[Bug 86147] inconsistent behavior with middle-click scrollbar dragging

[hdante]

Public bug reported:

The middle button, when used with a scroll bar slider, gives
inconsistent results. When a vertical scroll bar slider (in nautilus,
evince, gedit, etc.) is near the top of the page, middle clicking on it
locks the top portion of the slider near the mouse pointer. When a
vertical bar slider is near the middle or bottom of the page, middle
clicking on it locks the middle portion of the slider near the mouse
pointer.

Steps to reproduce:
1. In Nautilus, scroll to the top of some page.
2. Middle click the scroll slider and drag the pointer around. The top portion of the slider will be locked to the mouse pointer.
3. Scroll to the middle of the page.
4. Middle click the scroll slider and drag the pointer around. The middle portion of the slider will be locked to the mouse pointer.
5. Scroll to the bottom of the page.
6. Middle click the scroll slider and drag the pointer around. The middle portion of the slider will be locked to the mouse pointer.

What should have happened:
In all cases, the middle portion of the slider should be locked to the mouse pointer.

PS: in Firefox, the slider has a different behavior and this bug doesn't
happen.

** Affects: nautilus (Ubuntu)
     Importance: Undecided
     Assignee: Brian Murray
         Status: Needs Info

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inconsistent behavior with middle-click scrollbar dragging
https://launchpad.net/bugs/86147