Strange lag when clicking and dragging to scroll

[Daniel van Vugt]

There's a strange lag in click-and-drag scrolling visible in System Settings > Background.

Test case:
  1. Open System Settings > Background
  2. Click on a location you will remember.
  3. Drag the mouse down/up slowly.

Expected: Scrolling to follow the mouse immediately.
Observed: Scrolling does start at all until the cursor has moved some 20 pixels or so.

[Daniel van Vugt (vanvugt)]

Hmm, this is probably just a threshold to avoid accidental flicks when clicking. But the threshold is too high. It's annoying.

[Daniel van Vugt (vanvugt)]

Although such hysteresis should be time-based too. If the mouse button has been held for a second already then using space-based hysteresis is not helpful.