This needs the ITEM_MODIFICATION_ROUTINE to learn to delete items.
Condense the item change handlers into a single injected object
(ITEM_MODIFICATION_ROUTINE::CHANGE_HANDLER) and provide the basic
implementation that just takes some callables.
This simplifies the construction of the routines and also would make
a CHANGE_HANDLER object possible that can be reused between different
tools.
Using the new ITEM_MODIFICATION_ROUTINE system, drop in two new
tools: chamfer and line extend. These are two geometric operations
that are relatively common when editing footprints in particular.
Chamfer delegates the geometric calculations to a dedicated unit
in kimath/geometry.
Describe the actions of the fillet tools is a generic way, so that the
same general pattern can be used for other tools that modify shapes on
the BOARD.
Basically, an "ITEM_MODIFICATION_ROUTINE" is defined, which is
configured and called multiple times, calling back to the EDIT_TOOL when
it modifies or creates an item.
The motivation here is to make it easier to slot in new line-based
tools like chamfer, extend and so on without having to redo the
complicated item, selection and commit handling each time, and keep the
core "routines" simple and decoupled from the EDIT_TOOL's
internals.
This also resolves#15094 because the new commit handling does the right
thing when items were "conjured up" for the fillet (e.g. when a
rectangle is decomposed into lines).
Fixes: #15094
John Beard