[Bug 1479014] Re: "Cancel", "Next", and "Sign In" functioning incorrectly on login or locked screen in "Sign In?" section

[The Unknown]

** Description changed:

  [Impact]
  
  There are three patches in this one fix. So there are three bugs which
  are fixed:
  
  - Bug [1]: If the "Next" button ever gets set to "Sign In", it won't
  get reset to next until the next question asked by pam.
  
  - Bug [2]: Normally the user isn't allowed to proceed passed
  the username question until they've filled it in.
  To ensure this, the authprompt code desensitizes
  the next button when the number of characters change to
  zero.
  Unfortunately it fails to desensitize the next button
  up front when the entry starts out empty.
  
  - Bug [3]: Users are not allowed to cancel if the verification has not
  started yet and they are typing in their username.
  
  These are rather important things to be fixed as they make the login
  process more confusing and difficult.
  
  How the bugs are fixed:
  
  - Bug [1] fix: Reset "Next" button to "Next" when asking for username.
  
  - Bug [2] fix: Disallow the user to press "Next" when the username field
  is empty up front.
  
  - Bug [3] fix: authPrompt no longer ignores the request to cancel before
  a user has started verification and is still typing in their username.
  
  [Test Case]
  
  - Reproduce Bug [1]:
  
  On the first login screen (or log out - not lock), click "Sign In?",
  then before doing anything else click "Sign In", if the button allows
  you to press it and is not greyed out, then you have successfully
  reproduced this bug.
  
  - Reproduce Bug [2]:
  
  On the locked screen click "Sign In?", then before doing anything else
  press "Cancel". If nothing happens, you have successfully reproduced
  this bug.
  
  - Reproduce Bug [3]:
  
  On the locked screen click "Sign In?", then in the username field, start
  entering your username (or any text), then instead of pressing "Next",
  press "Cancel", if nothing happens then you have successfully reproduced
  this bug.
  
- [Regression potential]
+ [Regression Potential]
  
- As these patches have already been put to practical use in the upstream
- version, and the patches which have been put to use in this version,
- have originated from those patches, I would say that the risk of
- regression is minimal.
+ 1. You may notice that we only fade the authentication prompt back in if
+ the auth prompt status is "VERIFICATION_SUCCEEDED". It's possible for it
+ to be "NOT_VERIFYING" if the authprompt gets reset for some other reason
+ in the interim.
+ 
+ 2. You may also notice that the user session crashes when the login
+ screen is reactivated.

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https://bugs.launchpad.net/bugs/1479014

Title:
  "Cancel", "Next", and "Sign In" functioning incorrectly on login or
  locked screen in "Sign In?" section

Status in Ubuntu GNOME:
  Triaged
Status in gnome-shell package in Ubuntu:
  Triaged
Status in gnome-shell source package in Vivid:
  Triaged

Bug description:
  [Impact]

  There are three patches in this one fix. So there are three bugs which
  are fixed:

  - Bug [1]: If the "Next" button ever gets set to "Sign In", it won't
  get reset to next until the next question asked by pam.

  - Bug [2]: Normally the user isn't allowed to proceed passed
  the username question until they've filled it in.
  To ensure this, the authprompt code desensitizes
  the next button when the number of characters change to
  zero.
  Unfortunately it fails to desensitize the next button
  up front when the entry starts out empty.

  - Bug [3]: Users are not allowed to cancel if the verification has not
  started yet and they are typing in their username.

  These are rather important things to be fixed as they make the login
  process more confusing and difficult.

  How the bugs are fixed:

  - Bug [1] fix: Reset "Next" button to "Next" when asking for username.

  - Bug [2] fix: Disallow the user to press "Next" when the username
  field is empty up front.

  - Bug [3] fix: authPrompt no longer ignores the request to cancel
  before a user has started verification and is still typing in their
  username.

  [Test Case]

  - Reproduce Bug [1]:

  On the first login screen (or log out - not lock), click "Sign In?",
  then before doing anything else click "Sign In", if the button allows
  you to press it and is not greyed out, then you have successfully
  reproduced this bug.

  - Reproduce Bug [2]:

  On the locked screen click "Sign In?", then before doing anything else
  press "Cancel". If nothing happens, you have successfully reproduced
  this bug.

  - Reproduce Bug [3]:

  On the locked screen click "Sign In?", then in the username field,
  start entering your username (or any text), then instead of pressing
  "Next", press "Cancel", if nothing happens then you have successfully
  reproduced this bug.

  [Regression Potential]

  1. You may notice that we only fade the authentication prompt back in
  if the auth prompt status is "VERIFICATION_SUCCEEDED". It's possible
  for it to be "NOT_VERIFYING" if the authprompt gets reset for some
  other reason in the interim.

  2. You may also notice that the user session crashes when the login
  screen is reactivated.

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