A UI Extension generally refers to a component that implements the ui_extension API. They are also commonly refered to as panels.

Its an API that allows a component (a UI Extension Host) to insert a window created by another component (UI Extension) into one of its windows as a child window. UI Extensions come in two forms: multiple instance extensions, of which allow hosts to make as many instances of its window as they want. Single instance windows only have one instance of its window created at any one time.

In order to create UI Extension aware components, you will need:

• The foobar2000 SDK
• The UI Extension SDK
• Microsoft Visual C++

Also recommended is the current Microsoft Platform SDK.

If you are unaware of how to set up the foobar2000 SDK, and create foobar2000 components, please read the foobar2000 FAQ first. Reading the plugin development tutorial is also worthwhile.

You should extract the UI Extension archive to the foobar2000\ui_extension sub-directory of your SDK root folder. You should then proceed to insert the ui_extension project into your workspace, and add it as a dependency of your project.

You should include the header “../ui_extension_with_helpers.h” as appropriate in your code.

UI Extension hosts must implement the ui_extension_host interface, whilst panels should implement the ui_extension interface.

View doxygen generated documentation of the interfaces

Some example components you can look at are:
Album list panel
ASCII playback buttons
History
Simple spectrum panel
Track info panel
Static control panel
Extended search panel

• ui_extension_host::override_status_text, ui_extension_host::restore_status_text have no HWND parameter. This hinders the functionality of panel-hosts.
• No method to retrieve whether a component supports multiple instances or not.
• A method to create a configuration dialog for a ui_extension instance may be useful.

• Rename TYPE_LAYOUT to TYPE_SPLITTER
• Add a subclass for splitter panels
• Add methods for displaying a configuration dialog for UI Extensions
• ui_extension_host API will no longer be single instance only
• Implement methods in ui_extension_fcatory to retrieve whether extension is single or multiple instance
• Add HWND parameters to ui_extension_host::override_status_text and ui_extension_host::restore_status_text functions

What will become of the tabbed panel stack which currently uses the TYPE_LAYOUT flag IIRC? The name “splitter” doesn't seem to fit there, perhaps the flag should be renamed to TYPE_CONTAINER instead.
— foosion 2005/03/16 21:34