When an Ubuntu Touch app tries to use data, but no data connection is available, there is no user-visible explanation of what is going on or how to fix it.
A device might have no data connection because:
(a) it is in Flight Mode, or
(b) Wi-Fi is otherwise turned off, or
(c) there is no cellular data connection, because:
- the device has no SIM, or
- it is not connected to a carrier, or
- cellular data is turned off, or
- the carrier is refusing data traffic (for example, because you are over quota), or
- it is roaming and data roaming is turned off.
(This list is not necessarily complete.)
In cases where immediate connectivity is not vital, an app might detect that it is not available, and use queued actions or placeholders. For example, a mail client might store offline messages that you wanted to send, remember which messages you wanted to delete and file, and so on. Similarly, a Dash screen that usually returns online search results might show only offline results, with some sort of indication that you need to go online for online results to appear.
But where an action absolutely requires connectivity to be useful, Ubuntu should provide some sort of standard UI explaining why you are offline and, where possible, explaining what to do to go online.
If this message is modal, probably it should be limited so that it does not appear more than once before an app is unfocused (whether by focusing a different app, or the phone locking), and so it does not appear more than once every five minutes or so.
The design should take into account the Wi-Fi prompt (bug 1287210), so that there aren't two prompts jostling each other.
[Originally reported by David Isaacs.]
Quick note that I'm not tagging this for rtm14/qa-