I've built a Photoshop extension before. That API lets me listen for document events, so my extension can perform work in response to what the user is doing in the document.
I'm seeing some mention of HTML events (like event handling for buttons). With this, my plugin can handle events within the context of the plugin's modal UI.
But what I'm wondering is if there is a way for my plugin to react to user-initiated events in the document. Say, for example, if the user changes a font in a text object, I'd like my plugin to be notified of the change. Is this possible?