The value entered here determines how far a tool must be moved before painting starts. This is measured in image pixels, and so may involve a large distance on the screen at higher magnifications.
The set distance should not normally be larger than about a third of the size of the tool, so that the edge of a drawn line doesn't "break up". You can however deliberately use this behaviour to create a special tool.
A value of 0 specifies that the tool is permanently active irrespective of mouse movement; much like a spraycan but valid for every tool.
