Unity Greeter to support logging in on any display in a multi-monitor setup

[Stewart Wilson]

For a multi-monitor setup, the Greeter should be shown on the Primary display (at it's native/last-used resolution) on startup. All other displays show a minimal secondary screen (each at their native/last-used resolution: see the spec for full details on how the resolution of each display is determined on boot-up).
The user can log in on another display simply by moving the cursor across to the display they wish to log-in on.
The Greeter will follow the cursor across to the new display. Keyboard shortcuts are also available to move the Greeter onto another display. Hold down Super and press the number of the display you wish to move the Greeter onto.
When the user logs in on a display, this display will then become the new Primary display.

When the Greeter is used for the lock-screen, the Greeter will appear on the display which contains the mouse cursor upon locking. Unlocking does not affect the Primary display.

Please see the Multi-Monitor specification for more details:
https://docs.google.com/a/canonical.com/document/d/1aHvJ-iIw-59bXTYBmIhQqEx0za2h9jpFE_RhZ2VOvJc/edit?hl=en_US#bookmark=id.48eaevlgunt0

Please also refer to the Multi-Monitor Greeter prototype attached to this bug.

[Robert Ancell (robert-ancell)]

Multi-monitor support was added in unity-greeter 0.2.2, however it uses whatever layout gnome-settings-daemon provides by default. With a monitor already plugged in this is mirror (it's the same in a Unity session) and span if a monitor is plugged in after boot. The correct behaviour should probably be to match the Unity session, so for the default to be span gnome-settings-daemon probably needs the defaults changed.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Kim Nguyễn (kim.nguyen)]

With latest version (0.2.6-0ubuntu1) there are several shortcommings. Configuration is the following:
- front monitor DELL 16:9 1680x1050 hard-coded to Primary in xorg.conf
- left monitor is DELL 4:3 1280x1024 rotated counterclockwise (property set in xorg.conf)
- Intel core i5 clarkdale integrated chipset, fully accelerated (compiz/unity/webgl etc... run flawlessly)

Problems:
- although intially my mouse cursor is centered on the primary monitor, the greeter defaults to the left one. moving the cursor
"fixes" the problem (the login dialog jumps on the correct monitor) but:
- even though my machine as decent specs (core i5 4 core, 4GB ram, graphic card described above) the switch of the login dialog
is *very* slow and laggy. With the previous issue, the following happens:
(1) cursor and login window are on different screen. so I move my mouse left to give focus to the correct screen
(2) dialog starts to be redrawn (i guess) on the right screen but the process is very slow.
(3) cursor arrives on the left screen. I start going to the keyboard to log in.
(4) dialog jumps to the right screen, loosing focus, while mouse is still is on left screen.
(5) step 1 to 4 are repeated until I can "catch-up" with the login screen (by moving fast enough or waiting long enough for the
dialog to jump back and forth which it does not always do)