Blender Git Loki

Fix: Breakdowner value would jump when starting the tool a second time during a Blender session

As reported on the Blender Institute Podcast 009. See my comment on the cloud blog
for further details.

When used a second (or third, etc.) time, the breakdowner's (Shift-E) percentage value
would initially be the last-used value (e.g. 33% or 75%), before suddenly jumping
to another value as soon as the mouse moves. The cause of this behaviour was that it
was initially reusing the value from the previous time the operator was run, but then
as soon as the mouse moved, it would snap to the percentage implied by the mouse position.

(Note: The mapping from mouse position to percentage is "absolute" - i.e. the percentage
is based on how far across the 3D view the mouse is, instead of being some kind of
relative offset thing).

To make things a bit less jumpy, I've changed the behaviour so that the mouse position
always gets used immediately, instead of having it jump suddenly only when making
some mouse movement.