Unity Greeter - Panel should be centred vertically

The input panel is centered with the following logic:

* The grid starts in the center of the screen so that the grid doesn't look uneven at the edge of the screen.
* The input panel is placed as vertically as it can while still aligning it to the grid (on my 1366x768 screen there are 19 rows so the panel aligns exactly. On other resolutions there might be an even number of rows which will cause the panel to have to be slightly above or below the center line).
* The panel is assumed to be three rows high (which is what it was only allowed to be in the past). In the case of the remote login box (and other cases) this panel needs four rows high. So in my case the remote login panel is not centered anymore (it has 7 rows below and 8 above) and this again will vary for differing resolutions.

What resolution are you using and can you measure the grid spacing in your case?

Counting 7 spaces above, 4 below for the session menu. Sorry for the bad picture.

Updating status as Calum has attached further info to the bug report.

What should we do for a panel of even grid size? The normal login panel is 3 grids tall (one above, one below). An even grid panel would not be able to be centered perfectly. Do you prefer the extra grid on the top or bottom?

Also, I'd appreciate guidance on how to present a list of sessions that is longer than the screen. Some sort of scrollbar? I don't think we have a unity-style scrollbar to use that would fit in (without some work on the theme side).

Marking Won't Fix for raring, as I likely won't be able to get to this (getting this off my status radar). If someone else wants to pick it up, be my guest and re-open! Otherwise, hopefully we can get to it in S.

How about making it "float", i.e. click and drag or move the entire list on touch/hold event, and on mouse wheel/scroll-gesture.
That would maintain the current design, and remove the need for making new scroll bar graphics, as well as solve bugs where the list goes off screen.

Fixing this would lessen bug #1068605