As the title says. Currently user is able to change geometry if OVP is
set on labels. This is because `doEnforceControlParameters` reads mouse
position every mouse move and calculates angle from it, resulting in a
new angle every time mouse is moved.
So, this patch basically reads the position before it was set, and once
it is set, locks the position of the mouse and calculates angle from it
which will be maintained until user cleans the OVP or makes a new
primitive.
ced9c0dd4f