Implements comprehensive drag and drop for all-day events, allowing movement within the header and conversion to timed events when dragged into the calendar grid.
Optimizes column detection with a cached bounding box strategy, improving performance and accuracy. Refactors event conversion logic and renames related event bus events for clarity.
Addresses two key issues related to dragging events to the header: the premature removal of the original event element and the creation of duplicate all-day events.
The original event is no longer removed when dragging to the header; it is now only removed upon a successful drop.
Also, it prevents the creation of duplicate all-day events by checking for existing all-day events before creating new ones, using DOM queries to ensure accurate state.
