header_message.tpl is used to alert the user to a new Piwik update available.
Propose adding an in-app message box, useful for:
Also, plugins should be able to display messages in this box. See use case in #1804.
Note: maybe the Admin UI yellow box confirmation message could also be used/refactored to use this in-app message system.
We should also plan to display a piwik.org message somewhere, for example:
The message would be read from api.piwik.org and be cached for 24 hours or so?
Another use case for the in-app message box, to display a Notice message when there is no log for a given website (when problem with tracking code, or server config for example). See #404
Moving to 2.x; we now display Inline help. I think until we have real strong use case, messages can be displayed in the existing "info box" if need be?
This was implemented in the Notification mechanism: https://github.com/piwik/piwik/blob/master/core/Notification.php