[Gnucash-changes] r13352 - gnucash/trunk - Fix "default limit" QOF eventing stuff; thanks Andi.

[Derek Atkins]

Neil Williams <linux at codehelp.co.uk> writes:

>> They should always be specified as based off some constant identifier,
>> rather than a particular value.  I'm not sure what you mean.
>
> Why? This probably sounds obvious to you but if new identifiers are expected 
> to be based on QOF_DEFAULT_LIMIT + n, then I need to ensure this assumption 
> is in the API docs because it certainly would not be obvious to me. I expect 
> it's just something you've covered elsewhere that I haven't anticipated but 
> I'd like to be sure. (Blame it on me being self-taught.)

Events should always be a power of 2.  This way bitmasking events
works quickly and efficiently.  It does, however, limit the number
of events you can have.

>> > I thought nobody wanted to iterate over event identifiers?
>>
>> I have no idea how that relates to this...?
>
> I thought you were using the << operator to create some way of iterating 
> through the list of available event identifiers somewhere but couldn't see 
> why. Derek's pointer to bitmasking cleared that up.

No, << operator is just a bit-shift operation.  The construct:

   1 << x

Is a way to make a set of bitmasks.


One suggestion I had was to do something like:

   #define QOF_MAKE_EVENT(x)    (1<<x)

Then you can do:

  #define QOF_EVENT_A  QOF_MAKE_EVENT(0)
  #define QOF_EVENT_B  QOF_MAKE_EVENT(1)
  ...

and then in the API code:

  #define APP_EVENT_A QOF_MAKE_EVENT(QOF_EVENT_BASE+0)
  #define APP_EVENT_B QOF_MAKE_EVENT(QOF_EVENT_BASE+1)
  ...

-derek

-- 
       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
       warlord at MIT.EDU                        PGP key available