Chapter 23: Drag and Drop

Drag and drop is an efficient feature, yet isn't used as much as it could be.

Interior/exterior drag and drop

Source-and-Target Paradigm
an idiom in which manipulating logical objects represents some behind-the-scenes processing.

To be truly exterior capable, an object must be able to accept a drop of anything from any other object, regardless of the originating program.

If objects are drag-and-drop compliant, they are possible targets, called drop candidates.

Drop candidates must visually indicate their receptivity

Bounce - logic to ignore extra transitions if they occur with a few milliseconds of the first one.
Debounce all drags

Mouse vernier function - the user can quickly shift into a mode that allows much finer-resolution for mouse-based manipulation of objects.
insertion target - visually see where source would be dropped (e.g. reordering Powerpoint slides)

Other Drag-and-Drop Interaction Issues:

Any scrollable drag-and-drop target must auto-scroll