[Tickit-dev] Drag/Drop events on Windows - same event structure?

[Paul "LeoNerd" Evans]

Merry Christmas all :)

I'm doing that most traditional of christmas-time activities; namely
the parental visit involving spending spare time sitting writing code.
Today I thought I'd have a quick hack at putting mouse drag/drop events
into libtickit. As ever, this takes as its inspiration the perl unit
tests, on the aim to recreate the same API shape.

  https://metacpan.org/source/PEVANS/Tickit-0.54/t/29window-dragndrop.t

Currently, the drag/drop events just contain the same mouse button and
position information that regular mouse events have, so these could be
implemented by extending the TickitMouseEventType enumeration:

  typedef enum {
    ...,
    TICKIT_MOUSEEV_DRAG_START,
    TICKIT_MOUSEEV_DRAG_OUTSIDE,
    TICKIT_MOUSEEV_DRAG_DROP,
    TICKIT_MOUSEEV_DRAG_STOP,
  } TickitMouseEventType;

Something I've been considering for a later version though is to put
window information in the events too. That on a drag-over/outside/drop
event you'd also be told what the start window was, and on a stop
event you'd be told where the drag eventually stopped. This would
involve adding some TickitWindow*-typed fields to whatever event info
structure was representing drag events. 

The summary of the question then is:

  Should window drag events reuse the existing mouse structure, or
  invent their own?

Issues on each side:

  Reuse:
    - Needs adding a 'source' or 'destination' window field that
      term-level events don't use
    + Simplifies handling code

  New structure:
    - Two different kinds of events with similar routing/handling
      structure that have to be handled the same in the window layer
    + Cleaner API split

I'm slightly leaning toward the first idea, largely because it involves
less code duplication and gets something working currently; but I'd be
interested to hear people's thoughts...

-- 
Paul "LeoNerd" Evans

leonerd at leonerd.org.uk
http://www.leonerd.org.uk/  |  https://metacpan.org/author/PEVANS
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