Plasma Calendar data engine & widget future plans

[John Layt]

Hi guys,

I'm currently revising the KHolidays library to be more useful, in particular:
* Return a date range, not just a single date
* Support non-Gregorian calendars (Islamic & Jewish holidays, etc)
* Add holiday type (Public, School, Financial, Religious, Cultural, etc)
* Split holiday region files by type / sub-region / etc, i.e. allow separate 
selection of national, provincial and religious holiday files, etc
* Add file metadata for region, language, name, etc.
* Proper translation of holiday region name (but not holiday names 
themselves)

I'm planning to use the Plasma Calendar as a test client for these changes and 
so want to add the following:

* Support multiple holidays on each day
* Support multiple holiday regions at once
* Choose which holiday region(s) to highlight as days off
* Tool-tip on hover over day showing any holidays

Of course, this is it is also a start on how to display PIM data from Akonadi 
(if not yet the two-way integration).  I'm not sure if anyone is planning to 
work on that yet, but decisions on how to display holidays will affect pim and 
so need to be thought about together.

Some points that will need input from you and the usability guys:

* How do we highlight holidays, just stick to the current halo, or support 
multiple methods such as halo colour, day number colour, day number 
bold/italic, and cell background colour/shade.

* Do we provide users the option of choosing the highlight method for each 
holiday type, or not to highlight some types?  Or do we impose 'sensible' 
options?

* How do we highlight multiple holidays and types on the same day cell?  Do we 
rank holiday types so we show only a single highlight for each day, apply 
ranking at the highlight method level, or try show all types at once?  (See 
bug 46262 for some user suggestions on PIM display in general).  Has anyone 
used other calendar applets that do this well that we can learn from?

* How to show Weekends (shading of cell or day header?) and Day of Religious 
Observance (red day number? possibly do same for all religious holidays?).

* In configuration, for selecting multiple holiday regions I was thinking to 
have all the available regions listed like the timezones are, but with two 
tick-boxes, one for "show on calendar" and another for "show as days-off".

As always we need to balance features with ease-of-use and not end up with a 
visual mess.

Just on pim/akonadi integration, I think the obvious interaction would be 
double-click on a day opens KOrganizer on that day, right-click on a day puts 
options in the menu for add/edit pim 'stuff' for that day.  That's not my 
immediate priority, but we should think about it in general terms to see if it 
would clash with the holidays handling.

Thoughts?

John.