Requirements

1. The handles should be updated correctly and never make canvas artifacts/leftovers when a shape is moved/transformed
2. The settings dialog should have the following new options:
   1. Handle Size
   2. Minimal Grab Distance (configured separately for mouse and stylus)
   3. Drag Threshold (configured separately for mouse and stylus). This option will tell Krita how to distinguish clicks and drags (should the driver do that for us?)
3. When size or grab/drag distance of the shape handles is changed, the tool should redraw the canvas automatically and correctly (without artifacts)

Technical Requirements

1. Right now the handles are painted/handled in an ad-hoc way, so we can neither control their size nor drag/grab distance.
2. We need some centralized system for painting/handling the handles

Technical Proposal