin Interface Ideas

[Nick Hebner]

Hello All,

I was thinking of writing a plugin tonight using the shiny new plugin
interface (thanks Jan!), but ran into a roadblock with the way that the
plugin interface is currently designed. This experience has got me thinking
about how plugins will interact with the core down the road, so I wanted to
start a discussion about it.

My idea for a plugin was to add a new camera subsystem based on a seperate
camera library. With the current plugin interface, this would be possible by
creating a new node type which exposes all of the needed functionality. This
functionality would of course be almost identical the functionality
currently provided by the CameraNode. It would be great if instead of
imlementing a new Node, I could instead simply implement a new Camera object
and make this usable by the existing CameraNode.

Another potential shortcoming of the current design is a plugin may only
export a single Node type. What if someone wanted to package a number of
nodes within a single plugin and have all of these nodes registered when it
is loaded.

With these issues in mind, it seems to me that a more generic loading
procedure would be beneficial for plugin development in the future. We could
require generic plugin interaction event handlers (for example onload(),
onunload(), etc) to be exported, and allow a plugin to define the behavior
of these events. With this approach, node plugins could register
NodeDefinitions (as many as they want) with the registry, and other types of
plugins could do other things. We would not assume that a plugin simply
implements a single new Node.

This generic approach lends itself to support for altering subsystem
implementations via plugins. For instance, say we wanted to use DirectX to
do our rendering, we could create a DisplayEngineRegistry in the core that a
DirectXDisplayEngine plugin could register with in its onload(). Or in my
case, I could register my new Camera type with a CameraRegistry.

I'm sure that these ideas are not new, and were probably considered while
designing the current plugin interface, but I just wanted to start a dialog
on the topic. So, anyone have any thoughts on this? Discuss.

Thanks,

Nick
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