[Modal] Large modals with less background and detachable: false get cut with wrong top positioning

[lubber-de]

Bug Report

The #1013 unfortunately introduced another positioning issue when detachable:false is used and the modal is a bit larger

Steps to reproduce

1. Look at http://jsfiddle.net/bkh17Lgy/
2. Click on "Show modal" at the bottom
3. See the modal is cut at the top

Expected result

Modal is displayed centered

Actual result

Modal gets cut because top position has wrong calculated value

Testcase

2.7.8 with applied #1013

http://jsfiddle.net/bkh17Lgy/

2.7.8

http://jsfiddle.net/bkh17Lgy/1

Screenshot

2.7.8 with applied #1013

2.7.8

Version

2.8.0 - develop branch

[lubber-de]

@prudho Do you have time to investigate into this again?

[prudho]

@lubber-de Actually no, work is swallowing my whole time... Feel free to take a look at it if you want !